Edwin Powell Hubble

Astronomer

• Born: November 20, 1889
• Birthplace: Marshfield, Missouri
• Died: September 28, 1953
• Place of death: San Marino, California

American astronomer

Twentieth-century American astronomer Edwin Hubble is credited with the discovery that countless galaxies exist beyond the Milky Way, previously believed to be the only galaxy in the universe. He also identified the outward expansion of those galaxies, disproving the centuries-old belief that the universe was static. He produced the first outline of the observable universe, revolutionizing conceptions of its size, structure, processes, and history.

Primary field: Astronomy

Specialties: Observational astronomy; theoretical astronomy; cosmology

Early Life

Edwin Powell Hubble was born in Marshfield, Missouri, the third of eight children born to Virginia Lee James, a homemaker, and John Powell Hubble, a businessman. He moved with his family when he was twelve years old to Wheaton, Illinois, and in 1906 won a scholarship to the University of Chicago, where he studied physics, chemistry, astronomy, and mathematics, as well as Latin, Greek, and French. He graduated in 1910 and was selected as a Rhodes Scholar, spending the next three years in England at Queens College, Oxford University. There, perhaps in compliance with his father’s wishes, Hubble studied Roman and English law, although he retained his love of astronomy. John Hubble died in 1913, and that year Edwin completed his studies at Queens and returned to the United States, where he taught Spanish, physics, and mathematics at New Albany High School in Indiana.

At the end of the school year in 1914, Hubble wrote to his former astronomy professor Forest Ray Moulton to tell him that he wanted to enter a graduate program in astronomy, but lacked the necessary funds. With Moulton’s help, Hubble obtained a position as an assistant at the Yerkes Observatory of the University of Chicago, and Hubble began work on a doctoral degree in astronomy, completing his degree in 1917.

Following graduation, Hubble was offered an astronomer position by George Ellery Hale, director of the Mount Wilson Observatory in Southern California; but instead, he applied for an officer’s commission in the US Army during World War I, serving in France and attaining the rank of major. Honorably discharged in 1919, Hubble then joined the staff of the Wilson Observatory, a position he held for more than three decades until his death. Hubble married Grace Burke in 1924; they had no children.

Life’s Work

In 1923, Hubble used the 100-inch Hooker Telescope, then the largest telescope in the world, to view Cepheid variables in what was then known as the Andromeda nebula. Cepheids are stars that cycle from brighter to dimmer and back over a fixed period of time. They had been used to measure the distance between objects in the galaxy since the early 1900s, when American astronomer Henrietta Swan Leavitt’s observations of Cepheid brightness made it possible for scientists to use mathematical calculations to determine galactic distances. Using Cepheid stars, Hubble was able to prove that the Andromeda nebula was an independent galaxy and not a cluster of gasses and stars in the Milky Way as was previously believed.

In 1924, Hubble gained international recognition and was acknowledged for launching a new era in celestial inquiry when the New York Times reported his findings that spiral nebulae, which appeared as whirling clouds, are in fact galaxies—stellar systems that are immense, of varying size, and at great distances from the Milky Way galaxy. This revolutionized mainstream conceptions of the size and expanse of the universe.

In 1925, Hubble developed the Hubble sequence, or the Hubble tuning-fork diagram, a classification scheme for galaxies based on their shape or appearance. He categorized galaxies into three broad types: spiral, elliptical, and lenticular, with variations within each type. The small percentage of galaxies that did not fit into this three-tiered scheme were classified as irregulars. This classification system of galaxies remains in use today.

By 1929, Hubble, with his assistant Milton Humason, produced evidence that the outer galaxies were receding from each other at thousands or even hundreds of thousands of miles per second. He proposed that groups of galaxies were bound by gravity and would travel together in space, showing a relationship between the speed of recession of the galaxies and their distance from each other: The farther a galaxy is, the faster it appears to be receding. This distance-velocity relation is called Hubble’s law.

In 1936, Hubble published his major findings in the book The Realm of the Nebulae (1936), which contained his views on the structure of the universe and its expanding nature. Hubble’s findings revealed innumerable galaxies throughout the universe, comparable in size to the Milky Way and separated by unimaginably large voids. He also determined that, if considered on a large-enough scale, the universe is isotropic (it has neither a centernor an edge) and homogenous (it is generally the same in composition throughout).

In 1931, Einstein publicly thanked Hubble for his evidence of a dynamic universe, which supported cosmological considerations in the general theory of relativity more concisely than had Einstein’s own rationale. Using Hubble’s findings, scientists could determine the rate at which galaxies move and the distance that separates them. Furthermore, by retracing galaxies’ paths, astronomers could infer the amount of time that has passed since all matter and energy in the universe existed in a state of utmost density. The number they reached using this technique, called the “Hubble time,” gave a close estimate of the age of the universe, believed to be about 13.7 billion years. Thus, Hubble and other astronomers provided the observational reasons, and Einstein and other physicists provided theoretical reasons, for assuming an explosive origin to the universe and its subsequent expansion, popularly called the big bang theory.

In 1942, the United States was involved in World War II, and Hubble was asked by the government to lead the US Army’s Ballistics Research Laboratory at the Aberdeen Proving Ground in Maryland. He remained there until December of 1945, when he returned to Mount Wilson Observatory. He was awarded the Medal of Merit for his services at Aberdeen. Back at Wilson, Hubble continued his work on cosmology, seeking to learn whether the expansion of the universe would cease or continue forever. In 1949, Hubble was the first to use the newly completed 200-inch Hale Telescope at Mount Palomar in California.

Hubble died in 1953 from heart failure.

Impact

Hubble’s natural inclinations, curiosity, and talents prompted him to decipher and analyze the riddles of the universe. By the time of his death, he had become the world’s foremost astronomer. The Hubble crater on the moon and Asteroid 2069 Hubble are named in his honor. The Hubble Space Telescope, put into orbit in 1990, has supplied valuable research data and images that have lead to many discoveries in the field of astrophysics. In fact, the telescope was used to observe supernovae of a special type in order to continue research on the expansion of the universe, whose leaders were honored with the 2011 Nobel Prize in Physics.

Hubble’s discoveries that the universe is made up of countless and ever-changing and moving galaxies formed the basis of modern cosmology. He equipped cosmology with a new vocabulary and a new set of concepts for further study. His work initiated a fundamental shift in the pattern of cosmological thought comparable to the work of Nicolaus Copernicus and Galileo Galilei.

Bibliography

Christianson, Gale E. Edwin Hubble: Mariner of the Nebulae. New York: Farrar, 1995. Print. A comprehensive and detailed biography of Hubble.

Hetherington, Norriss S. Hubble’s Cosmology: A Guided Study of Selected Texts. Tucson: Pachart, 1996. Print. An interpretative, evaluative framework for understanding some original Hubble papers.

Hubble, Edwin. The Realm of the Nebulae. 1936. New Haven: Yale UP, 1982. Print. Hubble’s own story of his research.

Kanipe, Jeff. Chasing Hubble’s Shadows: The Search for Galaxies at the Edge of Time. New York: Hill and Wang, 2006. Print. Interprets findings of the Hubble Space Telescope on the expansion of the universe.

Sharov, Alexander S., and Igor D. Novikov. Edwin Hubble, the Discoverer of the Big Bang Universe. Trans. Vitaly Kisin. Cambridge: Cambridge UP, 2005. Print. Recounts the growth of Hubble’s scientific thought and consequential discoveries.