A hundred years ago, astronomer Edwin Hubble dramatically expanded the size of the known universe. At a meeting of the American Astronomical Society in January 1925, a paper read by one of his ...

An expanding universe of galaxies But Hubble wasn’t done. His second major discovery also transformed astronomers’ understanding of the universe.

Finding what’s out there Space Week is Oct. 4-10, so here are some of NASA’s latest discoveries and why Edwin Hubble’s history-making photo, taken on this day in 1923, revolutionized astronomy.

One large Milky Way galaxy or many galaxies? 100 years ago, a young Edwin Hubble settled astronomy’s ‘Great Debate.’ Hubble transformed astronomers’ understanding of the universe.

An expanding universe of galaxies But Hubble wasn't done. His second major discovery also transformed astronomers' understanding of the universe.