Allan Sandage
Encyclopedia
Allan Rex Sandage was an American
astronomer
. He was Staff Member Emeritus
with the Carnegie Observatories
in Pasadena, California
. He is best known for determining the first reasonably accurate value for the Hubble constant and the age of the universe
.
in 1948. In 1953 he received a Ph.D.
from the California Institute of Technology
; the German
-born Wilson Observatory-based astronomer Walter Baade
was his advisor. During this time Sandage was a graduate student assistant to cosmologist Edwin Hubble
. He continued Hubble's research program after Hubble died in 1953. In 1952 Baade had shaken the astronomical world by announcing his determination of two separate populations of Cepheid variable
stars in the Andromeda Galaxy
, resulted in a doubling of the estimated age of the universe
(from 1.8 to 3.6 billion years). Hubble had posited the earlier value; he had only considered the weaker Population II Cepheid variables as standard candles. Following Baade's pronouncements, Sandage showed that astronomers' previous assumption, that the brightest stars in galaxies were of approximately equal inherent intensity, was mistaken in the case of H II region
s which he found not to be stars and inherently brighter than the brightest stars in distant galaxies. This resulted in another 1.5 factor increase in the calculated age of the universe, to approximately 5.5 billion years. Throughout the 1950s and well into the 1980s Sandage was regarded as the pre-eminent observational cosmologist, making contributions to all aspects of the cosmological distance scale, ranging from calibrators within our own Milky Way
Galaxy, to cosmologically distant galaxies.
Sandage began working at the Palomar Observatory
. In 1958 he published the first good estimate for the Hubble constant, revising Hubble's value of 250 down to 75 km/s/Mpc, which is close to today's accepted value. Later he became the chief advocate of an even lower value, around 50, corresponding to a Hubble age of around 20 billion years.
Sandage performed photometric studies of globular cluster
s, and calculated their age to be at least 25 billion years. This led him to speculate that the universe did not merely expand, but actually expanded and contracted with a period of 80 billion years. The current cosmological estimates of the age of the universe, in contrast, are typically of the order of 14 billion years. As part of his studies on the formation of galaxies in the early universe, he co-wrote the paper now called ELS after the authors Olin J. Eggen
, Donald Lynden-Bell
and Sandage, first describing the collapse of a proto-galactic gas cloud into our present Milky Way Galaxy. He later defended the paper in 1990.
In his 1961 paper "The Ability of the 200-inch Telescope to Discriminate Between Selected World Models," he suggested that the future of observational cosmology would be the search for two parameters: the Hubble constant H0 and the deceleration parameter q0. This paper influenced observational cosmology for at least three decades as it carefully laid out the types of observational tests that could be performed with a large telescope. He also published two atlases of galaxies, in 1961 and in 1981, based on the Hubble classification scheme.
In 1962 Sandage studied the possibility of directly measuring
the temporal variation of the redshift of extra-galactic sources. This analysis became known as the "Sandage–Loeb test".
Sandage is noted for his discovery in the M82 galaxy
of jets erupting from the core. These must have been caused by massive explosions in the core, and they have apparently been occurring for at least 1.5 million years.
Sandage was a prolific researcher; during his career he published over 500 papers. Until his death he continued to be an active researcher at the Carnegie Observatories
, still publishing several papers a year.
later in his life. He wrote several essays on the subject of religion and science, which appeared in publications such as Science and the Spiritual Quest: New Essays by Leading Scientists (New York, NY: Routledge, 2002). On November 13, 2010, Sandage died of pancreatic cancer
at his home in San Gabriel, California
. He was 84 years old.
Named after him
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
astronomer
Astronomer
An astronomer is a scientist who studies celestial bodies such as planets, stars and galaxies.Historically, astronomy was more concerned with the classification and description of phenomena in the sky, while astrophysics attempted to explain these phenomena and the differences between them using...
. He was Staff Member Emeritus
Emeritus
Emeritus is a post-positive adjective that is used to designate a retired professor, bishop, or other professional or as a title. The female equivalent emerita is also sometimes used.-History:...
with the Carnegie Observatories
Carnegie Institution for Science
The Carnegie Institution for Science is an organization in the United States established to support scientific research....
in Pasadena, California
Pasadena, California
Pasadena is a city in Los Angeles County, California, United States. Although famous for hosting the annual Rose Bowl football game and Tournament of Roses Parade, Pasadena is the home to many scientific and cultural institutions, including the California Institute of Technology , the Jet...
