B56133

The Science Magazine of the Max Planck Society 1.2017

Extreme Space

PUBLIC FINANCE BIOPHYSICS COAL RESEARCH LEGAL HISTORY Taxes That Vanish Cells on the A Perspective Ruling by the Book into Thin Air Catwalk for Life and the Cross Dossier – The Future of Energy

Find out how we can achieve CO2 neutrality and the end of dependence on fossil fuels by 2100, thus opening a new age of electricity.

siemens.com/pof-future-of-energy

13057_Print-Anzeige_V01.indd 2 12.10.16 14:47 ON LOCATION Photo: Annelies Kusters

In the Streets of Mumbai

A modern metropolis in India: many different ethnic groups come together every day. A wide variety of languages can be heard, and very often, people who have no common language have to communicate with each other. People involuntarily resort to gesticulation, and their counterparts usually have no trouble understanding what is meant. But gestures can also be defined terms in a language of their own – the sign language of the deaf. Things get particularly interesting when sign language – here in its Indian form, of course – and spontaneous gestures are used in parallel and in combination. This is precisely what Annelies Kusters from the Max Planck Institute for the Study of Religious and Ethnic Diversity and her team are studying in the streets of Mumbai. Kusters is interested in both the potential and the limitations of gesture-based communication. Being deaf herself, she makes it a point to involve deaf people in her research work. They can contribute greatly to these studies because they are very skilled in the creative use of gestures – both conventionalized and spontaneous – in conversations with the hearing as well as with other deaf persons. The researchers observe and document the experiences of both hearing and deaf participants in conversa- tions combining oral, gestural and written communication. And they also study what role the various surround- ings play. It makes a difference, of course, whether a conversation takes place at the market, in a loud street, or in a quiet environment. Here, two researchers from Kusters’ team watch a deaf businessman using facial expres- sions and gestures to negotiate with a hearing shop owner.

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On the street: Demonstrators remind the public that Apple owes the Irish 18 EXTREME SPACE 10 government 13 billion euros.

18 Frantic Finish PERSPECTIVES Supernovae portend cosmic catastrophes. When a massive star slides Pearls for the Chancellor into an energy crisis at the end of its life, or a sun that has already 06 died is overfed with matter, the end is an explosion of unimaginable 06 Threefold Leibniz Prize proportions. What exactly happens here? Scientists at the Max Planck 07 “Brexit will be more complicated Institute for Astrophysics make supernovae explode on the computer. than some imagine” 08 Welcome to Cyber Valley 26 Traps in Space-Time 08 Commitment to Scholars at Risk Black holes are a permanent fixture in science fiction literature. 09 Dec laration of Principle on In reality, there is hardly a more extreme location in the universe. Animal Research These mass monsters swallow everything that ventures too close to them. It sounds quite simple, but the nature of black holes is complex. 09 On the Net A group at the Max Planck Institute for Gravitational Physics wants to solve some of the puzzles these exotic cosmic bodies present. VIEWPOINT 34 Cosmic Particle Accelerator 10 Taxes That Vanish into Thin Air Black holes, pulsars, remnants of exploded stars – these celestial bodies International corporations such accelerate particles to enormous energies and emit high-energy gamma as Apple, Starbucks and Amazon radiation. The two observatories known as H.E.S.S. and MAGIC make this have for years successfully avoided extreme spectral region accessible. Astronomers at the Max Planck paying tax on their corporate Institutes for Nuclear Physics and Physics use these high-tech detectors. profits. Why is it so difficult for the international community to counter these tricks?

FOCUS

ON THE COVER On a clear night, the starry sky appears calm and peaceful. In reality, 18 Frantic Finish however, all hell breaks loose in the heavens: stars absorb matter from other stars, suns explode and black holes greedily devour gas and dust. In short, there are a lot of 26 Traps in Space-Time

extreme places in the universe – and they hold particular appeal for researchers. 34 Cosmic Particle Accelerator Cover: Optical: DSS; illustration: NASA/CXC/M.Weiss; photos this page: NASA/ESA/Hubble Heritage Team (lg. image), picture alli ance/Pacific Press Agency

4 MaxPlanckResearch 1 | 17 On his head: Ben List does yoga On the lookout: Researchers On the wall: This fresco from almost every day – but in the lab, he are testing various enzymes for 1338 warns against bad judges 56 does it solely for the photographer. 64 synthetic photosynthesis. 70 and unjust dominion. right)

to

(left SPECTRUM BIOLOGY & MEDICINE CULTURE & SOCIETY

42 Electronics at Record Speed 48 Cells on the Catwalk 70 Ruling by the Book and the Cross Institute

42 My Contribution to Arctic Sea Life is motion and interaction with The Spanish Conquistadors found it the environment. This is equally surprisingly easy to conquer the New Planck

Ice Melt true of cells, but for cells to get World. However, it required more Max

43 Scrambled Letters with – Consequences from one place to another, they not than violence and cruelty to rule the only have to be able to move, they territory. Researchers are investigating A Nose for Oxygen 43 also have to interact with their the media through which the Spanish Florence

in 43 Superlative Coating environment. Researchers are study- crown consolidated its dominion. 44 Guided by Light ing how they manage this. Institut 44 Monkeys with a Knack for Language 45 The Turbulent Heart of Eta Carinae REGULAR FEATURES MATERIALS & TECHNOLOGY 45 Skin Stem Cells in a Test Tube 03 On Location 45 Pushing the Boundaries of 56 A Perspective for Life 16 Post from Tel Aviv, Israel Kunsthistorisches Microscopy Personal Portrait: Ben List On the Trail of German-Israeli 46 A Well-Rounded Star Cultural History 46 Water Ice in the Eternal Polar Night 78 Flashback ENVIRONMENT & CLIMATE 47 The Enemy of My Enemy Is My Friend A Foul Enemy in Fowl Microbiology;

47 The Fastest Fliers in the Animal 64 Metabolism 2.0 80 Max Planck Community Kingdom The scientists picked out just 17 80 PhDnet Prioritizes Communication Terrestrial 47 Looking Out for Others Means enzymes for the first synthetic and Equal Opportunities for Longer Life metabolic pathway that is able to 81 ERC Funding Times Seven MPI convert carbon dioxide into other 81 Symposium in the Age of Brexit organic molecules. But does the cy- 82 Award for Going the Extra Mile Vinken; cle they sketched out on the draw- 83 Research Establishments ing board also work in living cells? 83 Publisher’s Information Frank

Cover: Optical: DSS; illustration: NASA/CXC/M.Weiss; photos this page: NASA/ESA/Hubble Heritage Team (lg. image), picture alliance/Pacific Press Agency Photos:

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Pearls for the Chancellor

Scientists present innovative projects to politicians

Interactive presentation: Martin Wikelski from the Max Planck Institute for Ornithology shows State Secretary for Economic Affairs Rainer Sontowski, German Chancellor Angela Merkel and Federal Minister of Research Johanna Wanka (left to right) the minute size of the transmitters with which he follows the wanderings of animals.

including German Chancellor Angela Merkel, Federal Minister of Research Johanna Wanka and State Secretary for Economic Affairs Rainer Son- towski. On the other hand, the researchers’ pre- sentations took on an unusual format: interact- ing directly with their guests, the scientists pre- sented their work at a desk with a touchscreen. Under the motto “Pearls of Research for Practical Applications” they had to summarize their work in just a few minutes – succinctly and in an easi- ly comprehensible manner. The gamut of topics ranged from virtual reality and forecasting earth- quakes using animal sensors to the early detec- tion of reading and writing problems and com- bating antibiotic-resistant germs. The concept The presentation event with scientists from the Max Planck proved a winning formula. The Chancellor praised the viv- Society and the Fraunhofer-Gesellschaft was a first in two re- id, comprehensible presentation of the projects. In conclu- gards. On the one hand, the audience in the Max Planck sion, she promised to continue to advocate for reliable finan- Society’s Harnack House in Berlin included prominent guests cial framework conditions for research in Germany.

Threefold Leibniz Prize

Ralph Hertwig, Frank Jülicher and Joachim P. Spatz to receive Germany’s highest scientific honor

When the German research community universal physical principles from the com- face between materials science and cell bestows the Gottfried Wilhelm Leibniz plex world of living matter.” In addition, biophysics. Spatz studies cell adhesion, Prizes, each endowed with 2.5 million eu- Joachim Spatz, Director at the Max Planck which deals with questions relating to ros, there will also be three scientists from Institute for Medical Research, will be hon- how cells bind together and how they at- the Max Planck Society in attendance at ored for his outstanding work at the inter- tach to surfaces. the ceremony in Berlin in March. Ralph

Hertwig, Director at the Max Planck Insti- Prizewinning trio: Joachim P. Spatz, Ralph Hertwig and Frank Jülicher (left to right) Photos: David Ausserhofer (top), Tom Pingel, Norbert Michalke, Daniel Etter (bottom, left to right) tute for Human Development, is receiving the prize for his pioneering research on the psychology of human judgments and deci- sion-making. “This body of work is expand- ing our understanding of the capabilities and limits of human rationality,” writes the jury. One of the world’s leading scientists in the field of biophysics, Frank Jülicher, Di- rector at the Max Planck Institute for the Physics of Complex Systems, will also be awarded the prize. As the jurors empha- size, he understands how to “elucidate the

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“ Brexit will be more complicated than some imagine”

Jürgen Basedow explains why the British are facing arduous negotiations and why little will change initially

In June 2016, a majority of British citizens British submit their official application to voted for the United Kingdom to leave the leave. If the negotiations haven’t been con- European Union. Upon taking office, the cluded after 24 months and the deadline is country’s new Prime Minister, Theresa May, not extended, all EU contracts and rules announced that she would quickly put the will cease to have legal force in England decision into practice. And she promised without it being clear what regulations that “the power of EU laws in this country will then apply. Theresa May wants to pro- will end forever.” Jürgen Basedow, Director vide for this contingency. at the Max Planck Institute for Comparative and International Private Law, believes that If EU provisions are converted into British law European laws will continue to apply in the anyway, what will change for the British? UK for a long time to come. Initially, this arrangement will give compa- nies and citizens in the UK legal certainty. Mr. Basedow, why can’t the British – as a Tory Later, parliament will decide whether all the Jürgen Basedow MP put it – simply “offer to retain free trade, standards will really be retained or what is write a letter and leave?” to be changed. However, the difficulties for Jürgen Basedow: The United Kingdom has the British arise not in their own country, been a member of the European Union for but in the remaining EU states. If the Unit- 44 years. In that time, far-reaching con - ed Kingdom is no longer a member of the That’s why the subject of free movement tracts have been concluded and hundreds EU, British companies and service providers will certainly be the most difficult point. of regulations and directives enacted cover- will lose many advantages on the continent. Theresa May announced that “Norway is ing a wide variety of different areas. For ex- Lawyers, financial advisors, architects and not a model.” On the other hand, the EU ample, there are extensive rules governing many others will no longer be readily able won’t budge from its freedoms of move- consumer protection in product liability, or to work in Germany, France or Sweden, for ment –of that I’m certain. So the Norwe- the ban on misleading advertising, to name instance. The disadvantages will be most gian model might still come after all, at two cases. There are clear specifications in clearly revealed in the area of judicial rul- least as an interim solution if time is press- labor laws covering how workers’ health ings. The decisions of British courts will no ing. I can hardly imagine that the UK will must be protected, or the rights of works longer be automatically recognized in EU talk about every single act of law – especial- councils. There are common regulations on countries. This will affect even such simple ly as the negotiations with the EU won’t be social security, environmental protection, cases as a car accident and the question of the only ones. insolvency proceedings, the certification of which insurance company has to pay. medicines, etc. If the British leave the EU, What else is there? they will have to define what will replace The British want to settle such matters during The EU has concluded many international all these standards. the exit negotiations ... treaties with non-member countries that That depends on how long they wish to ne- won’t automatically continue to apply to Theresa May announced that she will intro - gotiate. If you look at the enormous vol- the United Kingdom if the country leaves duce a “Great Repeal Bill” in the next session of ume of EU regulations, it certainly can’t be the EU. These include, for instance, agree- the British parliament starting in May 2017. done in two years. I would estimate that ments on liability in the areas of aviation,

Photos: David Ausserhofer (top), Tom Pingel, Norbert Michalke, Daniel Etter (bottom, left to right) What does this entail? the negotiations will take eight or ten copyright and environmental protection, as First, it’s a question of repealing the Act years – unless you take a ready-made mod- well as many trade agreements. China an- with which the country accepted the rules el, namely the contracts with Norway, Ice- nounced that it is interested in concluding of the EU upon its entry in 1972. This has to land and Liechtenstein. However, all free- a free trade agreement with the United be done at the time of the UK’s departure. doms of movement apply in those coun- Kingdom and said at the same time that At the same time, the “Great Repeal Bill” is tries – free movement of people, goods and Britain should provide 500 people to work intended to convert European standards – capital and freedom of services. And the out the details. Not only does this show that is, mainly EU regulations – into na- free movement of people also covers the that Brexit will be much more complex than tional law. This conversion is necessitated right of establishment and the free move- some imagine, it also underscores that the by the lack of time available: according to ment of labor. EU is more than a union of member states: Article 50 of the Lisbon Treaty, countries it is a player on the world stage. That won’t have only two years to negotiate an exit. But that is precisely what the British don’t be so easy to replace.

Photo: MPI for Comparative and International Private Law The clock begins ticking as soon as the want; they want less immigration. Interview: Mechthild Zimmermann

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Welcome to Cyber Valley

Science and business forge research alliances in the area of artificial intelligence

At the launch in Stuttgart: Theresia Bauer, Minister for Science, Winfried Kretschmann, Minister President, Volkmar Denner, Managing Director of Bosch, and Martin Stratmann, President of the Max Planck Society (left to right)

gart-Tübingen area. This ambitious project was kicked off in December by Winfried Kretschmann, Minister Presi- dent of Baden-Württemberg, Martin Stratmann, President of the Max Planck Society and the other project partici- pants. The Max Planck Institute for In- telligent Systems, the Federal State of Baden-Württemberg, the Universities of Stuttgart and Tübingen, and the companies, Bosch, Daimler, Porsche, BMW, ZF Friedrichshafen and Facebook want to strengthen research and devel- opment in the area of artificial intelli- gence in Cyber Valley. Together they are creating one of the largest research Intelligent systems will shape our fu- expedite this development, partners alliances in this field in Europe. ture: in the form of self-driving vehi- from science and business followed the Baden-Württemberg alone will invest cles, household assistants or tiny ro- initiative of the Max Planck Society more than 50 million euros in the proj- bots in medical technology. In order to and created Cyber Valley in the Stutt- ect in the coming years.

Commitment to Scholars at Risk

Max Planck Society joins international network defending the human rights of scholars worldwide

The MPG is now a member of the “Scholars at Risk” (SAR) network, along with other prestigious international scientific facilities. The aim of the initiative is to support scientists around the world who are under threat from, for instance, war or violence. The network brings people and guest facilities together, but it also supports its 400 members with counselling and takes on the research work when ev- idence of the risk has to be provided for scholarship applications. The same is true of the Philipp Schwartz initiative by the Alexander von Humboldt Foundation (AvH), in which universities or even MPIs have until April 21 to submit applications for full 24-month scholar- ships for researchers at risk. Information and the application form are available on the AvH website. The point of contact at Adminis- trative Headquarters for SAR is Barbara Spielmann, Coordinator for International Relationships.

The Scholars at Risk initiative condemns the implementation of U.S. President

Trump‘s executive order on immigration. Photos: State Ministry of Baden-Württemberg (top),Margaret Coons / Scholars at Risk (bottom)

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Declaration of Principle on Animal Research

White paper emphasizes indispensability of animal research, as well as special ethical responsibility

The Senate of the Max Planck Society has adopted a white paper on animal research. It underscores that animal studies are indispensable in basic research, but it also acknowledges the special responsibility of every scientist, and subscribes to a culture of welfare. A further important concern is the transparent presentation of research to the public. The pa- per is the result of the extensive deliberations of a commit- tee boasting an international line-up of well-respected researchers from the life sciences, as well as behavioral re- searchers, ethicists, specialists in communication and per- sonalities from the field of research policy. In the future, the Max Planck Society aims to dedicate itself to the best possible implementation of the principles of the 3Rs. This stands for Replacement, Reduction, Refinement – the re- placement and reduction of animal research and the mini- mization of stress for the animals. A fourth R for Responsi- bility completes the principles. For example, the sentience, consciousness and intelligence of different species of animals are to be investigated and animal research continually reas- Protection from a single source: In the future, the Max Planck Society sessed on this basis. aims to promote a culture of welfare in animal research.

On the Net

Award-Winning Video Female pioneers of science Why We Research with Animals An international jury has awarded the On International Women’s Days, three The animal research portal of the Max Planck film Biomaterials – Patent women Max Planck scientists celebrated Max Planck Society has been updat- Answers from Nature, which portrays the scientific accomplishments of three ed. Numerous articles, background the research conducted by Peter Frat- early female researchers – also highlight- information, statistics and multi- zl at the Max Planck Institute of Col- ing the often daunting social obstacles media content explain why animal loids and Interfaces, the 2016 Technol- these women had to overcome to perse- research is indispensable for basic ogy Prize. The prize is awarded by the vere in their fields: Caroline Herschel, Ada research today and doubtless in Goethe Institute from a selection of Lovelace, and Sofia Kovalevskaya. Astron- the future, which animals are used films shown at the annual Science Film omer Caroline Herschel was the first wom- for research and how researchers Festival, which brings science to the an to be honoured with the golden medal live up to their responsibilities. The screen: entertaining, creative, stimu- of the Royal Astronomical Society. Ada white paper on animal research lating – and always instructive. Aiming Lovelace is considered to have written in- and a flyer for the public relations to make insights from the natural sci- structions for the first computer program work of the Max Planck Institutes ences accessible to a broad public, it at- in 1848. Russian Sofia Kovalevskaya was are available for download there. tracts considerable attention, above all to become the world’s first female profes- www.mpg.de/animal-studies-in- in Southeast Asia, North Africa and the sor of mathematics. Read more on: basic-­research Middle East. www.mpg.de/female-pioneers-of-science www.youtube.com/maxplancksociety Photos: State Ministry of Baden-Württemberg (top),Margaret Coons / Scholars at Risk (bottom) Photo: Wolfgang Filser/MPG

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Taxes That Vanish into Thin Air

International corporations such as Apple, Starbucks and Amazon have for years success- fully avoided paying tax on their corporate profits. Aided by tax competition between nations, they shift their money to countries that have low tax rates and that guarantee that only domestic profits will be taxed. Our author explains why it is far from easy for the international community to counter these tricks.

TEXT WOLFGANG SCHÖN

he announcement by the European Com- (that is, Apple had paid all of the tax it owed). Can mission that it would oblige global player European law compel a state to levy taxes to which Apple to pay back taxes totaling more than it attaches no importance? 13 billion euros attracted some of the most The stir this case created even on the other side prominent international press headlines of the Atlantic clearly illustrates the global dimen- in summerT 2016. The recipient was to be the Repub- sion of the problem. Word soon spread that Europe lic of Ireland, where Apple had been “stashing” un- had declared a tax war on US industry and the US usually high profits in its subsidiaries since the 1990s. tax authorities. For years now, Amazon, Google and Starbucks have been confronted with similar pro- ceedings. US politicians, in an outpouring of wrath, pointed out that Apple might well demand to offset Word soon spread of a tax war additional taxes paid in Europe against its tax bill in the US. against US corporations and the In practice, the aforementioned 13 billion euros US tax authorities would vanish from the US budget and reappear in its Irish equivalent. Treasury Secretary Jack Lew, along with some leading voices in Congress, protested in It will come as a surprise to no one that Apple reject- unusually sharp terms, and some observers interpret- ed this demand. It does, however, seem odd that the ed the subsequent report that the US Department of Irish tax authorities should decline to collect these Justice was threatening Deutsche Bank with fines in taxes. Both sides – the tax authorities and the com- the region of 15 billion dollars for capital market mis- pany – maintain that everything was above board conduct as another move in this dispute. >

10 MaxPlanckResearch 1 | 17 Photo: picture alliance/Pacific Press Agency euros in back taxes. back in euros in call to declined Irishgovernment, which the against protesting were They logo. Apple the of shape the in balloon black a floated symbolically Dublin in tors 2016 autumn In names: their Blackening , demonstra , 13 13 billion billion

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In order to understand this conflict, one must first The first thing that comes to mind, of course, is the appreciate why Ireland is reluctant to enforce this loss of tax revenues. When billions in profits aren’t payment – it’s not as if the country is swimming in taxed anywhere, the corresponding tax income is cash. The reason is that, for many years, Ireland has missing in a national budget somewhere – but in set great store by offering a reliable and invest- which one? In Ireland? In the United States? Or ment-friendly tax system for global players. And in- should the profits be taxed where Apple’s customers tegral to this self-image is a self-imposed commit- are located – for example in other European coun- ment to abide by long-term promises. tries? Under the terms of the applicable tax agree- Apple received just such a promise decades ago ments, however, these countries do not have the regarding the taxation of its Irish subsidiaries. The right to levy tax on profits on cross-border supplies. gist of this agreement is that these subsidiaries will As a result, France, for instance, has called for Goo- be taxed only on the proportion of profits account- gle and other companies to be taxed in the future on ed for by their (small-scale) domestic output in Ire- the basis of their “digital presence,” but this propos- land. This excludes the (significantly higher) profits al has not yet prevailed. made by these subsidiaries resulting from the use of Is it not more a question of equitable taxation? the Apple brand and technology in the European, Is this another instance in which, as so often, the rich pay nothing and the poor pay everything? This point of view is one that is emphasized again and again in civil society. The problem is simply that the State aid sanctions can be deemed contributions companies make to a country and its to apply only if the tax authority economy include not only their tax payments, but also jobs and investments. For this reason, countries fails to abide by its own rules are frequently willing to forgo a high tax take in or- der to attract companies to their shores. So the “little man” can also be a winner. And who African and Asian markets. These profits – it has been can blame a company for responding to such fiscal revealed – are not taxed anywhere: not in the US (be- offers? Tax competition is intensified by the highly cause they are not paid over to the parent company mobile nature of corporate functions: mobility of in California) and not in Ireland (because they are capital, mobility of intangible goods and services, not related to production in Ireland). mobility of management personnel. In this compe- These corporate profits that are “parked” in no- tition, the non-mobile factors – namely the work- man’s-land between producer and consumer are force – can’t keep pace. known in international parlance as stateless income. This brings us to a third consideration, one that It is estimated that, with the aid of this technique, stirs the emotions: the competition between compa- US companies alone have more than two trillion dol- nies. The opportunity for multinational corporations lars in cash holdings lodged with overseas subsidiar- to profit from the tax competition between countries ies (predominantly in tax havens). strengthens their position relative to local competi- In recent years – driven primarily by politicians, tors who are unable to enjoy such preferential treat- but also by non-governmental organizations – a va- ment. The classic example here is the local booksell- riety of initiatives have been launched at both the na- er who loses his customers to Amazon. tional and the international level to counter these Amazon was long able to supply the German mar- practices. As understandable as this uproar may be, ket with books via a subsidiary in Luxembourg with- however, it is proving difficult to identify where the out being subject to corporation tax in Germany – actual evil-doing lies. something the Munich-based firm of Hugendubel is

12 MaxPlanckResearch 1 | 17 unable to avoid. This clearly highlights the relation- In the following years, however, discussion of inter- ship between the international tax system and the national corporate taxation slipped into the back- European rules on competition. ground. After the turn of the millennium, it wasn’t The German government made it clear years ago tax competition, but international tax evasion that that one of the central purposes of its participation in occupied the global foreground. From the acquisi- the determination of international tax policies was to tion of CDs listing Germans’ savings accounts in ensure a level playing field for market players both Switzerland, Luxembourg and Austria to the identi- large and small. Similarly, in its decision on Apple, the Commission in Brussels was primarily concerned that Apple enjoyed tax treatment in Ireland that was out of step with the taxation of independent companies that Corporations use the scope don’t form a part of international corporate structures. The competition between states thus also impacts that countries offer them competition between companies. But there are lim- its to the use that can be made of European compe- tition law: only if a national tax authority fails to ties – revealed by a data leak – of those behind se- abide by its own rules and regulations can state aid cretive Panama-registered companies, or even the sanctions be deemed to apply under European law. tough sanctions threatened by the United States As the US Treasury rightly points out, the European against banks the world over that refuse to disclose Commission has no authority to undertake any fur- details of US account holders, all of these cases re- ther standardization of international fiscal policy to volve around the unambiguously unlawful conduct suit its own interests. of putative tax payers. Their guilt is as easy to assess Neither the phenomenon of tax competition nor as the identity of the state to which the unpaid tax- its political fallout is new. In the 1990s, in particu- es are due. lar, tax competition became a central topic of discus- New standards have made inroads in this area sion among both economists and legal experts. Even worldwide in recent years, as the international inter- before the turn of the millennium, the tax practices change of information has reached huge proportions of tax havens and other preferential tax regimes had in terms of both quality and quantity. The introduc- begun to pervade the realms of international poli- tion in the coming year of a common reporting stan- tics. In 1998, the member states of the European dard will enable over 100 countries to automatical- Union agreed to a code of conduct that paved the ly exchange tax data. This has nothing to do with way for the restriction or abolition of a wide range competition between companies – despite the unfor- of preferential taxation treatment alternatives for tunate confusion consistently encountered in the foreign investors and business undertakings. political sphere. Also in 1998, the OECD published an influential It is only since 2012 that the issue of taxing inter- report on harmful tax competition that still guides national corporations has reappeared on the broader the political agenda today. This report accepts the ex- political agenda – but it has done so with unforeseen istence of healthy tax competition, in which states force and at multiple levels. At the national level, ac- compete by equitable means (primarily by reducing tivity has been most in evidence in the United States tax rates in general) for real investment and business and the United Kingdom, where special committees activity. But it condemns harmful tax competition, appointed by the Senate and the House of Commons as characterized for instance by preferential treat- – with strong support from civil society – have been ment for individuals, lack of transparency and devi- examining the tax practices of large corporations and

