Hubble and its fellow observatories give us an unprecedented, crystal-clear look at the far reaches of the cosmos. Explore these orbiting pioneers and learn what they've discovered. 3 min read The ...

The two keys to Edwin Hubble's breakthrough discovery were forged by others in the 1910s. The first key, the period-luminosity scale discovered by Henrietta Leavitt, allowed astronomers to ...

Photo: Andromeda nebula plate with Hubble's handwritten circle around the variable star he discovered In 1919 American astronomer Edwin Hubble began work at the Mount Wilson Observatory in ...