12 April 2023

Richard Ellis Receives 2023 Gruber Cosmology Prize

This post is adapted from a Gruber Foundation/Yale University press release:

Jo BovyAAS member Richard Ellis (University College London) will receive the 2023 Gruber Cosmology Prize for his pioneering work both studying galactic evolution dating to the cosmic dawn and designing innovative instruments with which to do so.

The prize, which is cosponsored by the International Astronomical Union, honors a leading cosmologist, astronomer, astrophysicist, or scientific philosopher for theoretical, analytical, conceptual, or observational discoveries leading to fundamental advances in our understanding of the universe. Ellis will receive the $500,000 award as well as a gold laureate pin at a ceremony that will take place in July at the "Shedding New Light on the First Billion Years of the Universe" conference organized by the Galaxies, Etoiles et Cosmologie (GECO) team of the Laboratoire d'Astrophysique of Marseille, in Marseille, France. The citation cites his "broad contributions in the fields of galaxy evolution" as well as his role as "the driver of many frontier instrumental developments in optical Astronomy."

His dual proficiency in observation and instrumentation would alone make Ellis an anomaly among astrophysicists. That his contributions in both areas have proved revolutionary might well make him unique.

As an observer, Ellis has redefined cosmology, the science that studies the growth of the universe. Because the speed of light is finite, astronomers can trace the evolution of galactic structures in reverse, starting with the nearest and most mature and extending to the earliest and most primitive. Over the decades Ellis has repeatedly led surveys of galaxies farther and farther, earlier and earlier across the cosmic landscape.

In a series of landmark studies in the 1990s and 2000s he reconstructed the evolutionary processes that galaxies have undergone in the last 7 billion or so years, or well more than halfway back to the Big Bang. In subsequent surveys he and his collaborators have probed two significant stages far earlier in the development of the universe.

First was the era of reionization, a period within the first billion years after the Big Bang when neutral hydrogen atoms were split into positively charged protons and free electrons. That process, in turn, would have occurred during the emergence of the first galaxies from the gravitational collapse of primordial, opaque clouds of neutral hydrogen — a period of first light which cosmologists have come to call the cosmic dawn, and which Ellis and collaborators determined to have occurred about 250 million years after the Big Bang.

As "the leading authority on galaxy evolution," as one Gruber nominator called him, Ellis has for decades been a fixture on astronomical projects requiring deep probes. In the mid‐1990s he was the sole Europe‐based member on the committee to outline the scientific goals for what was then the Next Generation Space Telescope and is now the James Webb Space Telescope. He was a natural fit for the Supernova Cosmology Project, one of the two teams that discovered evidence that the expansion of the universe is accelerating (2007 Gruber Prize; 2011 Nobel Prize). Ellis was also the principal investigator on the 2012 Hubble Ultra Deep Field campaign, which provided the first census of star‐forming galaxies less than a billion years after the Big Bang.

As Ellis’s observations have taken him farther and farther across the universe into realms that were previously inaccessible, he has found himself needing to adopt or invent new tools.

One challenge was to observe the light from distant galaxies. In order to do so, Ellis was one of the first astronomers to use massive galaxy clusters as gravitational lenses that (as Einstein’s general relativity predicted) magnify the otherwise inaccessible light behind them.

Realizing the challenges of efficiently studying faint galaxies, Ellis devoted much of his career to promoting innovative instruments. He devised, funded, and oversaw the development of several forms of spectrographs that allow astronomers to study gas compositions in the earliest star‐forming galaxies. In turn, those instruments have helped other cosmologists make discoveries about the fundamental nature of the early universe.

Ellis has also occupied many prestigious academic, research, or administrative positions, including: senior scientist at the European Southern Observatory; director of the Palomar Observatory (now Caltech Optical Observatories); director of the Institute of Astronomy at Cambridge University. In 2017 he returned, as a professor of astronomy, to University College London, from which he received his Bachelor of Science in astronomy in 1971.

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