Born: Marshfield, Missouri, November 20, 1889
Died: San Marino, California, September 28, 1953
Hubble initially studied law and took a degree at Oxford in that subject. However, his interest turned to astronomy and after World War I, he began working at the Mount Wilson Observatory which boasted a 100-inch telescope.|
He began to study the luminous patches of fog, or nebulae, some of which had first been studied by Messier, some 150 years before, and which, at that time, were like large questions marks in the sky. It was known that the Magellanic Clouds lay outside of our galaxy, and that some of the nebulae were clouds of dust and gas within our galaxy, illuminated by stars shining within them, but the luminosity of others, for example, the M31 nebula could not be explained.
In 1924, Hubble was finally able to enlarge the M31 nebulosity and see the stars within it, some of which were Cepheid variables. Using the period-luminosity law developed by Shapley and Leavitt, Hubble was able to calculate that the Andromeda galaxy was about 800,000 light-years away, eight times further away than the most distant star of our galaxy, the Milky Way. This distance was later found to be slightly under-estimated, but there was no doubt that Andromeda lay outside our own galaxy.
Hubble went on to place other nebulae, farther still, their distances ranging into billions of light-years. He classified the galaxies according to shape, and theorised about the evolution of galaxies. He studied the radial velocities of galaxies and suggested that the speed at which a galaxy was receding from us, was directly proportional to its distance, supporting the expanding universe theory. He also deduced from this, that at a vast distance from ourselves, the speed of recession of galaxies would approach the speed of light, and we would thus never be able to know that part of the universe. This is known as the Hubble radius, and it has been calculated at 13 billion light years. To put it another way, the knowable universe is a sphere with a diameter of 26 billion light-years.
The efforts of Hubble founded the study of the universe beyond our galaxy, and led to the development of the "big bang" theory of the universe.