Edwin Hubble (1889 - 1953) was an American astronomer who transformed the scientific understanding of the cosmos. He demonstrated that spiral nebulae are galaxies lying far beyond the Milky Way and showed that the universe is expanding, a relationship now expressed as Hubble's law. [1] His observations established the framework of modern observational cosmology. [2]
Early life and education
Edwin Powell Hubble was born on 20 November 1889 in Marshfield, Missouri, and grew up near Chicago, where he distinguished himself in both academics and athletics. [1] He studied mathematics and astronomy at the University of Chicago before travelling to England as a Rhodes Scholar at The Queen's College, Oxford, where he read law. [1] After briefly practising law and teaching, he returned to science and completed a doctorate in astronomy at the University of Chicago's Yerkes Observatory in 1917. [1]
Career at Mount Wilson
Following service in the United States Army during the First World War, Hubble joined the staff of the Mount Wilson Observatory in California in 1919. [1] There he gained regular access to the 100-inch Hooker Telescope, then the most powerful in the world, whose light-gathering capacity allowed him to resolve individual stars within distant nebulae and to measure their properties in unprecedented detail. [1]
Galaxies and the expanding universe
In the early 1920s Hubble identified Cepheid variable stars in the Andromeda Nebula and other spiral nebulae. Because the intrinsic brightness of Cepheids can be inferred from their pulsation period, he used them to show that these systems lie far outside the Milky Way. [1] This established that the universe contains countless separate galaxies and vastly enlarged the known scale of the cosmos. [1] In 1929 he reported that galaxies recede from one another at speeds roughly proportional to their distance, a relationship now called Hubble's law and widely taken as evidence that the universe is expanding. [3] He also introduced a classification of galaxies by shape, the Hubble sequence, which remains in use. [4]
Legacy
Hubble's discoveries supplied the observational foundation for modern cosmology and for the Big Bang model of an evolving universe. [2] He received numerous honours, including the Gold Medal of the Royal Astronomical Society, the Bruce Medal and the Franklin Medal. [1] He died on 28 September 1953 in San Marino, California. [1] The Hubble Space Telescope, launched in 1990, was named in his honour, and the present rate of cosmic expansion is expressed through the Hubble constant. [2]
