A Secret Number in Astronomy1

INTERNATIONAL SPACE SCIENCE INSTITUTE SPATIUM Published by the Association Pro ISSI No. 19, August 2007 Editorial

This issue of Spatium is devoted to though his means were nothing the history of astronomy, more pre- more than a pair of simple lenses Impressum cisely to its evolution in Europe and packed in a tube of cardboard called the area adjacent to the Mediterra- telescope, the shiny objects that nean Sea. It is a play on different now suddenly became visible chal- stages: In the early days of astron- lenged the human spirit enough to omy, the observation of heavenly let him make every effort to im- SPATIUM process was on the one hand a vital prove the miraculous device even Published by the necessity to tune agricultural activ- further. In that sense, the history of Association Pro ISSI ities to the changing seasons and on astronomy is also the history of the the other hand the Sun was wor- evolution of technology and today’s shipped as the inexhaustible source extensive use of space-borne instru- of light and life. Early astronomers ments for astronomical research is were priests therefore linking the nothing else than a continuation of Association Pro ISSI art of objective observations with Galiei’s use of telescopes some 400 Hallerstrasse 6, CH-3012 Bern the richness of pious inspirations. years ago. Phone +41 (0)31 631 48 96 see The initially united stages splitted All these different stages - and many www.issibern.ch/pro-issi.html off when scientists found that the more - were the subject of a most for the whole Spatium series wandering of the Sun, the Moon fascinating lecture Prof. Giovanni and the other celestial bodies is F. Bignami, then at the University President ruled by nothing else than a set of of Pavia, now President of the Ital- Prof. Klaus Pretzl soulless mathematical functions. On ian Space Agency, gave the Pro ISSI University of Bern the religious stage, emerging dog- audience in November 2006. The Layout and Publisher mas incorporated suitable world present text follows loosely the lines Dr. Hansjörg Schlaepfer models that received the status of of his presentation; may it provide CH-8173 Neerach eternal truth irrespective of the our readers the same wealth of Printing continued progress made on the inspring thoughts as Prof. Bigna mi’s Stämpfli Publikationen AG stage of science. Galileo Galilei con- talk offered his attentive audi - CH-3001 Bern tributed to further deepening the ence... ditches between the two stages by stipulating that a hypothesis, in or- Hansjörg Schlaepfer der to be scientifically acceptable, Neerach, August 2007 must be provable everywhere at any time. This of course was provoca- Front Cover tive news for the clerical establish- The recently found sky disk of Ne- ment which did not hesitate to bra, Central Germany, is the most denounce him of heresy and to ancient image of the sky. Dating prohibit him to further teach his back to 1600 B.C., it represents the findings: the two stages had entered Sun, the Moon and – probably - the a state of fierce war for the next Pleiades. It is assumed to have served centuries. determining the beginnings of new seasons for agricultural purposes, Galilei even added a third stage that but it certainly served religious tra- is the use of technical means to ditions as well. (Credit: Landesamt overcome the limitations of the hu- für Archäologie Sachsen-Anhalt, man senses to observe nature. Al- Germany, Hansjörg Schlaepfer)

SPATIUM 19 2 4440: A Secret Number in Astronomy1

Dr. Hansjörg Schlaepfer, Neerach

Introduction from millennia over centuries to 4,000 Years of decades, the last 40 years have given us astronomy from space, yielding a Naked Eye view of celestial objects over the Mankind has been looking at stars whole electromagnetic spectrum, Astronomy with naked eyes for the last 4,000 i.e. the most important channel years collecting data and under- through which the sky sends us in- standing important astronomical formation about itself. In decoding facts. Since Galileo Galilei gave us such information, gathered from From Early Testimonies... the telescope, 400 years ago, astron- telescopes in space, we have, once omy from the ground has reached again, vastly surpassed the work There was a time – not too far back a profound comprehension of our done over the previous centuries - when the night sky was really dark universe; infinitely greater than had and created entirely new scientific and crowded with uncountable been possible in the previous mil- disciplines such as planetology or stars. The Milky Way was the won- lennia. In a spectacular acceleration, cosmology. derful lane that leads from the ho-

Fig. 1: Summer solstice over Stonehenge. The great stone circle was erected between 3000 B.C. and 1600 B.C. It consists of a circular structure, exactly aligned with the rising Sun at the solstice. (Credit: Andrew Dunn)

1 The present text follows a lecture by Professor Giovanni F. Bignami, President, Italian Space Agency, Rome, for the Pro-ISSI audience on 13 November 2006 and is freely retold by Hansjörg Schlaepfer.

SPATIUM 19 rizon to the zenith and down again moon between the rivers Euphra- about the Sumerian endeavours to to the opposite side. Today, atmo tes and Tigris the Sumerian culture understand the processes in the sky spheric pollution absorbs most of prospered at that very time. The in order to sow and to harvest at the this faint radiation and the scatter- Sumerians are known to have de- appropriate time. No doubt, the ing from the ubiquitous artificial veloped not only what could be need for sufficient food and water light sources hides the beauties of called the first “professional” astron- supply was at the root of their in- the night sky to most of us. Fortu- omers but also the means to be- terest in astronomy and, since fer- nately, mankind has evolved under queath much of their broad knowl- tility of the fields was a gift from the clear night skies and has been im- edge. They invented a form of gods at that time, religious and sci- pressed by the silently wandering writing in clay with a wedge-shaped entific endeavours could co-evolve stars. We do not know the begin- stylus thereby producing docu- in untroubled harmony... nings of their observations; the eons ments that survived the many mil- since have erased most, if not all, of lennia since. Thanks to these docu- While the Euphrates and the Tigris the traces of early astronomical en- ments, we know that the Sumerian were the source of wealth for the deavours. Interestingly though, priests studied the stars and knew Sumerians and the later Babylo these seem to have evolved inde- to correlate astronomical align- nians, another large river, the Nile, pendently(?) at many different ments with the changing seasons. was the cradle for the Egyptian civ- places all over the world some 4,000 Based on their observations they set ilization. The Nil’s periodic inunda- years ago. One of these places is up a calendar consisting of a year tions, lasting from July to October, Stonehenge, UK (Fig. 1), of which with twelve months, each of which required the mastering of the cal- the oldest traces date back as far as began at the first sighting of the new endar to tune agricultural activities 3000 B.C. The megalith’s precise moon. Sometimes, based on a re- to the river’s habits: the Egyptians orientation towards the rising Sun spective royal order, the eleventh broke a year down into 365 days, at summer solstice is a clear indica- months had to be repeated, in or- which was largely sufficient for tion, that astronomy played an im- der to bring the lunar calendar in practical purposes, and it seems that portant role in the life of their line again with the Sun’s. A Sume- further efforts to understand the constructors. rian day consisted of six watches, mechanics of the heavens were not each being two double hours long. made, at least until the later Helle On the Continent, more precisely Each hour was divided into 60 min- nistic period. in Central Germany, another mile- utes, and each minute was divided stone of early astronomical endeav- into 60 seconds. The year had nom- Not a great river, but a long sea shore ours from that time period was inally 360 days, and so their heav- was the key asset of the classic Greek found recently: the sky disk of Ne- ens were divided into 360 degrees. civilization that evolved approxi- bra, see the front cover. Dating back Many of these ancient concepts mately at the same time on the to 1600 B.C., it represents man- have survived thousands of years northern shores of the Mediterra- kind’s very first known image of the and constitute today our counting nean Sea. The great Greek philoso- sky. The latest analytical technolo- system for time and angles, while in phers Socrates2 and Plato3 laid the gies were used to unravel some of the other areas the decimal system, foundations of our western philoso- the disk’s secrets: it is thought that presumably of Indian origin, has be- phy. Socrates’ thinking and Plato’s di- its designers had contacts to the come the standard system. alogues are characterized by mythic- eastern Mediterranean area, to allegoric symbols for describing the Mycenae and even further to Mes- The cuneiforms, as the Sumerian world: their real world is that of the opotamia, where in the fertile half- clay tablets are called, tell us also ideas, while the human perception

