Edwin Hubble

Edwin Hubble

Edwin Hubble

In the 1920s the American astronomer Edwin Hubble was the first to prove that there are galaxies outside the Milky Way.

By using Cepheid variable stars to calculate the distance of the Andromeda Nebula (as it was then known) from the Earth, Hubble showed that it was a separate galaxy and not a gas cloud in the Milky Way. Later, by comparing the relative velocities of galaxies (measured as red shifts) with his measurements of their distances from the Earth, Hubble showed that the further away a galaxy is from any point in space, the faster it appears to move because of the expansion of the Universe – Hubble's Law.

Image: Hubble at Palomar Observatory (credit: Emilio Segre Visual Archives/AIP/SPL)

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Edwin Hubble


An American astronomer measures the Universe's expansion.

About Edwin Hubble

Edwin Powell Hubble (November 20, 1889 – September 28, 1953) was an American astronomer who played a crucial role in establishing the field of extragalactic astronomy and is generally regarded as one of the most important observational cosmologists of the 20th century. Hubble is known for showing that the recessional velocity of a galaxy increases with its distance from the earth, implying the Universe is expanding, known as "Hubble's law" although this relation had been discovered previously by Georges Lemaître, who published his work in a less visible journal.

Edwin Hubble is also known for providing substantial evidence that many objects then classified as "nebulae" were actually galaxies beyond the Milky Way. American astronomer Vesto Slipher provided the first evidence for this argument almost a decade before.

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