In 1920, astronomers Harlow Shapley and Heber Curtis held a Great Debate. Shapley argued that the spiral nebulae were small ...

Predictions are uncertain, but the solar system may be pushed farther from the galactic core or even ejected entirely from ...

The center of our Milky Way galaxy is hidden from the prying eyes of optical telescopes by clouds of obscuring dust and gas.

The Andromeda nebula, M31 ... It seemed that these redshifted galaxies were all moving away from the Milky Way. Hubble’s results suggested the farther away a galaxy was, the faster it was moving away ...

Astronomers spent a decade compiling this special image with the Hubble Space Telescope and then stitched together 600 photos ...

While the events observed around Sgr A* are dramatic, this black hole is not as active as some at the center of other ...

The Andromeda galaxy, then known as the Andromeda nebula ... idea that there could be enormous stellar systems outside the Milky Way—but astronomers now just call these systems galaxies.