2 Socrates, 470 B.C. – 399 B.C., ancient Greek philosopher. 3 Plato, 427 B.C. – 347 B.C., ancient Greek philosopher.

SPATIUM 19 of the physical world is at best a world’s largest counting up to lunar theories together with his nu- blurred image. In contrast, for Aris- 900,000 scrolls. Of course, such an merical trigonometry, he was prob- totle4, a pupil of Plato, the visible ap- impressive collection of knowledge ably the first to develop a reliable pearances became real and the world attracted the very best scientists of method to predict solar eclipses. of the ideas an imperfect approxima- the time. Eratosthenes of Kyrene7, tion of the empiric reality: this was one of the first directors of the li- In contrast to Aristarchos, Claudius the dawn of science. brary, is known for having found Ptolemy9 found the Earth at the the Earth’s perimeter around centre of the universe three hun- Regarding astronomy, it was Aris- 200 B.C. He observed a draw well dred years later. Ptolemaeus used tarchos of Samos5, who approached in Syene, Upper Egypt, illuminated Hipparchos’ system to explain the nature under this new paradigm. He by the Sun at summer solstice right motions of the Sun, the Moon, and estimated the diameter of the Sun. down to its floor, while at the same the five planets known at that time. The result was a factor of twenty time a well in Alexandria was illu- It was accurate enough to predict too short, but nevertheless, Aris- minated only partially at an angle the position of the planets for na- tarchos’ Sun had a volume equalling of 7.2°. The distance between the ked-eye observations. Ptolemaeus 250 Earth volumes making it much two cities was known from the authored three major oeuvres which greater than the Earth. It was noth- royal couriers to be 5,000 stadia. strongly influenced astronomy, of ing else than a logical consequence From these data he was able to es- which one is the Mathematical Syn- to assume the Earth to circle the timate the Earth’s perimeter at taxis (in Greek called MEI∑TH Sun (and not vice versa): the mod- 39,250 km, just within 2% of the ∑YNTAΞI∑, translated in Arabic as ern heliocentric world model was exact value. Al Magiste and later in Latin as Al- born. magest). The Almagest is our most important source of information on Alexander the Great6, the most ... to the First Great ancient Greek astronomy, see Fig. 2. successful military commander of Astronomers... It includes a star catalogue contain- the ancient world, was a contem- ing 48 constellations with the same porary of Aristotle. He enlarged On the northern shores of the Med- names as we still use today. the accessible world towards Cen- iterranean Sea, most probably in tral Asia and India thereby boost- Nicaea, now Izmir, Turkey, Hip- ing not only trade and economic parchos8, the greatest astronomer in ...to the Decline of Euro- evolution, but cultural exchange ancient times, saw the light of the pean Astronomy... with the newly discovered civilisa- day in 190 B.C. He was the first to tions as well. He founded many cit- derive accurate quantitative models Ptolemaeus’s death in 168 and the ies, for example Alexandria in for the motion of the Sun and the destruction of the Alexandrian li- Egypt, which soon became the Moon. To this end, he made use of brary that occurred presumably at centre of the known world. Here, observations and knowledge accu- approximately that time brought the a famous Museion was erected, that mulated over centuries before. He evolution of western science to a is a temple for the Muses, or – in was also the first to compile a trig- sudden end. In addition, the philo- modern terminology – an academy onometric table allowing him to sophic schools of the late Roman of sciences. Its library became the solve any triangle. With his solar and Empire were oriented backward to

4 Aristoteles (English: Aristotle), 384 B.C., Stageira, Greece – 322 B.C., Chalkis, ancient Greek philosopher. 5 Aristarchos of Samos, 310 B.C., Samos, Greece – 230 B.C., Alexandria, Egypt, ancient Greek astronomer and mathematician. 6 Alexander the Great, 356 B.C., Pella, Northern Greece - 323 B.C., Babylon (today Iraq), King of Macedon. 7 Eratosthenes of Kyrene, 276 B.C. – 195 B.C., ancient Greek mathematician, geographer and astromer. 8 Hipparchos, 190 B.C., Nicaea, Asia Minor – 120 B.C., Rhodes, Greece, ancient Greek astronomer, geographer, and mathematician. 9 Claudius Ptolemaeus (English: Ptolemy), 90, Alexandria (?), Egypt – 168, Alexandria, Hellenistic mathematician, geographer, astronomer, and astrologer.

SPATIUM 19 ment unifying elements from Juda- ism and Christianity. The new religion, the Islam, rapidly developed an impressive unifying power: its in- fluence eventually reached Andalu- sia in the west and Central Asia and China in the east. Like some 900 years before, under Alexander the Great, economy, handcraft and trade re-flourished. Damascus, later Baghdad, became the new world’s capitals. And in contrast to the pa- rochial Christianity, the evolving Is- lamic culture was open to new ideas and science was seen as an important cultural accomplishment. Un- der Kalif Al Mansur, around 760, sages from all over the world con- vened to make up the world’s intel- Fig. 2: A late copy of the Almagest by Ptolemy translated in Latin around 1451. The drawings illustrate the computation of the duration of solar and lunar eclipses. lectual centre in Baghdad. The works of the ancient Greek thinkers were translated meticulously into Arabic Plato, thereby creating an intellectual Christian doctrines with Hellenistic and the classic Almagest of Ptolemy substrate that did not aim at scien- thinking, the new movement began was not only studied but further de- tific progress. Even worse, the ini- to extinct everything not literally in veloped also, see Fig.3. It was en- tially suppressed Christianity became line with the Bible. That became the riched by the Hindu-Arabic nu- state religion. It was a fundamental- destiny for the vast majority of the meral system, now called the Arabic ist movement that addressed mainly great testimonies of ancient human numerals. Kalif Al Mamun ordered the “poors in spirit”, social strata that thinking, including for example the the construction of a new great ob- were far away from any interest in Almagest. A chance for survival had servatory near Baghdad in 829 and science. The Ptolemaic system of a only those works that had been com- Muhammad Al Fagan was one of geocentric world was formulated piled or copied elsewhere by late- the leading astronomers there. He just at the right time to enter the Roman librarians. authored a book entitled “Elements Christian dogmatic system, where it of Astronomy”, which served as a firmly stood for the next 1,400 years. standard text book in Europe until In 529, Iustinianus I10 closed the ...to Arabian Astronomy ... the end of the 16th century. academy of Athens, the last Helle nistic school: the long dark night of Fortunately though, science found Towards the year 1000, the centre the medieval time in Europe had be- a new culture medium on the east- of Arabic astronomy moved slowly gun. Although some early Christian ern side of the Mediterranean Sea: to the west, first to Egypt, then to philosophers, like for example Ori- In 622, Muhammed12 founded a the Moorish Castile in Spain. Un- gen11, tried to reconcile the evolving new religious and political move- der the Kalifs of Cordoba, astron-

10 Flavius Petrus Sabbatius Iustinianus, 482, Iustiniana Prima (today Serbia) – 565, East Roman Emperor. 11 Origenes, (English: Origen), 185, Alexandria, Egypt (?) –254, Tyros, today Leban (?), one of the early fathers of the Christian Church. 12 Muhammed, 570, Mecca (today Saudi Arabia) – 632, Medina, founder of the Islam.

