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Allan Rex Sandage

Allan Rex Sandage

Astronomer Allan Rex Sandage (born 1926) took it as his life's work to find out how old and how large the universe is. His work led him to conclude the universe is 15 billion to 20 billion years old. Sandage is credited with the discovery of quasars, small blue cosmic objects that may be places where stars are born.

Became a Stargazer

Born on June 18, 1926, Sandage was an only child. His father was a business professor at Miami (Ohio) University and his mother was the daughter of the president of a Church of Jesus Christ of Latter Day Saints (Mormon) school. On quiet Ohio nights, Sandage enjoyed watching the stars through a friend's telescope. Soon he was keeping an eye on the skies day and night. As a teenager, he kept a record of sunspots he observed over a period of four years. Young Sandage read writings by British astronomer and mathematician Arthur Stanley Eddington and The Realm of the Nebulae (1936) by Edwin P. Hubble.

After studying physics and philosophy at Miami University, Sandage served in the U.S. Navy as an electronics specialist during World War II. After the war, he earned a bachelor's degree in physics from the University of Illinois in 1948 and a Ph.D. from the California Institute of Technology in 1953.

While still a student, Sandage worked at the Palomar Observatory with astronomers Hubble and Walter Baade, trying to discover the secrets of the universe through the world's largest telescope at that time. Sandage later used the 100-inch Hooker telescope on Mount Wilson and the 200-inch Hale telescope on Mount Palomar to uncover mysteries such as the evolution of stars.

Measured the Universe

In 1952, Sandage joined Carnegie Observatories, where he became involved in investigating the origins of the universe. During his first year, he equated the luminosity of the globular clusters M92 and M3 to the luminosity of the sun. He found that stars in those globular clusters were as much as 12 billion years old.

In September 1953, Hubble died of a heart attack. Sandage continued the painstaking work that Hubble had begun. He found that gathering data and eliminating errors were daunting tasks. Still, after much analysis, he found that Hubble's original estimates of the universe's age were more conservative than the data seemed to indicate. Sandage's results in 1958 seemed to show that the universe was 7 to 13 billion years old, much greater than Hubble had thought. By 1975, Sandage began to think the universe was even more ancient, perhaps 15 or 20 billion years old.

To determine the age of a star, Sandage looked at a classic color-magnitude diagram. He plotted the brightness of stars against their colors or temperatures. How bright a star is depends on its age, mass, and chemical makeup. Sandage looked at the relationships between stars that belong to younger clusters and stars that belong to older clusters to find clues to stellar evolution.

Working with Gustav Tammann, of the University of Basel, Switzerland, and Dr. Abijit Saha, of Kitt Peak National Observatory, Sandage found that the universe is expanding at a speed of about 55 kilometers/second/ megaparsec. This speed indicates that the universe is about 14 billion years old. Some stars have since been calculated to be about 15 billion years old, which bolsters Sandage's theory.

As an observational cosmologist, Sandage built on the work Hubble began in the 1920s and 1930s. Before long, Sandage was known as Mr. Cosmology, or the Super Hubble. Hubble-Sandage variable stars take their name from the energetic astronomer and his mentor.

Discovered Quasars

In 1964, Sandage and his colleague Thomas Matthews discovered sources of concentrated radio energy in distant space. They called them quasars, short for quasi stellar radio sources. The center of a quasar is thought to be a black hole that sucks in gases and other materials that form the discus shape associated with quasars. Quasars are very bright, probably about 1,000 times brighter than the Milky Way Galaxy. They are thought to be the most distant objects in the universe: in 1968 Maarten Schmidt found that they are located on the edge of the known universe.

Wrote on Religion

Unlike some scientists who see religion and science as opposed, Sandage believes they are complementary. In an article he wrote for Truth Journal, Sandage said science should take religion seriously and religion should respect science. "Science makes explicit the quite incredible natural order, the interconnections at many levels between the laws of physics, the chemical reactions in the biological processes of life, etc.," he wrote. "But science can answer only a fixed type of question. It is concerned with the what, when, and how. It does not, and indeed cannot, answer within its method (powerful as that method is), why."

Defended Theories

Observational cosmologists disagree on how to measure distances between Earth and the stars. Critics have often attacked Sandage's premise that the universe is always expanding, and others have questioned his findings. But time proved Sandage's measurements to have validity, even if they were not accepted at first by all his peers.

When Sandage and Tammann found that some scientists were selecting stars and galaxies that were too bright to represent "standard candles"—a measurement scientists use to determine distances between Earth and celestial objects—Sandage found new ways to take measurements. While critics ignored Sandage's findings, he and his team looked into Type 1A supernovas to correlate galactic rotational velocities with brightness.

Sandage's skirmishes with his colleagues and critics over the expansion rate of the universe were so heated at times that they were sometimes called the "Hubble Wars." Despite all the controversy over his work, Sandage was always regarded as one of the top observational cosmologists in the world.

Sandage's book Lonely Hearts of the Cosmos, was published in 1991. In retirement, Sandage lives in Pasadena, California, with his wife, Mary Lois. They have two sons, David and John.


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Current Biography Yearbook, January 1999.


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