Jeremiah Ostriker, one of the most influential astrophysicists of the 20th century, has died at the age of 87. His work reshaped our understanding of the Universe, revealing it to be dominated not just by stars and galaxies, but also by mysterious dark matter and dark energy. From 2001 to 2004, Ostriker held the Plumian Professorship of Astronomy and Experimental Philosophy at the University of Cambridge’s Institute of Astronomy.
In the early 1970s, Ostriker and his colleague Jim Peebles showed that galaxies like our Milky Way should fly apart unless embedded in massive halos of invisible matter -- what we now call 'dark matter'. Two decades later, working with Paul Steinhardt, he helped revive Einstein’s cosmological constant as a way to explain observations suggesting the Universe’s expansion was speeding up. That idea, once controversial, became central to the modern cosmological model after being confirmed by observations in 1998.
Alongside his theoretical work, Ostriker was instrumental in launching large-scale international collaborations, including the Sloan Digital Sky Survey, a project that has mapped millions of galaxies, and, making its data freely available to astronomers around the world, has resulted in a huge range of astronomical discoveries. His influence extended far beyond his own research: he was a mentor to generations of scientists across the world, and remained deeply engaged with new ideas and discoveries into his final years.
Professor Cathie Clarke, co-director of the Institute of Astronomy, said "Jerry was a highly visible and interactive presence in the department during his years as Plumian Professor. He was a regular at the IoA's coffee and teatimes, engaging in spirited scientific conversations; indeed his support of the importance of these events in the scientific life of the IoA led him to donating funds to improve the biscuits served! While in Cambridge, Jerry was a Fellow of Clare College and played an important role in advising the College on matters of finance and alumni relations."
Ostriker never lost his sense of wonder for the cosmos. “As an astrophysicist, you get a perspective on humankind,” he once said. “Sweating on this little grain of spinning sand.” As Professor Martin Rees put it, “Some scientists come up with pioneering ideas on novel themes; others write definitive ‘last words’ on already-established topics. Jerry was in the first category. “He wrote among the earliest papers — now classics — on the nature of pulsars, the evidence for dark matter and on galaxy formation and cosmology. His flow of papers continued into his 80s. He enthusiastically engaged in new data and in computational techniques. He inspired younger colleagues and collaborators, not just at Princeton but around the world.”
Martin Rees added " I was privileged to know Jerry since my student days, and to benefit from his ideas and insights — especially of course during the years he spent in Cambridge."