SPATIUM 19 ...to the Revival of Euro- pean Astronomy

Under the increasing Mongolic pressure the Arabian astronomy came to an end, while the occident was fortunately about to leave the dark medieval times and to become open for science. At that time, many precious goods were imported over the Silk Road from the east. It is probably on that path that the art of printing reached Europe around 1300. Initially, it was used to deco- rate clothes for religious purposes exclusively. The art of paper making, originally invented in China also, was imported during the Moorish conquest of Andalusia. The first paper mill was established in 1120 near Valencia; later mills were founded in Italy and Germany Fig. 3: An example of a late Arabic book based on Ptolemy’s Almagest. The Picture shows a page of Nasir ad-Din at-Tusi’s “Memoirs on Astronomy”, written in around 1400. In 1452, the German the fourteenth century. goldsmith Johannes Gutenberg invented the moveable type printing omy saw a first, albeit transitory, In the vicinity of Tabriz, in today’s in Mainz. This new technology was revival in Europe in the 11th and north-western Iran, an observatory quicker and more durable than the 12th century, but the “reconquista” was founded in 1259 that had a previous laborious woodblock by the Castilian Christians not large library counting as much as printing, which required the differ- only brought the Arabic presence 400,000 manuscripts. Some 200 ent letters to be carved out from a in Europe, but also their scientific years later, in 1420, the Mongol solid block of wood. This new tech- endeavours to an end. A land mark Ulugh Begh ordered the construc- nology rapidly spread through Eu- of occidental philosophy of that tion of an observatory on the Silk rope: in 1469, the first print press time is the Divina Comedia by Road in Samarkand, today Uz- was established in Venice, 1470 in Dante13, one of the masterpieces of bekistan. He personally developed Paris, 1473 in Krakow, Poland, and world literature, firmly rooting in the first star catalogue that was not it took more than 150 years for the the classic scholastic tradition. simply an improvement of Ptole- first printing press to start operat- my’s oeuvre, but contained many ing in North America (1638). Fortunately, astronomy sparked off new elements. This catalogue even- again in the eastern parts of the Ar- tually became known in Europe Of course, the Church knew to put abic empire, more precisely in Bagh- and went into press in 1655, at a the promising technology rapidly dad and Megara, where new astro- time, when it was already outdated into its service; but also scientists nomical institutions were established. by insights of European scientists. began to exploit printing for their

13 Dante Alighieri, 1265, Florence, Italy – 1321, Ravenna, Italy, Italian poet and philosopher.

SPATIUM 19 was printed, see Fig. 4. At first, the “De revolutionibus” did not cause any worries even though its con- tents were in contradiction to the official dogmas that adhered to the Ptolemaic world model. Rather, it took some 60 years for the clerical establishment to recognize the ex- plosive force of that book and to put it rapidly on the “Index Libro- rum Prohibitorum”, the list of the prohibited books considered a danger to the true faith.

At about the same time, Giordano Bruno15, another adherer of the heliocentric world model and an early proponent of an infinite and homogeneous universe, was accused of heresy by the Roman inquisition. As he refused to recantate, he was burned at the stake in Rome and all his works were placed on the In- dex, where they remained for the subsequent 400 years.

Fortunately though, ideas cannot be extirpated by burning their propo- nents. Far to the north, in safe distance from the Roman inquisition, 16 Fig. 4: Nicolas Copernicus: De revolutionibus orbium coelestium (1543). the Dane Tycho Brahe was about to study law together with a variety of other subjects that attracted the youngster’s interest. The solar needs. One of earliest great Euro- world model. But around 1515 his eclipse in 1560 impressed him so pean scientists, who used the art of friends urged him to publish and deeply that he stopped his studies printing, was Nicolas Copernicus14. even the clerical establishment in- and began to devote himself to as- His Commentariolus (Little Com- vited him to go into press. It was in tronomy. As an intended lawyer he mentary) was initially nothing more 1543 only, the year of Copernicus’ was used to work precisely and he than a handwritten text outlining death, that his seminal oeuvre “De quickly became aware of the need some of his ideas on a heliocentric revolutionibus orbium coelestium” to improve and enlarge the available

14 Nicolas Copernicus, 1473, Thorùn (Prussia) – 1543, Frombork, Poland, mathematician, astronomer, jurist, physician, diplomat, and soldier. 15 Giordano Bruno, 1548, Nola, Italy – 1600, Rome, Italian philosopher, priest, cosmologist, and occultist. 16 Tycho Brahe, 1546, Knudstrup, Denmark – 1601, Prague, Danish astronomer.

SPATIUM 19 astronomical instruments, and to construct entirely new ones, Fig 5. Assisted by his diligent sister Sophia he was able to make astronomical measurements of unprecedented precision.

Unfortunately for Sophia and Ty- cho, King Christian IV succeeded King Frederic II, who had been a strong supporter of their astronomical research. Brahe decided to leave Denmark and to move to Prague in 1599. There, during the last two years of his life, he was assisted by the young Johannes Kepler.

Thanks to its outstanding accuracy, Brahe’s work marks the climax of naked eye astronomy, but also its end, as new means for observing the sky had silently emerged in the meantime that bore the potential of a quantum leap in astronomy...

Fig. 5: Tycho Brahe at work. Brahe is depicted in the centre of the image together with his assistant reading the scale on the right, the assistant responsible for the time reading on the right bottom and the assistant taking the notes on the left bottom.

SPATIUM 19 shey18 in Middelburg. Incidentally, 400 Years of they found that the combination of two such lenses brought a new qual- Astronomy with ity to the image as compared to that Telescopes produced by a single lens. Lipper- shey, a clever businessman, immedi- ately recognized the potential of the children’s invention and successfully Small Things Change the started building and selling pairs of World lenses as telescopes all over Europe. Murano, a small town on an island in the Venetian lagoon, had been a Such a novel device came to Pisa in commercial port since many cen- Italy, specifically to Galileo Galilei19. turies when in 1291, the Venetian The first of six children, young Ga Republic decreed its glassmakers to lileo wanted to become a priest. At move to Murano as the glassworks his father’s urging, however, he en- represented a severe fire danger to rolled for a medical degree at the the city of Venice. These glassmak- University. But soon, Galilei recog- ers had developed and refined tech- nized that medicine was not his fa- nologies to produce a variety of vourite field. He then switched to precious glass types amongst which mathematics, a decision for which were reading stones of the best then humanity remains deeply indebted available quality (Fig. 6). Such read- as it was the prerequisite for Galilei ing stones were a necessity not only to become the father of modern in the Serenissima17, but found their physics. At the age of 25 already, he customers far abroad, for example was appointed the chair of mathe- in the Netherlands. The legend tells matics at the University of Pisa. A that on a sunny summer morning mere three years later, Galilei moved some children played in the shop of to the University of Padua to teach the spectacles maker Hans Lipper- geometry, mechanics, and astron- Fig. 7: A telescope used by Galileo omy. During these fertile years as a Galilei (upper table) and an excerpt of professor, Galilei made his signifi- his astronomical diary of 1610. cant discoveries in both pure and applied science. He pioneered the use of quantitative experiments device enthusiastically for various whose results could be analyzed purposes such as for military infor- subsequently with mathematical mation gathering or for merchants methods. Just three years after Lip- who found it useful for their ship- pershey’s invention, in 1611, Gali- ping business. Galilei on his part was lei built his first own telescope that more interested in gaining scientific Fig. 6: A reading stone. (Credit: Carl he presented to the then wealthy insights. Those came along very Zeiss) Venetians. Those welcomed Galilei’s quickly: in January 1610 already he

17 La Serenissima, a name for the Republic of Venice, from the title Serenissimo, literally meaning “the most serene”. 18 Hans Lippershey, 1570, Wesel, Germany – 1619, Middelburg, the Netherlands, Dutch lensmaker. 19 Galileo Galilei, 1564, Pisa – 1642, Arcetri (Italy), Italian physicist, astronomer, and philosopher.