Photo: picture alliance/Pacific Press Agency ation from recognized rules for calculating profit. exposing these to the public eye. >

1 | 17 MaxPlanckResearch 13 In Germany, the issue has been less prominent – sive tax practices of large corporations that have given that the relatively high effective tax rate to been the subject of complaint. This adds to the de- which large German companies are subject is still bate a moral dimension that frequently impedes an regarded as a positive factor. At the international objective analysis. Among other things, an answer is level, the members of the G20 seized the initiative still lacking to the question of where to draw the line and commissioned the OECD in Paris to prepare a between acceptable and aggressive tax planning. report and an action plan on base erosion and prof- This approach also overlooks the fact that corpo- it shifting (BEPS) – that is, on the attempts planned rations, after all, can only exploit the scope that by multinationals to reduce the potential bases on states have offered them in the first place. Without which tax can be assessed, and on the cross-border tax competition, there can be no tax planning – so transfer of profits. if one wants to combat tax planning, one must first In an unparalleled intellectual and organization- look at tax competition. Such competition is not al masterstroke, by the end of 2015, under the um- easy to prohibit – what is needed instead is a consen- brella of the OECD and with the participation of in- sus on common rules, that is, reconciliation between dustrialized, newly industrializing and developing fiscal jurisdictions. countries across the world, an impressive package The BEPS project offers two principles for reori- entation: the principle of once-only taxation and the principle of taxation on the basis of economic reali- ty. However, both approaches suffer from blurred The question of where value lines that could endanger the success of the entire creation takes place is not easy undertaking. For example, inherent in the goal of once-only taxation is the idea that distorted compe- to answer tition between multinational and local companies can be prevented if it is assured that all corporate profits will attract a substantial rate of tax at least of rules, minimum standards and agreements had once. Such profits should not be parked somewhere been developed with the intention of placing inter- free of tax in a tax haven, nor exempted from tax national fiscal policy on a new footing. More than through the exploitation of regulatory differences. 100 countries are now engaged in implementing The German government has made it a declared these resolutions. principle of its international fiscal policy to avoid In parallel with this, the European Commission double non-taxation, but this intention doesn’t solve put forward numerous proposals to combat aggressive the problem of who should levy the once-only tax. tax planning, some of which have since been adopt- Let us take the profits made by Apple in the Europe- ed as binding directives by the Council of Ministers. an markets as an example: should these be taxed in The coming years will show whether these efforts to the consumer states (where, as a general rule, the com- harmonize the rules of the game have been success- pany has no fiscal presence)? Or in Ireland (where the ful – with the process being assisted by a multilateral subsidiaries are in fact registered, but maintain only instrument that will enable thousands of double tax- minimal business operations)? Or in the United States ation agreements to be modified simultaneously. (where the brand and technology were developed, but If one takes a closer look at the BEPS initiative, it as yet no profit payments have been received)? It is first becomes apparent that the perspective has obvious that none of the countries involved is mak- changed. Whereas at the end of the 1990s the focus ing a serious effort to grab these profits. was clearly on regulatory competition between According to the recent pronouncements of the

tax-gathering states, more recently it is the aggres- G20, the OECD and the European Commission, on Photo: picture alliance/Pacific Press Agency

14 MaxPlanckResearch 1 | 17 VIEWPOINT_Public Finance

the principle of “taxation follows value creation,” the attribution of corporate profits and taxation rights should be determined by the location at which value is created. This should make it possible to effectively undermine the purely tax-driven trans- fer of profits to functionless companies situated in tax havens. The program sounds convincing, but it has its limitations, given that the question of what eco- nomic reality means and where value creation takes place is not easy to answer. Where, exactly, is the source of Apple’s billions in profits: California, where the brands and patents are developed? Chi- na, where the hardware is manufactured? Europe, where iPhones and iPads are purchased? Or indeed Ireland, where the relevant brand and patent rights are held by a subsidiary? THE AUTHOR This isn’t a question that can be answered strict- ly scientifically. As a successful export nation, the Wolfgang Schön, born in 1961, is Director at the Federal Republic of Germany is keen for the location Max Planck Institute for Tax Law and Public Finance of production to have priority, whereas India, as a in Munich. He also teaches at Ludwig-Maximilians- major importer of services, would wish to broaden Universität München (LMU), where he is an honor- its access to the corresponding profits made by for- ary professor of civil, commercial, economic and eign providers. Viewed globally, it is evident that, in tax law. His scientific work is focused on, among recent years, the market states have managed some other things, the barriers to state tax sovereignty piecemeal expansion of their access to taxation. Tax and the issues of tax and corporate law as com­ competition supports this in that production may be petitive factors. Schön also serves as Chairman of relocated, but customers cannot. the Board of the European Association of Tax Law At this point, it is apparent that the attempt to Professors and Vice President of the German align international taxation with economic reality Research Foundation (DFG). can ultimately lead to still more competition. The competition for the artificial transfer to profits is overlaid and replaced by still fiercer competition to attract actual business activities and investments. The latest political developments indicate that this competition is unlikely to cease. sensus achieved by the OECD remains to be seen – Shortly after the Commission announced its de- many important documents were in dispute even be- cision in the Apple affair, the British government let fore the US presidential election. it be known that, in the aftermath of Brexit, the Unit- The long-term strength of fiscal coordination is de- ed Kingdom would seek to heighten its profile as a pendent on whether and to what extent nations per- tax-friendly location for investment – without the ceive greater value in a global consensus than in indi- barriers imposed by European competition law. vidual political strategy. The coming years will provide Whether, following Donald Trump’s election victory, an answer. The task of fiscal science lies in clearly iden-

Photo: Axel Griesch the United States will stand by the fiscal policy con- tifying the premises and options for such strategies.

1 | 17 MaxPlanckResearch 15 Post from Tel Aviv, Israel

On the Trail of German-Israeli Cultural History

Max Planck scientists cooperate with partners in around 120 countries worldwide. Here they relate their personal experiences and impressions. For her doctoral thesis, art historian Anna Sophia Messner from the Kunsthistorisches Institut is tracing the life and work of female German- Jewish photographers in Israel – which has resulted in a variety of encounters between the past and the present.

My work in Israel is a bit like a treasure hunt. Every time I’m here, I discover new sources. Since completing my studies, I’ve specialized in German-Jewish cultural and art history. I’m particularly interested in artists who emigrated from Germany to Palestine in the 1930s. Due to the wealth of material, I had to narrow down the topic for my dissertation, and now I’m studying the life and work of German-Jewish photographers. Like numerous other Ger- man Jews, they had fled from the Nazis. Back then, there was a saying: “Do you come from Germany or from conviction?” There was certainly some truth to it. Many Germans held tightly to their German language and culture in exile and hardly identified with their new home at all. Some also later moved on to other countries, which is one of the reasons why the photographers were forgotten. My field research took me to archives, museums and private collections. My research be- gan with the sisters Gerda and Charlotte Meyer from Berlin, who opened a photography studio in Haifa in the mid-1930s. Their portraits were highly valued: they photographed

famous personalities such as Arturo Toscanini, David Ben-Gurion and Golda Meir. In the Graphic: iStockphoto

16 MaxPlanckResearch 1 | 17 RUBRIK TITEL

Anna Sophia Messner , 35, studied art history, Jewish history and culture, and

classical archaeology at Ludwig-Maximilians- Universität München (LMU), and completed language programs at the Hebrew University of Jerusalem. She curated exhibitions at the Jewish Museum Munich and the city’s municipal archives, and publishes on Jewish and Israeli artists. From 2012 to 2015 she worked as a scientific assistant at the LMU Institute for Art History. Since 2015 she has been working on her doctorate in connection with the Max Planck Research Group “Objects in the Contact Zone – The Cross-Cultural Lives of Things” at the Kunst historisches Institut in Florence. ­

1940s, they compiled documentation for industry, including for the Iraq Petroleum Com- pany, which had refineries in Haifa. Both later left the country again, one to Canada and the other to England. Since I started researching, more and more stories like this one have come to light. The pho- tos and documents turn up in attics and basements, and sometimes even in garbage dumps. I have developed a network of Israeli colleagues who tell me when new material has been discovered. I also talk to relatives and contemporaries of the deceased, most of whom in- sist on speaking German with me. Even the children of the German emigrants frequently still speak their parents’ language quite well, though the German may sound somewhat old-fashioned to modern ears – it’s just how people spoke in Germany in the 1930s. Life here in Tel Aviv is the same as in any other international metropolis. It’s a bit like liv- ing in a bubble, because you don’t usually hear too much about the Israeli-Palestinian con- flict, which is definitely present in other cities. In Jerusalem’s Old City, for example, there might be tensions particularly on religious holidays, especially around the Temple Mount. This is evident, for example, from the increased military and security controls around the city. Nevertheless, people in Israel try to lead a largely normal day-to-day life. One question I’m frequently asked is how people treat Germans in Israel. I’ve had only good experiences. Particularly the third generation – people my age – are very open toward Germany. They’re interested in the country their grandparents came from and are happy to connect with Germans. Some are even learning the German language. I have since built up a large professional network here and made friends. That’s another reason I keep com-

Graphic: iStockphoto Photo: Private collection ing back to Israel.

1 | 17 MaxPlanckResearch 17 FOCUS_Extreme Space

Frantic Finish

Supernovae portend cosmic catastrophes. When a massive star slides into an energy crisis at the end of its life, or a sun that has already died is overfed with matter, the end is an explosion of unimaginable proportions. What exactly happens here? Hans-Thomas Janka from the Max Planck Institute for Astro- physics in Garching wants to get down to the nuts and bolts. He simulates supernovae on the computer and makes them ex- plode in the virtual world – meanwhile even in three dimensions.

TEXT HELMUT HORNUNG

n February 24, 1987, short- non for many years. It is by no means ly after midnight, Ian Shel- as far removed from our daily life as ton is sitting in the dark- some would think, because the calcium room of the Las Campanas in our bones and the iron in our blood observatory near the city originate from the nuclear melting pots of LaO Serena in Chile. The Canadian as- deep in the interiors of the stars. These tronomer is developing pictures of the elements were released during large Large Magellanic Cloud, a neighboring numbers of supernovae, and mixed galaxy of our Milky Way. As the imag- with others to form the stuff that life on es in the fixing solution become clear- Earth was ultimately made on. Our ex- er and clearer, he immediately recog- istence is therefore closely connected nizes a bright star that doesn’t belong with the cosmos via the most violent there. Shelton goes outside into the explosions since the Big Bang. clear night, looks up to the sky and dis- The zoo of supernovae is very di- covers the spot of light in the Large verse and confusing to the layperson. Magellanic Cloud with his naked eye. Astronomers have classified around a The scientist knows immediately: what dozen different types of supernovae. he is observing is a supernova, the clos- However, “fundamentally, we differ- est one in 383 years. entiate between thermonuclear and “Supernova 1987A opened up a new core-collapse supernovae,” Janka says. chapter in research,” says Hans-Thom- The criteria used are the lines of hydro- as Janka. The scientist at the Max Planck gen, helium and silicon that occur in Institute for Astrophysics has been the spectra – that is, in the decomposed studying this astronomical phenome- light – and also the shape of the light

18 MaxPlanckResearch 1 | 17 Photo: NASA/ESA/Hubble Heritage Team section of this cosmic web. cosmic this of section a shows image The supernova. the by released once was that – gas nebula Cirrus the observe now astronomers disaster, the of site the At The end of a star: Around Around star: a of end The 18,000 years ago, a massive sun exploded. 1 | MaxPlanckResearch 17MaxPlanckResearch

19 curves. The spectra of thermonuclear supernovae (Type Ia) have no hydrogen and no helium lines, but strong lines of the element silicon. According to one conceivable scenario, the explosion is caused by the “overfeeding” of a white dwarf, the burnt-out core of a sun of relatively low mass. Such a stellar remnant sometimes has a partner star to which it is bound by gravitational forces. It is also gravity that enables the white dwarf to extract large amounts of gas from the surface of its partner. The matter flows onto the white dwarf, where it accumulates. This process, called accretion, causes the dwarf to constantly increase in mass. At some stage, its mass reaches around 1.4 solar masses. If this limit, which is named for as- trophysicist Subrahmanyan Chandra­ sekhar (1910 – 1995), is exceeded, the worst-case scenario becomes reality: the white dwarf begins to contract. This contraction releases gravitational ener- gy, which heats the crystal-like mix of carbon and oxygen; in this phase, the star resembles an extremely compressed

Light shows in the sky: Supernova 1987A (arrow), taken shortly after its flare-up as a bright star in the Large Magellanic Cloud. The small image shows the remnant of the explosion just over ten years later; three bright rings are clearly visible. Photos: ESO; Robert P. Kirshner and Peter Challis, Harvard University, STScI, NASA

20 MaxPlanckResearch 1 | 17 FOCUS_Extreme Space

Degenerate iron core S and Si fuse to Fe O fuses to S and Si Ne fuses to O and Mg C fuses to Na, Ne and Mg He fuses to C H fuses to He Non-fusing layer

Layers full of energy: Different nuclear burning processes occur in a massive sun. After the fusion of sulfur and silicon to iron, production stops. The sphere of iron in the core finally collapses further into a dense object – a neutron star or a black hole.

diamond. In its interior, the first step is to helium. When the supply of fuel is grees at their centers. The carbon fuses the formation of islands in which ther- exhausted, this is not the end by a to sodium, neon and magnesium; neon monuclear reactions occur. Silicon and long shot. Although the intense radia- to oxygen and magnesium; oxygen to nickel are formed. The ignition sources tion means the star continuously los- sulfur and silicon. The star literally has spread at subsonic speed (deflagration) es energy, it compensates this deficit a warmer and warmer glow around its and burn from the center of the star through the contraction of its interior heart. Above three billion degrees, the outward toward its surface. – which results in a massive increase in subsequent fusion steps follow one an- This causes instabilities, leading in pressure and temperature. other at an ever-increasing speed. With- turn to turbulence, which interacts in only a few months and then after with the thermonuclear flame and rap- THE STAR BALLOONS INTO only a few days, nickel, cobalt and final- idly increases its surface area. Finally, a A GIANT ly iron are forged. detonation wave builds up that propa- Now the end has been reached: since gates at supersonic speed and blows the In this phase, the star increases its sur- iron has the highest binding energy per ball of gas to pieces – a supernova ex- face area: it balloons into a giant with nucleon, no more energy can be gener- plodes. “Unfortunately, it has not yet a radius measuring a hundred to a ated from its fusion. The structure of been possible to observe even a single thousand times that of the Sun. Its lu- the star now resembles that of an on- precursor system of such an explosion minosity also increases considerably, ion: the core of iron slag is surrounded directly, which is why we are still spec- now shining several million times by layers of silicon, oxygen, neon, car- ulating about other possibilities,” says brighter than the Sun. “The subsequent bon and helium, with the hydrogen Hans-Thomas Janka. fate of the star is now decided,” says layer at the very outside. This type represents only around Janka. “If the temperature in the stellar The Chandrasekhar limit mentioned one quarter of all supernovae observed, core increases sufficiently, the ash from above, which the iron core now ap- whereas most violent stellar deaths the previous fusion process can ignite.” proaches, again plays a role in how the can be attributed to a single massive Helium, for example, burns at around story continues. The density of the core star (Type II). This means the precur- 200 million degrees Celsius to form car- has increased to 10,000 tons per cubic sor star has at least eight or nine times bon and oxygen. centimeter. Electrons are squeezed into the mass of our Sun. The giant first At the end of this chain, stars with the protons to form neutrons. This re- spends several million years quietly the stated eight or nine solar masses duces the pressure inside the core,

Photos: ESO; Robert P. Kirshner and Peter Challis, Harvard University, STScI, NASA Illustration: Christoph Schneider based on a diagram by Achim Weiss – MPI for Astrophysics and unspectacularly fusing hydrogen develop temperatures of 800 million de- which now collapses in fractions of a >

1 | 17 MaxPlanckResearch 21 FOCUS_Extreme Space 22 star evenfurther. Theimpactofthe The latterinevitablycompressesthe wardly directed gravitational pressure. and the radiationpressure, and the in- play between the outwardlyacting gas ly disturbedforsometime–theinter- ic equilibriumhasalreadybeensevere central object.Thedelicatehydrostat- plunge unceasinglyontothemassive In any case, the inner layers of the star SEVERELY DISTURBED THE FRAGILE EQUILIBRIUMIS at thecenterofdyingstar. a largeinitialmass,blackholeforms can getevendenserstill.Ifthecorehas greater density:aneutronstar. Butit second toanobjectof10,000times MaxPlanckResearch 1 MaxPlanckResearch 0.65 0.53 seconds seconds | 17 - seconds 0.70 0.61 the collapsingstellarlayers,”explains the centeronlongjourneythrough to balancethemassiveenergylossfrom out to be much too weak. It isn’t able mechanism. “Suchashockaloneturns of apurelyhydrodynamicrebound cause theexplosiondirectlybymeans that thereisnowaytheshockwavecan scenario ingreaterdetail,theyfound When theastronomersconsidered simple,” saysHans-ThomasJanka. pernova flaresup. sands ofkilometerspersecond–asu- lope withspeedsofuptotensthou- side and rips apart the stellar gas enve- and travelsfromtheinsidetoout- well forlong:ashockwavebuilds up matter atsupersonicspeeddoesnotgo seconds Or maybenot?“Ifonlyitwerethat these elusive phantoms race every sec- these elusive phantoms raceevery through whichmorethan66billionof in theirway–likeourthumbnail, etrating practicallyanythingthatgets cles succeedalmosteffortlesslyinpen neutrinos. Thesenearlymasslessparti- were bringing another engine into play: As earlyasthemid-1960s,scientists the star’s ironcore.” shock losesitspower, itgetsstuckin ter only100to200kilometers,the the MaxPlanckresearcher. Inshort,“af 600, to 800 first the in from range red) orange, (yellow, matter of bubbles the of diameters The neutrinos. of transfer energy the by driven is and asymmetric is explosion The formation. its after time the to refer images partial four the in seconds the center; its at star neutron a already is There process. the in turbulence violent to rise gives and disrupted is masses of star A computer: the on Explosion gy withthem. vast amounts of ener- are able to carry onds. And,accordingtoJanka,they stumbling aboutinitforseveral the staratspeedoflightafter ticles manage to leave the interior of says Janka.Itwasfoundthatthepar the mechanismofneutrinotransport,” saw researchers succeed indescribing cade ofdevelopmentwork,the1980s theoretical assumption.“Afterade- neutrinos, thisfindingbolstersthe much toodistanttomeasuresuch of theseghostparticles. around theworldregisteredtwodozen Cloud, severalneutrinoobservatories light flashfromtheLargeMagellanic Around threehoursbeforethevisible a distanceofsome166,000light-years. from to 20solarmasseswasobserved Sanduleak -69°202withamassof15 the dayexplosionofastarcalled 24,1987.Thatwas events ofFebruary pernovae hasbeenknownsincethe ond. Thattheyalsoplayaroleinsu- in the last image. last the in So whatactsasthedrivingforce? Although alllatersupernovaewere and 1,500 1,500 kilometers kilometers 15 15 solar solar 300 sec-

- - -

Computer graphic: Andreas Marek, Hans-Thomas Janka – MPI for Astrophysics Computer graphic: Andreas Marek, Hans-Thomas Janka – MPI for Astrophysics

Computer graphic: Elena Erastova and Markus Rampp, Max Planck Computing and Data Facility (MPCDF) bluish line in this image indicates the shock wave of the supernova. the of wave shock the indicates image this in line bluish page on sequence the research: in made been has that was soonsuspectedthatthe failure was neutrino heating inefficient after all? It ply wouldn’t explodeproperly. Was the – andweredisappointed.The starssim simulate supernovaeonthe computer nova,” saysHans-ThomasJanka. by neutrino heating to ignite a super- neutrino energyneedstobedeposited White arguedthatonly1percent ofthe physicists StirlingColgateandRichard process is surprising: “American astro- renewed power. Theefficiencyofthis neutron star and give the shock wave ly conductive gas (plasma) around the of neutrinos. These heat the electrical- which in turn produces vast numbers into internalenergyofthematter, star, thegravitationalenergyconverts As thestellarcorecollapsestoaneutron from simulation computer This gas: of ball Seething In the1980s,theoreticiansbegan to - more likelyduetothemodelsused– cayed into cobalt. “We had actually ex the outerlayerandradioactively de for example, which was ejected far into ly movedtowardtheoutside –nickel, been deepinsidethedyingstar sudden This meansthatelements thathad have takenplaceduringtheexplosion. A thorough mixing evidently must AFTER ONLY AFEW WEEKS GAMMA LIGHTBECOMESVISIBLE ploded,” thescientistrecalls. metry hadtobe present whenitex- that ahigh degree ofasym observations Supernova 1987A.“We learnedfrom were one-dimensional.” But then came –thatis,they had sphericalsymmetry Janka’s specialty. “Atthattime,theystill 2015 22 shows the end of a star of of star a of end the shows is around ten years older and was still a two-dimensional computation. The outer, outer, The computation. two-dimensional a still was and older years ten around is 20 solar masses in three dimensions – and with it, the progress progress the it, with and – dimensions three in masses solar - - - - Hans-Thomas Janka, “in these simula - motions and turbulence. “In fact,” says plasma, aswellconvective mass between theneutrinosand the stellar accurate accountofinteractions very ial symmetry. Theresearchers nowtook sional modelswhosestarspossessedax- worked meticulouslyontwo-dimen early 2000s,Jankaandhiscolleagues became increasinglycomplex:inthe powerful, thetheoreticalscenarios,too, onion flyingaway. isn’t assimpletheideaoflayers Janka. We thenknewthat,inreality, it turned upafterjustafewmonths,”says nate fromthedecayofcobalt.Butthey gammaquanta,whichorigi observe year aftertheexplosionbeforewewould pected that itwouldbemorethana As computersbecameevermore 1 | MaxPlanckResearch 17MaxPlanckResearch 500 km