. He is best known for determining the first reasonably accurate value for the Hubble constant and the age of the universe
Age of the universe
The age of the universe is the time elapsed since the Big Bang posited by the most widely accepted scientific model of cosmology. The best current estimate of the age of the universe is 13.75 ± 0.13 billion years within the Lambda-CDM concordance model...
.
| (96155) 1973 HA | 27 April 1973 |
Career
Sandage was one of the most influential astronomers of the 20th century. He graduated from the University of IllinoisUniversity of Illinois at Urbana-Champaign
The University of Illinois at Urbana–Champaign is a large public research-intensive university in the state of Illinois, United States. It is the flagship campus of the University of Illinois system...
in 1948. In 1953 he received a Ph.D.
Ph.D.
A Ph.D. is a Doctor of Philosophy, an academic degree.Ph.D. may also refer to:* Ph.D. , a 1980s British group*Piled Higher and Deeper, a web comic strip*PhD: Phantasy Degree, a Korean comic series* PhD Docbook renderer, an XML renderer...
from the California Institute of Technology
California Institute of Technology
The California Institute of Technology is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering...
; the German
Germans
The Germans are a Germanic ethnic group native to Central Europe. The English term Germans has referred to the German-speaking population of the Holy Roman Empire since the Late Middle Ages....
-born Wilson Observatory-based astronomer Walter Baade
Walter Baade
Wilhelm Heinrich Walter Baade was a German astronomer who worked in the USA from 1931 to 1959.-Biography:He took advantage of wartime blackout conditions during World War II, which reduced light pollution at Mount Wilson Observatory, to resolve stars in the center of the Andromeda galaxy for the...
was his advisor. During this time Sandage was a graduate student assistant to cosmologist Edwin Hubble
Edwin Hubble
Edwin Powell Hubble was an American astronomer who profoundly changed the understanding of the universe by confirming the existence of galaxies other than the Milky Way - our own galaxy...
. He continued Hubble's research program after Hubble died in 1953. In 1952 Baade had shaken the astronomical world by announcing his determination of two separate populations of Cepheid variable
Cepheid variable
A Cepheid is a member of a class of very luminous variable stars. The strong direct relationship between a Cepheid variable's luminosity and pulsation period, secures for Cepheids their status as important standard candles for establishing the Galactic and extragalactic distance scales.Cepheid...
stars in the Andromeda Galaxy
Andromeda Galaxy
The Andromeda Galaxy is a spiral galaxy approximately 2.5 million light-years from Earth in the constellation Andromeda. It is also known as Messier 31, M31, or NGC 224, and is often referred to as the Great Andromeda Nebula in older texts. Andromeda is the nearest spiral galaxy to the...
, resulted in a doubling of the estimated age of the universe
Age of the universe
The age of the universe is the time elapsed since the Big Bang posited by the most widely accepted scientific model of cosmology. The best current estimate of the age of the universe is 13.75 ± 0.13 billion years within the Lambda-CDM concordance model...
(from 1.8 to 3.6 billion years). Hubble had posited the earlier value; he had only considered the weaker Population II Cepheid variables as standard candles. Following Baade's pronouncements, Sandage showed that astronomers' previous assumption, that the brightest stars in galaxies were of approximately equal inherent intensity, was mistaken in the case of H II region
H II region
An H II region is a large, low-density cloud of partially ionized gas in which star formation has recently taken place. The short-lived, blue stars forged in these regions emit copious amounts of ultraviolet light, ionizing the surrounding gas...
s which he found not to be stars and inherently brighter than the brightest stars in distant galaxies. This resulted in another 1.5 factor increase in the calculated age of the universe, to approximately 5.5 billion years. Throughout the 1950s and well into the 1980s Sandage was regarded as the pre-eminent observational cosmologist, making contributions to all aspects of the cosmological distance scale, ranging from calibrators within our own Milky Way
Milky Way
The Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...
Galaxy, to cosmologically distant galaxies.
