Marissa Gebhard | May 8, 2015
University of Notre Dame astrophysicist Nicolas Lehner led a team of scientists who used NASA’s Hubble Space Telescope to identify an immense halo of gas surrounding the Andromeda Galaxy, the nearest major galaxy to Earth. The halo stretches about a million light-years from Andromeda, halfway to the Milky Way. The discovery will tell astronomers more about the evolution and structure of giant spiral galaxies such as the Milky Way and Andromeda.
“Halos are the gaseous atmospheres of galaxies,” said Lehner, the lead investigator. “The properties of these gaseous halos control the rate at which stars form in galaxies.” The gargantuan halo is estimated to contain at least as much mass in its diffuse gas as half of the stars in the Andromeda Galaxy.
Using the Hubble Space Telescope, scientists have observed halos around other galaxies, but never before has such a massive halo been observed so near to Earth beyond the Milky Way.