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FOCUS_Extreme Space

tions, the symmetry is destroyed as er required is enormous – 16,000 pro- imum as conventional Type II superno- soon as the explosion begins. Hydrody- cessors have to work in parallel for vae. The problem is: “These objects are namic, turbulent fluctuations occur, months to compute one model. This all extremely far away. We can often similar to convective flows in the would take a single, modern PC 8,000 register only the light curves, and the Earth’s atmosphere.” years. What it boils down to, according spectra are not conclusive in detail,” Janka’s then-doctoral student An- to Janka, is this: explosions driven by says Hans-Thomas Janka. dreas Marek generated the first com- neutrinos also occur in 3-D. But the as- What causes these supernovae? The plete two-dimensional supernova mod- trophysicist states two clear objectives researchers can only speculate. After an el at the Max Planck Institute for Astro- that he and his colleagues will be striv- initial explosion, a magnetar, for exam- physics between 2003 and 2006. The ing to achieve in the future with the ple – a neutron star with an extremely Institute purchased a 128-core comput- three-dimensional computations: “We strong magnetic field (MaxPlanck- er especially for this purpose and in- want to use fully self-consistent simu- Research 1/2017, page 26 ff.) – could be- stalled it at the neighboring Garching lations and all relevant microphysics to come involved to drive this explosion computing facility, where it was used confirm the explosion mechanism further and amplify it enormously. The solely for this simulation – which was quantitatively for many stellar masses. second possibility is that the shock successful: “The supernova exploded!” And we want to compare the models wave of the supernova propagating out- says Janka. The effort had paid off – as with the observations.” ward interacts with dense matter shed had the efforts of Janka and his doctor- by the star before the explosion. al student Markus Rampp: the research- ULTRABRIGHT EMITTERS KEEP As a further alternative, the scien- ers wrote the extremely complex pro- THE ASTRONOMERS GUESSING tists consider so-called pair instability gram codes for the computer simula- supernovae. This scenario is based on a tion. These algorithms were intended It could then also be possible to solve a star with 100 to 200 solar masses or to improve the neutrino transport. Jan- mystery that has increasingly moved even more. Such a heavyweight has a ka doesn’t want to go into detail, but into the research spotlight in recent brief life and collapses as soon as it when he talks of “three-dimensional years: ultrabright supernovae, or super- reaches the stage at which carbon fuses equations with spatial coordinate and luminous supernovae, as astronomers in the center. At temperatures of one momentum space,” even the layperson call them. The scientists observed the billion degrees, photons with very high quickly realizes that these matters are first example of this type in 2010. Al- energies start to spontaneously convert fairly complicated. though they sight more than 1,000 stel- into electrons and their antiparticles, This is all the more true for three-di- lar explosions in total every year, only the positrons. This “pair formation” mensional simulations that only be- a few dozen of these tremendously leads to a rapid drop in radiation pres- came part of the scientists’ repertoire in bright emitters are known, which are sure – gravitation gains the upper hand, the last few years. The computing pow- up to 100 times as bright at their max- the nuclear combustion of carbon and oxygen accelerates at an explosive rate and the star could become a supernova. Astronomers still don’t know which of the three scenarios is the right one. They know from investigations of the light curves that superluminous super- novae apparently don’t always release the incredibly large quantities of nick- el – several tens of solar masses – that would be expected from pair-instabil-

Stellar kick: The neutron star (white cross) left behind by the supernova experiences a kick in the direction (arrow) opposite to the stronger side of the asymmetric explosion. Elements such as titanium and nickel (blue and green) are produced in greater amounts in the hemisphere that points away from the direction of neutron star motion. The astronomers observe this geometry for supernova remnants in space – in perfect agreement with theoretical models such as this simulation. Computer graphic: Annop Wongwathanarat et. al, arXiV: 1610.05643

24 MaxPlanckResearch 1 | 17 Supernovae in his focus: Hans-Thomas Janka from the Max Planck Institute for Astrophysics in Garching studies the largest explosions in the universe since the Big Bang. To investigate the physics that determines these events, Janka develops theoretical models based on complex computer programs.

ity supernovae. A viable theory must scopes have discovered in nature, to the nova 1987A. The latter therefore still provide an adequate explanation of delight of the researchers: in the Cassi- turns out to be a lucky break for sci- this fact. opeia A remnant and, so the prediction, ence, even though it is now 30 years Nickel is also the topic of Janka’s probably also in what remains of Super- since it flared up. most recent work, which has just been

published in the Astrophysical Journal. It deals with what dying stars leave be- hind – supernova remnants. Observa- TO THE POINT tions and measurements of high-ener- l Some stars meet a spectacular end as supernovae. The dozen or so different types gy radiation at X-ray and gamma wave- that have been observed can be classified into two theoretical groups.

lengths with satellite telescopes such as l In the case of supernovae of Type Ia, the probable scenario is that a white dwarf NuSTAR and Integral show that radio- fed by a companion explodes; in the case of all other types, it is a massive star active elements such as titanium-44 whose core collapses. and nickel-56 contained in the ejected l The researchers found that the neutrino-heating mechanism plays a crucial role material are not distributed symmetri- in the explosion of core-collapse supernovae. cally around the remnant neutron star. l Astronomers today use complex three-dimensional models to simulate the physical According to the theory, this is be- processes in supernovae and can put several aspects of the theory to a test with cause the compact stellar object re- the aid of actual observations. ceives a kick into the opposite direction of an asymmetric explosion – with con- sequences for the immediate cosmic GLOSSARY environment: “The radioactive ele- Antiparticles: As far as is known, nearly every particle has an antiparticle that is identi- ments should have been explosively cal in terms of mass, lifetime and spin. In contrast, electric charge, magnetic moment produced predominantly in the hemi- and all charge-like quantum numbers are equal in magnitude, but have the opposite sphere of the massively deformed gas sign. The positron, for instance – the antiparticle of the electron – has a positive charge. remnant that is opposite to the direc- Plasma: A mixture of neutral and charged particles (partially ionized) or only charged tion of motion of the neutron star,” particles, such as electrons and atomic nuclei (completely ionized), that is also called the says Hans-Thomas Janka. That is what fourth state of matter. Plasmas frequently occur at high temperatures. Stars consist of hot gas and plasma, for example. the theoretical 3-D models forecast.

Computer graphic: Annop Wongwathanarat et. al, arXiV: 1610.05643 Photo: Axel Griesch And that is precisely what the tele-

1 | 17 MaxPlanckResearch 25 FOCUS_Extreme Space

Traps in Space-Time

Black holes are a permanent fixture in science fiction literature. In reality, there is hardly a more extreme location in the universe. These mass monsters swallow everything that ventures too close to them: light, gas, dust and even entire stars. It sounds quite simple, but the nature of black holes is complex. Maria Rodriguez, Minerva Group Leader at the Max Planck Institute for Gravitational Physics in Golm, wants to solve some of the puzzles these exotic cosmic bodies present.

TEXT FELICITAS MOKLER

or a long time it seemed that with 62 solar masses. Only a few months work of Newtonian gravitational theo- they existed only in the minds later, the researchers registered gravi- ry and the corpuscular theory of light. of theoretical physicists – black tational waves of source GW151226 At the beginning of the 20th cen- holes. But since at least a year from a similar system. These events tury, Albert Einstein revolutionized our ago now, we finally have clari- gave the space-time structure a violent understanding of gravitation – and thus ty: theyF really do exist. On September shake – and provided impressive con- also of matter, space and time – with his 14, 2015, gravitational waves caused firmation of the existence of the mass general theory of relativity. His idea re- space-time to oscillate to a measurable monsters. (MaxPlanckResearch 2/2016, placed the classical concept of gravity extent in the American LIGO detectors page 78 ff.) as the direct interaction between two for the first time. masses that move through rigid, Euclid- The detection of the undulation of EINSTEIN’S THEORY REPLACES ian space. Instead, it held that three-di- space-time predicted 100 years earlier THE CLASSICAL CONCEPT mensional space and time are united to by Albert Einstein (1879 to 1955) is si- form a four-dimensional space-time multaneously deemed to be experimen- Naturalists John Mitchell (1724 to 1793) and are themselves now deformable tal proof of the physical existence of and Pierre Simon de Laplace (1749 to and dynamic. A mass such as the Sun black holes. The first measured signal 1827) were already speculating in the bends space-time in its vicinity – the GW150914 originated from two black late 18th century about dark stars or larger and, in particular, the denser a holes with 36 and 29 solar masses, re- dark astrophysical bodies whose gravi- mass, the stronger the effect. spectively, that used to orbit one anoth- ty was so strong that light couldn’t es- The motion of a second, smaller er in a kind of binary star system until cape them. The ideas of the two re- mass, such as a planet, then follows this they finally merged into one object searchers were still within the frame- curvature. If the local curvature chang-

Under the spell of gravity: Black holes have been keeping astrophysicists busy for more than a century. None has yet been observed directly, but the discovery of gravitational waves at least shows that these bizarre structures really do exist. Graphic: Alain r/CC-BY-SA 2.5

26 MaxPlanckResearch 1 | 17 Graphic: Alain r/CC-BY-SA 2.5 FOCUS_Extreme Space

es because a mass accelerates across this the black hole,” says the Minerva Group (1873 to 1916) in the metric that bears space, this change propagates at the Leader at the Max Planck Institute for his name. The so-called event horizon speed of light as a gravitational wave in Gravitational Physics in Golm. that shields the interior of the black the space-time structure. There is no escape for either matter hole from the outside world is defined Einstein used Riemannian geome- or light. This is what makes it so diffi- by the Schwarzschild radius, which de- try as the mathematical basis for dy- cult for astronomers to observe these pends on the mass. “Its shape is a per- namic space-time. Black holes emerge objects. The explanation is simple: in fect sphere for conventional black holes, from the field equations, which de- order to leave a conventional celestial which don’t rotate and have no electric scribe the curvature of space brought body such as Earth, objects require a charge,” says Rodriguez. The researcher about by matter and, conversely, the minimum kinetic energy that depends investigates the boundary surfaces of effect of curvature on matter, as a nat- on the body’s mass. The velocity that black holes with different properties. ural solution for matter concentrated rockets require, for example, is called But black holes with no angular at one point. The gravity there is in- the escape velocity. For a black hole, momentum are probably very rare in finitely large, and space-time has an this velocity corresponds to the speed nature. This is because these objects infinitely large curvature: mathemati- of light. are formed, for instance, when partic- cally, it is a singularity. ularly massive stars have exhausted “Physically, however, such infinities GRAVITY EVENTUALLY GAINS the supply of fusionable material in don’t tell us anything,” says Maria Ro- THE UPPER HAND their interior toward the end of their driguez. “What is relevant is the separa- life. The temperature there then drops tion from the point mass below which How space-time behaves under these and thermal and radiation pressure are gravity becomes so strong that nothing conditions was first described in 1916 no longer sufficient to counteract the can escape from it and can only fall into by astrophysicist Karl Schwarzschild star’s gravitation. The stellar interior implodes and the once free electrons are pushed into the positively charged atomic nuclei. Event horizon In such a supernova, the neutrinos re- leased in this process transport a large Ring singularity portion of the energy away and hurl the outer stellar shell into space. The matter in the core, in contrast, con- tracts more and more under its own gravity. If the original mass of the star was more than eight solar masses, the ultimate result is a black hole. Since stars usually rotate about their own axis and the angular momentum is con- served, they pass it on to the black hole. Astronomers are still puzzled by the birth of the particularly massive black Ergosphere Inner horizon holes – with a few million to a billion solar masses – that are presumed to lie at the centers of galaxies. They may pos- sibly have formed from the first gener- Clear structures: The physics might be complex, but the explanation of the structure is simple. ation of extremely heavy stars that, The graphic shows a rotating black hole with a ring singularity in the center and the inner having become a black hole, rapidly ac- horizon. The event horizon is something like the surface of the black hole; when something disappears behind it, it is truly out of this world. The ergosphere marks the region in which creted more and more mass and thus

every object is forced to co-rotate. more and more angular momentum. Graphic: designergold, based on original material from the MPI for Gravitational Physics

28 MaxPlanckResearch 1 | 17 Engine at the center: Centaurus A is around 15 million light-years away, making it the nearest radio galaxy, but it also emits intense X-ray and gamma radiation. The jet structure visible in this image is apparently caused by the activity of the central black hole with around 55 million solar masses.

The hypothesis of so-called primordial black hole is called its ergosphere and high-energy jets in around 20 active black holes, according to which these is ellipsoid in shape. Matter from out- galaxies or quasars. These objects prob- cosmic heavyweights formed shortly side that gets caught up in it doesn’t ably have an extremely massive, rapid- after the Big Bang together with the necessarily plunge directly into the ly rotating black hole at their center,” first galaxies, is also being discussed. As- space-time trap, but rather initially says the Max Planck researcher. tronomers also speculate about the ex- co-rotates with it. Nevertheless, it is un- To be able to correctly interpret istence of medium-weight black holes, able to escape from it. these phenomena, the researchers are with 100 to one million solar masses, “Unless the matter is electrically attempting to compute the behavior that could be present at the centers of charged,” says Rodriguez, because the of rotating black holes and the physi- large globular clusters. co-rotating charged matter causes a cal processes in their immediate vicin- magnetosphere to form. Some of the ity according to the laws of the gener- PARTICLES ARE EJECTED charged particles are deflected along al theory of relativity. Analytically, they the magnetic field lines. Depending on have initially succeeded in doing this When a black hole rotates, its event the sign of the charge and the orienta- only for very slowly rotating black horizon deforms slightly. Furthermore, tion of the field lines, the particles then holes, but Maria Rodriguez is interest- the space-time of its immediate vicini- fall more rapidly into the black hole – ed in the very opposite: objects that ty and the matter located there rotate or are ejected along the rotational axis. rotate about their own axis at almost

Graphic: designergold, based on original material from the MPI for Gravitational Physics Photo: ESO/WFI (optical); MPIfR/ESO/APEX/A.Weiss et al. (submillimeter); NASA/CXC/ CfA/R.Kraft et al. (X-ray) with it. This sphere of influence of the “Astronomers have since observed very the speed of light. >

1 | 17 MaxPlanckResearch 29 30 itation withtheotherthreefundamen inordertounifygrav- to stringtheory strong force. be moresuitablefordescribing the modynamics ultimatelyturned outto electromagnetic force. Quantum chro- neutrons, withtheweakforce andthe quarks togethertoformprotonsand the strongforce, whichkeepsthe tounify tempted tousestringtheory composed of quarks. Thescientists at- of anatomicnucleusarethemselves ered thatthebuildingblocks(nucleons) At thattime,particlephysicistsdiscov- string theory.” Rodriguez. “We usedamethodfrom adopting asystematicapproach,”says be foundeitherbytrialanderroror the same formalism. “Thesolution can ofrelativityonthebasisoneand ry the fieldequationsofgeneraltheo- electrodynamics and, simultaneously, To thisend,shesolvestheequationsof of the configurations from five to two and three dimensions. three projections and the two are to five Depicted from momentum). (angular rotation configurations and the of mass on depend shapes diagram Their The dimensions. dimensions. spatial five for three than solutions more in analytical holes black depicts of horizons event of AEI), Institute, configurations Einstein surface (Albert possible Physics computed Gravitational for Rodriguez Maria Institute Planck Max the at postdoc a as time her During mathematics: Advanced MaxPlanckResearch 1 MaxPlanckResearch However, scientistslaterreturned This theory originated in the 1960s. originatedinthe1960s. This theory | 17 - ible) tube. describe thecableasalong, thin(flex al dimensionsarerequired in orderto sional,” saysRodriguez.Two addition- experience itsworldasone-dimen - only thedirectionstraight ahead and crawls throughacablewillregister large. “Anant,forexample,that either particularlytinyor really doexist–couldbethattheyare ditional dimensions–ifindeedthey The reason we can’t perceive these ad- ONLY ONEDIMENSION AN ANTINACABLEKNOWS basis,” saysMariaRodriguez. of space-timeformapurelyheuristic dimensions atall.Thefour doesn’t specifythenumber ofspatial ofrelativity,the generaltheory sinceit quite compatiblewiththeconceptof six furtherspatialdimensions.“This is mensions of space-time,it introduces tal forces. Inadditionto thefourdi

Surface of the event horizon - - the center of our Milky Way. Its vicini- are generated. also somecasesinwhichno jetsatall tions,” saysMariaRodriguez. Thereare tions naturefavorsunderwhich condi- still havetofindoutwhichofthesolu- ly focusedorbroadlyfannedout.“We energy involved:theycanbeextreme- ly fromeachotherintermsofformand cate thatthejetscandiffersignificant- stellar explosion. counterparts thatweregeneratedbya spiral galaxiesandtotheirlessmassive heavyweights aspresumablyexistinall to such extremely massivecosmic lar momentum;itcanbeappliedboth holes isindependentofmassandangu- el togeneratejetsforrotatingblack unified inonetheory. Rodriguez’mod- ent dependenciesondistance,canbe mental forces act,aswell astheirdiffer gy regimesinwhichthefourfunda With thisextension,thedifferentener One example here is the object at The researcher’s computationsindi Angular momentum

- - - -

Photo: Private collection; graphic: Maria Rodriguez Photo: Private collection; graphic: Maria Rodriguez

Graphic: UCLA Galactic Center Group – W.M. Keck Observatory Laser Team had speculatedshortlybefore thisthat him. TheoreticianJacobBekenstein – theHawkingradiationnamed after could emit a specific form of radiation the mid-1970sthatblackholes really Stephen Hawking already proposed in momentum andcharge,isincomplete. such asmassand–possiblyangular fewproperties, mation aboutonlyvery jects canbepersuadedtorevealinfor- view thatsaysthesecompactob- ferent way. Perhapstheconventional their presencefeltinacompletelydif- million solarmasses. mers todayassumeithasaround4.5 ments onotherstellarorbits,astrono- hole. Thanks tomoreaccurate measure spatial area,itcouldonlybeablack lar masses.Limitedtosuchanarrow tral objecttobearound3.7millionso searchers estimated the mass of the cen- 15.2years. of riod compact radiosource, which hasape- liptical orbit of the star S2 about the pletely reconstructedtheextremelyel his colleagues,amongothers,com the aid of earlier images, Genzel and to travelfromtheSunPluto.With parison, lighttakesaroundfivehours tance of just 17 light-hours. By com- ittarius A*.Thiscorrespondstoadis- milli-arcseconds fromthe source ofSag star S2cametowithinadistanceof12 howthe (ESO)inChiletoobserve ry - at theEuropeanSouthernObservato ferometers oftheVery LargeTelescope when theastronomersusedinter- of thegalaxy. Sagittarius A*radiosource atthecenter orbits ofindividualstarsaroundthe the for ExtraterrestrialPhysicsobserved leagues from theMaxPlanck Institute work, ReinhardGenzelandhiscol- no high-energyjets.Inyearsofhard ty emitsradioemissions,butthereare The breakthroughcamein2002, Using Kepler’s thirdlaw, there But maybeblackholescouldmake ------namic entropy. represent a measure for thethermody- the surface of the event horizon could Bekenstein and Hawking were the first Bekenstein andHawkingwerethefirst information is contained in the system. tem: thehigherentropy, themore sure oftheinformationcontentasys- Entropy canbeconsideredtoamea- BE PRESERVED INFORMATION MAY POTENTIALLY the Milky Way. The gravity of the object forces nearby stars onto more or less elliptical orbits. orbits. elliptical less or Between more onto stars nearby forces object the of gravity The Way. Milky the around with hole black A center: the Around Keck telescope in Hawaii. in telescope Keck 1995 0.1" and and 2014 , astronomers measured these motions very accurately using the the using accurately very motions these measured astronomers , 4.5 million solar masses lurks at the heart of to compute the entropy of a black hole, to computetheentropyofablackhole, tum physics. String theory also tackles alsotackles tum physics.Stringtheory contradicted bytheconceptsofquan- destroyed inthehole;this,however, is ofrelativity,ory informationcouldbe black hole.Within thescopeof with entropyandinformationina been abletofullyclarifywhathappens was formed.Scientistshavestillnot the precursorstarfromwhichhole but itdidn’t matchatallwiththatof the problem of entropy and provides the problemofentropyandprovides 1 FOCUS_Extreme Space | MaxPlanckResearch 17MaxPlanckResearch S102 S38 S20 S19 S16 S5 S2 S1

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Max Planck Innovation is responsible for the technology transfer of the Max Planck Society and, as such, the link between industry and basic research. With our inter- disciplinary team we advise and support scientists in evaluating their inventions, Drama in three acts: A star is torn apart by the tidal effect of a black hole (left). It then devours a portion of the stellar debris, heating up strongly in the process (center). This, in turn, leads to a gigantic outburst of radiation, which subsides again in time (right). filing patents and founding companies. We offer industry a unique access to the innovations of the Max Planck Institutes. solutions for a finite entropy content. thought to be the site of an extremely itational wave signals from black holes. The information from the event hori- massive black hole with 6.6 billion so- Most recent estimates have shown that Thus we perform an important task: the zon would then possibly become avail- lar masses. In this way, the researchers the sensitivity of the LIGO detectors transfer of basic research results into able to an external observer. hope to find out whether jets really are during the recently launched measure- In this context, earlier work that formed in the ergosphere of a black ment campaign should be high enough products, which contribute to the economic Maria Rodriguez produced during her hole, or in a disk of matter further out to either confirm or exclude them. and social progress. postdoc phase at the Max Planck Insti- after all. Gravitational wave astronomy will thus tute in Golm, in the research group of Certain effects of quantum gravita- one day shed some further light on the Director Hermann Nicolai, could also tion, in contrast, should affect the grav- nature of black holes. become interesting again. At that time,

she developed a whole catalog of solu- tions for black holes in higher dimen- sions based on string theory. In the TO THE POINT three-dimensional representation we l The gravity inside a black hole is infinitely large, and space-time has an infinitely are familiar with, they look like a large curvature. However, this mathematical singularity has no meaning from a Connecting Science sphere, a donut-like ring, either on its physical point of view. own or orbiting a sphere, similar to the l What is crucial is the separation from the point mass below which gravity be- comes so strong that nothing more can escape from it. This boundary is identified ringed planet Saturn; or like two en- by the event horizon. This is a perfect sphere for black holes that aren’t rotating twined rings. In the higher dimensions, and have no electric charge. all these surfaces are interconnected to l But static black holes are very rare in nature. The researchers are therefore and Business give a solution. attempting to compute the behavior of rotating black holes and the physical If black holes really do emit a spe- processes in their immediate vicinity according to the laws of the general theory cific type of radiation, it will probably of relativity. be extremely difficult to measure it l Analytically, such computations have been successful only for very slowly rotating even at some time in the future. But black holes. Maria Rodriguez, on the other hand, investigates objects that rotate about their own axis at almost the speed of light. She uses string theory methods maybe it will soon be possible to check for this purpose. specific effects from Rodriguez’ models for conventional black holes with the aid of observations. GLOSSARY A network of radio telescopes spread LIGO: The Laser Interferometer Gravitation Wave Observatory consists of two detectors all over the world is currently being set sited in the US states of Louisiana and Washington. This is where gravitational waves up, the so-called Event Horizon Tele- were first discovered on September 14, 2015. Although the installation, which is called scope. The astronomers want to use Advanced LIGO in its present upgrade stage, is located in the US, Max Planck researchers made a significant contribution to the discovery through hardware, computer programs this and the Very Long Baseline Array and models. to image the galactic center with much Riemannian space: An object from the branch of mathematics known as Riemannian better resolution. In addition, they geometry with special properties. For instance, the shortest connections between want to look more closely at the heart different points aren’t necessarily straight lines, but can be curved lines. And the angular of the active galaxy known as M 87, sum of triangles can be greater or less than 180 degrees.

which has a high-energy jet. This is Computer graphic: NASA/CXC/MPI for Extraterrestrial Physics

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Probedruck Computer graphic: NASA/CXC/MPI for Extraterrestrial Physics Probedruck mi_anzeige_1/1_englisch_1#29C8F 17.02.201113:53UhrSeite1 Connecting Science and Business C M Y CM and social progress. products, which contribute to the economic transfer ofbasicresearch resultsinto task:the animportant Thus we perform innovations ofthe MaxPlanck Institutes. auniqueaccesstoWe the industry offer patentsfiling andfounding companies. scientists inevaluating their inventions, team we adviseandsupport disciplinary andbasicresearch. With ourinter-industry Society and,assuch, the linkbetween the technology transfer ofthe MaxPlanck Max Planck Innovation isresponsiblefor MY CY CMY K Illustration: M. Weiss/CfA FOCUS_Extreme Space

Cosmic Particle Accelerator

Black holes, pulsars, remnants of exploded stars – these celestial bodies accelerate particles to enormous energies and emit high-energy gamma radiation. The two observatories known as H.E.S.S. and MAGIC, whose construction was supervised by the Max Planck Institutes for Nuclear Physics in Heidelberg and Physics in Munich, make this extreme spectral region accessible.

TEXT THOMAS BÜHRKE

f you ask Werner Hofmann about world – to observe this faint radiation. the most recent discoveries of the Moreover, it requires a trick, which H.E.S.S. observatory, he quickly H.E.S.S. also uses: the High Energy Ste- starts to discuss a recently com- reoscopic System. pleted sky survey. “After a total of The gamma radiation can’t pass I 3,000 hours of observation time, spread through Earth’s atmosphere, but it still over ten years, we found 77 new celes- makes itself felt on the ground. If it tial bodies that were previously un- penetrates into the air, it gets itself known in this energy range,” says the into a violent exchange of blows with Director at the Max Planck Institute for the electric fields of atoms. This pro- Nuclear Physics in Heidelberg. He su- duces new particles that continue Mass monster shines pervised the construction of the obser- their journey toward Earth’s surface brightly: The galaxy PKS vatory, and has been honored for this like an avalanche. Individual charged 1441+25 belongs to the many times, most recently with the particles tear along faster than the group known as quasars. A black hole at the center Stern-Gerlach Medal of the German speed of light. of the galaxy attracts Physical Society (DPG). This sounds surprising, but the matter, some of which is This one sentence summarizes the speed of light in air is slightly lower ejected outward at difficulties that astrophysics has to than in a vacuum. It also means there almost the speed of light in the form of two jets; overcome with respect to high-energy is no violation of Einstein’s law, which the illustration shows gamma radiation: It takes a lot of time states that a body cannot move faster one of these jets. Illustration: M. Weiss/CfA – and the largest telescopes in the than the speed of light in a vacuum. >

1 | 17 MaxPlanckResearch 35 At the heart of the Crab nebula: The remnant of a supernova whose light reached Earth in the year 1054 contains a pulsar (small image). Behind this object is a neutron star that rotates about its own axis 30 times per second, emitting pulsed radiation as it does so. The MAGIC telescopes recorded gamma radiation with a record-breaking energy of 1.5 trillion electron volts.

