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Evolution of the universe and Earth’s place in cosmos – The 2019 for Physics

This was an unusual Nobel prize in that existence of the microwave background. Over the years, he has been awarded a it was awarded ‘for contributions to our In the now well-known story, Peebles number of medals and prizes including understanding of the evolution of the un- gave a talk on his subject at the Applied the Heineman Prize, the Gold Medal of iverse and Earth’s place in the cosmos’. Physics Laboratory of the Johns Hopkins the Royal Astronomical Society, the This is a broad area which could include University following which Arno Penzias Gruber Prize, the and, almost anything in astronomy. James and Bob Wilson contacted Dicke for help now, culminating with the Nobel Prize. Peebles was awarded one half of the in understanding the mysterious noise Along the way, he has published several Prize ‘for theoretical discoveries in phy- picked up by their radio dish at Bell books, including the Principles of Physi- sical cosmology’ which was really a rec- Labs. Penzias and Wilson were awarded cal Cosmology which has taught many ognition of a lifetime of work while the Nobel Prize in 1978 for the discovery people . Jim Peebles and won of the cosmic microwave background has truly been awarded the Prize for his the other half of the Prize ‘for the discov- and it seems only fair that Dicke should entire life’s work. ery of an orbiting a solar-type have had a share in the prize (it went to The other half of the prize was shared star’: a very specific if notable discovery. Kapitza, who was certainly a deserving by Michel Mayor and Didier Queloz for While undeniably deserved, either award recipient). the specific discovery of the first planet could have been given anytime in the last Peebles has had an outstanding career around a star in 1995. The 25 years for the exoplanet discoveries focused on physical cosmology and has first planet had been discovered only a and 50 years for the cosmology work. played an important role in moving the few years earlier by Wolszczan and Frail Phillip James Edwin (Jim) Peebles was field from speculation into the firm mod- through observations of pulsar timing, born in a suburb of , the only els and predictions that we have today. but pulsar environments are notably city in the province of in He has discussed how he was always un- inhospitable. Mayor had been working , on 25 April 1935. He went to a sure of the basic axioms of cosmology, on high resolution spectroscopy for radi- small school there and then to the Uni- namely isotropy and homogeneity to the al velocity measurements and when, with versity of Manitoba where he started in point where he felt it was unrealistic to Queloz, he turned his attention to 51 the engineering school. Like many of us, have a theory of the Universe. He played Pegasi, they were found the first planet he did not find engineering very exciting a major role in showing not only that around a normal-type star, opening the and switched to physics in his third year. such a theory made sense but in putting floodgates of exoplanet detections. Then, as now, the University of Manito- together the framework for that theory. Michel Gustave Édouard (Michel) ba was largely a teaching institution and He was amongst the first to run computer Mayor was born in Lausanne, Switzer- it was not until he joined Princeton that simulations of the cosmic structure land on 12 January 1942. He obtained an he learnt about new areas in research. formation. This is now a core research M Sc from the University of Lausanne in After a brief flirtation with particle phys- area in astronomy with each new model 1966 and a Ph D from Geneva Observa- ics, he joined Robert Dicke’s group on greeted with great enthusiasm. Peebles tory in 1971. He spent most of the next gravity physics. Bob Dicke played a ma- has made contributions to more areas of four decades at Geneva Observatory be- jor role in Peebles’ career and his admi- cosmology than can be discussed here coming Director of the Geneva Observa- ration and gratitude to Dicke is clear, and I will close by simply mentioning his tory in 1998. He retired in 2007 but, of even now. Dicke, himself, was one of contributions to , , course, continues to do ground-breaking those rare talents who was primarily an and galaxy evolution. research at the Observatory. experimentalist and an instrument builder but with the theoretical foundation to create new areas of physics. Peebles re- ceived his Ph D in 1962 under the super- vision of Dicke and has remained at Princeton ever since. He is now the Professor of Science, Emeritus. Peebles first began his work in physi- cal cosmology with a work suggested by Dicke. Dicke had been exploring the idea of an oscillatory universe in which the heavy elements from one universe would have been destroyed by the high tem- peratures of the next. Although not par- ticularly interested or convinced by the idea, Peebles did work out the radiation James Peebles Michel Mayor Didier Queloz due to the hot Universe and predicted the Source: © Nobel Media.

