2000 Gruber Cosmology Prize

Allan Sandage has defined the fields of observational cosmology and extragalactic astronomy for most of the last forty years. Modern cosmological research had its beginnings with the great work of Edwin Hubble in the 1920’s and 1930’s, which established what were then called spiral nebulae as separate distant “island universes”, i.e., galaxies. Hubble demonstrated the expansion of the universe, and laid the roots of galaxy classification still used today. Using the powerful Hale 200-inch telescope at Palomar Observatory in Southern California, Sandage continued and expanded upon Hubble’s program on a large number of fronts.

Sandage has quantified the expansion of the universe in many important ways. In particular, in close collaboration with Gustaf Tammann of the University of Basel, Switzerland, he relentlessly pursued the value of the Hubble Constant, which determines the rate of expansion, through detailed observations of galaxies. He made the essential measurements of globular cluster stars to determine their ages, and showed the correspondence with the expansion age of the universe from the Hubble Constant.

Sandage was the first to recognize the existence of quasars without strong radio emission, leading the way to the discovery of some of the most distant objects in the universe. He has thoroughly explored the observational characteristics of galaxies, their stellar populations, their clustering properties and their evolutionary history. He led the first major redshift survey of galaxies, creating a three-dimensional map of the galaxy distribution, and used it to explore the dynamics of the local Universe. He developed new observational techniques and opened new areas of inquiry in fields ranging from the pulsations of stars, to tests of cosmological models at great distances, to searches for quasars.

Sandage’s papers have set the research agenda for hundreds of astronomers in all these areas. His lifetime contribution to extragalactic astronomy and cosmology, and his influence on his colleagues, is unmatched by any other astronomer.

By Michael Strauss
Department of Astrophysical Sciences
Princeton University

Phillip James E. Peebles was born in Winnipeg, Canada, Province of Manitoba, on April 25, 1935. Living in the tiny town of St. Vital and graduating in a high school class of 12, his interests in science were not tapped until his college days. Although planning to study engineering at the University of Manitoba, he encountered four inspirational physics professors who sparked a career in physics. He received his BS degree from the University in 1958 and moved next to Princeton University, intending to study particle physics.

Instead he became the only student of his influential mentor, Robert Dicke, to enter into theoretical physics. Under Dicke's influence Peebles gradually moved from studies of gravity to astronomy and from astronomy to cosmology. Dicke also planted the original seed that inspired Peebles to look for the presence of background radiation in the universe. In 1965, as a result of Peebles' post doctoral research, he and Dicke boldly predicted the existence of cosmic background radiation. In 1966 he began work on the theoretical calculations that would make cosmological studies an important topic for physicists. His book Physical Cosmology (1971) established the framework for a series of challenging new theoretical proposals that helped shape the field of cosmological studies. In 1984 Peebles was named Albert Einstein Professor of Science at Princeton University.

Peebles has written many influential and provocative articles in addition to his important books. His contributions have been recognized with honorary degrees from the University of Toronto, University of Chicago, McMaster University, University of Manitoba, University of Newcastle-upon-Tyne, and the Université Catholique de Louvain. He has also received important awards, including the Eddington Medal of the Royal Astronomical Society (1981) and the Gold Medal of the Royal Astronomical Society (1998).

Professor Peebles and his wife, Alison, live in Princeton, New Jersey, where they share an interest in gardening and in exploring nature. Although he plans to retire from his faculty position at Princeton in the near future, he does not plan to discontinue his life long pursuit of understanding the nature of the cosmos.