SPATIUM 19 10 discovered three of Jupiter’s four largest moons: Io, Europa, and Cal- listo. A mere four nights later, he discovered Ganymede, Jupiter’s fourth moon. In his diary (Fig. 7), he noted that the moons appeared and disap- peared periodically, which he at- tributed to their movement behind Jupiter. From this, he concluded that they were orbiting the planet. Unsuspectingly, Galilei published his discoveries in a small treatise called “Sidereus Nuncius” in 1610. The oeuvre was devoted to the Medici for the housing they offered him at their court. But the gener- ous patrons did not realize what worries the booklet was about to cause: Galilei’s finding of a planet that is orbited by smaller bodies was revolutionary, to say the least, as the officially still accepted geocentric world model required all celestial bodies to safely circle the Earth. Equally important from a scientific point of view was Galilei’s trendset- ting approach of making his claims visible for everybody, in contrast to the dogmatic approach to defining the truth “ex cathedra”. The “Sidereus Nuncius” made Galilei a dangerous subject for the clerical establishment which did not hesitate to denounce him of heresy. Ga lilei went to Rome to defend himself against the accusations, but, after lengthy trials he was finally forbid- den in 1616 to either advocate or teach Copernican astronomy fur- Fig. 8: Saturnian impressions: The upper table shows an excerpt of Christiaan Huy- thermore. In addition, he was con- gens’ observations of Saturn of 1655. The middle table presents a false colour image of fined in Siena. Totally blind, he was Saturn in the infrared acquired by the Hubble Space Telescope in 1998. The table be- allowed to retire to his villa in low shows the Saturnian ring system observed by the Cassini spacecraft in 2004. Arcetri, where he died quietly in 1642.

SPATIUM 19 11 Again in a safe distance from the mia nova”, 1609, while the third is The Quest for Astronomical inquisition, more precisely in the contained in the later “Harmon- Discoveries Imperial Free City of Weil der ices mundi”, 1619. When Kepler Stadt, now in the German state of heard of Galileo’s telescopic dis- The seventeenth century saw Eu- Baden-Württemberg a boy was coveries, he started theoretical and rope in a deep crisis; the Thirty Years’ born in 1571. Nothing in the early experimental investigations of teles War was fought between 1618 and life of Johannes Kepler20 would cope optics as well. He published 1648, basically a conflict between have indicated that this youngster the results in “Dioptrice”, 1611, Protestants and Catholics, but also a of fragile health was later to be- where he described an improved dispute on the role of the religion in come one of mankind’s most telescope also, now known as the the modern state. Devastating fam- prominent scientists. His father astronomical or Keplerian tele- ine and disease all over Europe was Heinrich died when Johannes was scope, using two convex lenses that one of its terrible consequences. five, and his mother was tried for can produce higher magnification Nevertheless, in some isolated spots, witchcraft. Still, she showed him a than Galileo’s combination of con- science was able to survive. Far to the comet in 1577 that left a long trace vex and concave lenses. south of Europe, Giovanni Dome not only on the sky but in the nico Cassini22, a contemporary of youngster’s mind as well. He began Kepler’s oeuvre was a seminal suc- Christiaan Huygens, studied math- studying theology, but soon it cess and found enthusiastic readers ematics and astronomy and became turned out that he was an excel- all over Europe. One of those was a professor for astronomy at the Uni- lent mathematician, so he switched the Dutchman Christiaan Huy- versity of Bologna. In 1665, he de- and became a teacher of mathe- gens21 who was building his own termined both the rotation periods matics and astronomy in Graz, Aus- telescopes at that time. He man- of Jupiter and Mars, and was one of tria. In early 1600, Kepler met Ty- aged to improve their imaging per- the first to observe the polar caps of cho Brahe near Prague, where he formance to such an extent as to Mars. On invitation by the Roi So- stayed as a guest. He was allowed allow him the discovery of Saturn’s leil, Louis XIV, Cassini moved to to analyze some of Brahe’s obser- moon Titan in 1655. He also ex- Paris. Based on his collaboration vations of Mars. Brahe was im- amined Saturn’s planetary rings, with Christiaan Huygens, he devel- pressed by Kepler’s theoretical abil- and found that they must consist oped and used very long air tele- ities and soon allowed him further of rocks. But Huygens was not scopes. In 1672, he was able to mea access to his data. Two days after only a diligent observer, but also a sure the distance of Mars by Brahe’s unexpected death in late gifted physicist: he derived the triangulation and thereby to refine 1601, Kepler was appointed his wave nature of the light and devel- the dimensions of the solar system. successor as imperial mathemati- oped the probability theory as well. Specifically, he determined the value cian: he inherited his master’s And his hobby, as to say in mod- of the astronomical unit (AU), just records as well as the responsibil- ern terms, was the existence of life 7 % short of the currently accepted ity to complete the unfinished on other planets: he published his value of 149,597,870,691 metres. work. During the following years reasoning in the book “Cosmo Cassini discovered also Saturn’s and after careful analysis of Brahe’s theoros”, presumably one of the moons Iapetus, Rhea, Tethys, and data, Kepler realized that the plan- very first oeuvres on exobiology. Dione and the gap separating the two etary orbits follow three relatively parts of the Saturnian rings that later simple mathematical laws. Two of received the name Cassini Division them are derived in the “Astrono- in his honour.

20 Johannes Kepler, 1571, Weil der Stadt, Germany – 1630, Regensburg, German mathematician, astronomer and astrologer. 21 Christiaan Huygens, 1629, The Hague (the Netherlands) – 1695, The Hague, Dutch mathematician, astronomer and physicist. 22 Giovanni Domenico Cassini, 1625, San Remo, France – 1712, Paris, Italian/French astronomer, engineer, and astrologer.

SPATIUM 19 12 In England, struck also by religious Naturgeschichte und Theorie des quarrels, another genius was about Himmels”, 1755, where he cor- to revolutionize physics and the ob- rectly derived the theory of the evo servational means in the hands of lution of planetary systems based on astronomers. Sir Isaac Newton23 Newtonian mechanics. According published the “Philosophiae Natu- to Kant, our solar system has been ralis Principia Mathematica” in formed out from a form of nebula 1687, where he described the uni- where the different planets concre- versal law of gravitation and the tized independently from each three laws of motion, laying the other. In addition, he saw our solar groundwork for classical mechan- system as being merely a smaller ics. This allowed him to derive Kep version of the fixed star systems, ler’s laws of planetary motion from such as the Milky Way and other Fig. 9: The 12 m telescope built by a purely theoretical point of view. galaxies. William Herschel. He showed that the motion of objects on Earth and of celestial bod- The early eighteenth century al- increasing size during his lifetime. ies is governed by the same set of lowed Europe to recover from its The largest and most famous one is natural laws. The unifying and pre- sufferings finally and art and sci- a reflecting telescope with a 12 m dictive power of his laws became ences were reaching new highs. It focal length and an aperture of central to the advancement of the was the time of the baroque, the 126 cm, see Fig. 9. This instrument heliocentric system at the time. time of Johann Sebastian Bach and allowed him to discover planet Ura- Based on his studies of the proper- Georg Friedrich Händel. Music was nus in 1781, which prompted him ties of light, he concluded that any the favourite subject of the young to give up his career as a musician refracting telescope (based on lenses) William Herschel25 in Hanover, and to become a great astronomer. must suffer from the dispersion of Germany. Born around 1738 as one Later, Herschel discovered Mimas light into the different colours. This of ten children, young Friedrich and Enceladus, two Saturnian led him to invent the reflecting Wilhelm came to the Hanoverian moons, and Titania and Oberon, telescope today known as the New- Guards regiment, which was or- two moons of Uranus. From stud- tonian telescope. dered to England in 1755, when the ying the proper motion of stars, he crowns of England and Hanover was the first to realize that the solar While Newton’s mirror telescope were united under George II. A system is moving through space, and constituted a major progress in ob- gifted youngster, Friedrich quickly he determined the approximate di- servational astronomy, another star learned English and at the age of rection of that movement. He also in mankind’s history did not even nineteen, he changed his name to studied the structure of the Milky need to observe the universe with Frederick William Herschel. He be- Way and concluded correctly that his eyes, but rather used the over- came a successful music teacher, it has the shape of a disk. whelming power of his rational bandleader and composer like his thinking to develop theories on the father, but eventually he got inter- While the Northern Italian Valtel- evolution of the solar system: Im- ested in mathematics and astronomy lina valley is well known for its fine manuel Kant24. Besides an enor- also. He started polishing mirrors wine made of the Nebbiolo grape, mous wealth of philosophical oeu- and building telescopes of which he it is certainly not so for scientific vres, he wrote the “Allgemeine constructed over 400 of various and importance. But in the rural town

23 Sir Isaac Newton, 1643, Woolstrope, Lincoln (UK) – 1727, Kensington, founder of classical mechanics. 24 Immanuel Kant, 1724, Königsberg (Prussia) – 1804, Königsberg, German philosopher. 25 Sir Frederick William Herschel, 1738, Hanover (Germany) – 1822, Slough (UK), German-British astronomer and composer.