But in the air, these particles generate – is located on Roque de los Mucha- eque, who is responsible for coordinat- a flash of light that lasts only a few bil- chos, a 2,400-meter-high mountain on ing the scientific work of MAGIC. lionths of a second – a “superphotic La Palma in the Canary Islands. It has Of all 178 currently known celestial bang,” as it were. two telescopes, each with 17-meter col- bodies that emit high-energy gamma This very weak Cherenkov radiation lecting mirrors. radiation, 105 were discovered with can be observed with large telescopes H.E.S.S. alone, and 34 with MAGIC – a on the ground. High-energy gamma as- TWO OBSERVATORIES success that put H.E.S.S. among the tronomy thus uses the atmosphere as DISCOVER 139 SOURCES world’s top 10 observatories in 2009, to- an enormous fluorescent screen. The gether with the Hubble Space Telescope. Cherenkov pool of light has a diameter “MAGIC and H.E.S.S. together can ob- The gamma radiation sources are of 250 to 500 meters on the ground. If serve the whole of the northern and evidence of the most violent events in this pool includes a telescope, the ori- southern hemispheres,” says Masahiro the universe, for instance of stellar entation and the intensity of the flash Teshima, Director at the Max Planck In- explosions and their consequences. of light can be used to determine the stitute for Physics in Munich. The two When a star has consumed its fuel at energy of the gamma radiation and the observatories complement each other the end of its life, energy production direction from which it comes. slightly in their abilities, as well: comes to a halt. The center collapses The H.E.S.S. observatory is located “Thanks to their stereoscopic view and within fractions of a second under the in the highlands of Namibia and com- their large mirrors, the MAGIC tele- effect of gravity. The outer regions, in prises four telescopes, each with 12-me- scopes can detect radiation with lower contrast, explode, shooting out into ter collecting mirrors and a 28-me- energy than H.E.S.S., but H.E.S.S. is space and shining brightly. A superno- ter-diameter reflector. Its counterpart more sensitive at very high energies va flares up. MAGIC – Major Atmospheric Gam- and has a more detailed resolution,” If the collapsing core has less than

ma-Ray Imaging Cherenkov Telescopes says Teshima’s colleague David Pan- three solar masses, a neutron star forms Photos: NASA/HST/ASU/J. Hester et al. X-ray: NASA/CXC/ASU/J. (large image); (small image)

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In a neutron star, matter is so strongly compressed that one teaspoon of it » on Earth would weigh as much as one million long-distance trains.

– an extremely compact, rapidly rotat- the Crab nebula – the remnant of a su- their antiparticles – called positrons – ing sphere with a diameter of 20 kilome- pernova explosion whose flare-up was are accelerated to almost the speed of ters. Matter is so strongly compressed in first discovered in April 1054 by a monk light in the magnetic field and finally such an object that one teaspoon of it in Flanders. At its center is a pulsar that annihilate, but this process can likely on Earth would weigh as much as one rotates about its own axis 30 times per explain only gamma radiation with en- million long-distance trains. second. It can now be observed in all ergies of up to a few billion electron The magnetic field of the former spectral regions, from radio waves to volts (GeV). A different mechanism star is also compressed in this collapse. visible light to high-energy gamma ra- must be responsible for most of the re- This dipole field resembles our Earth’s diation. While it is thought to be the cently observed gamma pulses. field with north and south poles, but is best-investigated supernova remnant, The researchers currently assume several billion times stronger and ro- it still throws up new mysteries time that high-energy, charged particles tates several million times faster. Ac- and time again. form a “reactive mixture” with pho- cording to the current way of thinking, tons of UV and X-ray radiation around electrically charged particles break THE MAGNETIC FIELD 1,500 kilometers above the surface of loose from the star and are accelerated PLAYS THE KEY ROLE the pulsar in that the particles transfer along the axis of the magnetic field into their energy to the photons and up- space at almost the speed of light. Thanks to MAGIC, the researchers were grade them to high-energy gamma This process generates radiation in recently able to register pulsed gamma quanta. This process is called the in- a complex manner, predominantly in radiation from this object with a re- verse Compton effect. the direction of motion – like a car cord-breaking energy of 1.5 tera-elec- The gamma radiation that H.E.S.S. headlight. The swarm of particles thus tron volts (TeV), or 1.5 trillion electron and MAGIC registered is therefore a generates two light cones that point volts. This is the most energetic pulsed secondary effect. The actual cause are into space from both the north and radiation ever measured in a star. For particles that are accelerated under ex- south poles of the neutron star. comparison, visible light has an energy treme cosmic conditions. Since no In many cases, the axis of the mag- of two to three electron volts. conversion process is perfect, the sci- netic field is inclined at an angle to the To obtain these results, which were entists think that the primary particles axis of rotation. The two light cones published in early 2016, the MAGIC have more energy than the gamma ra- thus sweep through space like the beam team had to evaluate 320 hours of ob- diation they produce. of light from a lighthouse. If they hap- servations from the period from Octo- Things in the surrounding explo- pen to sweep across Earth, the tele- ber 2007 to April 2014. “The only thing sion cloud, which expands at a speed of scopes detect radiation pulses with the that is clear is that the very strong mag- 1,500 kilometers per second, are very rotational frequency of the celestial netic field of the Crab nebula plays a turbulent – and it is an efficient accel- body. Astrophysicists call this a pulsar. key role,” says Razmik Mirzoyan, erator, too. This hot gaseous cloud is These objects are deemed to be cosmic spokesperson of the MAGIC collabora- permeated by magnetic fields that ac- laboratories in which physical process- tion and project leader at the Max company it as it moves away from the es and theories can be tested under ex- Planck Institute for Physics in Munich. star. A game of nuclear table tennis treme conditions. In order to unravel how this cosmic takes place: electrically charged parti- In 1989, astrophysicists discovered accelerator works, astrophysicists and cles, mainly hydrogen nuclei (protons), a celestial body in the high-energy particle physicists have to work togeth- are pushed to and fro between magnet-

Photos: NASA/HST/ASU/J. Hester et al. X-ray: NASA/CXC/ASU/J. (large image); (small image) gamma region for the first time. It was er. They conclude that electrons and ic field fronts and continuously gain

1 | 17 MaxPlanckResearch 37 FOCUS_Extreme Space

Computer simulations indicate that the ultrafast protons can exert » a pressure and disperse interstellar clouds.

energy in the process – until they are so The protons and electrons whiz around H.E.S.S. provided part of the answer at fast that they can escape from this ping all over the Milky Way and, in the pro- the start of 2016. An analysis of mea- pong. This process only works if the cess, possibly also impact on Earth. surement data from the years 2004 to magnetic fields are in motion. Austrian physicist Victor Franz Hess 2013 demonstrated that the gamma ra- (1883 to 1964) discovered this cosmic diation coming from the center of our IN CAPTIVITY FOR radiation more than 100 years ago on Milky Way is so energetic that an accel- SEVERAL CENTURIES balloon flights. The name of the tele- erator there must be speeding up pro- scope array in Namibia also commem- tons to up to 1,000 trillion electron “Until recently, we expected that the orates him. volts (1 peta-electron volt). The re- particles remain trapped in the nebula Although the currently known ce- searchers therefore call it a pevatron for millennia before they can escape,” lestial bodies produce cosmic radiation (MaxPlanckResearch 2/2016, page 42). explains Jim Hinton, who heads the with energies of up to 100 trillion elec- Current findings indicate that this Non-Thermal Astrophysics Department tron volts (100 TeV), particles with radiation is caused by a gigantic black at the Max Planck Institute for Nuclear much higher energies are measured. hole because, over the past 20 years,

Physics in Heidelberg. “But according Where do they come from? large numbers of astronomical observa- Photo: Axel Griesch to our measurements, they escape after only several centuries.” As current models suggest, these findings are probably also relevant for the evolution of the Milky Way. The ultrafast particles break away from their accelerators at some stage and form a “gas” that is spread throughout the galaxy. “Computer simulations in- dicate that the ultrafast protons can exert pressure and disperse interstellar clouds,” explains Hinton. This would mean that the cosmic particles sup- press star formation in a galaxy. These studies are still in their infancy, but they show that the effect these parti- cles have on the evolution of the uni- verse is still far from being understood.

Good view from here: Razmik Mirzoyan (left) and David Paneque from the Max Planck Institute for Physics observe the universe with the two MAGIC telescopes on La Palma. The picture shows the researchers standing on a construction model for a new gamma radiation telescope that is also set to be built on La Palma.

38 MaxPlanckResearch 1 | 17 Cosmic accelerator: A source of intense radiation sits at the center of the Milky Way. This artist’s impression (small image) shows processes that contribute to the generation of high-energy gamma radiation. Protons (blue spheres), which are accelerated by the black hole Sagittarius A* at the center, interact with clouds of molecules in the vicinity. This produces pions, among other things, which decay almost immediately into gamma radiation photons (yellow waves). Photo: Axel Griesch

tions have shown with increasing accu- international Pierre Auger Observato- However, the large distances involved racy that our Milky Way rotates about ry in Argentina. Their origin is com- make it very difficult to detect it. Of a black hole concealing a mass of pletely unclear. The main candidates the 13 most distant objects currently around 4.5 million Suns. This object, are thought to be centers of galaxies known, eight were discovered by MAG- called Sagittarius A*, is surrounded by that accommodate black holes but are IC, two by H.E.S.S., one by the two of a hot disk of gas from which it draws in much more massive and considerably them together and two further ones and then swallows matter. more active than the center of our with VERITAS, the Very Energetic Radi- The H.E.S.S. researchers conclude Milky Way. ation Imaging Telescope Array System from the data that the cosmic accelera- with four 12-meter telescopes located tor in the galactic center has been in GRAVITATIONAL TRAPS COLLECT in the US state of Arizona. The objects continuous operation for tens of thou- SCORES OF GAS AND DUST emitted the radiation registered when sands of years. However, the exact de- the universe was at most only two thirds tails of how and where the particles are Astronomers know of types of galaxies of its present size. brought up to speed are not clear. It that could be responsible: quasars, ra- MAGIC currently holds the dis- takes place either in the immediate vi- dio galaxies and blazars. The supermas- tance record with its detection of the cinity of the black hole or in the sur- sive black holes at their centers can be two active galaxies PKS 1441+25 and rounding disk, where some of the mat- as heavy as several billion solar masses B0218+357. “We were able to track ter that falls toward the mass monster and collect vast amounts of gas and dust down these objects because we have is ejected again and accelerated in mag- – sometimes even entire stars – from used various technical measures to in- netic fields. their surroundings. This releases sig- crease the sensitivity of MAGIC tenfold The mystery of the most energetic nificantly more radiation – including for low-energy gamma radiation since particles of cosmic radiation thus re- high-energy gamma radiation – than is it was commissioned,” says Max Planck mains unsolved. Particles with up to emitted by all the stars in the surround- researcher David Paneque. “This short-

Photo: X-ray: NASA/CXC/MIT/F. Baganoff et al. (large image); graphic: Dr. Mark A. Garlick/H.E.S.S. Collaboration (small image) 100,000 PeV have been detected by the ing galaxy. ened the observation time needed for

1 | 17 MaxPlanckResearch 39 Top Specialist for high energies: Werner Hof- mann, Director at the Max Planck Institute for Nuclear Physics in Heidelberg, supervised the construction of the H.E.S.S. observatory in Namibia. Bottom Intense source: The galaxy IC 310, which is 260 million light-years away, experien- ces violent outbursts of radiation. These are presumably connected to the magnetic field that surrounds a central, supermassive black hole. The inset shows the inner region of IC 310 in high resolution in the radio wave region.

very distant objects to one hundredth of the original value.” PKS 1441+25 is an example of a so- called blazar, a celestial body that often exhibits very powerful radiation bursts. The Fermi space telescope detected one of these eruptions in April 2015. A glob- al alarm was immediately triggered at selected observatories, and when MAG- IC directed its sights toward this object, the gamma radiation was up to 100 times more powerful than normal. This outburst was also observed by other telescopes, for example in the visible and X-ray ranges (MaxPlanckResearch 1/2016, page 44).

LIKE LOOKING INTO A BRIGHT HEADLIGHT

This is where the special characteristic of blazars comes into play. The central supermassive black hole accretes mat- ter from the surrounding gaseous disk, and in doing so, diverts some of it – probably as a result of magnetic fields – into two beams or jets that shoot out into space in opposite directions at right angles to the disk. In the case of a blazar, one of the two jets is coinci- dentally directed toward Earth, mean- ing that the astronomers and their in- struments look into it as if into a bright headlight. the jet. “The mixture of particles and separation of 260 million light-years “We believe that the outburst took magnetic fields gives rise to turbulence puts it more in the galactic neighbor- place far away from the black hole in a and shocks in which the particles expe- hood. On November 13, 2012, MAGIC compact region inside this jet,” says rience strong acceleration and thus pro- recorded radiation outbursts of previ- David Paneque. Compact here means duce radiation,” says the researcher. ously unknown intensity. roughly as big as our planetary system, A further highlight is the observa- What was surprising about this out-

but not filling the whole diameter of tion of the radio galaxy IC 310, whose burst was that it lasted less than five Photo: Christian Föhr/MPI for Nuclear Physics (top); photo and graphic: MPI, based on original material from H. Wilson (bottom)

40 MaxPlanckResearch 1 | 17 FOCUS_Extreme Space

Exactly what happens in the immediate vicinity of the black holes » and further out in the jets is still nowhere near final clarification.

minutes. This allows conclusions to be the Pierre Auger Observatory, that 99 in Chile, the researchers again have drawn about the size of the region that plunge into the terrestrial atmosphere the whole sky in their sights. flared up, because no object can illumi- with extreme energies. “If everything goes according to nate faster than light takes to travel The successes of H.E.S.S. and MAG- plan, we can start with the construction across it. The region from which the IC have led to the decision to create an as early as 2017,” says Masahiro Teshi- gamma radiation originated must international successor project: the ma. And his colleague Werner Hofmann therefore be significantly smaller than Cherenkov Telescope Array (CTA). This from Heidelberg adds: “With the CTA, the black hole with a mass of 300 mil- observatory will be established at two the observation times needed will be a lion solar masses whose diameter mea- locations: in the Chilean Andes and on hundred times shorter than those of sures around 23 light-minutes. La Palma, the current location of MAG- H.E.S.S. or MAGIC.” So things are look- “We assume that the black hole ro- IC. With 19 telescopes on La Palma and ing good for astroparticle physics. tates rapidly and is surrounded by a

magnetic field,” says Paneque. As a re- sult, strong electric fields occur in the polar regions, which accelerate elec- TO THE POINT trons and their antiparticles (positrons) l to almost the speed of light. These then Astronomers currently know of 178 celestial bodies that emit high-energy gamma radiation. It can be observed indirectly from the ground with telescopes such as generate the gamma radiation when H.E.S.S. and MAGIC. they interact with their surroundings. l The Crab nebula, a supernova remnant, is among the best-investigated objects. This can be imagined to be some- Researchers registered pulsed gamma radiation with a record-breaking energy thing like flashes of lightning that dis- of 1.5 trillion electron volts from the center of the pulsar.

charge every few minutes. The light- l At the heart of the Milky Way sits a cosmic accelerator that accelerates protons ning in space releases its energy over a to energies of up to 1,000 trillion electron volts (1 peta-electron volt). region the size of our planetary system. l The Pierre Auger Observatory in Argentina has even detected particles of up to All of this takes place very close to the 100,000 PeV from the cosmos. Their origin is completely unclear. The main candi- black hole. “With these observations, dates are thought to be centers of galaxies with black holes that are much more massive and considerably more active than that in the Milky Way. we are trying to look directly into the machinery at the center of the galaxy, as it were,” says Razmik Mirzoyan. GLOSSARY LOCATIONS ON LA PALMA AND Electron volt: A unit of energy, abbreviated eV. If an electron is accelerated in an electric IN THE CHILEAN ANDES field, its kinetic energy changes by one electron volt when the accelerating voltage is one volt. In the largest accelerator on Earth, the LHC, protons are accelerated to approximately Exactly what happens in the immedi- 7 TeV (7 x 1012 eV). The most energetic particles in the cosmic radiation have energies of 20 ate vicinity of the black holes and fur- more than 10 eV. The energy of radiation can also be stated in the unit eV. ther out in the jets is still nowhere near Jets: Bundled beams of matter in which particles fly into space in a specific direction at al- most the speed of light. They are produced when a black hole accretes gas from a rotating final clarification. The researchers are disk. As this happens, only a portion of the gas in the disk plunges into the gravitational trap also puzzling over the question of – the other portion streams away at right angles to the plane of rotation in the form of jets. whether active galaxies produce those

Photo: Christian Föhr/MPI for Nuclear Physics (top); photo and graphic: MPI, based on original material from H. Wilson (bottom) cosmic radiation particles detected with

1 | 17 MaxPlanckResearch 41 SPECTRUM

Electronics at Record Speed

Ultrashort laser flashes generate current a million times faster than in modern microprocessors

Electronic components could be made hand, stimulate the electrons so quick- to run much faster by accelerating ly that the relatively slow atoms no their electrons with light. Using ex- longer cause interference. Not only is tremely short laser pulses, researchers the current generated a million times at the Max Planck Institute of Quan- faster; the conductivity of the materi- tum Optics in Garching recently made al increases by a factor of ten quintil- electrons oscillate at petahertz fre- lion – that’s one followed by 19 zeros. quencies – around 1,000 times faster The researchers also discovered a way than the clock speeds of modern mi- to detect the quantum current: the croprocessors. The current produced electrons emit light at their oscillation in the process doesn’t fit the classical frequencies, which is easier to measure model of charge transport. As a quan- than the current itself. tum current, it doesn’t simply flow (www.mpg.de/10805872) from the negative pole to the positive pole of a battery. Instead, the electrons oscillate extremely rapidly in the quantum realm. This state can’t be achieved with ordinary current sourc- Laser pulses (large sine wave) generate electric currents at petahertz frequencies es, as atoms, which also vibrate, cause (small sine waves in the electronic compo- the electrons to oscillate out of sync. nent sketched here). Currents are revealed Ultrashort laser flashes, on the other by the UV radiation emitted.

My Contribution to Arctic Sea Ice Melt

Measurements reveal the correlation between CO2 emissions and summer ice shrinkage

Every ton of carbon dioxide released by humans on the planet causes the summer sea ice in the Arctic to shrink by three square meters. Dirk Notz, a scientist at the Max Planck Institute for Meteorology, and Julienne Stroeve, a researcher at the US National Snow and Ice Data Center, came to this conclusion by analyzing measurements. They also discovered that, because they underestimate the increase in thermal radiation in the Arctic, many cli- mate models predict a slower rate of ice melting than is observed in real life. The data also clearly shows that lim- iting global warming to two degrees Celsius, as called for by the most recent UN climate conventions, won’t be enough to prevent summer ice melt in the Arctic Sea. (www.mpg.de/10817029)

Scientists, including researchers from the Max Planck Institute for Meteorology, taking samples of Artic Sea ice near Spitzbergen

for later analysis. Graphic: MPI of Quantum Optics (top); photo: Dirk Notz (bottom)

42 MaxPlanckResearch 1 | 17 SPECTRUM

Scrambled Letters with Consequences Superlative The large size of the human brain is probably due to a minor genetic mutation Coating

A surface with two-micrometer- high nanocolumns transmits almost all of the incident light

Antireflective coatings will soon be a lot more effective. Researchers at the Max Planck Institute for Intelligent Systems in Stuttgart have found a way to produce, on glass surfaces, nano- structures that reflect almost none – and transmit almost all – of the inci- dent light. They have developed a method to produce conical columns The swap of a single letter (red) in the code of the ARHGAP11B gene resulted in modern humans producing more stem cells in the brain than apes. measuring around two micrometers high on surfaces. Along surfaces coat- About one and a half million years thals, but not in chimpanzees. After ed with such columns, the refractive ago, a tiny but fateful misspelling oc- the mutation, the ARHGAP11B gene index changes continuously. Most curred in the three-billion-letter-long was able to develop its full potential. light in the visible and shortwave spec- text of the human genome: a C was re- According to researchers at the Max trum is therefore able to penetrate the placed by a G in the ARHGAP11B gene. Planck Institute of Molecular Cell Bi- surface over a relatively wide range of This gene causes stem cells to multiply ology and Genetics in Dresden, the angles of incidence. Conventional an- and form new nerve cells. ARHGAP11B point mutation caused more stem cells tireflective coatings and shorter na- was created by a partial doubling of a to form in the cerebrum of modern noscale columns are antireflective predecessor gene after the evolution- humans. Consequently, our brains only within a narrow range of the light ary lines of humans and apes separat- grew in size, endowing us with the in- spectrum and work only at very limit- ed. It occurs only in humans and our tellectual skills that characterize hu- ed angles of incidence. The new anti- closest, now extinct, relatives, the mans, such as language and thought. reflective coating could find applica- Denisova hominids and the Neander- (www.mpg.de/10851125) tions in high-power lasers, cameras and microscopes, as well as in touch- screens and solar modules. (www.mpg.de/10797830) A Nose for Oxygen

Mice have specialized neurons in the nasal mucosa that let them detect the oxygen content of the air

The mouse’s keen sense of smell is – in the oxygen concentration of the 99.8 % 92.8 % hardwired in its genome: more than a air. The rodents can therefore smell a thousand genes are dedicated to syn- decrease of an odor − an ability that thesizing receptor molecules for the ol- has yet to be found in any other ani- factory sense, including one for a gas mal. The key to this ability lies in the 0.2 % 7.2 % that we humans wouldn’t normally Gucy1b2 and Trpc2 genes, which con- think of as having an odor: oxygen. tain information for molecules in- A glass plate on which nanocolumns have According to scientists at the Max volved in signaling pathways in type B been etched (illustrations on the left) Planck Research Unit for Neurogenet- cells. However, it is still unknown ex- reflects just 0.2 percent of light falling on ics in Frankfurt, mice can sniff out the actly which receptor detects the oxy- it at an angle of 30 degrees and is trans- oxygen content of the air with the gen content. Nor do the researchers parent to the remaining 99.8 percent. At the same angle of incidence, a plate help of type B neurons in their nasal know whether type B cells that re- without the surface nanostructure (illus- mucosa. These cells are activated in re- spond to low oxygen levels also occur trations on the right) transmits only 92.8 percent of light, reflecting 7.2 percent. Graphic: MPI of Quantum Optics (top); photo: Dirk Notz (bottom) Graphic: MPI of Molecular Cell Biology and Genetics (top), Zhaolu Diao (bottom) sponse to a decrease – however slight in humans. (www.mpg.de/10843354)

1 | 17 MaxPlanckResearch 43 Microswimmers can be precisely guided to targets to guided precisely be can Microswimmers Monkeys withaKnackforLanguage Guided byLight SPECTRUM 44 entists attheMaxPlanckInstitutefor and noticewhenaruleisviolated.Sci- nize the rules for combining syllables three-month-old infantsalreadyrecog- Even babieshaveasenseofgrammar: babies similar to manner a in syllables of sequences complex process Macaques through liquids. it possibletousealightsource toguidemicroswimmers from thelightsource. This orientationmechanismmakes of themicroswimmertoother, propellingitaway the concentrationdifferential,waterflowsfromoneside the bead and the carbon-coated side. To compensate for the soluteconcentrationbetweenuncoatedsideof stance partiallyseparate.Thisgivesrisetoagradientin ing it warm up. As a result, the waterandorganic sub- sure tolight,thecarbonlayerandliquidsurround- microbeads coatedwithcarbonononeside.Uponexpo- tems inStuttgartandtheUniversityofuseglass searchers at theMax Planck InstituteforIntelligentSys- croswimmers withthisability, knownasphototaxis,re- a lightsource orawayfromit,asrequired.To endowmi- solved organicsubstance,theyareabletomovetoward many microorganismspossess:inwatercontainingadis Tiny swimmingobjectscan nowmimicanabilitythat MaxPlanckResearch MaxPlanckResearch sing s. She laughs. He sing. You I laugh. (www.mpg.de/ 1 | 17 10756646 ) measured electricalbrainactivityon ments ofthisability. Theresearchers monkeys alsopossessatleasttherudi- in Leipzighavenowdiscoveredthat Human CognitiveandBrainSciences - slowly than humans. than slowly more them learn monkeys the though rules, these recognize babies month-old three- and Macaques aren’t. “you” and “I” whereas “s”, an by – distances variable at – followed are “she” and “he” syllables initial the example, for English, In rules. ic specif- follow syllables languages, many In (www.mpg.de/ have toactivelysearch fortherules. tening, like babies or macaques,and nize languagepatternsbymerelylis ability as adults: they no longer recog- mates. However, evenhumanslosethis line splitofffromthatofotherpri arisen beforethehumanevolutionary rect. Thisabilitymustthereforehave notice whenasyllablestringisincor- caques’ brainpatternsthattheanimals baby. Theycouldalsotellfromthema similar tothatofathree-month-old tivity patternoftheanimals’brainis They discoveredthattheelectricalac- rule-compliant stringsofsyllables. mals listenedtomeaninglessbut the scalpofmacaqueswhileani autonomously away from a light source. light a from away autonomously navigate carbon with side one on coated beads Glass darkness: the toward Traveling 10821435 , only in German) , only - - - -

Graphic: Celia Lozano/MPI for Intelligent Systems/University of Stuttgart (top), photo: MPI for Human Cognitive and Brain Sciences (bottom) SPECTRUM

The Turbulent Heart of Eta Carinae Detailed images of the binary star system show the collision zone of the stellar wind

Eta Carinae is a massive and very bright binary star system. The heavier partner is one of the biggest and brightest stars in the sky, weighing in at around 100 solar masses. A team headed by Gerd Weigelt from the Max Planck Institute for Radio Astronomy in Bonn has studied Eta Carinae with the help of near-infrared interferometry for the first time. They obtained images of the area between the two stars in which the stellar winds from each star crash into each other at speeds of more than ten million kilometers an hour. With- in the collision zone, the temperature rises to many tens of 1 arcsec millions of degrees − hot enough to generate X-rays. Until now, it wasn’t possible to spatially resolve this central re- Interstellar storm: The left image shows the Homunculus Nebula around gion. The astronomers used a new image processing tech- the massive binary star system Eta Carinae. On the right is a high-definiti- on image of the wind collision zone in the central area of the system. This nique, which they applied to images taken by the AMBER area is around 100 times larger than the diameter of each of the two stars. instrument of the European Southern Observatory’s Very The yellow ellipse shows the orbit of the binary star system. The two red Large Telescope Interferometer (VLTI). (www.mpg.de/10794673) dots indicate the positions of the two stars at the time of the observation.