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Didier Queloz was born in Neuchâtel, netary systems had been our own Solar ing work in dark matter. It is a shame Switzerland on 23 February 1966 and System with its very organized nine pla- that so few women have been recognized completed his undergraduate and gradu- nets: four rocky planets near the Sun and for their work and it would have made a ate education at the University of Gene- four gassy planets far away plus Pluto. It strong statement if the Committee had va, and still holds a professorship there. was still an open question whether there not overlooked such a deserving candi- He joined the Cavendish Laboratory of were planets around other stars at all and date. the University of Cambridge in 2013 as a Frank Drake’s famous equation only put I can do no better than to close with professor and has been there since. planets around 50% of other stars. Now, Peebles own words: winning awards and Mayor had been working on more not only was one other system found but prizes are ‘very much appreciated’ but accurate ways to determine radial veloci- it was a very different system with a hot one should ‘enter it [science] for the love ties and over the years developed spec- Jupiter, a Jupiter-sized planet where of the science.’

trometers that could measure velocities Mercury should have been. Soon many first at levels of a few km/s and then, more such systems were found and it be- 1. Peebles interview with Alan Lightman: after Queloz joined, to levels of a few came clear that our system was unusual https://www.aip.org/history-programs/niels- metres/s. The culmination of their work in being so apparently normal. Exopla- bohr-library/oral-histories/33957 was the ELODIE echelle spectrograph. nets were a career-ending field when 2. Peebles interview with Martin Harwit: The student (Queloz) had been using the Mayor and Queloz found 51 Peg b; now https://www.aip.org/history-programs/niels- spectrograph to look at radial velocity no proposal can be put in without stating bohr-library/oral-histories/4814 3. Princeton announcement of Nobel Prize: measurements of the Sun-like star 51 its impact on exoplanetary studies and, https://www.princeton.edu/news/2019/10/08/ Pegasi, which is a (barely) naked eye star even more, on searching for extra- princetons-james-peebles-receives-nobel- about 50 light years from the Sun. He terrestrial life. prize-physics found that the star was jiggling back and Mayor and Queloz have both had pro- 4. James Geach in the Conversation: https:// forth with a peak velocity of about 50 ductive careers after their discovery with theconversation.com/nobel-prize-in-physics- m/s and, after convincing themselves that contributions to other instruments and james-peebles-master-of-the-universe- their answer was correct, Mayor and programmes but, in their case, the Nobel shares-award-124916 Queloz published their paper in Nature was awarded strictly for this one discov- 5. A Jupiter-mass companion to a solar-type as ‘A Jupiter-mass companion to a solar- ery that opened up the entire field. With- star by Mayor & Queloz: https://www. type star’, a publication with over 2300 out 51 Peg b, there would have been no nature.com/articles/378355a0 6. Queloz website at Cavendish: https://www. citations. Despite initial scepticism, this Kepler and no TESS. astro.phy.cam.ac.uk/directory/prof-didier- result was soon confirmed by Butler and Winning the Nobel prize is a matter of queloz Marcy using the Lick Observatory and chance. There are many who deserve the 7. Announcement: https://www.nobelprize.org/ the floodgates opened for exoplanet dis- Prize but did not get it – E. C. G. Sudar- prizes/physics/2019/prize-announcement/ covery, with the deluge coming after the shan springs to mind. As I said earlier, flights of Kepler and now TESS, which this Prize could have been given long Jayant Murthy, Indian Institute of is finding 50 a month. back and, if it had been given five-years , Koramangala, Bengaluru It is hard to overstate the impact of the ago, the late Vera Rubin would have 560 034, India. 51 Peg discovery. The paradigm for pla- been a strong candidate for her pioneer- e-mail: [email protected]

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