SPATIUM 19 13 of Ponte in Valtellina, Giuseppe no less than 7,646 stars. While he goddess of grain Ceres and his spon- Piazzi26 saw the light of the day in was at his regular nightly work in sor, King Ferdinand I. The Ferdi- 1746. He began his career with theo early 1801, Piazzi made the discov- nandea part of the name had to be logical studies and finished his no- ery of his life: a heavenly body he dropped later for political reasons, vitiate at the convent of San Anto- identified as a fixed star at first. But while the reference to the immor- nio, Milan. Later, he studied at upon repeating the measurements tal goddess could be maintained various Italian universities and be- during the following nights, he without causing worries. Ceres came a professor for dogmatic the- found that this star had shifted turned out to be the first, and larg- ology in Rome. But he was not only slightly. Therefore it would rather est, of the asteroids in the belt be- a gifted clergyman, but an excellent have been a planet, or as he called tween Mars and Jupiter. Under the mathematician as well. In 1780, one it cautiously, a new star. Unfortu- terms of a 2006 International As- year after the French revolution, he nately, he was not able to observe tronomical Union resolution, Ceres was called to the chair of higher this new star any longer as it was is now called a dwarf planet, just like mathematics at the academy of Pa lost in the glare of the Sun. Even the former planet Pluto. lermo, Sicily, where the Bourbon worse, he was unable to compute King Ferdinand I of the Two Sicilies its orbit with the then available Giuseppe Piazzi had the fortune to was on the throne. A fervent sup- methods for regaining it after pass- find a wealthy patron willing to supporter of astronomy he gave Piazzi ing the Sun. Fortunately, the Ger- port his scientific endeavours. Oth- a major grant for building an ob- man mathematician Carl Friedrich ers are wealthy enough to devote servatory. In order to acquire the Gauss27, another star in the science themselves to their passion like for best available instruments, Piazzi firmament, read about Piazzi’s dis- instance the British William Lassell28, went on a shopping tour through- covery and difficulties and, after who made a fortune by brewing out Europe, specifically to Paris and some weeks of intense calculations, beer. But he was not only interested to England. The equipment he had developed a new method of orbit in fine beverages, but also in astron- acquired was placed on top of a determination that allowed Piazzi omy; so he decided to build an ob- tower of the Royal Palace in Pa to successfully locate the new star servatory near Liverpool which he lermo. Observations began in 1791, again. Gauss published his results in equipped with a respectable 24-inch and the first report was published 1809 under the name of “Theoria reflector telescope. Like many oth- just one year later. The excellent motus corporum coelestium in sec- ers, he ground the mirrors himself equipment – and the clear sky of tionibus conicis solem ambientum” to an excellent quality, but in con- Sicily – allowed him to make scien- (theory of motion of the celestial trast to others he pioneered an equa- tific contributions soon, such as to bodies moving in conic sections torial mount of his telescope for easy estimate more precisely the obliq- around the Sun), which was to be- tracking of celestial objects as the uity of the ecliptic, the length of the come a major cornerstone of the Earth rotates. Et voilà: spectacular tropical year, and the parallax of the art of astronomical computation. discoveries did not wait for long. In- fixed stars. He saw the necessity for Then only, it became clear that Pi- vited by William Herschel to ob- a revision of the existing star cata- azzi’s assumption was correct and serve Neptune, he discovered Tri- logues and for the exact determina- this object was not a comet but ton, its largest moon in 1846, in tion of their positions. In 1803, he much more like a small planet. Pi- 1848 he independently co-discov- published a list of 6,784 stars and in azzi named it Ceres Ferdinandea, ered Hyperion, a moon of Saturn, 1814 a second catalogue containing honouring the Roman and Sicilian and in 1851 Ariel and Umbriel, two

26 Giuseppe Piazzi, 1746, Ponte in Valtellina (Italy) – 1826, Naples, Italian monk, mathematician, and astronomer. 27 Carl Friedrich Gauss, 1777, Brunswick, Lower Saxony (Germany) – 1855, Göttingen, Hanover, German mathematician and scientist. 28 William Lassell, 1799, Bolton, Lancashire (UK) – 1880, Maidenhead, British astronomer.

SPATIUM 19 14 new moons of Uranus. Lassell real- omy in Berlin. Upon his return to over anything that had appeared ized that the atmospheric conditions Italy he assumed the post as secondo before. This forced him, however, in Liverpool were unfavourable for astronomo at the famous observa- to set up a new nomenclature of astronomy at that time already and, tory at the Brera Palace in Milan. the Martian topography that was thriving for new discoveries, he de- Although the instruments were consistent with his observations. cided to move to Malta, where he outdated, Schiaparelli made the Exploiting his intimate knowledge made further observations until his best use of the available resources, of classical literature and the Bible, death in 1880. and in April 1861 he succeeded in he chose the names for the topol- making a major discovery: Hespe- ogy of Mars that are still valid to- ria, the 69th asteroid. However, po- day, Fig. 10. His map was the first The Martian Saga litical turmoil suddenly changed to include surface features called his life. In 1860, Giuseppe Garibaldi “canali” by Schiaparelli. This term The next to silently enter the as- dispossessed the King of the Two was later mistranslated to the Eng- tronomical scene is Giovanni Vir- Sicilies, and in 1861 Victor Em- lish “canals”, a failing that played ginio Schiaparelli29. As hydraulic manuel II became the first King of an important role in the planet’s engineer and civil architect he re- the united Italy. The new sovereign subsequent mystification. ceived an appointment as a teacher provided Schiaparelli with a tele- of mathematics in an elementary scope of far superior quality that Unfortunately, Schiaparelli lost eye school in Turin in 1856, which allowed him to study the planets sight in his older years. This in turn however did not fully satisfy him. in more detail. During the fall of was recognized as the chance of his “Without taking into account my 1877 Mars was close to the Earth. life by one of his diligent readers, almost absolute poverty”, as he This constellation prompted Schi- Percival Lowell30. The seminal mis- wrote later, he decided to devote aparelli to study this neighbouring translation of the “canali” to the himself to astronomy. In 1857, a planet carefully for the purpose of English “canals” triggered the busi- small stipend terminated his pov- drawing up a new map. Thanks to nessman, a descendant of the dis- erty at least partially, and enabled his meticulous observations, the tinguished and wealthy Boston him to receive training in astron- result was a tremendous advance Lowell family, to set up his own observatory. In search of the best- suited site, he travelled throughout the United States to finally choose Flagstaff, Arizona, at an altitude of over 2,500 m, where he built an excellent observatory. Lowell’s be- lief was that the Martians were keeping their planet alive via a global channel network that brings water from the Martian polar caps to the equatorial zones. He published this hypotheses in three books including detailed maps of the Martian surface: this was the beginning of the Martian saga and Fig. 10: The map of Mars by Giovanni Virginio Schiaparelli, 1890. the intelligent Martians.

29 Giovanni Virginio Schiaparelli, 1835, Savigliano (Italy) – 1910 Milan, Italian astronomer. 30 Percival Lowell, 1855, Boston (USA) – 1916, Flagstaff, Arizona, US American astronomer.

