COMMENT OBITUARY Donald Lynden-Bell (1935–2018) Astrophysicist who predicted that galaxies have black holes at their hearts. n 1969, Donald Lynden-Bell became generated friction among the team, some the first astrophysicist to suggest that of which Lynden-Bell diffused by regaling super massive black holes in the cores of us with funny stories. On one occasion, he Igalaxies might generate the profuse energy gave a hilarious recitation of the Patrick put out by quasars — the astonishingly lumi- Barrington rhyme that begins “I had a duck- nous distant bodies identified by astrono- billed platypus when I was up at Trinity…”. mer Maarten Schmidt earlier that decade. To account for the flow, we hypothesized Lynden-Bell proposed that quasars are pow- that there should be many more galaxies ered by the release of gravitational energy behind and beyond the Galactic plane than as material falls into the deep potential well had been assumed. Dressler nicknamed this of the black hole, a process that is much concentration the Great Attractor. (Indeed, more efficient than thermonuclear fusion working with cosmologist Ofer Lahav at (D. Lynden-Bell Nature 223, 690–694; 1969). around the same time, Lynden-Bell identi- CAMBRIDGE UNIV. ASTRONOMY, SMITH, INST. AMANDA Over the following decades, he was proved fied a significant over-density of galaxies.) right. We now know that black holes are At meetings in 1986, theorists greeted the almost ubiquitous in galaxy cores and seem results with alarm, and observers were to have a central role in galaxy evolution. sceptical. At a workshop in Santa Cruz, In the past 20 years, the motions of stars at California, astronomer Amos Yahil dubbed the centre of the Milky Way have revealed our team the ‘seven samurai’ as a nod to our a black hole that is four million times as disregard for conventional cosmology. massive as the Sun. And the Hubble Space merger was not initially a happy one, and Lynden-Bell continued to publish Telescope has shown that black holes with Donald did not relish his first years at the influential work on many subjects. These masses of millions to billions times that of helm. But he threw himself into new pro- ranged from accretion disks and jets, the the Sun lie at the core of almost all massive jects, including a plan to build a telescope for violent relaxation of stellar systems, stellar galaxies. Lynden-Bell and Schmidt shared the institute (sadly never realized). dynamics and spiral structure to general the first Kavli Prize for Astrophysics, in He was generous with his ideas and relativity. His extensive studies of the Milky 2008, for their contributions to understand- time, and was always curious to know Way and its satellites will be tested in April ing quasars. what students were up to, often quizzing 2018, when the next tranche of results Lynden-Bell died on 6 February 2018. them in the corridor. Although he was emerges from the European Space Agency’s Born in 1935 in Dover, UK, he studied math- always supportive, his sharp mathemati- Gaia satellite. He wrote several papers on ematics at the University of Cambridge, cal insight and booming voice could some- statistical mechanics with his wife, Ruth followed by a PhD there in theoretical times be intimidating. He was renowned Truscott, a professor of chemistry at Queen’s astronomy with Leon Mestel. for taking on young scientists at squash. University Belfast; they married in 1961 and In the early 1960s, he spent two formative Student victories were rare. raised two children, Marion and Edward. years at the Carnegie Observatories in In the early 1980s, he joined six collabora- Donald loved sharing the joy and Pasadena, California. Using measurements tors in what, at the time, was a huge survey excitement that a life in science had brought of the composition and orbits of stars taken of more than 400 elliptical galaxies. The him. Fifty years after their first sojourn in by Olin Eggen and Allan Sandage, the three team — Sandra Faber, her former students California, he and three friends — astrono- developed a model for the formation of the Alan Dressler and David Burstein, together mers Nick Woolf, Wal Sargent and Roger Milky Way, based on the rapid collapse of a with Gary Wegner, Roberto Terlevich, Griffin — returned to the western United large spherical gas cloud (O. J. Eggen et al. Lynden-Bell and I — formulated a new States and relived some of the hikes and Astrophys. J. 136, 748; 1962). This was the method for determining the distances to gal- road trips of their youth. This expedi- standard picture for the formation of the axies. Combining this with measurements tion was made into a 2015 film, Star Men, Milky Way and other galaxies until the late of how fast the galaxies were moving away, by Alison Rose. Gentle and captivating, it 1980s, when it was overtaken by the hierar- we traced their motions across the sky. It explores comradeship and ageing. Donald chical-assembly model used today. Lynden- revealed a remarkably coherent flow — with travelled around the country to introduce Bell returned to Cambridge in 1962 and a speed much greater than predicted — in the film and answer questions. moved to the Royal Greenwich Observatory the direction of the constellation Centaurus Donald Lynden-Bell was a towering, at Herstmonceux, Sussex, in 1965. By this and close to the plane of the Milky Way, stimulating, analytical theorist of the sort time, he was an astronomer of international where dust obscures our view of the Uni- that is increasingly rare in these days of stature. verse beyond. Could the corrections used high-performance computers. ■ In 1972 he went again to Cambridge, as to account for this dust have given rise to a the first director of the Institute of Astron- misleading result? Roger Davies is professor of astrophysics omy — an amalgamation of the Cambridge Lynden-Bell was tenacious in scrutiniz- at the University of Oxford, UK. He worked Observatories and the Institute of Theoreti- ing these data, and he formulated a test to with Donald Lynden-Bell as part of the cal Astronomy, which had been founded five ensure that the selection of galaxies had seven samurai for a decade from 1979. years earlier by astronomer Fred Hoyle. The not introduced bias. The intense work e-mail: [email protected] 166 | NATURE | VOL 555 | 8 MARCH© 22018018 Mac millan Publishers Li mited, part of Spri nger Nature. All ri ghts reserved. .