The 2006 observations by the Spitzer Space Telescope revealed that the Andromeda Galaxy contains approximately one trillion stars, more than twice the number of the Milky Way's estimated 200 to 400 billion stars. The Andromeda Galaxy's mass is estimated to be around 1. 76 times that of the Milky Way Galaxy (~0. 8-1. 5×1012 solar masses vs the Milky Way's 8. 5×1011 solar masses), though a 2018 study found that the Andromeda Galaxy's mass is roughly the same as the Milky Way's. The Andromeda Galaxy, spanning approximately 220,000 light-years, is the largest galaxy in the Local Group, which is also home to the Triangulum Galaxy and other minor galaxies.