SPATIUM 19 15 The Birth of Modern Astronomy

While Lowell’s work strongly fos- tered the general public’s interest in space research, it had only a limited impact on space science. The con- trary is true for another American, who in his younger years studied law in Oxford, but was fascinated by astronomy also: Edwin Hubble31. After studies at the University of Chicago he was offered a position at the Mount Wilson Observatory in California, where the world’s largest telescope was just completed Fig. 11: Aerial view of the European Southern Observatory Paranal site with at that time. His main interest was the Visible and Infrared Survey Telescope in the foreground and the four Very Large focussed on the cepheids, a class of Telescopes in the background (Credit: Gerhard Hüdepohl, ESO) stars that periodically brighten and dim again with a frequency which is a uniform function of their static and eternal. To this end he had von Braun33 in the German Peen- brightness. Therefore, the intrinsic to tune the equation appropriately emünde who was developing liq- brightness can be inferred from the by introducing an artificial term, uid-fuel rocket engines for aircraft period, independently from their which became known as the cos- and jet-assisted take-offs as well as actual distance from the Earth, mological constant. When he learnt for long-range ballistic missiles. Af- qualifying them as the ideal yard about the findings of Hubble, Ein- ter WWII, his group was trans- sticks to measure distances in the stein quickly cancelled this term ferred to Fort Bliss, Texas, where universe. Based on these findings and qualified it as the biggest blun- these “Prisoners of Peace” continued he discovered the proportionality der of his life. their work in rocketry and helped between the distances of the ce the United States to build up an pheids and their velocity away from That was around 1929, when not own rocket programme. In 1946, the Earth, more precisely with their only scientific breakthroughs the first US-built V2 rocket was red shift. He was able to plot a trend shocked the world, but also the col- launched at White Sands Missile line that showed that the universe lapse of the Wall Street stock mar- Range. The American government, is rapidly expanding: the Big Bang ket followed by a global economic however, was not really interested was born. This in turn was bad news crisis. In Germany, Hitler came to in their work at that time and only for Albert Einstein32 on the other power some years later. World War embarked on a modest rocket- side of the Atlantic, who, some years II broke out. Science and engineer- building programme. That, how- before, had formulated his cosmo- ing were forced to serve the devel- ever, changed dramatically from logical equation: in line with the opment of new and more efficient one day to the other, when in au- general consensus at that time he weapon systems. This was the case tumn 1957, the Soviet Sputnik 1 had assumed that the universe is also for a group around Wernher spacecraft beeped around the Earth

31 Edwin Powell Hubble, 1889, Marshfield, Missouri (USA) – 1953, San Marino, California, US American astronomer. 32 Albert Einstein, 1879, Ulm (Germany) – 1955, Princeton (USA), theoretical physicist, Nobel Prize 1921. 33 Wernher Magnus Maximilian Freiherr von Braun, 1912, Wirsitz (Prussia) – 1977, Alexandria, Virginia (USA), German scientist.

SPATIUM 19 16 as the first artificial satellite. Al- though it was not equipped with a 40 Years of science payload, it marked the Space-Based dawn of a new era in astronomy: from now on, the technical means Astronomy were available to transport scientific instruments to space, where they could observe the universe unhampered by the partially opaque There is no doubt: space technol- atmosphere, and even more, to visit ogy has allowed astronomers to and to probe celestial objects in make quantum steps in the under- situ, at least within our solar standing of the universe in a way system. that exceeds all what has been done in the millennia before. The sheer It is, however, interesting to note number of past, current and planned here that the space age did not ter- space missions requires us to con- minate the research with Earth- centrate on some of the most im- borne systems. Rather, rapid tech- portant milestones in the history of nological progress made numerous space-based astronomy. discoveries with Earth-bound teles copes possible. One of the most famous sites of astronomy is the La The Moon Silla (Fig. 11), one of the driest places on Earth, where the European The Moon with its distance of Southern Observatory (ESO) in- about 384,000 km from the Earth ternational organization operates a offers itself as a natural first object suite of the most advanced tele- for space missions. Indeed, only two scopes from its headquarters at years after Sputnik 1, i.e. in 1959, Garching near Munich, Germany. the history of space-based astron- As an example, just lately, ESO an- omy began with the launch of the nounced that Prof. Mayor of the Russian Luna 2 spacecraft, the very University of Geneva and his col- first space mission. On its journey Fig. 12: The Soviet Luna 3 space- leagues have discovered there the to the Moon, it discovered the so- craft. It was the first space probe to reach first extra-solar star that has an lar wind. It then splashed onto the an orbit around the Moon and to explore Earth-like planet just in the right surface of the Earth’s companion its far side (table below). distance to the central star to pos- thereby becoming the first artificial sibly harbour liquid water. This ex- object there. In the same year, in late tra-solar planet will be a hot can- 1959, the Luna 3 spacecraft reached craft performed a spectacular first didate for the search for life beyond a Moon orbit that allowed for the soft landing on the surface of the the boundaries of the solar system exploration of the far side that had Moon and returned the first de- with future space missions. never been seen before, Fig. 12. tailed images from its surface, Fig. 13. During the subsequent years, the Soviets rapidly improved their mas- The unexpected advent of the So- tering of space technology and went viet Sputnik 1 spacecraft caused an on with the Luna programme. It outright shock in the western world: was in 1966 when the Luna 9 space- the United States multiplied their

SPATIUM 19 17 space effort to catch up with the Soviet Union. On 25 May 1961, President John F. Kennedy an- nounced the objective of landing an American astronaut on the Moon before the end of the decade. To this end, NASA was created, and the financial backing of space pro- grammes was dramatically in- creased. A co-ordinated country- wide approach in such different areas as large rocket motors, com- puter and telecommunication technology, and many others, allowed NASA to realize President Kennedy’s vision on 20 July 1969: Neil A. Armstrong, mission commander of Apollo 11, became the first human to set his foot on the surface of the Earth’s companion. “That’s one small step for a man, Fig. 14: US Astronaut Neil A. Armstrong. The picture shows him unfurling the one giant leap for mankind”, he re- solar wind experiment of the University of Bern. (Credit: NASA)

ported to ground control. The mis- Since 1972, when the last humans sion was a complete success, not explored the Moon, it was visited only with regard to human explo- by automated probes only, such as ration of space, but also in the field the US Clementine spacecraft in of space science: a few minutes af- 1994 and ESA’s first mission to the ter stepping onto the dusty Moon Moon, SMART-1, in 2005. Current surface, Armstrong rolled out the plans of NASA as well as ESA in- solar sail experiment developed by tend to exploit the Moon as an at- Professor Johannes Geiss of the tractive first outpost when it comes University of Bern (Fig. 14), thereby to travelling to Mars. This vision, executing the first man-tended however, may turn into reality in space experiment. It consisted of an the 2030 time frame only. aluminium foil that trapped the particles arriving from the Sun. Upon its return to the laboratories The Planets in Bern, the trapped particles were out-gassed from the foil and ana- The success of Soviet spacecraft lyzed to unravel the secrets about prompted NASA to devise space sci- the composition of the Sun and the ence missions also. The first success- history of the solar system. The ex- ful US spacecraft was Mariner 2, that Fig.13: The Soviet Luna 9 space- periment was successfully repeated reached an orbit around Venus in craft. It was the first probe that landed on the Moon and returned images from three times during subsequent 1962. Its instruments confirmed Ve- its landing site (table below). Apollo missions. nus to be a very strange world cov-

