PROFILE

Profile of Ewine F. van Dishoeck he infinite vastness of space, pleasant conversation, he invited van the infinitesimal compactness of Dishoeck to study with him at Harvard a single molecule; comprehend- for a few months, which she did in 1980 ing the size of either object can after receiving her master’s degree in Tbe mind-boggling, and understanding from . ‘‘And that pe- the nature of either can be a life’s work. riod was enough for the Dutch authori- Yet for the past 25 years, astrophysicist ties to give me a grant to do research in has made a career this field, even though there wasn’t for- of bridging the gap between space and mally a professor in that field,’’ she says. the single molecule. As Professor of Molecular Astrophysics at the University East to West Coast of Leiden (Leiden, The ) as Upon completing her Ph.D. thesis on well as director of Leiden’s Raymond photodissociation and excitation of in- and Beverly Sackler Laboratory for As- terstellar molecules in 1984, van Disho- trophysics, van Dishoeck has spent her eck received one of Harvard’s Society of career studying the chemistry and evolu- Fellows positions, which allowed her to tion of the myriad molecules sprinkled continue her research in Dalgarno’s lab- throughout the universe. oratory, where she had made frequent Of particular interest to her are inter- visits while completing her degree. The stellar clouds, regions that appear jet opportunity presented a small problem, black in optical wavelengths but are however, in that de Zeeuw, whom she densely packed with the raw materials had recently married, received a fellow- that give birth to stars and planets. Ewine van Dishoeck ship at the Institute for Advanced Study Along with a multitude of collaborators in Princeton, NJ. ‘‘Interestingly, we had in Europe and the United States, van the opportunity to have two positions Dishoeck, elected to the National Acad- At Leiden, van Dishoeck found that in the Princeton area or two positions in emy of Sciences as a foreign associate in physics interested her, and her interests the Harvard area,’’ she says, ‘‘but the 2001, has studied the chemical evolution began shifting toward chemical physics, advice we got from some of the more of the molecules within these clouds as and especially quantum chemistry, on senior people was that in the long run, they condense into stellar and planetary which she did her senior project. van it’s better at the earlier stages to take bodies. As summarized in her Inaugural Dishoeck was determined to continue the steepest road in terms of your ca- Article in this issue of PNAS (1), which with quantum chemistry in graduate reer so that later on you have the better is also part of a Special Feature on school, but soon after she started, the papers to be together in one place.’’ Interstellar Chemistry, recent improve- professor who specialized in quantum And because Harvard was the best place ments in astronomical instrumentation chemistry at Leiden died. ‘‘The way for van Dishoeck, and Princeton the have enabled van Dishoeck and other [Ph.D. programs] work in Holland is best place for her husband, they decided molecular astrophysicists to observe in that you can only do a thesis under to live apart for the time being. detail low-mass protostellar regions sim- a full professor,’’ says van Dishoeck, At Harvard, van Dishoeck’s work was ilar to those around the Earth’s primi- ‘‘and it became clear that the university principally a continuation of her thesis tive sun, thus providing some of the first wouldn’t come to a consensus on a re- project, studying the photodissociation clues about the chemical origin of the placement for quite some time.’’ Thus, of molecules in interstellar clouds or solar system. if van Dishoeck wanted to stay at Lei- comets (2–4). She studied ‘‘how rapidly den for her graduate work, she needed a molecule falls apart under UV radia- A Not-So-Chance Encounter to find another field of study. tion and what are the basic molecular Although born and raised in Leiden, van At that time, van Dishoeck’s boy- processes by which this occurs,’’ she Dishoeck’s brief stopover in the United friend, , was studying as- says. ‘‘We know this process from our States as a youth launched her scientific tronomy and had just finished a course own atmosphere and ozone. There’s a journey. When she was 12, her father, a on the and the re- prime example of a molecule that is recently retired professor of ear, nose, cent discoveries of interstellar mole- photodissociated into an oxygen mole- and throat medicine, was invited to cules. van Dishoeck recalls that he told cule and an oxygen atom, which