Pushing the Skin Stem Cells in a Test Tube Boundaries of Microscopy New method could reduce animal research

It is now possible to observe individu- Wounds have to be healed; lost hairs animal research superfluous. Until now, al proteins at work in cells. To achieve have to be replaced. To achieve this, the scientists searching for the causes of this, a team of researchers headed by skin uses stem cells in the hair follicles. skin cancer have had to conduct re- Stefan Hell, Director at the Max Planck If it were possible to successfully culti- search on mice. Scientists at the Max Institute for Biophysical Chemistry in vate such stem cells in the lab, one of Planck Institute for Biology of Ageing Göttingen, have developed the MIN-

Photos: ESO (top left) and Gerd Weigelt/MPIfR (top right); MPI for Biology of Ageing (bottom) the benefits would be to make a lot of in Cologne have now succeeded in cul- FLUX fluorescence microscope, which tivating mouse skin stem cells in the can resolve two fluorescent proteins lab. Supplied with growth-promoting even if they are separated by only a chemical messengers, skin stem cells few nanometers – the limit of what survive for long periods in a gel consist- is possible in living cells. The team ing of natural skin proteins. In addi- achieved this feat by cleverly combin- tion, the researchers found that the ing two Nobel prizewinning methods: method can also be used to cause ma- they identify individual fluorescent ture cells to revert to the stem-cell state. molecules by randomly switching the In the future, researchers could carry molecules on and off, and then deter- out experiments with such stem cells mine their precise positions by stimu- instead of on living skin, and even use lating them with a doughnut-shaped them to test the effects of new cancer laser beam. The researchers exploit drugs. The Cologne-based scientists the fact that they know the precise in- now hope to adapt their technique to tensity profile of the laser beam. The human cells. whole process takes place so rapidly (www.mpg.de/10866807) that it is even possible to follow the path of a protein through a cell. And the resolution is determined only by Hair follicle stem cells in cell culture under the microscope (blue: cell nucleus; green: the size of the fluorescent molecules. 0 µm 75

Graphic: Celia Lozano/MPI for Intelligent Systems/University of Stuttgart (top), photo: MPI for Human Cognitive and Brain Sciences (bottom) keratin; red: actin). (www.mpg.de/10878921)

1 | 17 MaxPlanckResearch 45 A Well SPECTRUM Researchers measure the shape of Kepler Kepler of shape the measure Researchers 46 than our own Sun. own our than rounder much star this making kilometers, three just is radius polar the and radius equatorial the between difference the that show oscillations star’s The measured. been Kepler star The rect sunlight. permanently darkzoneinto aregionthatissometimesexposedtodi- suring 3.8kilometersacross, thebrightdepositsextendedbeyond ingly brightareasintheirinterior. Inonerelativelyyoungcratermea- dark areas,theresearchers found10cratersontheimages withsurpris- ly eternaldarkness.Among 634identifiedcraterswithpermanently were abletophotographdepositsofwatericeinareasshrouded innear- res’ highnorth.Thetwoframingcamerasachievedaspecial feat:they ed byGöttingen-basedscientistsrecentlypublishedareport onCe and hasnowalmostcompletelymappeditssurface.Ateam head tute forSolarSystemResearch inGöttingenatthe celestial body has pointeditson-boardcamerasfromtheMaxPlanck Insti- Ceres betweenMarsandJupitersinceMarch 2015.Theprobe The USspaceprobeDawnhasbeenorbitingthedwarf planet Eternal PolarNight Water Iceinthe the northern polar region of the dwarf planet Ceres planet dwarf the of region polar northern the surveying are probe space Dawn the of cameras The MaxPlanckResearch MaxPlanckResearch is the most perfectly round natural celestial body that has ever has that body celestial natural round perfectly most the is 11145123 Deneb (www.mpg.de/ - Rounded Star 1 | KEPLER 17 10861571 11145123 Vega ) 11145123 Milky Way Milky

SUN with unprecedented accuracy - - pared the frequencies of oscillations that are are that of oscillations frequencies the pared com They oscillates. star the that fact the ed exploit astronomers the measurements, their For round. extremely is ball gas words, the er oth In kilometers. of 1.5 million radius mean star’s to the relation in small astonishingly is difference This Earth. from light-years 5,000 ed of Kepler 11145123, radius lar locat object an po the and radius equatorial the between ters kilome of three just foundadifference They accuracy. unprecedented with star rotating of aslowly flattening the have now measured of Göttingen University the and Research tem Sys for Solar Institute Planck Max the from zon Gi- Laurent by headed somewhat. Ateam them force to tends flatten centrifugal axis, their on spin they As spheres. aren’t perfect Stars for Solar System Research in Göttingen detected water. detected Göttingen in Research System Solar for Institute Planck Max the from cameras framing the which in craters ten indicate numbers The Ceres. on lationships re- elevation the show colors The pole: north the of view A equator.center to the the from distance the pole to and the star the center of the from distance the measurements: two between difference the calculated they From this, latitudes. at dominate higher that those more at equator pronounced with the (www.mpg.de/ -7.9 Elevation (km) Elevation 10827169 9.4 ------)

Photos and graphic: Mark A. Garlick (top); Nature Astronomy (bottom) Photos and graphic: Mark A. Garlick (top); Nature Astronomy (bottom)

Photos: MPI for Medical Research/U. Mersdorf and M. Fischer (top); MPI for Ornithology (bottom) The FastestFliersintheAnimalKingdom identified a new champion among the for Ornithologydiscovered. Theyhave searchers attheMaxPlanckInstitute structure. Thisbeliefismistaken, asre- sistance resultingfromtheir wing ered slowbecauseofthegreater airre- in contrast,havealwaysbeenconsid- of over110kilometersanhour. Bats, flight, dartingacrosstheskyatspeeds hold thespeedrecordforhorizontal aptly namedswiftfamily, forexample, tion foraircraft engineers.Birdsofthe as inspira- unsurpassed andstillserve The flightcharacteristicsofbirdsare record speed current the holds aviator,skillfulalso a it just isn’t bat free-tailed Brazilian The die sothatothersmaylive.Forthesin cells thatareinfectedfirst.Theymust the partnershipdoesn’t benefitthe cal Research inHeidelberg,however, at theMaxPlanckInstituteforMedi biotic partner. According to scientists tion –whenaparasitebecomessym ganism, however, itcanmeansalva- bad news.Forasingle-cellmarineor In humans,aviralinfectionisusually Is MyFriend The EnemyofMy A single-cell organism protects itself from viruses with viruses with viruses from itself protects organism single-cell A nm 100 - - - - (www.mpg.de/ – forbatslonger-than-averagewings. aerodynamic shapeoftheirbodyand reach suchhighspeedsthankstothe The bats,whichweighjust12grams, hour –andthatwithoutatailwind. at speedsofover160kilometersper tailed bat,whichzipsthroughthenight acrobats oftheair:Brazilianfree- (www.mpg.de/ al defensemechanisms. gle-cell organismsthatusesuchunusu searchers are now looking for other sin from infectionbygiantviruses.There ed organismsarethereforeprotected ticles butnoCroVparticles.Uninfect- both ism thatissimultaneouslyinfectedby from multiplying.Asingle-cellorgan viruses, theypreventthegiantviruses host cellsatthesametimeasgiant gle-cell organisms:iftheyreachnew types. Thesemavirusessaveothersin rus, itreleasesparticlesofbothvirus viously been infected with the mavi- til itbursts.However, ifacellhaspre host cell to churn out giant viruses un- the cellsurface,viruscauses mortal threat.Afterattachingitselfto sis, agiantviruscalledCroVposes gle-cell organism Cafeteria roenbergen- hour, is a case in point. in case a is hour, of speeds reach can which bat, free-tailed Brazilian The wings. stubby broad, with those than faster fly usually wings narrow long, with Animals (pink). mavirus the and blue) (dark CroV virus giant the of Particles relationship: Close viruses releases only mavirus par ) 10851301 10820081 kilometers an kilometers 160 ) ------Longer Life for OthersMeans Looking Out childless elderly people who care for for care who people elderly childless also found that five researchers The years. within died half around trast, con- by offspring, their to dedicated actively weren’t who those Among still alive the initial ten after years survey. were children their assisted active ly or grandchildren their for cared 70 than more of data survival compared team international An participated. Berlin in Development Human for stitute In Planck Max the which in study a of finding the is That longer. live others support and help who people Elderly (www.mpg.de/ impact.” a have and negative to stress lead could it that, Beyond moderate. like are is of commitment degree if the only ly effects “Positive longevity. for recipe a is others for caring that lieve be- doesn’t Development, Human for Institute Planck Max the at Director Hertwig, Ralph However, effect. the from also benefit or neighbors friends and 103 and 500 people between the ages of of ages the between people . Half the grandparents who . Half the grandparents 1 | MaxPlanckResearch MaxPlanckResearch 17 10873883 )

SPECTRUM 47 - - - BIOLOGY & MEDICINE_Biophysics

Cells on the Catwalk

Life is motion and interaction with the environment. This is equally true of cells within an organism, but for cells to get from one place to another, they not only have to be able to move, they also have to interact with their environment. Joachim Spatz and his team at the Max Planck Institute for Medical Research in Heidelberg are studying how cells manage this. In his search for answers, the winner of the 2017 Leibniz Prize puts cells through their paces on catwalks and obstacle courses to test their adhesive properties.

TEXT CATARINA PIETSCHMANN

he adult human body com- Many cells have to cover distances of distinguish whether the surface is hard prises 100 trillion cells – an various lengths within the body: or soft by essentially tugging on it. “It’s almost unimaginably large during embryonic development, for like us probing the ground,” Spatz says. number, a one followed by example, but also during continuous “If it’s soft enough, I can safely fall to 14 zeroes. The cells of our remodeling processes in the adult the ground. If it’s made of stone, I’d bodiesT form organs such as the heart and body, cells must migrate from their better not. “Cells adapt their behavior kidneys, and tissues such as the skin and place of origin to the sites where they in a similar manner. “If a stem cell per- nerves. Some drift through the highly are needed. To do this, they have to ceives a hard environment, it will ma- branched vascular system in the form of know where they are and where they ture into bone or tissue cells. If, in con- blood cells, while others patrol the body need to go. trast, the substrate is soft, it matures for the immune system. But regardless into a nerve cell.” of the task they perform for the body as RECEPTORS SENSE THE Cells are even able to estimate the a whole, every cell is an individual. ENVIRONMENT number of small molecules near them. “Each must be able to perceive its envi- This gives them a sense of how import- ronment and respond to it,” says Joa- But how does a cell interact with its en- ant the latter are as chemical messengers chim Spatz. The biophysicist headed the vironment? “For one thing, it detects and whether a response is appropriate. New Material and Biosystems Depart- chemical signals via receptors on the “It is also important for migrating cells ment of the Max Planck Institute for In- cell membrane,” Spatz explains. Small to know how densely a surface is cov- telligent Systems until the end of 2015. molecules attach themselves to mem- ered by molecules,” Spatz says. “If the In 2016, he and his team moved to the brane-spanning proteins and activate distance between the molecules is 60 Max Planck Institute for Medical Re- signaling pathways in the cell’s interi- nanometers or more, the cells are unable search in Heidelberg. Together, they are or. Depending on the information to read the information.” devising biophysical experiments, mea- transmitted, genes are revved up, throt- In order to observe the behavior of suring techniques and model systems to tled or switched on or off. individual cells, Spatz’s coworkers have investigate the motility and adhesion of In addition, the cell also perceives developed a sort of cellular catwalk,

individual cells and cell collectives. its underlying surface tactically. It can which they call cellwalks. Each cellwalk Photo: MPI for Intelligent Systems

48 MaxPlanckResearch 1 | 17 A cell holds fast: Adhesive proteins concentrate at binding sites (yellow) to form a textured surface (blue). A meshwork of actin proteins (red) links adhesion points across the cell. Photo: MPI for Intelligent Systems

1 | 17 MaxPlanckResearch 49 Jacopo Di Russo studies the migration behavior of human skin cells and measures the force the cells exert to cling to a surface. To do this, he binds various proteins to gels to alter the properties of the surface.

consists of a polymer surface coated cell type. Even within a single cell line from Heidelberg University Hospital with ultrafine gold particles. The gold there are “tortoises” and “hares” be- approached Spatz: couldn’t they put a acts as anchoring points for biomole- cause the speed is also determined by “real” protozoon, namely the malaria cules – peptides, for example, or anti- the cell’s stage of development. organism Plasmodium, on the cellwalk bodies, to which, in turn, cell receptors Cells, of course, have no feet, but for a change? can bind. This provides support for the they do have something similar. They The tropical disease, which is caused cell, because without these “nubs,” the crawl forward on sheet-like exten- by the bite of an infected Anopheles surface would be far too slippery. By sions, called lamellipodia. The cell mosquito, still claims half a million varying the base polymer, the spacing membrane bulges out and spreads for- lives every year. The mobility of the between the anchoring points can be ward. “It’s comparable to us taking a pathogens, which are injected into the adjusted to 30, 50, 70, 100 or 150 nano- step forward,” Spatz explains. The human skin from the mosquito’s sali- meters. For the cellwalk, a small piece lamellipodium adheres to the sub- vary glands, is crucial for the “success” of the synthetic surface is placed in a strate by rearranging and aligning pro- of the infection. “The sickle-shaped culture dish with nutrient solution. In- tein molecules in the cell’s interior – sporozoites move at a top speed of 10 dividual cells are then placed on top of integrins as well as actin and myosin micrometers per second, nearly 100 it, the microscope is focused and the filaments. The rest of the cell body is times faster than human cells,” camera is activated. then pulled forward, and the anchor- Frischknecht explains. “We’re interest- ing site is released again. This process ed in finding out how they do it.” MIGRATION AT A SNAIL’S PACE is repeated for each “step” – a form of Sporozoites drill through the skin locomotion also used by amoebas. until they reach a blood capillary. They How fast do cells actually move? “On In recent years some members of are then carried by the bloodstream to average, 30 micrometers an hour, but Spatz’s team have conducted research the liver, where they multiply for the they can reach a brisk 50 micrometers not only in Stuttgart but also on the first time. Until now it was a puzzle ex- an hour,” says Spatz with a chuckle. campus of the University of Heidelberg, actly how sporozoites move forward. They can travel about one millimeter a where word about their work on cell The only thing that was clear was that day, assuming they are fit enough. How- migration soon got around. One day they neither crawl nor paddle like bac-

ever, the speed of travel depends on the parasitologist Friedrich Frischknecht teria and single-cell algae, because they Photo: Wolfram Scheible

50 MaxPlanckResearch 1 | 17 BIOLOGY & MEDICINE_Biophysics

» Malaria pathogens move nearly 100 times faster than human cells.

form neither lamellipodia nor flagella. A comparison of various mutants, each they are connected by a meshwork of “Sporozoites glide gracefully without of which lacks a different protein, actin molecules. “The parasite causes changing their shape thanks to special yielded fresh insights. “We can now di- the membrane proteins to move to- proteins on their surface,” Kai Matu­ rectly observe what actually happens. ward the posterior end and then repels schewski explains. The scientist at the If protein X is missing, the parasite is them,” Matuschuweski explains. The Max Planck Institute for Infection Biol- unable to hold on; if Y is missing, it motion is similar to that of a millipede ogy in Berlin and professor at Hum- sticks fast to the surface,” Matuschew­ – except that these so-called feet con- boldt University is the third member of ski explains. sist only of single molecules and are so the project. small that they can’t even be seen un- The Plasmodium experiments didn’t TINY PROTEIN FEET der an electron microscope. The force require a non-slip cellwalk, but an ob- the parasite has to exert to hold and stacle course to imitate the parasite’s re- In its cell membrane, a sporozoite has then release itself can be measured lentless progress through the skin. a huge range of proteins that are re- with the help of optical tweezers. This Spatz constructed a miniature bed of quired for locomotion, some of which provided further insights into how the nails, of sorts, from polymers through perform identical functions. Hundreds single-cell organism moves. which the parasites can glide as if of them are situated at the anterior The malaria organism has a com- through a forest of ultrafine needles. end of the tiny cell body, to which plex life cycle, in the course of which

Below Malaria parasites (yellow) crawl over a surface studded with tiny columns. If the sin- gle-cell organisms have the same curvature as the columns, the pathogens, which mea- sure just one hundredth of a millimeter in length, begin to circle around the obstacles. Right A migrating cell. It forms contact points with the surface at specially struc- tured sites located at the ends of thread-like processes (small image). At these points, it 250 mm senses the properties of the surface and uses

Photos and graphic: MPI for Intelligent Systems (2) the anchoring points to pull itself forward.

2 µm Photo: Wolfram Scheible

1 | 17 MaxPlanckResearch 51 Above Jacopo Di Russo, Katharina Quadt and Medhavi Vishwakarma (from left) preparing a new experiment in which they will modify and measure the movement of cell collectives. Below The protein merlin (green dots) controls the direction of travel of follower cells: 1 Without physical or chemical stimulation, merlin blocks the formation of lamellipodia. Without these protuberances, the cell is unable to move. 2 + 3 If, in contrast, the leader cell pulls on the cell behind it, merlin in both cells leaves its site on the cell membrane, allowing a lamellipodium to form. The follower cells are then able to follow the leader cells. The signal molecule Rac1 (red dots) must also be activated for a lamellipodium to form. The cells always migrate toward areas of higher concentrations of activated Rac1. 4 If Rac1 is inactivated (gray dots), merlin again blocks the formation of lamellipodia at the cell membrane.

1 Follower cell Leader cell it takes on various forms. However, ex- Whether it’s a small cut to a finger, a perts agree that the sporozoite is a scraped knee or deep cuts following an promising – if not the most promising operation, epithelial cells have to – target for a vaccine, for the sole rea- “rush” into the wound to close it and son that only around 100 pathogens begin rebuilding the tissue. This sounds Merlin Actin Inactive Rac1 2 are present immediately after an infec- simple, but it is a highly complex pro- Force tion. In the later stages of infection, cess. It has been compared to marching Lamellipodium there are billions. “Ideal vaccine can- in lockstep. Joachim Spatz calls it col- didates are antibodies that block two lective cell migration. It is one of the or three of the pathogen’s proteins processes that no longer function prop- Active Rac1 involved in movement,” Matuschew­ erly in chronic wounds. 3 ski says. If the sporozoite is unable to glide, it literally gets stuck in the MIGRATION UNDER skin, and the infection is stopped in A MICROSCOPE its tracks. Having studied the movements of The scientists needed a suitable wound 4 individual cells in detail, Spatz’s team model for their experiments. They cov- turned its attention to the migration ered the bottom of a petri dish with a behavior of entire groups of cells. They nutrient medium and grew epithelial posed the question: how exactly does a cells on it. They blocked a region of the

wound heal? dish to prevent the cells from migrat- Photo: Wolfram Scheible; graphic: MPI for Intelligent Systems

52 MaxPlanckResearch 1 | 17 BIOLOGY & MEDICINE_Biophysics

» Mechanical tension at tissue edges promotes wound healing.

ing into it. As soon as they removed the like snaps. At the same time, the actin blockade, the cells started to colonize skeleton in the interior of the cell the free space. Their movements were reaches out to neighboring cells for recorded by a microscope camera, stability. “The edge of a cell collective which took snapshots of the process ev- is sort of like a herd of sheep that has ery ten minutes. been penned behind a fence,” Spatz After just a few hours, bulges ap- says. The actin fence is under mechan- peared in the originally straight wound ical tension. If the curvature is the edges. “That’s because some cells move same everywhere, as in the case of a faster than others,” Spatz says. In oth- circle or a straight line, it’s difficult to er words, the repair crews don’t ad- break away from the herd. “Neighbor- vance in ordered lines. Rather, there are ing cells take off together and jockey leaders, “pioneering” cells that the oth- for the lead. Eventually, one prevails 100 µm ers trail along behind. “They form the and the others fall behind.” However, vanguard of the collective and can eas- a cell that marches out of the corner ily be identified because they’re bigger of a square, for example, has no neigh- and move ahead of the others.” bors and automatically becomes a Wound healing in a petri dish: Epithelial What makes a cell a leader? And leader. Surgeons unknowingly exploit skin cells migrate together into a region how do they communicate with the this effect when they make zigzag scal- with no cells. The colored paths show the cells’ movements over a period of more other cells in their tow? To answer pel cuts rather than straight ones, thus than five hours. these questions, the researchers varied stimulating subsequent cell migration their experiments. They covered the into the wound. bottom of the petri dishes with a hy- The researchers first measured the drogel, which cells find slippery, and ONE LEADS, THE COLLECTIVE speed and direction of motion of each sowed the epithelial cells within only FOLLOWS cell in a collective. “That showed us a small geometrical shape in the cen- that domains of 20 to 30 cells form that ter. As soon as the colonies filled these The researchers suspect that, at least in then quickly march together in one di- circular, triangular or square areas, the principle, every cell has leadership po- rection,” Spatz explains. These cells researchers briefly exposed the gel to tential. Whether they can exploit that form what is termed the persistence UV light. This transformed the slip- potential depends largely on their po- length, that is, the distance over which pery surface into a non-slip surface, sition at the edge of the wound. If the cells march in a coordinated manner in and the epithelial cells quickly set off. position is not crucial, for example if one direction. “We found that leader cells tend to the edge of the wound is straight, then Then the real work began. “In mo- form at places with a pronounced cur- the cell rows in the rear determine lecular cell biology, we know hundreds vature, for example in the corners,” which cell becomes the leader. Ulti- of proteins that serve as signal mole- Spatz says. This is easily explained: the mately, the decision regarding the lead- cules for cell migration,” Spatz says. contacts between the cells are me- ership of a collective is not made inde- “We switched off the gene for each mi- chanically stabilized by what are pendently by the leader cell, but by the gration-associated protein so that the known as tight junctions – short struts collective as a whole. This decision is cell was unable to synthesize that pro- of membrane proteins such as cadher- physically regulated in the collective by tein. Then we measured the persistence ins. If the cadherins of cell A match purely mechanical means. The ques- length of the mutants by biophysical those of cell B, the extracellular do- tion that remains is how the leader means.” The scientists were amazed to Photo: Wolfram Scheible; graphic: MPI for Intelligent Systems Photo: MPI for Intelligent Systems mains of those proteins click together communicates with its followers. discover that very few of the proteins

