Galaxies, Milky Way The Milky Way and Andromeda galaxies are approaching each other. With current technology, how long would it take before we could directly measure the apparent increase in size of Andromeda?
Exoplanets, Milky Way, Planets, Robotic Spaceflight, Solar System Saturn spacecraft not affected by hypothetical planet 9
Exoplanets, Milky Way, Planets, Solar System Early Mars bombardment likely enhanced life-supporting habitat