then, spend 6 months in San Diego, CA. van her, ‘‘Well, isn’t this something for of course, is a large cause for the ozone Dishoeck took her first science class in you?!’’ van Dishoeck knew nothing hole.’’ the San Diego public school system. She about but learned that the van Dishoeck also studied molecules remembers that her science teacher, preeminent expert of the interstellar as diagnostic tools for studying certain who as a female and African-American medium was Alex Dalgarno at Harvard processes in interstellar clouds. ‘‘For in the 1960s had undoubtedly overcome University (Cambridge, MA). That sum- example, if you look at the beautiful some obstacles to reach her position, mer, as fate or fortune would have it, nebulae in the sky, you want to know did an outstanding job of fostering in van Dishoeck and her boyfriend were how warm or how dense they are,’’ she van Dishoeck an interest in science and camping in Canada’s Mont Tremblant says. ‘‘So we spent some time looking providing career inspiration. When van National Park and heard that the park at the excitation of various molecules Dishoeck returned to The Netherlands, was hosting a major astronomy confer-

her high school chemistry teacher ence. ‘‘We got up the courage to go up This is a Profile of a recently elected member of the National opened up the wonderful world of mole- to this conference and see if Professor Academy of Sciences to accompany the member’s Inaugural cules for her, and she went on to study Dalgarno was there,’’ she says. Dalgarno Article on page 12249. chemistry at the University of Leiden. was indeed present, and after a brief, © 2006 by The National Academy of Sciences of the USA

www.pnas.org͞cgi͞doi͞10.1073͞pnas.0604740103 PNAS ͉ August 15, 2006 ͉ vol. 103 ͉ no. 33 ͉ 12229–12231 Downloaded by guest on September 25, 2021 board, the Short Wavelength Spectrom- eter, had been built in The Netherlands. The principal investigator for that project, Thijs de Graauw, had guaran- teed time on the satellite, and he kindly offered some time to van Dishoeck. The ISO was scheduled to launch in 1992, but as is common with such space projects, multiple delays pushed the launch to 1995. The delay was actually a blessing in disguise. In 1992, Mayo Greenberg, who had set up Leiden’s first astrophysics laboratory in the 1970s, reached the mandatory retire- ment age of 70. At the time, van Disho- eck felt it was important to keep the astrophysics laboratory up and running. ‘‘The ball sort of got in the court of as- tronomy, and they turned to me and said, ‘Well, Ewine, is this something for you to take under your wing?’ and I said, ‘Well, I’m not really a laboratory person,’ but I could see that [Green- berg’s] lab was set up to do exactly the kind of experiments that we needed to do in order to interpret the data from van Dishoeck, with husband Tim de Zeeuw, in front of the APEX 12-m telescope, Atacama Large Millimeter the ISO satellite.’’ So, by scraping Array (ALMA) site, Chajnantor, Chile, 2005. money together from various sources, van Dishoeck took over the laboratory and kept it going for several more pro- because the ratios can tell you about only when you go to longer wavelengths ductive years, while she collected her how often and how hard a molecule col- that you start to find something.’’ first observations from the ISO satellite. lides.’’ In turn, van Dishoeck notes, ‘‘We were able to identify several new these values could be related to molecu- Return to Holland species in the solid state and at the lar parameters, and so these molecules van Dishoeck spent two fruitful years at same time learn more about the chemi- could be turned into long-distance ther- CalTech, but in 1990, her husband was cal evolution of these regions in which mometers and pressure gauges, thus al- offered a full professorship at the Uni- new stars are being formed,’’ she says. lowing for the design of comprehensive versity of Leiden. van Dishoeck was models of these clouds (5). offered an associate-level position at After her Fellows program concluded, Leiden, one that included many grants ‘‘If you look at van Dishoeck reunited with her husband to help start her own research group. at Princeton for one year as a visiting ‘‘Both of us really enjoyed the United the beautiful nebulae professor, ‘‘which was very nice. Cer- States, and I certainly would have loved tainly after two and a half years, we had to stay a little bit longer at CalTech,’’ in the sky, you want more than enough of this commuting!’’ she says of the tough decision to return she says. In 1988, van Dishoeck and her home, ‘‘but [Leiden’s] combination was to know how warm or attractive enough for the two of us to husband moved to the West Coast, move back. I’m still a very frequent visi- where she accepted a faculty position at how dense they are.’’ tor to CalTech and Harvard, [and] I still the California Institute of Technology have very good collaborations there.’’ (CalTech, Pasadena, CA) in a new pro- She adds that there was one other Some of the highlights included carbon gram: cosmochemistry, a subset of the major reason for coming back to The dioxide, methane, and formic acid ices, geology and planetary sciences depart- Netherlands: the European Space which are extremely difficult to detect ment. At CalTech, van Dishoeck began Agency (ESA) was set to launch a new from ground observatories because of expanding her work to a third line of satellite, the Infrared Space Observatory interference by these molecules in research, by using molecular diagnostics (ISO). ‘‘That was important because in Earth’s atmosphere (6–8). van Dishoeck to study the different stages of star and infrared wavelengths, you can see not and colleagues also found hot water and planet formation to understand how just gas-phase molecules but also solid- carbon dioxide gas, as well as some un- these stellar bodies are born. This field state species,’’ she says. ‘‘That gave me usual gaseous compounds, such as the had just opened up after the completion an infrared complement to what I was methyl radical (CH3), an intermediate of powerful new ground-based tele- doing at the submillimeter telescopes, product in reactions involved in hydro- scopes, such as the CalTech Submillime- which was important since a lot of mole- carbon synthesis (9–11). CH3, which is ter Observatory and the James Clerk cules are freezing out on to the grains in extremely reactive and unstable on Maxwell Telescope (JCMT). ‘‘These re- the cold parts and then coming off Earth, had been studied by Nobel laure- gions in which stars and planets are be- again in the warmer part and triggering ate Gerhard Herzberg in the 1950s. ‘‘He ing formed are basically very dusty,’’ she a rich gas-phase chemistry. You need had always said that these are the kinds explains, ‘‘and that means they are com- both wavelengths to put the story to- of molecules you would see in outer pletely black at the optical range. It’s gether.’’ One of the four instruments on space, but it wasn’t until we got the

12230 ͉ www.pnas.org͞cgi͞doi͞10.1073͞pnas.0604740103 Zagorski Downloaded by guest on September 25, 2021 infrared spectrum that we were finally survey and map the nearby large molec- instrument on the horizon is the Her- able to identify it,’’ says van Dishoeck. ular clouds, such as in the Chameleon schel Space Observatory, with which van and Perseus star systems. This work Dishoeck has been involved for many Finding Baby Planets helped uncover additional protostars years. ‘‘Herschel will be looking in the van Dishoeck’s work on stellar evolu- lurking in the darkness, such as the new- far infrared spectrum and will be partic- tion, as well as that of other researchers, born star HH 46͞47 within the Vela ularly well suited to look for water, was interesting in its own right but was constellation (12), which was one of the which is a key molecule in all of chemis- not considered particularly relevant by Spitzer Space Telescope’s earliest try,’’ she says. ‘‘That’s another future some because the results could not be discoveries. line of research, the chemical evolution related to Earth’s solar system. ‘‘With The high sensitivity of the Spitzer of water. Where does it form, where the ISO satellite, we only had the sensi- Space Telescope also allows for a better does it freeze out as ice, and where does tivity to look at high-mass stars, like glimpse of the icy and dusty disks that it get back into the gas phase?’’ those in Orion, which are 10,000 times rotate around newly forming stars as van Dishoeck has also been exten- more luminous than the sun,’’ explains they collapse, rings that may someday sively involved in planning other next- van Dishoeck. ‘‘Our star is just a very condense into planets. These protoplan- generation instruments, such as the ordinary star.’’ Over the past 5 years, etary disks have been difficult to study Atacama Large Millimeter Array however, technology has improved to be because they have far less mass than the (ALMA) in Chile. ALMA will combine sensitive enough to study the chemistry star they orbit, and depending on their 50 single telescopic dishes to act as one. of low-mass stars like the sun as well as angle, can obscure the star light. van Further down the road, the James Webb even smaller objects such as brown Dishoeck and colleagues managed to Space Telescope will eventually succeed dwarfs that are not massive enough to study some potential protoplanetary the Hubble. ‘‘So that is sort of the bal- ignite hydrogen and become true stars. disks with fortunate alignments and ance that you now have. When you are ‘‘So that is the new part of the story,’’ found interesting characteristics. In ad- a young student or a postdoc, you’re van Dishoeck says. She reviews some of dition to some of the first discoveries of fortunate that other people have put in the recent contributions to this story in water, ammonium, and methane ices in the time to promote these instruments her PNAS Inaugural Article (1). these disks (13), she and her group have with which you can do your research, Many of the findings in van Dishoeck’s also found large amounts of hydrogen and now our generation has to be the Inaugural Article are connected with the cyanide (HCN) and acetylene (C2H2) drive for the facilities with which future Spitzer Space Telescope, NASA’s suc- gases, both of which are building blocks students can do their research,’’ says van cessor to the ISO that was launched, for some of life’s essential compounds: Dishoeck. Such a forward-thinking per- again after a lengthy delay from the amino acids and nucleic acids (14). spective is important because these large original planned date, in 2003. ‘‘I am Although the presence of these prebi- astronomical facilities usually take fortunate to be part of one of these big otic molecules should not receive too 20–25 years to advance from conception legacy programs in which you give a much hype, according to van Dishoeck, to fruition. ‘‘For example, for the Her- group of people, in my case a group led she believes that these protoplanetary schel Space Observatory, I had my first by Neal Evans from the University of disks, especially around low-mass stars, meeting on it in 1982, when I was still a Texas, a large amount of observation represent the future of interstellar graduate student,’’ says van Dishoeck. time with the caveat that your data be- chemistry research once the technology Now, years later, the Herschel is set for come public immediately,’’ she says. ‘‘So to observe these tiny objects, by galactic a 2008 launch date—barring any unex- it’s basically a program you’re carrying standards, is available. Besides the pected delays, of course. out for the community.’’ One of the Spitzer Space Telescope, such technolo- main objectives of Evans’ group was to gies will soon be on the way. One such Nick Zagorski, Science Writer

1. van Dishoeck, E. F. (2006) Proc. Natl. Acad. Sci. E. F., Schutte, W. A., Tielens, A. G. G. M. & 11. Feuchtgruber, H., Helmich, F. P., van Dishoeck, USA 103, 12249–12256. Whittet, D. C. B. (1998) Astron. Ap. 336, 352–358. E. F. & Wright, C. M. (2000) Astrophys. J. 535, 2. van Dishoeck, E. F. & Dalgarno, A. (1984) Icarus 8. Schutte, W. A., Tielens, A. G. G. M., Whittet, L111–L114. 59, 305–313. D. C. B., Boogert, A. C. A., Ehrenfreund, P., de 12. Noriega-Crespo, A., Morris, P., Marleau, F. R., 3. van Dishoeck, E. F. (1987) J. Chem. Phys. 86, Graauw, Th., Prusti, T., van Dishoeck, E. F. & Carey, S., Boogert, A., van Dishoeck, E., Evans, 196–214. Wesselius, P. R. (1996) Astron. Ap. 315, L333– N. J., Keene, J., Muzerolle, J., Stapelfeldt, K., et al. 4. van Dishoeck, E. F. & Black, J. H. (1988) Astro- L336. (2004) Astrophys. J. Suppl. Ser. 154, 352–358. phys. J. 334, 771–802. 9. Helmich, F. P., van Dishoeck, E. F., Black, J. H., 13. Pontoppidan, K. M., Dullemond, C. P., van Disho- 5. van Dishoeck, E. F. & Black, J. H. (1986) Astro- de Graauw, Th., Beintema, D., Heras, A., Lahuis, eck, E. F., Blake, G. A., Boogert, A. C. A., Evans, phys. J. Suppl. Ser. 62, 109–145. F., Morris P. W. & Valentijn, E. A. (1996) Astron. N. J., Kessler-Silacci, J. & Lahuis, F. (2005) As- 6. de Graauw, Th., Whittet, D. C. B., Gerakines, Ap. 315, L173–L176. trophys. J. 622, 463–481. P. A., Bauer, O. H., Beintema, D. A., Boogert, 10. van Dishoeck, E. F., Helmich, F. P., de Graauw, 14. Lahuis, F., van Dishoeck, E. F., Boogert, A. C. A., A. C. A., Boxhoorn, D. R., Chiar, J. E., Ehren- Th., Black, J. H., Boogert, A. C. A., Ehrenfreund, Pontoppidan, K. M., Blake, G. A., Dullemond, freund, P., Feuchtgruber, H., et al. (1996) Astron. P. E., Gerakines, P. A., Lacy, J. H., Millar, T. J., C. P., Evans, N. J., Hogerheijde, M. R., Jorgensen, Ap. 315, L345–L348. Schutte, W. A., et al. (1996) Astron. Ap. 315, J. K., Kessler-Silacci, J. E. & Knez, C. (2006) 7. Boogert, A. C. A., Helmich, F. P., van Dishoeck, L349–L352. Astrophys. J. Letters 636, L145–L148.

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