1 | 17 MaxPlanckResearch 53 Medhavi Vishwakarma, Freddy Frischknecht, Joachim Spatz, Jacopo di Russo and Katharina Quadt (from left) analyzing data. The scientists have established that the protein merlin plays a key role in the collective migration of cells.

have anything to do with collective found that the protein leaves its origi- substances are released that convey di- movement. Only if the membrane pro- nal location to reappear in the interior rectional information to the cells along tein merlin is missing does the collec- of the cell. But why? They hypothesize the wound’s edge.” Spatz’s team, togeth- Profiles of Leading Women Scientists tive break apart. that the leader cell rushing ahead cre- er with the University of Heidelberg, has It is astonishing that the cell relies ates tension between the cells. “It’s like since repeated and confirmed the exper- on just a single type of molecule and a runner pulling another runner be- iments on human skin models. The project doesn’t have at least one backup pro- hind him by the hand,” Spatz explains. tein at the ready. Merlin is not a new Merlin is like a force sensor that re- UNCOORDINATED MOTION AcademiaNet is a database containing the discovery – it was already known from sponds to this tension. It disappears WITHOUT MERLIN profiles of over 2,200 outstanding women cancer biology. Unlike in the case of into the interior of the cell, leaving wound healing, a metastatic growth room on the membrane for the follow- The researchers also discovered that, researchers from all disciplines. wants to prevent the cellular “herd in- er cell to extend its lamellipodium and without merlin, more leader cells form, stinct” because single cancer cells are follow the leader. “If merlin didn’t do but the wound healing proceeds more Our objective more efficient and can progress into tis- that, the cell would be unable to follow, slowly, because the mechanism by sue more quickly than a group. They let because membrane-bound merlin acts which the cell collective moves is no The aim of our search portal is to make it the bloodstream carry them to distant essentially as a lamellipodium brake.” longer coordinated. easier to find female academics to fill leading regions of the body, where they estab- And because the protein makes room Spatz is currently also looking more lish themselves at suitable locations only at places where the leader cell closely at the movement of cancer cells. positions and to sit on executive committees. and begin to divide uncontrollably. pulls, the direction is automatically es- “Unlike healthy cells, they have a ten- “Merlin is a metastasis inhibitor,” Spatz tablished. This process continues down dency to ignore their environment. explains. “It’s a good sign when the the rows of the cell collective – literal- That’s bad for patients, but good for the protein is very active in cancer cells. ly pull by pull. So mechanical tension cancer!” Metastatic cancer cells reduce The partners The cells then tend to stay together and promotes the formation of cell collec- not only their merlin production, but are thus less likely to form metastases.” tives and thus wound healing. also that of cadherin contact proteins. It was already known that merlin is And how does the lead cell know They are therefore able to make them- positioned between the cell membrane which direction it must go in? “In our selves extremely long and narrow and and the cellular skeleton. The research- model, it can move in only one direc- slip between tissue cells to invade new ers observed collective cell migration tion, namely into the free space. In the regions of the body without being de-

after labeling merlin with a dye, and case of a real wound, however, signaling tected or stopped by other cells. Photo: Wolfram Scheible Would you like to find out more? www.academia-net.de 54 MaxPlanckResearch 1 | 17 BIOLOGY & MEDICINE_Biophysics

However, cell migration is not specific to wounds and cancer cells. It occurs TO THE POINT continuously everywhere in the body. l Membrane-bound proteins convey information about a cell’s environment, “If cells did not cluster together, com- such as the nature of the substrate. By remodeling its internal skeleton, the cell municate with each other and migrate can form small protuberances in the membrane, which it uses to move about. together, we wouldn’t exist. The migra- l When epithelial cells migrate into an uncolonized area, some of them become leader cells that the others follow. Such leader cells tend to develop at sites tion and interaction behavior of cells where the tissue edge has a pronounced curvature, for example at corners was the prerequisite for the evolution and edges.

of multicellular organisms – and thus l Merlin, a membrane protein, coordinates groups of migrating cells. It senses for life as we know it.” the physical tension that arises when a leader cell pulls on the follower cells, Communication with the environ- enabling the formation of small protuberances at the pulling points. The protu- ment is the lifeblood of cells, some- berances are then used for locomotion. thing they have in common with us, their one-hundred-trillion-cell collec- tives. What happens to people when GLOSSARY communication is cut off for extend- ed periods? They become lonely. Some Lamellipodia: Broad protuberances of the membrane at the anterior end of motile cells. They are also known as pseudopodia. A two-dimensional meshwork of thread-like actin may become despondent, while others proteins provides stability and tensile force. Lamellipodia are used for locomotion and might find that they are sufficient navigation, and for engulfing nutrient particles (phagocytosis). unto themselves. Yet others would Optical tweezers: A method that allows scientists to measure the forces that individual seek out old acquaintances or establish molecules exert on each other. Each of the molecules to be measured is placed on a new ones. Cells, in contrast, have no plastic bead that is held in position by two laser beams. As soon as the molecules start choice: they activate a built-in suicide to interact and attract each other, sensors measure the force that the lasers must exert to hold the beads apart. program and die.

Profiles of Leading Women Scientists

The project AcademiaNet is a database containing the profiles of over 2,200 outstanding women researchers from all disciplines.

Our objective The aim of our search portal is to make it easier to find female academics to fill leading positions and to sit on executive committees.

The partners

Photo: Wolfram Scheible Would you like to find out more? www.academia-net.de for Life for Perspective A TEXT His life, however, has been shaped just as much by a life-changing vacation experience. vacation life-changing a by much as just shaped been has however,life,His Max-Planck-Institut Kohlenforschung für makes Ben List catalysts excellent are molecules organicsmall that discovery The ing, ashehasbeeninvited to SanDi- a sunnywinter’s morning.Perfecttim- Prize reachesBenListinCalifornia on that heistobeawardedthe Leibniz to reportaboutit. ganic catalysisin2016,isanoccasion the pioneerreceivedinfieldofor- our university. TheLeibnizPrize,which usual coursesinceourtimetogetherat up again.Ben’s lifehadfollowedanun we had a lot to talk about when we met seen eachotherfornearly20years,so a longwhileagonow, andwehadn’t doing ourdoctoratestogether. Thatwas cause Ben List and I had spent two years portrait. Itwasdifferentinthiscase,be to knowthemandbeablesketcha A few hours is usually all it takes to get thing abouttheindividualsthemselves. T 56 MATERIALS& TECHNOLOGY _Personal Portrait MaxPlanckResearch 1 MaxPlanckResearch The telephonecallbearingthe news CATARINAPIETSCHMANN however, don’t discloseany- of theirpublications.These, ten sufficienttoreadacouple work ofaresearcher, itisof- o beabletowriteaboutthe | 17 - - this autonomy–particularlynowwith the conditionsIhaveatMaxPlanck, “But and whales swim past in January? where pelicanscruisethroughtheair withaviewofthePacific, oratory honest, that wasreally appealing. Alab Live anddoresearch here again?To be employer wantedtoenticehimaway. ego notonlytogiveatalk–another chemist, wasBenList’s great-great-grand hard (1834– family longbeforehistime. JacobVol- gene, itwasfirmlyestablished inhis If there is such a thing as a researcher HAD AMUSICALEDUCATION” “I WOULD HAVE LIKED TO HAVE Kohlenforschung since2005. ment attheMax-Planck-Institutfür the HomogeneousCatalysisDepart- The 49-year-oldscientisthasheaded be beaten,”saysBenListwithasmile. the Leibniz Prize – that simply couldn’t von Liebigand,likehim,awell-known , one of the pioneers of a new research field in chemistry. in field research new a of pioneers the of one ,

1910), astudentofJustus - -

the boyswereinterestedin music,it aged tolearnaninstrument, though.If early age.” He wasn’t positively encour- to havehadamusicaleducation atan for ourselvesalot.Iwould have liked the rageatthattime.“We hadtofend school. Thistypeofeducationwasall laden, ananti-authoritariannursery and histwobrothersgototheKinder- full timeasanarchitect, andBenList ents divorce. His mother now works ferent.” WhenBenLististhree,hispar to takethisroute.Butrealitywasdif- stand. “ItlooksasifIwaspredestined burg Concertoswasonthemusic er atChristmas,oneofBach’s Branden When hismother’s siblingsgottogeth class family in Frankfurt, recounts List. a NobelPrizein1995. gist andMaxPlanckcolleague,received lein-Volhard), adevelopmentalbiolo And hisaunt“Janni”(ChristianeNüss hard madehisnameasanephrologist. father. Hisgreat-grandfatherFranzVol- He grewupinanupper-middle- , Director at the the at Director , - ­ - - - ­

Photo: Frank Vinken Photo: Frank Vinken already done his exercises. his done already usually has he morning, the in office his into walks he When photographer. the for this doing only is List Ben – lab the in Yoga MATERIALS & TECHNOLOGY_Personal Portrait

CO2H NH O O O OH + (S)-proline H (30 mol%)

20 vol% 97% (96% ee)

Above A plan for a new research field: would happen automatically, was his The third semester courses included or- Ben List was the first to catalyze this chemi- mother’s view. You can do it! You can ganic chemistry, which meant lectures cal reaction with the amino acid proline, become anything you want – conduc- with Johann Mulzer. “They were abso- shown above the arrow – and achieved a yield of 97 percent. One of the two mirror-image tor, artist or a famous chemist. “She al- lutely perfect!” With no haste and a lot variants of the product was formed here with ways had this confidence,” says List of colored chalk, the specialist for en- an excess (ee – enantiomeric excess) of looking back. antioselective natural product synthe- 96 percent. Since then, many chemists have sis drew gigantic diagrams on the board been looking for purely organic molecules in order to use them as reaction accelerators. HIS AMBITIOUS GOAL: that he used to show the step-by-step THE SYNTHESIS OF VITAMIN B12 path by which complicated antibiotics Below Chemical kitchenette: The apparatus or hormones are created. There was no in which chemists produce new substances As a pupil, he was motivated by almost question about it, Ben List simply had are usually much more complex than the philosophical questions: What is the to join Mulzer’s team. equipment in most kitchens. They do have hotplates, though. world made up of? What are human And he had set himself an ambi- beings made up of? Chemistry prom- tious goal: vitamin B12 was to become ised to provide answers. Back then, his molecule! One can guess how com- List even thought chemists were plex the structure is from its cumula-

all-knowing. “Pretty naive,” he says to- tive formula C72H100CoN18O17P – and day. “But when I found out that they Mulzer didn’t warn him. “In my igno- don’t have answers for everything, I rance, I thought: one half for my was already fascinated by the disci- bachelor’s degree, the other as my pline.” After receiving his school-leav- doctoral thesis. That was the plan.” Vi-

ing certificate, the first thing he did tamin B12 was first synthesized in 1972 was to spend three months traveling by Albert Eschenmoser (ETH Zurich) around India with two friends. The and Robert B. Woodward (Harvard) to- others had already made arrangements gether. “More than 100 doctoral stu- for their university courses. “I was the dents and postdocs had spent ten years only one who hadn’t given it any working on it. And I thought I could thought at all. When I returned, my do it alone,” says List, with a shake of mother became surprisingly vehe- his head. His goal was to produce the ment: Well, Ben, you really should do molecule more elegantly and in fewer something now!” Study chemistry, of steps – and all by himself. At some course, and in Berlin, of course. (A stage, Mulzer put the brakes on. It cousin lived there.) List called directo- would be sufficient if he managed the ry assistance and asked for the number two top rings, the “northern side,” so of the University of Berlin. “Which to speak. The maiden ascent of a north one?” asked the irritated voice at the face was more like it. But List arrived at other end of the line. “Just choose the peak of the mountain and looked one!” Ben List laughs. “Yes, that is how down with pride. There was a “summa

I landed at FU Berlin.” cum laude” at the bottom. Photo: Catarina Pietschmann

58 MaxPlanckResearch 1 | 17 That could be it! Ben List and his colleagues team up to develop ideas for new reactions. Not unusual: their blackboard is the front pane of a fume hood, which permits any gases that may be released to be directly pumped out.

“Assembling a molecule piece by piece crazy – but exciting. That was what he reactions or molecules. “They all wore is highly elegant and aesthetic, almost wanted to do! “Without asking any- shorts and T-shirts, were addressed sim- a work of art.” Chemists call this proce- body, of course, let alone my disserta- ply as ‘Bill’ or ‘Nic’ – it was California, dure total synthesis. Reproducing nat- tion supervisor.” Ben List was used to after all! The activation threshold to get ural products in this way was absolute- making his decisions alone – this is into conversation was extremely low.” ly en vogue in the 1990s – but total where his anti-authoritarian education There was hardly any need for media- synthesis was never really practical. made itself felt. “I’ve also used it with tors – in contrast to the situation with There were always by-products, which my kids from time to time,” he adds, many molecules that are set up to react meant complex separation processes grinning. “You may only be 12, but if with each other. They need catalysts to and a lot of waste, says List today. you think it will do you good to eat ten lower the energy threshold that inhib- Wouldn’t it be better to selectively chocolate bars, then go ahead and do its them from coming into contact. control reactions with the aid of cata- it. I have faith in you. But my advice is: Biocatalysts in particular – that is, lysts – that is, in such a way that only I wouldn’t do it.” enzymes – rapidly accelerate specific re- the desired product is produced? Just actions, some by a factor of 1018! A cat- like enzymes often do in nature? That FROM 1999: THE EXPEDITION alytic antibody for the aldolase enzyme, would be truly elegant! At the end of INTO HIS OWN RESEARCH FIELD which “turbocharged” the process in the the 1980s, research into abzymes – an- Erlenmeyer flask by no less than a fac- tibodies that express catalytic activity, No advice, however well meant, would tor of 108, had just been discovered at like those formed by the immune sys- likely have put him off going to the the Scripps Institute. Ben List was now tem – was a hot-button topic. At the Scripps Research Institute. He managed able to go for it. “It was a euphoric time. Scripps Research Institute in La Jolla it with a fellowship from the Alexander I published 17 papers in renowned jour- (southern California), Richard Lerner von Humboldt Foundation. How cool! nals in less than two years.” tried to use abzymes to selectively cat- This is where researchers such as K.C. After a year, his girlfriend moved alyze just about any catalyzable reac- Nicolaou and Barry Sharpless were work- over from Germany. They had a very ro-

Photo: Catarina Pietschmann Photo: David Ausserhofer tion. List had read about it: sounded ing – names well known from chemical mantic wedding on the beach. At almost

1 | 17 MaxPlanckResearch 59 Would also look good in an art gallery: The chemists in Mülheim use the test tubes to investigate the products of chemical reactions. the same time, Richard Lerner offered going though List’s mind. Hadn’t he The next day, the reactants had reacted him a position as assistant professor at heard something about that at univer- completely, and 72 percent of the mix- the Scripps Institute. At the beginning sity? In a reaction that was later given ture had become one of two possible de- of 1999, Ben List set off on the expedi- the unwieldy name Hajos-Parrish-Ed- sired products. “Shortly afterward, we tion into his own research field with er-Sauer-Wiechert reaction, the amino achieved an enantiomeric excess of two members of staff. acid proline had been successfully used nearly 100 percent with a similar reac- “I wanted to design small organic as a catalyst – a bizarre thing to do at tion!” Enantiomers are the two versions molecules that act as catalysts.” That the time. But what if proline now of substances whose molecules have the was unknown territory. Nobody before worked with a mechanism similar to same structure, apart from the fact that him had pursued this concept. The con- that of an enzyme? And what if it cat- one enantiomer is the mirror image of ventional catalysts tried and tested in alyzed other reactions as well? the other. The two versions are chemi- industry were usually, and still are, cally so similar that it’s difficult to syn- mostly based on transition metals, such “YOU THINK: MAYBE THIS WAS thesize only one of them. Biologically, as palladium, nickel and titanium. They A CRAZY IDEA” the enantiomers usually behave differ- are expensive, often toxic, and have to ently: one of them can have a pharma- be separated off again in a complex pro- List took a glass flask, added a little pro- ceutical effect, the other possibly no ef- cess. Enzymes do it so much more gen- line and two reactants, and left it to be fect at all or even a harmful one. tly, with simple organic groups such as stirred overnight at room temperature. It is therefore hardly surprising that carboxylic acids, amines and alcohols. It was his first independent experi- the paper that was published in the “But the organic chemists put hardly ment. “I was very uncertain. You don’t Journal of the American Chemical So- any faith in their own molecules.” think: Ha! I designed this! And now I’ll ciety in 2000 both puzzled and fasci- What was known of the enzyme become world famous! No, it’s more a nated the scientific community and has whose antibody analog Ben List now case of: Hmm ... maybe this was an ex- since been cited 2,200 times. An organ- knows by heart was that an amino tremely crazy idea. Other people have ic catalyst! A cheap, edible molecule group and an acid radical were located probably tried this already and also that exists in the human body and isn’t

at the active center. Amino ... acid!, was know why it doesn’t work.” only catalytically active, but is even Photo: Frank Vinken

60 MaxPlanckResearch 1 | 17 MATERIALS & TECHNOLOGY_Personal Portrait

An organic catalyst! An inexpensive, edible molecule that exists in the human body – » and is even more selective than any other catalyst before? Amazing!

more selective than any other catalyst thought, and quickly forgot it again.” before it? How could that be? Amazing! It was December 26, 2004. After break- Three months later, a paper by David fast, they went to the pool one last MacMillan was published: he had dis- time. Theo and Paul, his three- and covered a similar reaction almost simul- five-year-old boys, are splashing about taneously in Berkeley. The doubters in the water; Ben List is reading on a now believed it, too. chaise longue when he hears a noise Then the avalanche started. “At that gets louder and louder. He looks first it was only a few, then later hun- toward the beach, and now he hears dreds of groups in the US, Japan, Chi- the shouts. Run! Run! RUN!! “I looked na and Europe were now catalyzing at my wife, we each grabbed one child their reactions with proline or similar and started to run.” organic catalysts and publishing their findings. Everyone wanted to be part THE GRAY SLUDGE SWEEPS of the trend. It was completely crazy,” BEN LIST ALONG WITH IT List remembers. He himself was in an uncertain situation: he now had a fam- The pool hut behind which he seeks ily, only a tiny team and still no ten- cover is made of wood – a piece of cake ure. But then finally he obtained a for the huge tsunami wave. The dirty, large grant from the National Institutes gray sludge rises rapidly, sloshes over of Health (NIH). the roof and takes the hut and Ben List In 2002, Alois Fürstner, Director of with it. Debris rains down on him. the Organometallic Chemistry Depart- “Paul, who had been in my arms only ment at the Max Planck Institute in a second ago, was suddenly gone.” Ben Mülheim, visited List in his office. List is pushed underwater, briefly sur- Fürstner had given a talk at Scripps and faces again and is then pulled down- was surprised. “What? You are Ger- ward for a long, long time. That’s it man? You have to come back to Ger- then ... what a pity ... a little early, is many! To us!” One week later, List flew what is going through his mind. “There Top Chemists use thin-layer chromatography to Mülheim. He was offered a perma- was no panic, more astonishment.” But to separate the different products formed in nent position, with the prospect of a he comes to the surface again, starts to reactions. To this end, they add a solvent to the substance mixture on one side of the chro- post as director – and he accepted. By fight and saves himself by climbing matography plate. When the solution creeps summer 2004, the director’s post was onto a tree. List has a number of cuts across the plate, the different products deposit already within his reach. Before he as- and a large wound on his foot. It had at different locations. The violet color makes sumes the post, List takes his wife and been an extremely narrow escape even it easier for the researchers to recognize the two sons for a vacation in the sun over for him – Paul couldn’t possibly have individual substances. Christmas – to the beaches of Khao survived it. He asks around: someone Bottom Unlike other reaction accelerators, Lak, Thailand. The trip would become had seen his wife, with a child. Thank the amino acid proline also catalyzes chemical a life-changing experience. God, she had obviously saved Theo. reactions of the small acetaldehyde molecule, On the last day of their vacation – When Ben List finally finds them, it is which is shown here. their suitcases were already packed – Paul who is with her. they were woken by a tremor. “Proba- “He was very pale, with injuries to his

Photo: Frank Vinken Photo: David Ausserhofer; graphic: MPI für Kohlenforschung bly one of the small earth tremors, we rib cage. I’m OK, dad, he whispered.” >

1 | 17 MaxPlanckResearch 61 MATERIALS & TECHNOLOGY_Personal Portrait

When you survive something like that, your values change. » You are alive, healthy, and you have your family. That’s all that matters.

Six months after the tsunami, Ben List Materials coated with catalysts aren’t becomes a Max Planck Director. only of interest for the production of Lying on his desk today are mole- chemicals. “Conceivable ideas include cules of catalysts, models from the 3-D covers for furniture, curtains or carpets printer. Compared with the newest that clean themselves when you put catalysts from List’s lab, proline looks water on them.” After all, detergents like David next to Goliath. “Since rel- also contain catalysts to break down atively large amounts of proline are dirt – just that these disappear in large needed, we searched for more effective amounts in the waste water and pose molecules.” With the most recent can- problems for water treatment plants. didate, a tree-like branched phosphor- “The only question is what the deter- ic acid ester, one forty-thousandth of gent manufacturers will think of our the amount of proline needed is al- idea,” says Ben List, laughing. ready sufficient. And this catalyst ac- celerates reactions that couldn’t be cat- LIST IS A CHEERFUL, A particularly nice prize: Ben List’s uncle alluded alyzed at all before! OPEN PERSON to the Leibniz Prize the chemist was awarded in Organic catalysts have since become 2016 with a framed Leibniz cookie. state of the art. There is hardly a phar- Now he is thinking about catalytic maceutical or chemical company that drugs: monoclonal antibodies armed doesn’t work with them. The technical with a catalyst that bond to cancer cells But no trace of Theo. A truck brings production of several drugs, including and convert a non-toxic active sub- them and other injured people 150 ki- the HIV drug Darunavir®, involves or- stance into a toxic drug only when it ac- lometers inland to a medical center. ganic catalysts such as proline. tually arrives at the tumor. “Selective or- While Paul is being treated, Ben List This is almost history as far as Ben ganocatalysis is interesting for other traipses nervously through the rooms. List is concerned. Working together areas as well, for instance in the produc- At the very back, a small young boy is with the textile research institute in tion of fragrances or in pest control.” sitting on a bed – it is Theo. An English- Krefeld, he has since chemically bond- Unlike his doctoral supervisor, who man had found him and brought him ed more advanced catalysts to nylon really belittled those in his seminars here. He has only a few small bruises. fabric with the aid of UV light. A hetero- who struggled with chemical brainteas- geneous catalyst is thus formed from a ers, sometimes in front of everyone (as ORGANIC CATALYSTS ARE homogeneous one that, like the reaction the author remembers), Ben List is con- STATE OF THE ART partners, for example, is dissolved in a sidered to be more of a soft boss. He has liquid. This has enormous advantages found his own form of “postmortem.” Unbelievable, they had all survived. for use in chemical production, because “I call it the shit sandwich,” he says with “The time afterward was pure euphoria. unlike homogeneous catalysts, hetero- a smile. “Excellent talk! Well done. The When you survive something like that, geneous ones don’t have to be separat- less pleasant (middle) part follows in pri- your values change,” says List. “You are ed from the reaction medium. “We put vate: This and that could be better. And alive, healthy, and you have your fam- a piece of cloth into the glass beaker, add that was rubbish! Finally, the encourag- ily. That’s all that matters.” As time the liquid reagent and stir. We then de- ing base: But I believe you have talent, passed, normality returned. The trauma cant it, quickly rinse the cloth and can and we can do this together!” was gone, but so was the euphoria. then reuse it.” And we can do this at List is a cheerful, open person – “What has remained until this day is least 400 times, as a very patient doctor- completely at ease and always atten-

my gratitude for everything I have.” al student incidentally discovered. tive. His calm, positive air is conducive Photo: David Ausserhofer

62 MaxPlanckResearch 1 | 17 When you survive something like that, your values change. You are alive, healthy, and you have your family. That’s all that matters.