Sandage began working at the Palomar Observatory
Palomar Observatory
Palomar Observatory is a privately owned observatory located in San Diego County, California, southeast of Pasadena's Mount Wilson Observatory, in the Palomar Mountain Range. At approximately elevation, it is owned and operated by the California Institute of Technology...
. In 1958 he published the first good estimate for the Hubble constant, revising Hubble's value of 250 down to 75 km/s/Mpc, which is close to today's accepted value. Later he became the chief advocate of an even lower value, around 50, corresponding to a Hubble age of around 20 billion years.
Sandage performed photometric studies of globular cluster
Globular cluster
A globular cluster is a spherical collection of stars that orbits a galactic core as a satellite. Globular clusters are very tightly bound by gravity, which gives them their spherical shapes and relatively high stellar densities toward their centers. The name of this category of star cluster is...
s, and calculated their age to be at least 25 billion years. This led him to speculate that the universe did not merely expand, but actually expanded and contracted with a period of 80 billion years. The current cosmological estimates of the age of the universe, in contrast, are typically of the order of 14 billion years. As part of his studies on the formation of galaxies in the early universe, he co-wrote the paper now called ELS after the authors Olin J. Eggen
Olin J. Eggen
Olin Jeuck Eggen was an American astronomer. Some sources incorrectly give his name as Olin Jenck Eggen.-Biography:...
, Donald Lynden-Bell
Donald Lynden-Bell
Donald Lynden-Bell CBE FRS is an English astrophysicist, best known for his theories that galaxies contain massive black holes at their centre, and that such black holes are the principal source of energy in quasars. He was a co-recipient, with Maarten Schmidt, of the inaugural Kavli Prize for...
and Sandage, first describing the collapse of a proto-galactic gas cloud into our present Milky Way Galaxy. He later defended the paper in 1990.
In his 1961 paper "The Ability of the 200-inch Telescope to Discriminate Between Selected World Models," he suggested that the future of observational cosmology would be the search for two parameters: the Hubble constant H0 and the deceleration parameter q0. This paper influenced observational cosmology for at least three decades as it carefully laid out the types of observational tests that could be performed with a large telescope. He also published two atlases of galaxies, in 1961 and in 1981, based on the Hubble classification scheme.
In 1962 Sandage studied the possibility of directly measuring
the temporal variation of the redshift of extra-galactic sources. This analysis became known as the "Sandage–Loeb test".
Sandage is noted for his discovery in the M82 galaxy
Galaxy
A galaxy is a massive, gravitationally bound system that consists of stars and stellar remnants, an interstellar medium of gas and dust, and an important but poorly understood component tentatively dubbed dark matter. The word galaxy is derived from the Greek galaxias , literally "milky", a...
of jets erupting from the core. These must have been caused by massive explosions in the core, and they have apparently been occurring for at least 1.5 million years.
Sandage was a prolific researcher; during his career he published over 500 papers. Until his death he continued to be an active researcher at the Carnegie Observatories
Carnegie Institution for Science
The Carnegie Institution for Science is an organization in the United States established to support scientific research....
, still publishing several papers a year.
Personal life
In 1959, Sandage married Mary Connelley, also an astronomer, with whom he had two sons, David and John. Sandage became a ChristianChristian
A Christian is a person who adheres to Christianity, an Abrahamic, monotheistic religion based on the life and teachings of Jesus of Nazareth as recorded in the Canonical gospels and the letters of the New Testament...
later in his life. He wrote several essays on the subject of religion and science, which appeared in publications such as Science and the Spiritual Quest: New Essays by Leading Scientists (New York, NY: Routledge, 2002). On November 13, 2010, Sandage died of pancreatic cancer
Pancreatic cancer
Pancreatic cancer refers to a malignant neoplasm of the pancreas. The most common type of pancreatic cancer, accounting for 95% of these tumors is adenocarcinoma, which arises within the exocrine component of the pancreas. A minority arises from the islet cells and is classified as a...
at his home in San Gabriel, California
San Gabriel, California
San Gabriel is a city in Los Angeles County, California, United States. It is named after the Mission San Gabriel Arcángel, founded by Junipero Serra. The city grew outward from the mission and in 1852 became the original township of Los Angeles County. San Gabriel was incorporated in 1913...