SPATIUM 19 18 ered with cool clouds over an ex- acterized by a temperature of 450 °C tremely hot surface. The subsequent and a pressure equalling 84 times that Mariner 4 spacecraft performed the of the Earth’s atmosphere, Fig. 16. Its first close-by trajectory with Mars in instruments witnessed a loud thun- 1964 and returned the first detailed der: Venera 13 became the first space pictures of its surface, Fig. 15. probe to record sound from another world. Within the class of planets, Mars and Venus are the prime objects of space It was in the mid-nineties that Mars missions thanks to their orbits that re-entered into the focus of plane- bring them relatively close to Earth. tary research. This planet is the clos- To reach the outer solar system, very est to the Earth and not too dissim- powerful launchers are required that ilar to our home planet. This qualifies provide the spacecraft with suffi- Mars as the preferred object for hu- cient energy, while a journey to the man exploration. In addition, Mars innermost planet Mercury requires is suspected to possess liquid water complex orbital manoeuvres to underneath its surface, which, at least bring the spacecraft down to the ap- theoretically, could be the basis for propriate orbit. The first space probe some actual or fossil form of life. In to reach Mercury was the US Mar- 1996, NASA launched the Mars iner 10 vehicle. Launched in 1973, Global Surveyor to successfully map Fig. 15: The US Mariner 4 spacecraft it became the first spacecraft suc- the planet’s surface paving the way (upper table) and the first close-up pic- cessfully exploiting the gravity field for subsequent exploration missions. ture of Mars (below). (Credit: NASA) of planets to change its trajectory: it One year later, the Mars Pathfinder flew by Venus and used its gravita- arrived at Mars together with the tional field to bring its perihelion rover Sojourner that explored the down to the level of Mercury’s or- Martian surface. This mission re- bit. This manoeuvre was originally turned huge amounts of detailed in- inspired by the orbital mechanics formation on the Martian surface. calculations of the Italian scientist End of 2003, ESA’s Mars Express Giuseppe Colombo34. The images mission entered a Martian orbit from transmitted by Mariner 10 in 1974 which it continues to transmit de- are still the best available informa- tailed three-dimensional images of tion on Mercury’s surface, as no the planet’s surface as well as infor- other spacecraft has visited this mation on its subsurface structure planet since. thanks to its surface-penetrating ra- dar sensor. In 2004, Mars received Breathtaking successes in the ad- the visit of the US twin Spirit and vancement of space technology took Opportunity, two remotely control- place on the Soviet side also. Their led rovers. Although their expected Venera 13 was the first spacecraft to life time was some 90 days they con- successfully land on the hostile sur- tinue to defy the hostile environ- Fig. 16: The Soviet Venera 13 space- face of Venus: the lander survived for ment and to successfully explore the craft (above) and a detail of the Venus two hours in an environment char- Martian surface. surface (below).

34 Giuseppe Colombo, 1920, Padova (Italy) – 1984, Padova, Italian mathematician and engineer.

SPATIUM 19 19 The Sun objective was to explore Jupiter and its four moons. On its way, it exe- Mastering complex orbital ma- cuted the first asteroid fly-by and noeuvres was one of the key requi- arrived at Jupiter in 1995, becom- sites for another milestone in space- ing the first spacecraft to orbit the based astronomy: Ulysses, a joint giant gas planet. One of the stun- ESA/NASA mission that was ning results of the Galileo mission launched from the US Space Shut- is that the moon Europa most prob- tle in 1990. Its objective was to ex- ably harbours a water ocean be- plore the Sun from high latitudes neath its icy surface which might for the first time. The first part of allow some form of life to develop, Ulysses’ orbit brought the spacecraft as liquid water is thought to be one away from the Sun towards Jupiter of the key ingredients for life36. whose enormous gravitational field was exploited to jettison it out of The dimensions of the universe by the ecliptic plane on an orbit over far exceed the capabilities of our the polar regions of the Sun (Fig. 17, imagination. Even the solar system, middle table). After 17 years of oper- nothing more than a tiny part of the ation, its suite of instruments con- Milky Way which itself is only one tinues to provide first-class scientific of billions of galaxies in the uni- data and to contribute to the un- verse, has dimensions which make derstanding of our most important its exploration lengthy endeavours star, the Sun35. that often exceed the active life of the scientists who invented the mission. The US Voyager 1 spacecraft The Outer Solar System (Fig. 18) is no exception thereof: launched in 1977, thirty years ago, One of the very landmarks in the it visited Jupiter and Saturn and was Fig: 17: The Ulysses spacecraft. outer solar system exploration is the first probe to provide detailed The current third orbit brings it from the US Pioneer 10 spacecraft. images of the moons of these plan- Jupiter towards the southern polar re- Launched in 1972, it was the first ets. It is now the farthest man-made gions of the Sun, then to the perihelion in August 2007, to the northern polar to visit the planet Jupiter, after object from Earth, still rushing away regions and back to Jupiter’s orbit again. which it followed an escape trajec- from the Sun at a faster speed than The table below shows example data re- tory out of the solar system. Its last any other space probe so far. In Au- turned by the Solar Wind Ion Compo- sition Spectrometer (SWICS) instru- weak signal was received in early gust 2006, it reached the milestone ment that was developed at the 2003, when it was 14 billion km of 100 Astronomical Units, that is a University of Bern. It displays the re- away from Earth, but it presumably distance of 15 billion km from the sults of solar wind measurements, more continues its journey into the realm Earth. It is assumed to have entered precisely the particle counts as a function of particle mass over particle mass of interstellar space. now the heliosheath, the region be- per charge ratio. (Credit: Physikalisches Just like Ulysses, the NASA Gali- tween the solar system and the Institut, Universität Bern) leo spacecraft was launched from a interstellar space37. At this distance, Space Shuttle flight also. Its main the signals from Voyager 1 take more

35 See also Spatium 2: Das neue Bild der Sonne. 36 See also Spatium 16: Astrobiology. 37 See also Spatium 17: The Heliosphere.

SPATIUM 19 20 joint ESA/NASA mission Huy- Comets and Interplanetary gens/Cassini was launched that Dust reached Saturn after a seven years journey in 2004. On Christmas Day So far, space missions concentrated 2004, the Cassini spacecraft jetti- on the exploration of the Moon and soned its twin, the Huygens probe, of the planets, as their gravity field towards Titan, where it arrived on helps to guide spacecraft on their 14 January 2005. A complex and final course to the target object. fully automatic sequence of re-en- Perfect mastering of celestial me- try manoeuvres was needed to re- chanics is required when it comes duce the probe’s relative speed from to explore smaller objects like com- some 40,000 km per hour to a ve- ets39. It was ESA’s Giotto probe that locity that allowed the use of para- succeeded in 1986 to execute the chutes. During descent, the probe first close fly-by of a comet and to explored the properties of the transmit the first detailed images of moon’s enigmatic atmosphere, and its cometary nucleus, Fig. 19. The transmitted the data via the Cassini orbiter to ground control on Earth. Then it performed successfully the first landing in the outer solar sys- Fig. 18: NASA’s Voyager 1 space- tem. The probe remained active for craft. Launched in 1977 it returned the a further 70 minutes at an ambient first detailed pictures of the giant planet’s temperature as low as –180°C, gath- atmosphere, of which a false colour image is shown in the table below. (Credit: ering the first images from the sur- NASA) face of Titan, while Cassini continues to orbit Saturn and to explore its many moons38. than thirteen hours to reach the control centre on Earth. The space- A further mission to the outer so- craft has reached escape velocity; to- lar system is NASA’s New Horizons gether with Pioneer 10, Pioneer 11, spacecraft currently heading to- and Voyager 2 it is now an interstel- wards Pluto to visit the dwarf planet lar space probe forever rushing away in 2015 for the first time and to ex- from the solar system. plore its moons Charon, Nix and Hydra. Launched in early 2006 by From the Voyager 1 mission, it was the powerful Atlas V-500 vehicle, known that the Saturnian moon Ti- the New Horizons spacecraft could tan is covered by a dense methane be inserted directly into an Earth- atmosphere. As on Earth methane and solar-escape trajectory with an is always the by-product of biolog- Earth-relative speed in excess of ical processes, Titan began to chal- 16 km per second qualifying it as lenge the international scientific the fastest spacecraft launch up to community. It was in 1997 that the now. Fig. 19 shows the Giotto spacecraft (upper table). Giotto executed the first visit to a comet at close quarters by fly- ing by the comet Halley in 1986. The 38 See also Spatium 15: Titan and the Huygens Mission. lower table shows the first ever image of 39 See also Spatium 4: Kometen. a comet’s nucleus. (Credit: ESA)