Relaxed thanks to a borderline experience: After Ben List and his family survived the 2004 tsunami in Thailand, the researcher knows that his career and his award are nice, but he could also live without them.

to a creative working atmosphere. “In love of Asia – but also a reminder of cookie with best wishes from his uncle my experience, creativity never ema- how fragile life is. Looking back, List – that’s fantastic. But life would be pos- nates from concentration and stress. sees the borderline experience as some- sible without all this. Maybe it is this Your thoughts can only flow when you thing positive, because it made him re- insight that gives Ben List the inner are relaxed.” And he has physically cre- alize what really counts. His career, all freedom to steadfastly go his own way. ated this space for himself as well – by the awards on the wall behind his desk After all, what’s the worst thing that moving the department up to the – one of the nicest is a framed Leibniz could happen? tenth floor of the Institute. Through a

long wall of windows, there is a com- manding view of the countryside. On the left, the industrial plants of Duis- GLOSSARY burg, some of which are already muse- Abzyme: The neologism coined from “antibody” and “enzyme” designates an antibody um pieces; in the middle, a lot of for- that has a catalytic effect. est around Mülheim and Oberhausen; Enantiomers always occur in pairs. Chemically, both variants have an almost identical and on the very right, the outskirts of structure but they differ in the spatial arrangement of their molecular parts, like an origi- Essen and in the distance Düsseldorf. nal and its mirror image, or the right and left hand that can’t be made fully congruent. When List walks into his office in the They behave in largely the same way physically and chemically; it is only with other enan- tiomers that they react differently. Most biomolecules, such as amino acids and sugars, morning, he has already done his yoga exist only in the form of one enantiomer, which is why enantiomers have different physi- exercises. He grins. “Standing on your ological effects. head gives you a different perspective Organocatalysis describes the selective catalysis with relatively small, purely organic on a lot of things.” molecules in which a metal isn’t part of the active principle. Until their catalytic effect A small Buddha figurine stands next was discovered, conventional wisdom held that only enzymes and metal catalysts were to the group of chairs, a present from suitable for selective catalysis.

Photo: David Ausserhofer Photo: David Ausserhofer his wife. It is a symbol of their shared

1 | 17 MaxPlanckResearch 63 Algae, like most higher plants, use the enzyme RuBisCO to fix carbon dioxide. RuBisCO is the most commonly used biocatalyst for this purpose, but it isn’t the most efficient. Scientists are there- fore experimenting with other enzymes and metabolic processes to more efficiently convert carbon dioxide into organic molecules. ENVIRONMENT & CLIMATE_Artificial Photosynthesis

Metabolism 2.0

Over 50 million genes and 40,000 proteins: combing through international databases for likely candidates, Tobias Erb and his colleagues at the Max Planck Institute for Terrestrial Microbiology in Marburg were faced with an overwhelming choice. In the end, the scientists picked out just 17 enzymes for the first synthetic metabolic pathway that is able to convert carbon dioxide into other organic molecules. Now they have to show that the cycle they sketched out on the drawing board also works in living cells.

TEXT KLAUS WILHELM

t sounds almost too good to be always been interested in how micro- Calvin cycle, which is described in ev- true: a means of counteracting the scopic life forms, such as bacteria, do ery biology textbook along with all the greenhouse effect, removing ex- things that chemists can still only enzymes involved. The Calvin cycle is cess carbon dioxide from the at- dream about,” he says. Erb spent the essential for life on Earth, as plants use mosphere and turning it into en- first years of his research career study- it to produce vital organic molecules, vironmentallyI friendly products. Car- ing bacterial enzymes – protein biocat- such as sugars, for other life forms. bon dioxide levels have risen by around alysts that initiate, accelerate or halt For a long time, the Calvin cycle 30 percent during the past 100 years, chemical reactions. was believed to be the only pathway for contributing greatly to global warming. carbon dioxide fixation. “But we’ve A method that removes excess carbon ALTERNATIVE TO RUBISCO since discovered a good half dozen dioxide from the atmosphere while also more,” Erb explains. “More than a third serving practical purposes would thus In his doctoral thesis, Tobias Erb turned of the carbon dioxide on this planet is be extremely welcome. his attention to the carbon cycle, the bound by microorganisms.” Nature has Nevertheless, Tobias Erb’s primary process by which atmospheric carbon thus devised various solutions to the aim isn’t the fight against climate dioxide is converted into various sugar same problem. They all work, but none change. The researcher first wants to compounds. In a purple bacterium, he is perfect. understand how gaseous carbon diox- discovered an enzyme with the un- One example is the carbon-diox- ide can be converted into organic mol- wieldy name crotonyl-CoA carboxy- ide-fixing enzyme in the Calvin cycle ecules. “Of course, if we could exploit lase/reductase (CCR). This introduces called RuBisCO. Erb describes it as “the the greenhouse gas as a carbon source carbon dioxide molecules into the bac- most underestimated enzyme on our using biological methods and remove terium’s metabolism. planet because it’s the most common.” it from the atmosphere in the process, Besides bacteria, plants are the main For every person on Earth, there are that would be a great side benefit,” says users of this process, known as carbon around five kilograms of RuBisCO in the Max Planck researcher. dioxide fixation. During photosynthe- the biosphere. The enzyme is able to Erb studied biology and chemistry, sis, plants harness sunlight as an ener- produce a pinch of sugar from the car- and even at an early age was fascinat- gy source to produce sugar from atmo- bon dioxide contained in the volume ed by the question of what makes life spheric carbon dioxide. To do this, they of a normal living room. Nevertheless,

Photo: MPI for Terrestrial Microbiology tick down to the smallest scale. “I’ve use a metabolic pathway known as the RuBisCO works relatively slowly and

1 | 17 MaxPlanckResearch 65 Malic acid Pyruvic acid Glyceric acid ...

Glyoxylic acid

rather sloppily: in a fifth of reactions, Other scientists have also set their ican scientist has already synthesized the enzyme erroneously grabs an oxy- sights on this goal. “Like the analytical the minimum genome of a bacterium gen instead of a carbon dioxide mole- chemists in the 18th century, we biol- in the lab and placed it in an empty, cule. Plants can afford such a cavalier ogists have tried to break down com- DNA-free bacterial shell. approach to energy efficiency, as they plex natural processes into individual In Germany, a project initiated in usually have sufficient light and there- building blocks in order to understand 2014 by the Max Planck Society and fore energy available. them,” says Erb. “But we will truly un- the German Federal Ministry of Educa- The CCR enzyme Erb discovered, in derstand how biological processes work tion and Research aims to promote contrast, acts as though it were turbo- only when we’ve reconstructed them synthetic biology. Groups from nine charged: it is 20 times faster than plant from basic building blocks.” Max Planck Institutes and the Univer- RuBisCO and fixes carbon dioxide two sity of Erlangen-Nuremberg are partic- to three times more efficiently – not LIFE FROM A PETRI DISH ipating. Unlike many other synthetic least of all because this enzyme practi- biology projects, this one aims to con- cally never makes an error. “CCR cata- Biology entered a new era – a phase of struct a minimum cell from individu- lyzes the most efficient carbon-diox- creation and construction – when it al components. ide-fixing reaction we know of,” the became possible to sequence the ge- Through this bottom-up approach, biologist says. It is essential for many nome of any desired organism and to artificial cells with specially designed bacteria because they often have less create artificial versions of genes. The metabolic pathways might one day be energy available. magic words: synthetic biology. Scien- created that produce drugs, vaccines or

Erb and his colleagues don’t just tists working in this field want to cre- biofuelsGraphic: MPI for Terrestrial Microbiology from carbon dioxide in the at- want to find out how CCR works and ate cells that they can reprogram to mosphere. what accounts for its amazing abilities; carry out new functions. One of the pi- Back to the laboratory of Erb and they also want to use the enzyme to oneers in the field is Craig Venter. His his team: Thomas Schwander opens mimic the carbon cycle in the lab and approach is to strip living cells of all the freezer and collects a wide assort- harness its abilities. “The challenge for components that aren’t absolutely es- ment of small vessels, each about half us biologists today is to replicate life sential for survival, thus creating a the size of a memory stick. They con- processes from the inanimate,” the re- minimalist cell that can then be en- tain a scientific breakthrough: the sub-

searcher explains. dowed with new properties. The Amer- stances and enzymes that together Graphic: MPI for Terrestrial Microbiology

66 MaxPlanckResearch 1 | 17 ENVIRONMENT & CLIMATE_Artificial Photosynthesis

Left page A specific enzyme is responsible for every reaction in the CETCH cycle. Crotonyl-CoA carboxylase/reductase (CCR), for example, facilitates the two carbon- dioxide-fixing reactions. This page, top Together with Tobias Erb, Nina Cortina is investigating the CETCH cycle. The Philippine scientist is an expert in mass spectrometry. In the foreground is a photospectrometer for carrying out measurements on enzymes. This page, bottom The researchers use such mass spectrometry instruments to analyze the reaction products of the CETCH cycle.

form a completely new metabolic pathway for carbon dioxide fixation. In 2011, Tobias Erb – then at ETH Zurich − outlined the cycle, called CETCH, complete with all the relevant biochemical reactions, in just two weeks. In addition to drawing on his knowledge of carbon dioxide metabo- lism, he consulted international data- bases listing more than 50 million genes and more than 40,000 enzymes and their respective functions. From those, Erb selected several dozen candidates that, together with the turbocharged CCR enzyme, could perform the desired functions in his artificial cycle: “After studying the nat- ural process of carbon dioxide fixation for so long, I was convinced that our designer pathway could also be real- ized in practice.” Even before moving from Zurich to the Max Planck Institute for Terrestrial Microbiology in Marburg, Erb set up a team “without hierarchies and with tal- ented researchers who want to push sci- entific boundaries.” Applying passion Graphic: MPI for Terrestrial Microbiology Photos: Thomas Hartmann (2) and consummate expertise, they trans-

1 | 17 MaxPlanckResearch 67 CF

1

2

3

4

Left The active center of the CCR enzyme (pink lines and bands; CF: cofactor NADPH): The position of the egg-shaped carbon dioxide molecule in the center was modeled on a computer. The amino acids im- portant for positioning the carbon dioxide molecule are shown en- larged: histidine (1), asparagine (2), phenylalanine (3) and glutamate (4). Right Erb first designed the CETCH cycle on the computer and later tested it with his team in the lab. The result: the first artificial carbon-fixing metabolic pathway.

lated their model from the drawing the other enzymes. Tobias Erb suspects materials for biodiesel or other organ- board into reality in a record time of that such corrective loops may also ic substances instead. just two years. play an important role in natural met- Carbon dioxide fixation requires The scientists tested the functional- abolic pathways. energy. The CETCH cycle is driven by ity of new enzyme candidates, modified Despite all the difficulties, the re- chemical energy or, more specifically, them and tried out new combinations searchers ultimately succeeded in cob- by electrons. The Calvin cycle of pho- until they worked optimally together. bling together the first man-made met- tosynthesis works with solar energy, “Despite all the laboratory technology, abolic pathway for carbon dioxide which is then converted into chemical this still involved a lot of manual work,” fixation. It involves 17 enzymes from energy. The researchers were therefore says Thomas Schwander. “Time and nine different organisms and includes able to compare the two processes to again we had to overcome new hurdles.” three designer enzymes that the scien- determine which is more efficient. For a long time the researchers were un- tists modified from existing enzymes Whereas the CETCH cycle consumes able to get the cycle going because one with the help of a computer so that only 24 to 28 light quanta to bind a car- of the enzymes only worked with an they work more precisely or catalyze bon dioxide molecule, natural photo- iron compound, which, however, other reactions. synthesis takes 34. “So we could fix caused the other proteins to flocculate. about 20 percent more carbon dioxide The enzyme therefore first had to be RAW MATERIALS ON TAP with the same amount of light energy,” modified so that it could work with the Erb points out. more suitable substrate oxygen. The enzymes are therefore natural in And that’s not even the upper lim- Another difficulty lay in that fact origin, but their combination to form it. Erb’s team is already working on de- that the cycle was initially plagued by a novel, highly efficient metabolic veloping even thriftier carbon dioxide numerous unwanted side reactions. As pathway doesn’t occur in nature. “Pre- cycles. In the future, these synthetic a result, it was slow and tended to grind sumably, the enzymes never had the fixation cycles might be coupled with to a halt quickly. It was only when the chance to come together in nature in solar cells. The electrons the solar cells scientists added other enzymes to the the course of evolution,” Schwander produce from sunlight could be used to original design that they were able to says. Erb’s carbon dioxide cycle culmi- convert carbon dioxide into other com- eliminate the unwanted reactions. nates in the formation of a compound pounds. Such visions no longer appear These additional enzymes acted as re- called glyoxylic acid. However, the cy- technically unfeasible. For example, re-

cycling forces to correct the errors of cle could be modified to produce raw searchers in the MaxSynBio network Graphic: MPI for Terrestrial Microbiology

68 MaxPlanckResearch 1 | 17

are working intensively on processes at the interface between chemistry, mate- TO THE POINT

rials science and biology. l The carbon-dioxide-fixing plant enzyme RuBisCO works slowly and frequently In the context of synthetic biology, makes errors. By comparison, the bacterial enzyme crotonyl-CoA carboxylase/ the CETCH cycle could also help to im- reductase (CCR) is around 20 times faster and more accurate. prove natural photosynthesis. Howev- l Together with 16 other enzymes, the CCR enzyme can be added to a test tube er, the genes for the enzymes involved to produce the CETCH metabolic pathway. The artificial cycle converts carbon in the CETCH cycle would first have to dioxide more efficiently than the Calvin cycle used by plants. be inserted into a living cell – a bacte- l Bacteria and plants could one day use the CETCH cycle to fix excess atmospheric carbon dioxide and convert it to useful organic substances. rium, an alga or a plant – which would then synthesize the desired product. In the next step, the Marburg-based scientists want to engineer bacteria to GLOSSARY use the CETCH genes as intended. “We Calvin cycle: A metabolic pathway in plants in which atmospheric carbon dioxide is can’t predict how our cycle of 17 reac- converted into sugar molecules. The cycle uses ATP as an energy source. The enzyme tions will behave in a cell in which RuBisCO makes it possible to convert carbon dioxide to the sugar ribulose-1,5-bisphos- 3,000 reactions of all kinds are taking phate (carbon dioxide fixation). The cycle must run three times, fixing three carbon place. We still have a few more years of dioxide molecules to produce one molecule of the sugar. The chemical energy required work ahead of us,” says Erb. for the Calvin cycle is obtained from the light reaction of photosynthesis. The biomodule of the CETCH cycle Synthetic biology: A young research field whose aim is to develop biological systems may eventually end up in Craig Ven- that don’t occur in nature. A first step is the construction of the simplest possible cell whose genome contains only information that is absolutely essential for the cell’s ter’s minimalist cell – or even better, in survival. There are two opposing approaches: some researchers try to reduce the com- an artificial cell to be created by the plexity of existing cells to the bare minimum (top-down approach), while others aim MaxSynBio network. In any case, it will to identify the building blocks that are absolutely vital for the cell’s survival and use still take some time for Erb’s dream of them to construct new cells (bottom-up approach). The objective is to simplify exist- ing biotechnological processes, but completely new products such as vaccines, medi- “creating an artificial metabolism 2.0 cines, diagnostic aids, biofuels and tailor-made materials could also be designed with that is able to produce any desired or- the help of synthetic biology. ganic compound from carbon dioxide” Graphic: MPI for Terrestrial Microbiology Photo: Thomas Hartmann to become a reality.

1 | 17 MaxPlanckResearch 69 R u l i n g by the Book and the Cross

The Spanish Conquistadors found it surprisingly easy to conquer the New World. However, it required more than violence and cruelty to rule the territory. A team of researchers headed by Thomas Duve at the Max Planck Institute for European Legal History is investigating the media through which the Spanish crown consoli- dated its dominion. Meanwhile, an international research group led by Carolin Behrmann at the Max Planck Institute for Art History in Florence is studying the importance of images in the consolidation and legi- ti­mation of law with a focus on Early Modern European history.

Handy and practical: Handbooks such as this prayer book helped priests and friars bring Christianity to the New World and, at the same time, establish the new system of law. KULTUR &CULTURE GESELLSCHAFT & SOCIETY_Rechtsgeschichte_Legal History

R u l i n g by the Book and the Cross

TEXT MICHAELA HUTTERER

he year is 1552, and Portu- guese printer João de Barrei- ra is lifting the leaves of a book from his printing press in Coimbra. One thousand pagesT in easily handled octavo, which he will later bind in modest goatskin. The first page proclaims it to be a “Man- ual de Confessores y Penitentes.” The author of this Manual for Confessors and Penitents was Martín de Azpilcue- ta, one of the leading canon lawyers and moral theologians of the age. Azpil- cueta, or Dr. Navarro, as he is known on account of his origins, was a man of clarity and learning, an adherent of late scholasticism, member of the highly re- spected school of Salamanca and a rec- ognized authority throughout Europe. Over 50 of his works are concerned with Catholic canon law, moral theology, criminal law and economic theories – large-format books for academic use. What moved this professor of can- on law to disseminate his knowledge for practical use, and in paperback for- mat at that? Could he have had any idea that this very work would become one of the most important sources of advice on day-to-day legal matters – in Spain and across the Atlantic, in the New World?

BESTSELLER IN THE NEW WORLD

“Few if any books in the second half of the 16th century were printed, translat- ed and compilated more often than Az- pilcueta’s handbook for confessors,” says Thomas Duve, Director at the Max Planck Institute for European Legal His-

Photo: Linga-Bibliothek, Hamburg/Otto Danwerth tory in Frankfurt. “And few, if any, were more widely disseminated in the New

1 | 17 MaxPlanckResearch 71 CULTURE & SOCIETY_Legal History

The clerics in the New World were skilled at integrating indigenous » beliefs and contexts into the Catholic faith.

says Duve, explaining his research ap- proach. He is reconstructing the means by which a new normative order was able to develop. The team is interested not just in the sophisticated literature of law, but also in works to which lit- tle value has generally been attached in traditional legal history research. Works that become accessible as im- portant sources only with the aid of import documents, inventories of book owners and library lists. These re- cords date from the time shortly after the eminently infamous conquistadors Hernán Cortés and Francisco Pizarro had overthrown the empires of the Az- tecs and Incas. The former centers of power were destroyed and Spanish cit- ies and settlements built upon their ru- ined walls. In 1573, King Philip II of Spain issued what amounted to an ur- banization program entitled “Orde- nanzas de descubrimiento, nueva po- blación y pacificación de las Indias”. David Rex Galindo, Otto Danwerth, Manuela Bragagnolo and project leader Thomas Duve By this time there were already 250 (from left) are investigating the role of simple clerics in consolidating Spanish dominion in Central and South America. towns and cities in existence. It was the rural areas that presented difficul- ties. How did a common code of con- World.” In other words, it was a best- the New World monasteries and offic- duct, adhered to by both settlers and seller. Duve’s team, comprising Manu- es of the 16th and 17th centuries, the indigenous people, come to be estab- ela Bragagnolo, Otto Danwerth and Da- few official legislative texts were far lished in border areas, where there vid Rex Galindo, have so far found outnumbered by summaries, commen- were few, if any, official guardians of more than 80 editions in archives and taries, breviaries and so-called epito- law and order? libraries in South and Central America mes: excerpts from important works of “The Church was of decisive impor- and in Europe. Working in cooperation moral theology and canon law were of- tance,” explains legal historian Thom- with a collaborative research center in ten compressed into tabular form. as Duve. It provided support for admin- Frankfurt, the scientists are focused on For Thomas Duve’s group, these istrators and founded monasteries, the issue of how, after the conquest, the “pragmatic” texts and the approaches churches and schools. Between 1511 Spanish crown managed to instruct its of the pragmatici, or semi-scholars, and 1620, more than 30 dioceses were overseas subjects to adhere to Europe- that were based on them are particu- established. Without this support, the an norms. How did they impose the law larly exciting. “As legal historians, we colonization process based on violence in their area of occupation? Which le- are keen to understand how a relative- and force of law could not have sur- gal sources and which media were ma- ly small group of invaders was able to vived. The number of clerics who jour- terial in implementing codes of con- dominate broad areas with highly de- neyed to America in the 16th century, duct in this way? veloped populations – quite apart some 5,400, far exceeded the total of Investigations into the production, from how we would view such activi- royal administrators. ownership and circulation of books ties from today’s perspective. To do It was Franciscans, Dominicans and show that scribes, officials, priests and this, we must consider all kinds of ev- Jesuits who studied the regions and bishops preferred to consult slim com- idence that can give us insights into their people, learned the indigenous

pendia rather than wordy volumes. In day-to-day life and its legal problems,” languages and thereby established the Photo: Michaela Hutterer

72 MaxPlanckResearch 1 | 17 beliefs and contexts into the Catholic faith.Catholic the into contexts and beliefs integratingindigenousatskilled were World New the in clerics The

Photo: Michaela Hutterer

Photo: MPI for European Legal History/Otto Danwerth can befoundinthemanual. marital, familyandinheritance law of taxationandusury. Alsoaspectsof steal,” Azpilcuetadiscusses questions 7th Commandment,“Thou shaltnot sonable prices.Inhischapter onthe ing varioustypesofcontractandrea- such awork.”Therearenormscover- topics thatonewouldnotexpectin detailed analysis: “It includesmany literature, OttoDanwerthhasmadea popular. Everinsearch ofpragmatic little handbookforconfessionwasso mative sources. and quicklybroughtforthpropernor- World values,andthatrefinedthem Catholic Christian values and Old in theNewWorld thatwasbasedon Duve. Inthisway, asphereoflawarose the constitutionofsphereslaw,” says and theassociatednormativeorder of thestructurescolonialdominance tributed decisivelytotheestablishment theological provenancewillhavecon- that this type of normative literature of booklets andmanuals.“We suppose vincial councils,butalsothroughtheir Clerics madethelaw – not just inpro- FINANCIAL TRANSACTIONS RULES FORPRICINGAND sick,” explainsDuve. widows, orphans,thepoorand their protectioninthesamewayas digenous population, who came under tives claimedjurisdictionoverthein- ages,churchmiddle representa- the of “Citing thenormsofpapalchurch to dispensejusticeonworldlymatters. der certaincircumstances, permitted Spanish crown,thebishopswere,un- ant pieceoflegislationissuedbythe the “SietePartidas,” most import- on king. Accordingtoacommentary name oftheLordandonbehalf sic principles of coexistence – in the of conduct.Theytransmittedtheba- Catholic faithwithitsvaluesandrules This mayexplainwhyAzpilcueta’s to explain complex legal contexts in a Azpilcueta’s strengthliesinhisability Mexico andPotosíinUpper Peru,” important silverminesinZacatecas in of such asemergedafterthediscovery cial transactionsintheNew World – problems ofeconomiclife and finan- terms, heoffered solutions to the acute structured andinunderstandable simple, true-to-lifemanner. “Clearly Bestseller: The Manual for Confessors and Penitents written by Martín de Azpilcueta, Azpilcueta, de influential an Martín by written Penitents and Confessors for Manual The Bestseller: of advice on day-to-day legal matters. legal day-to-day on advice of 16 th century expert on canon law, was one of the most important sources sources important most the of one was law, canon on expert century th missionary nephew.missionary his students, acquaintances andhis Spanish and Portuguese colonies from ca. Buthegatheredreports onthe cueta himselfneversetfoot inAmeri- a copyontheirshelves.Infact, Azpil- ple missionariestobishops soon kept scribes to senior officials and from sim- many colonialrepresentatives,from Danwerth explains.Nowonderthat 1 | MaxPlanckResearch 17MaxPlanckResearch

73 >

74 MaxPlanckResearch 1 MaxPlanckResearch | 17 He, too, wrote a handbook for confes- cate withtheindigenouspopulation. tocommuni- piled thefirstdictionary streets ofMexicoCity, notonlycom guage oftheAztecs,asachildon ple, whohadlearnedNahuatl,thelan- Franciscan AlonsodeMolina,forexam the indigenous“newChristians.”The mostly aimedatbringingthefaithto manuscripts appearedatthattime, sible texts. Manywritings, tracts and one whoknewhowtopencomprehen Azpilcueta, however, wasn’t theonly Institute for Art History in Florence. in History Art for Institute the of collection the from photographs of selection a inspect team, her on student PhD a Jäger, Felix and Behrmann Carolin Leader Group mann regardsimagesassociated with restricted totheearlymodernera.Behr the “Nomos of Images” project is not Frankfurt. However, thetimeframeof those posed by the legal historians in and addressesquestionssimilarto importance ofimage-basedtheology considersthe cism ofthe16thcentury withinSpanishlatescholasti theory Ages throughtothe21stcentury. ing andpracticefromthelateMiddle that helped make manifest legal reason- PhD students,sheinvestigatesimages gether with aninternational group of ifestation andIconologyofLaw.” To- search group“Nomosof Images. Man- artifacts,” explainstheheadofre- it alsorequiresobjects,symbolsand can’t becommunicatedin wordsalone, broader frame.“Thelawinitsentirety images inandforthelegalprocessa in Florenceanalyzestheimportanceof oftheMaxPlanckSociety Art History language faltered,imagesassisted. priests couldshowtotheIndians.Where cluded impressiveillustrationsthatthe – translationsintoNahuatl.Andhein- fered them – andthisis quite particular Spanish-speaking clerics,buthealsoof- sors. DeMolina,too,waswritingfor Carolin BehrmannoftheInstitutefor Her research intoimageandsymbol - - - - ­

Photo: Institute for Art History, Florence – Max Planck Institute/Micaela Mau CULTURE & SOCIETY_Legal History

From the Middle Ages, a visual language established itself to express norms » that the public could “read” – through allusion and allegory, without words.

legal meaning as “visual constitutions” that are gaining momentum today. She is interested in their use in the course of history through to the present day – not least in order to heighten the gen- eral awareness of their legal associa- tions: “There is a long tradition of using images to explain laws and prohibi- tions,” says the project leader. Beyond the confines of time and culture, her group is studying how mor- al and normative connotations have been communicated. Their interests range from classical works of art such as depictions of the Last Judgment dis- played in courtrooms to modest and less visible signs in the public sphere. For example, engravings on the walls of medieval houses often reflect the stan- dard dimensions of bricks or goods and thus pictorialize commercial law.