. He was 84 years old.
Honors
Awards- Helen B. Warner Prize for AstronomyHelen B. Warner Prize for AstronomyThe Helen B. Warner Prize for Astronomy is awarded annually by the American Astronomical Society to a young astronomer for a significant contribution to observational or theoretical astronomy....
(1957) - Eddington MedalEddington MedalThe Eddington Medal, named after Sir Arthur Eddington, is awarded by the Royal Astronomical Society nominally once every two years for investigations of outstanding merit in theoretical astrophysics.- Recipients :* 1953 Georges Lemaître...
(1963) - Gold Medal of the Royal Astronomical SocietyGold Medal of the Royal Astronomical Society-History:In the early years, more than one medal was often awarded in a year, but by 1833 only one medal was being awarded per year. This caused a problem when Neptune was discovered in 1846, because many felt an award should jointly be made to John Couch Adams and Urbain Le Verrier...
(1967) - National Medal of ScienceNational Medal of ScienceThe National Medal of Science is an honor bestowed by the President of the United States to individuals in science and engineering who have made important contributions to the advancement of knowledge in the fields of behavioral and social sciences, biology, chemistry, engineering, mathematics and...
(1970) - Henry Norris Russell LectureshipHenry Norris Russell LectureshipThe Henry Norris Russell Lectureship is awarded each year by the American Astronomical Society in recognition of a lifetime of excellence in astronomical research.-Previous lecturers:This list of lecturers is from the American Astronomical Society's website....
(1972) - Elliott Cresson MedalElliott Cresson MedalThe Elliott Cresson Medal, also known as the Elliott Cresson Gold Medal, was the highest award given by the Franklin Institute. The award was established by Elliott Cresson, life member of the Franklin Institute, with $1,000 granted in 1848...
(1973) - Bruce MedalBruce MedalThe Catherine Wolfe Bruce Gold Medal is awarded every year by the Astronomical Society of the Pacific for outstanding lifetime contributions to astronomy. It is named after Catherine Wolfe Bruce, an American patroness of astronomy, and was first awarded in 1898...
(1975) - Crafoord PrizeCrafoord PrizeThe Crafoord Prize is an annual science prize established in 1980 by Holger Crafoord, a Swedish industrialist, and his wife Anna-Greta Crafoord...
(1991)
Named after him
- Main-belt asteroid, 9963 Sandage9963 Sandage9963 Sandage is a main belt asteroid. It orbits the Sun once every 3.58 years.Discovered on January 9, 1992 by E. F. Helin, it was given the provisional designation "1992 AN". It was later renamed "Sandage" after Allan Sandage, an American astronomer....
(1992 AN)
Further reading
- Alan P. Lightman and Roberta Brawer, Origins: the lives and worlds of modern cosmologists, Harvard University Press, 1990. Interviews with modern cosmologists, including Sandage.
- Timothy FerrisTimothy FerrisTimothy Ferris is a science writer and the best-selling author of twelve books, including The Science of Liberty and Coming of Age in the Milky Way , for which he was awarded the American Institute of Physics Prize and was nominated for the Pulitzer Prize...
, The Red Limit: The Search for the Edge of the Universe, Harper Perennial, 2002. Non-technical description of research, primarily up to about 1980, on cosmology; Sandage was a key figure, and features accordingly. - Dennis OverbyeDennis OverbyeDennis Overbye is a science writer specializing in physics and cosmology.-Biography:Overbye received his B.S. in physics from M.I.T.—where he was a member of the Alpha Mu chapter of Phi Kappa Sigma—in 1966. He started work towards a master's degree in astronomy from U.C.L.A...
, Lonely Hearts of the Cosmos: the story of the scientific quest for the secret of the Universe, HarperCollins 1991, Back Bay (with new afterword), 1999. Historical account of modern cosmology told through the careers of the scientists involved, in which Sandage is the central character. Complementary to Origins. - Allan Sandage, The Mount Wilson Observatory. Centennial History of the Carnegie Institution of Washington, Vol. 1. Cambridge University Press, 2004. Sandage's account of the observatory where he worked, with the background to his own work with Hubble and others.