Edwin Hubble (1889 - 1953) discovered that many objects previously thought to be clouds of dust and gas and classified as "nebulae" were actually galaxies beyond the Milky Way.
He also showed that the recessional velocity of a galaxy increases with its distance from the earth. He inferred the recession velocity of the galaxies from their redshifts. This became known as "Hubble's law". Hubble's Law implies that the universe is expanding. See also Georges Lemaître)
The Hubble Space Telescope (HST) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. Hubble is one of the largest and most versatile space telescopes, and is well known as both a vital research tool and a public relations boon for astronomy. The HST is named after the astronomer Edwin Hubble, and is one of NASA's Great Observatories, along with the Compton Gamma Ray Observatory, the Chandra X-ray Observatory, and the Spitzer Space Telescope.