SPATIUM 19 21 object as well. The dust may stem its maximum radiative intensity, but from comets, which in the vicinity it blocks many other wavelengths of the Sun receive enough thermal preventing Earth-bound sensors to energy to evaporate some of their receive any information from the matter into space. But the dust may universe. An observatory outside be the in-fall from interstellar space the atmosphere could easily over- as well, making it even more prom- come these problems, and it is no ising. The objective of the US Star- wonder that such ideas had been dust mission (Fig. 20) was to collect put forward long before the re- samples of such dust and to return quired technological assets were at them back to Earth. More specifically, hand. This exactly is the case for the it was intended to capture both inter- Hubble Space Telescope (HST), stellar dust and cometary dust sam- Fig. 21, for which the preparative ac- ples from comet Wild 2 and its coma. tions had been initiated as early as The dust was captured by a specially in 1946. But great things require developed medium called aerogel, a their time: beset by delays and silicon-based solid with a porous, budget problems, it went into orbit sponge-like structure, in which in 1990 as a joint NASA/ESA en- Fig. 20: The Stardust spacecraft. The 99.8 percent of the volume is empty deavour only, and when it was there, upper table shows the spacecraft jettison- space. This medium served to decel- its main mirror was found to be de- ing the dust sample container back to the erate the high velocity dust particles fective. Fortunately though, the Earth, while on the lower table two im- without altering their chemical com- HST was the first spacecraft con- pacts of dust particles can be seen, that penetrated the storage material from the position and to conserve them safely ceived as an astronaut-tended in- right. (Credit: NASA) during the rest of the flight. After a strument that periodically would journey of more than 5 billion km, receive updates as the technologies comet Halley explored by Giotto is the sample container landed on Earth advance. Therefore, NASA decided a notable comet in the sense that it in 2006. In an unprecedented effort, to execute a repair mission with the is the first that was recognized as pe- the analysis of the dust particles is objective of upgrading the defec- riodic. Historical records show that currently executed by a great number tive mirror by a specifically de- Chinese astronomers observed the of scientists all over the world. signed lens that had to be installed comet’s appearance as early as in on the orbiting telescope by an as- 240 B.C. and regular observations tronaut. This was the great chance after 240 B.C. are recorded by Jap- The Universe for our Swiss astronaut Claude anese, Babylonian, Persian, and Nicollier, who, together with his other astronomers. While all the previously mentioned US colleagues, managed to per- missions were focused on a specific fectly execute the challenging re- It is obvious that celestial bodies like target object such as a moon, a pair work in a breathtaking extra- planets, moons and even comets are planet, a comet or interplanetary vehicular activity in late 1993. When scientifically attractive objects as they dust, a general purpose space-borne the telescope was switched on again contain much information on their telescope is doubtlessly an attractive after the repair and the now bright own evolution and that of the solar further application of space tech- and sharp images reached the con- system as a whole. It is, however, less nology. The Earth’s atmosphere is trol centre on the Earth, it became obvious that the interplanetary dust, transparent in some wavelengths, quickly clear that the HST is one that are the particles in the interplan- such as for instance in the visible re- of the most important milestones in etary space, is a promising scientific gion, where the Sun by chance has space-borne astronomy40.

40 See also Spatium 12: Ten Years Hubble Space Telescope.

SPATIUM 19 22 Outlook

Past and ongoing space missions have revealed an incredible amount of information about the solar system and the universe. But, the fas- cination of science is that an an- swered question always rises many new ones. Space research makes no exception thereof. One of the key open issues refers to the nature of the dark matter41. In the midforties already, the Swiss astronomer Fritz Zwicky became aware of the prob- lem that the dynamic behaviour of galaxies cannot be explained by the universal laws of Kepler taking into account the visible mass of the galaxies only. He therefore stipulated an additional source of gravitational pull to keep the stars together. This missing mass is called now dark matter, but its very nature remains unknown. Another puzzling discovery was made in the last few years: according to our expectation, the expansion of the universe should be continuously decelerating. But in contrast, it seems to be accelerated by a so far unknown force termed dark energy.

These are just two examples that challenge new generations of space scientists. Many problems remain open and may become the subject Fig. 21: The Hubble Space Telescope. Since its launch 17 years ago, the space- of fascinating discoveries in the craft has transmitted almost 500,000 images of more than 25,000 celestial objects. This years to come. And beyond all at- information allowed scientists all over the world to publish about 7,000 scientific pa- tempts to understand the mechan- pers. In celebration of its 17th anniversary a team of astronomers has assembled one of ics of the universe there remains the the largest panoramic images ever taken with HST: the lower table shows the central region of the Carina Nebula spanning over 50 light years. (Credit: ESA/NASA) question of whether the human spirit is really alone in this incredible vast universe.

41 See also Spatium 7: In Search of the Dark Matter in the Universe.

SPATIUM 19 23 SPATIUM

The Author

source”, and coincidentally means One of the key concerns of G. F. “it‘s not there” in the Italian Mila- Bignami is the co-operation be- nese dialect. This discovery won tween the two neighbouring coun- him 1993 the “Bruno Rossi” Prize tries Italy and France. This is why of the American Astronomical So- he served as a member of the Sci- ciety together with J. Halpern. entific Council of the French Cen- tre National de Recherche Spatiale From 1974 to 1975 G. F. Bignami was (CNRS) and later as a Director of a visiting assistant professor at the the Centre d’Etude Spatiale des Catholic University of America in Rayonnements at Toulouse. Washington DC, in 1970 he was a visiting scientist at the Max Planck G. F. Bignami’s scientific activities Institute für Kernphysik in Heidel- are linked to the majority of space berg, Germany. Later, he served the science missions. He held major re- Italian National Space Agency (ASI) sponsibilities for instance in ESA’s and the European Space Agency XMM-Newton mission as a Prin- (ESA) in several functions. He par- cipal Investigator for the European ticipated in ESA’s Astronomy Work- Photon Imaging Camera. Quite ing Group (1984–88), in ESA’s Space naturally, such an impressive scien- Giovanni Fabrizio Bignami re- Science Advisory Committee (1994– tific career led to a number of hon- ceived his laureate in physics in 98), he was an Italian Delegate to ours and awards amongst which 1968 at the University of Milan. ESA’s Science Programme Commit- only the Officier de l’Ordre Na- Here, he worked as an assistant to tee (1998–2002), then Vice-Chair- tional du Mérite de la République the Chair of Advanced Physics the man of ESA’s Science Programme Française can be mentioned here. next years. In 1971 he began his ca- Committee (1999–2002) and Chair- reer in science politics when he be- man of ESA’s Space Science Advi- An important endeavour of Bi came research scientist at the Ital- sory Committee (from 2002), just to gnami concerns public outreach ian Consiglio Nazionale delle give an incomplete list of his activi- and science popularization activi- Ricerche (Italian National Re- ties for ESA. On national grounds, he ties. He currently gives about 30 search Council). A fellowship al- served ASI as Director of Science public talks per year, writes regu- lowed him to work at the NASA (1997–2002) in a phase when his larly for major Italian as well as in- Goddard Space Flight Center from budget doubled from 50 M€ to ternational newspapers and maga- 1973 to 1975, where he was in- 110 M€. In early 2007, G. F. Bigna- zines. And last but not least, as a volved in the analysis and interpre- mi’s career culminated by the nomi- diligent student of old languages, he tation of gamma ray astronomy data. nation as President of the Italian published a book containing the During this research activity he dis- Space Agency. On the academic side, first English translation (in iambic covered one of the brightest neu- G. F. Bignami served as Professor in pentameters) of Galileo Galilei’s tron stars, the Geminga in the Physics at the University of Cassino, longest poem. Gemini constellation. Its name is a Italy, and Professor of Astronomy at contraction of “Gemini gamma-ray the University of Pavia (from 1997).