PUNISHMENT MUST BE VISIBLE

Equally important is the analysis of the places where justice is acted out: A warning to judges: The 1338 fresco by Ambrogio Lorenzetti in Siena’s Palazzo Pubblico “There is evidence of legal motifs in depicts Tyranny as the devil enthroned, surrounded by the vices avarice, arrogance and vanity. public buildings and courtrooms dat- ing back to the 13th century,” says Carolin Behrmann. Biblical themes and unjust dominion. Tyranny is rep- person in a manner for all to see, in were popular. “The image of Doubting resented as the devil enthroned, sur- an undignified posture, embarrassing Thomas who laid his finger in Jesus’ rounded by the vices avarice, arro- garments, disfiguring costume, with wounds was a popular motif in civil gance and vanity. On the other wall distorted facial features or bearing an courts,” explains the art historian, there are figurations of good gover- insulting message, are among the rep- pointing to the “Mercanzia,” the court nance with the virtues justice, courage, utation- and honor-based punishments of the five great Florentine guilds. The moderation and wisdom, in company imposed by pre-modern European crim- visual appeal to every judge acting in with peace and magnanimity. inal law,” explains Behrmann. that court was to come as close to the Another aspect of the Nomos proj- The forms and formats of humilia- truth as possible! Biblical kings served ect’s research is the advancement of tion varied widely from one era to an- as “exemplum iustitiae,” among them knowledge of the law: Which were the other: rings and chains still remain at- King Solomon, who appears in the evidentiary processes applied, and how tached to pillars and house fronts in courtroom of the Palazzo Comunale in were they supported by visual argu- busy squares as reminders of former Lucignano, Arezzo. ment? Behrmann touches on the broad pillories. Humiliation and deterrence But also the downside of legal judg- area of torture, the martyrdom of Chris- might also be enforced by the crude ment and power were depicted. The tian saints, and not least the historic im- iron mask of shame, or scold’s bridle, walls of the Palazzo Pubblico in Siena portance of the visibility of punishment and the coat of shame, a barrel-like confront images of ideal government that plays a significant role yet today. structure of wooden staves that the de- with the image of tyranny: the fres- Breaches of the law were often linquent was forced to wear. Although coes by Ambrogio Lorenzetti dating turned into a public spectacle. “Forms highly controversial, shaming sanc-

Photo: Institute for Art History, Florence – Max Planck Institute/Micaela Mau Photo: Institute for Art History, Florence – Max Planck from 1338 warn against bad judges of public humiliation that shamed a tions that depend on the public display

1 | 17 MaxPlanckResearch 75 CULTURE & SOCIETY_Legal History Erweitern Sie Ihren Horizont. Und zwar ins Unendliche.

ular. Splendor and opulence mattered, cessful PR by a bishop who sought to as an alternative to the richly bedecked replace the colorful, polytheistic beliefs Inca, Aztec and Mayan temples and cit- of the indigenous population with the ies. Visual imagery was harnessed in Virgin Mary? Either is possible. the form of detailed depictions of mar- Art and legal historians are agreed 2 | 2017

tyrdom and opulent images of the Vir- that a mission powered by the sword STERNE UND WELTRAUM sterne-und-weltraum.de gin Mary, which were soon to acquire alone wouldn’t have brought about a CHF a style of their own. permanent conversion to Christianity. In Sterne und Weltraum 14,80

Indigenous beliefs were skillfully “The Church at that time took on an (CH) erfahren Sie monatlich integrated, a particularly good exam- important role as intermediary and alles über Astronomie ple being the depictions of Mexico’s translator in the transatlantic clash of Saturn 8,50 EUR · & Raumfahrt!

national saint, the Virgin of Guada- civilizations,” explains Thomas Duve, (D/A/L) lupe. This image of Mary is not only adding: “The Spanish and indigenous Impressionen venerated in churches, but remains to elites didn’t live in isolation, they inter- aus dem Reich der Ringe this day ubiquitous in Mexican daily acted.” Franciscans and Jesuits studied life. According to legend, in December the indigenous peoples’ customs, tradi- 1531, Mary appeared to a Chichime- tions and concepts of law. And they can baptized under the name Juan Di- were skilled at what experts term “cul-

ego, asking that a church should be tural translation”: the ability to inte- built on the stones of a former Aztec grate indigenous beliefs and contexts Mexico’s national saint María de Guadalupe temple dedicated to the mother god- into the Catholic faith, not only in the features some important Aztec elements, such dess Tonantzin. The Bishop didn’t be- interests of education, but also to afford as the blue mantle worn by the former indigenous ruling class. The downcast sickle lieve him. Only when roses bloomed the necessary scope for reinterpretation. moon at her feet represents the vanquished in mid-winter and he recognized the In this way clerics and artists whose snake god Quetzalcoatl. image of Mary on Juan Diego’s coat did names are scarcely known today influ- Jetzt im Miniabo kennen he have the church built, unleashing a enced the reality of life in the New wave of conversions that culminated World at least to the same extent as the lernen und Prämie sichern: of the offender can still be found today, in mass, as well as forced, baptisms. famed conquerors. Their handbooks Drei aktuelle Ausgaben von a formal judicial sanction in criminal Did it really happen, or was it just suc- and art works still stand as evidence. Sterne und Weltraum für law (for instance in the US). nur € 16,50 statt € 25,50 im

In this way, the law established a vi- sual language that the public could Einzelkauf “read” – through allusion and allegory, TO THE POINT without words. Subject, composition l Catholic friars and priests played a major role in establishing Spanish dominion D 5496 and arrangement were no accident in in South and Central America. the 16th and 17th centuries, they were l In doing so, the clerics preferred condensed texts rather than the full official intentional. “In the early modern era versions of laws. we see a flood of laws passed and new GROSSTELESKOPE KOSMISCHE STRAHLUNG TWANNBERG FINSTERNISSE l The Spanish legal system was transmitted alongside the Christian faith, with codes of conduct derived from moral Die Laser-Tricks der Der Beschleuniger im Ein Meteoriten-Streufeld Schattenspiele von the Church skillfully integrating and reinterpreting indigenous traditions. Astronomen Zentrum der Milchstraße im Schweizer Jura Sonne und Mond theology, which again had to find a l Laws and prohibitions were also explained with the aid of imagery – in the New universally comprehensible form,” World as in Europe, using biblical scenes or symbolic depictions of vice and virtue. GRATIS says Behrmann. And just as a plethora of legal epitomes and compilations of major legal works emerged at this time, so too the works of art of the Baroque GLOSSARY provided a vivid clarity – in Europe and Allegory: The description of a subject in the guise of another subject. The portrayal the New World. of abstract characteristics in human form, such as the depiction of justice as a woman Churches and administrative build- with her eyes blindfolded and holding a balance in her hand. ings in the New World were designed Epitome or breviary: An extract or simplified précis of a more extensive work. on the principle of docere, delectare, Indigenous: Born in or native to a certain territory. The term is used, for example, in connection with peoples, languages and traditions. movere – they should teach, delight Jetzt bestellen: and move. Spanish painters travelled Conquistadors: The Spanish conquerors of Central and South America in the 16th to the colonies to decorate the blank and 17th centuries. Telefon: 06221 9126-743

walls of buildings both sacred and sec- Photo: Art Archive/FOTOFINDER.COM E-Mail: [email protected] www.sterne-und-weltraum.de/aktion/mpf416 76 MaxPlanckResearch 1 | 17 Photo: Art Archive/FOTOFINDER.COM Und zwar ins Unendliche. ins zwar Und Erweitern Sie Ihren Horizont.

STERNE UND WELTRAUM Astronomen Die Laser-Tricks der GROSSTELESKOPE Saturn aus demReich derRinge Impressionen Zentrum der Milchstraße Der Beschleuniger im KOSMISCHE STRAHLUNG im Schweizer Jura Ein Meteoriten-Streufeld TWANNBERG www.sterne-und-weltraum.de/aktion/mpf416 [email protected] E-Mail: Telefon: 06221 9126-743 Jetzt bestellen: Sonne und Mond Schattenspiele von FINSTERNISSE sterne-und-weltraum.de 2 | 2017 D 5496

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Flashback_Virus Research

A Foul Enemy in Fowl

Flu viruses are highly mutable − and thus able to swap hosts. Werner Schäfer at the Max Planck Institute for Virus Research in Tübingen suspected as early as the mid-1950s that bird flu can also pose a threat to humans. Decades later, his suspicions were confirmed.

TEXT ELKE MAIER

The birds began to die in the spring of Schäfer could well imagine a future as a 1997. Within the span of a few days, 7,000 researcher in Africa, but his plans were chickens on three poultry farms in Hong thwarted by the war. He was incarcerated Kong perished. A short while later, a and deported to Germany in 1940, where three-year-old boy who had been admit- he was drafted into the army as a veteri- ted to the hospital with flu symptoms nary officer. For a while he was based on died. Tests revealed that the same patho- the island of Riems, near Greifswald, to gen was the cause of death in both cases: work at the Reich Research Institute there a bird flu virus of the H5N1 type. After 18 in a program aimed at developing vaccines more people were infected, six of whom against influenza, rinderpest and bird flu. died, experts became alarmed. Was a new After the war, there were no immedi- flu pandemic imminent? ate prospects for a post as a virologist. The incident brought to mind images Without further ado, Werner Schäfer from 1918/1919, when the Spanish flu opened a veterinary practice in Usseln, claimed an estimated 50 million lives. To Hesse. Business flourished, and he had no ward off the danger, more than 1.2 million concerns about his family’s subsistence. chickens and hundreds of thousands of Nevertheless, he didn’t hesitate for a mo- other birds were slaughtered in Hong ment when Nobel laureate Adolf Buten- Kong’s poultry markets and on the sur- andt, then Director of the Kaiser Wilhelm Bird flu as a research field: Werner Schäfer rounding farms. In time, the scare passed Institute for Biochemistry in Tübingen, » dedicated much of his scientific career to − but the concerns remained. studying avian influenza. looked him up in the spring of 1948 and The Hong Kong outbreak is the first offered him a research post. After three documented case in which a bird flu virus not only infected hu- years as a rural veterinarian, the 36-year-old moved to Tübingen mans, but also killed them. However, fears had been circulating to head the Animal Virology Department. for quite a while that this could happen one day. Virologist Wer- The research team was initially housed in a ramshackle out- ner Schäfer at the Max Planck Institute for Virus Research in building of the Pharmacology Department. The annual budget Tübingen had already speculated about it in the 1950s. for equipment was a mere 10,000 marks. Despite this, Werner Schäfer was born in Wanne, Germany on March 9, 1912. He Schäfer was inordinately productive; he had learned how to im- originally wanted to become an architect and, after completing provise in Africa. His career soon took off. In 1954 he was elect- his secondary education, did an apprenticeship in carpentry. He ed a Scientific Member of the Max Planck Society. Two years lat- later changed his mind and studied veterinary medicine in Gies- er, he was appointed Director of the Biological and Medical sen. After earning his doctorate, he joined the Veterinary Hygiene Department of the newly created Max Planck Institute for Virus and Animal Infection Institute under Erich Traub, an expert in foot Research in Tübingen. and mouth disease. One of Schäfer’s main research interests was the virus respon- He then yielded to his thirst for adventure. In the summer of sible for avian influenza, now commonly known as bird flu. The 1939 – shortly after marrying – he headed for East Africa on a grant highly infectious pathogen affects birds in the wild as well as poul- from the German Research Council. In Tanzania, he set up a sim- try of all kinds. Infection leads to dyspnea, apathy, high fever and ple laboratory in a building on a German farm, where he began motor disorders. Infected animals usually die within a few days. to carry out research into animal diseases such as anthrax, black- The dreaded virus offered a number of advantages as a study leg, brucellosis and pseudorabies, which were threatening the object: It proved to be an excellent model for studying enveloped

country’s livestock. viruses. Moreover, public health policy forbade US competitors Photo: MPG

78 MaxPlanckResearch 1 | 17 RÜCKBLENDE_Lockstoffe

Epidemic source: Close contact between birds and humans favors the emergence of new influenza pathogens.

from working with the pathogen. The virus is easy to handle in the Today we know that avian viruses do, in fact, act as a natural gene laboratory and multiplies vigorously in incubated chicken eggs. pool from which new flu viruses can emerge that can potentially Heinz Schwarz, an electron microscopist who worked closely with infect humans. A tiny change to a protein building block is enough Werner Schäfer at the Institute, recalls: “Some of our colleagues pe- to enable the virus to evade the immune system and change its riodically drove in the Institute’s car, an Opel P4 dubbed Friedolin, host. The danger is especially acute in places where people and to a chicken farm in Tuttlingen to pick up pallets of eggs.” poultry live in close proximity, as in many Asian countries. Soon they were cultivating viruses at full speed. Schäfer’s aim Experts particularly fear the emergence of hybrid viruses: was to find out the functions of the various viral components and when a bird virus and a human virus come together in an infect- to determine the role they play in infections. To this end, he com- ed cell, they are able to exchange DNA segments to form a new bined electron microscopic structural analyses with physicochem- virus that spreads from human to human – a recipe for a pan- ical and immunological investigations and observed the course of demic. The Spanish flu may have been the result of such danger- the disease in experimental animals. ous liaisons. In the 1997 Hong Kong flu epidemic, the viruses “Schäfer was a true pioneer, since there was no DNA sequenc- made the leap from bird to human, but fortunately not from hu- ing at the time,” says Volker Moennig, veterinary professor at the man to human. University of Veterinary Medicine Hannover, Foundation who had Werner Schäfer presented his findings on viral kinship at a symposium in London in 1956. Luminaries including James Wat- Die Welt, November 5, 1991 son and Francis Crick, who had discovered the structure of DNA three years earlier, were in the audience. It proved to be an inter- It was Schäfer who surmised – correctly – that certain national breakthrough for Schäfer. There followed invitations bird viruses could act as an inexhaustible reservoir for the » from all over the world, and the “Tübingen Group” ranked among emergence of new influenza variants. the most pre-eminent virus researchers in the world. Werner Schäfer devoted 16 years of research to the avian flu earlier worked at the Institute in Tübingen. “The times were also virus. Thanks to his work, the pathogens have long ranked different with regard to handling the virus. Today, a laboratory among the best characterized of all animal viruses. Schäfer also safety rating of 3 would be mandatory.” laid the groundwork for the development of vaccines when he Despite the limited resources, Schäfer managed to character- discovered that a component of the viral envelope is sufficient ize the bird flu virus in detail. He noted an astonishing similarity to confer immunity in a host. This led to the development of to another pathogen – the causative agent of influenza A in hu- split-virus vaccines, which are still used today in some flu and mans. Under the electron microscope, both appeared to be stud- hepatitis B vaccines. ded with fine spikes, which Schäfer compared to the “detonators Schäfer finally closed the bird flu chapter of his career in the of a naval mine.” The viruses also shared many physicochemical early 1960s. At over 50, he switched to an entirely new research and immunological properties. For example, both pathogens were field: retroviruses, which were thought to play a role in the devel- able to infect mice, causing a pneumonia that proved fatal after a opment of cancer. In fact, oncogenes, which promote unbridled few days. The pathological changes in lung tissue caused by both cell growth, were discovered for the first time in the genomes of forms looked identical. Schäfer even managed to immunize mice retroviruses. Schäfer and his team investigated the role of the vi- against influenza A with the bird flu virus and vice versa. ruses in the development of leukemia and carried out successful The striking similarity of the two pathogens led Werner immunization experiments. Schäfer to a troubling conclusion: “It is conceivable that represen- In the 1980s, retroviruses made headlines when it was discov- tatives of this group occasionally change their host specificity so ered that they cause AIDS. By that time, Schäfer had already re- that a new type of influenza virus […] emerges,” he wrote in a sem- tired. The winner of many awards, he died in Tübingen on April 25,

Photo: MPG Photo: Yusuf Ahmad/Reuters inal work in 1955. He was to be proven right. 2000 at the age of 88.

1 | 17 MaxPlanckResearch 79 setting aminimumturnoutin elections the statusofrepresentatives at MPGby which bringdemocraticlegitimacy to garding thenewPhDnet statutes, over thelastthreeyears,particularly re cessors havedoneatremendous job up their program for 2017. “Our prede­ ties,” stated the new Board, summing communication andequalopportuni­ student community, such as improved strength totheMaxPlanckdoctoral to focusontopicsthatcanaddfurther team isliningupforanonlinemeet. new managingboardfor2017,soa conference. NowPhDnethaselecteda met regularlyfortheirweeklyvideo students atvariousMPGlocationshave For severalyearsnow, ahandfulofPhD and Equal Opportunities PhDnet Prioritizes Communication 80 Max Planck Society’s student platform elects new management board management new elects platform student Society’s Planck Max MaxPlanckResearch 1 MaxPlanckResearch “We areparticularly keen thisyear | 17 ­ magazine andourownblog.” in terms ofcommunicating PhDnet in procedure continuouslyimproved.” that thisisappliedinpractice,andthe at eachMPI.Ourtaskwillbetoensure handover meetinginMunich.” topic thatwearekeentoaddress atour tion time,forinstance,remains ahot prioritizing inthecomingyears. Vaca­ show uswhichtopicsPhDnet shouldbe inthespringthatwill planning asurvey person LeoBorchert –“soourteamis without theproperdata,”addsSpokes­ munication –withthenewO voice heardintheareaofscientificcom­ mann. “Butwealsointendtomakeour events andactivities,”saysLisaScheuer­ “There is no room for activities “There isnoroomforactivities “There isstillmuchtobedone ffspring

sity management. as wellorganizeseminars ondiver­ give fairconsiderationtoall lifestyles, individual workingconditions that PhDnet intendstocampaign formore appreciation ofequalopportunities, per year.” To heightenthe general families withjust20daysofvacation international doctoralstudentsand sue. Itisn’t easytosatisfytheneedsof time isalsoanequalopportunities­ According to Jana Lasser, “Vacation right). to left (HS, Hollerbach Teresa and (BMS) Scheuermann Lisa (CPTS), Lasser Jana Representatives Section and left) from (second Guerrero Gabriel Treasurer (right), Pérez Laso Rafael General Secretary right), from (third Borchert Leonard Spokesperson board: PhDnet The

Photo: Private collection Photo: Private collection Times Seven ERC Funding The ERCreceivedatotalofaround Technical UniversityofMunich(three). University ofHeidelberg(five)andthe Helmholtz Association(sixgrants),the framework programme,aheadofthe der theEU’s “Horizon2020”research in thisfourthroundofapplicationsun­ Germany’s mostsuccessfulinstitution million eurosinfunding.TheMPGwas ranks haveeachbeengranteduptotwo six male scientists from among MPG’s search Council(ERC),one femaleand Grants awardedbytheEuropeanRe In thecontestforConsolidator sought-after funding boosts funding boosts sought-after receive researchers Planck Max and global level, this conference cannot cannot conference this level, global and European the at uncertainty growing the of view “In EU. the exit to tention that the UK its in would declare firmed con Commons of House the which on day on the very projects tion on specific collabora their consolidate to posium in assem bled Berlin for a sym “matchmaking” Cambridge of University the and MPG the from scientists nonetheless: symbolic but chance, by purely was It Symposium intheAgeofBrexit to explore thepossibilitiesfor intensifyingcollaboration intheneurosciences Researchers atBritain’s University ofCambridge andtheMPGmetrecently attheHarnackHouse

­ - - - - - 2,300 applicationsandawarded314 are aimedatscientistswhoreceived Grants, whichareawardedannually, Consolidator Grants.The represented, predominantly by Group by predominantly represented, from Cambridge and the Six MPG. MPIs were neuroscientists expert of pair a by delivered each nine presentations, dual comprised February early in posium British our partners.” with cooperation continued for son. “It is signal an of a important desire Hans Bill President Vice MPG said al,” usu as business as regarded be simply THE ERC GRANTEES grant at the University of Barcelona); and Glenn van de Ven, MPI for Astronomy for MPI Ven, de van Glenn and Barcelona); of University the at grant ERChis with research doing be (will Science of History the for MPI Omodeo, Pietro Systems; Technical Complex of Dynamics the for MPI Klamt, Steffen Biochemistry; of MPI Mizuno, Naoko Biochemistry; of MPI Gruber, Stephan Research; Medical MPI for Barends, Thomas Genetics; and Biology Cell Molecular for MPl Alberti, Simon The centerpiece of the two-day sym of two-day the centerpiece The - - - scientific cooperation. cooperation. scientific for mechanisms established of end the to spell were if Brexit might that left be gaps the close to serve could format symposium the “matchmaking” forward, Going initiatives. new for environment dynamicproductive a nurtured itself the coordination collaborations, existing of development ongoing the ditionto ad in success: a event the deemed alike Leaders. Participants and organizers organizers and Participants Leaders. scientific institution. implement theirprojectataEuropean most 12yearspriorandwhowishto their doctorates at least seven and at MAX PLANCK COMMUNITY MAX PLANCK 1 | MaxPlanckResearch 17MaxPlanckResearch -

81 MAX PLANCK COMMUNITY

Award for Going the Extra Mile

Two Administrative Headquarters staff members honored for their outstanding commitment

The MPG awards the Commu­ nitas Prize for particular com­ mitment to our scientific or­ ganization. As President Strat­ mann has emphasized, the award is independent of hierar­ chies, and this year it goes to two members of staff at Admin­ istrative Headquarters. He also encouraged Directors to nomi­ nate dedicated colleagues at their institutes. Both prizewinners work at the Max Planck House in Mu­ nich and were themselves – as is commonly the case at HQ – formerly active scientists, which may well be why they are so “hands on.” Verena Mauch is one of a team of just under 20 “IL-ers” in the Institute Li­ aison department, the first, personal point of contact for MPIs wishing to address over­ arching administrative inqui­ ries to Headquarters. Orga­ nized by Sections, each “IL-er” is responsible for certain individual institutes that in effect Award ceremony at the Scientific Council meeting: become “their” MPIs – in Verena Mauch’s case, those are President Stratmann with the prizewinners, Verena Mauch the MPIs for Biological Cybernetics, Molecular Cell Biolo­ and Christiane Walch-Solimena (right). gy and Genetics, and Psychiatry. tute and Yale University, and who worked as a Group Lead­ “PERFORMANCE BEYOND ALL EXPECTATIONS” er at the MPI for Molecular Cell Biology and Genetics be­ fore moving to Headquarters. Since 2009 she has been the Verena joined the MPG while studying for a doctorate at Scientific Assistant to the President for life sciences and the Radboud University after a period of employment in medicine. In this capacity, she also assumed responsibility The Hague. As MPG President Martin Stratmann explained for coordinating the “discussion year on animal studies” when the awards were presented at the Scientific Council initiated by President Stratmann. meeting in late February, she receives the prize for her “per­ Christiane Walch-Solimena met this enormous chal­ formance beyond all expectations,” both in day-to-day lenge with “genuine devotion, patience and empathy,” as business, such as preparing appointment interviews, and in the President explained – for instance in integrating a wide responding to crisis situations, such as the recent campaigns variety of experts including scientists, animal facility man­ by animal rights activists. agers, lawyers, IT experts and communications specialists. The second prizewinner was Christiane Walch-Solimena, She was also instrumental in helping prepare content for who holds a doctorate in biochemistry and was formerly a the policy paper on animal studies in basic research that

researcher at two MPIs, the Howard Hughes Medical Insti­ was successfully presented to the Senate in late 2016. Photo: Amac Garbe

82 MaxPlanckResearch 1 | 17 SCHLESWIG- Research Establishments HOLSTEIN Rostock Plön Greifswald MECKLENBURG- WESTERN POMERANIA Institute / research center Hamburg Sub-institute / external branch Other research establishments Associated research organizations Bremen BRANDENBURG LOWER SAXONY The Netherlands Nijmegen Berlin Italy Hanover Potsdam Rome Florence Magdeburg USA Münster SAXONY-ANHALT Jupiter, Florida NORTH RHINE-WESTPHALIA Brazil Dortmund Halle Manaus Mülheim Göttingen Leipzig Luxembourg Düsseldorf Luxembourg Cologne SAXONY Bonn Jena Dresden Marburg THURINGIA Bad Münstereifel HESSE

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