Andromeda and the Milky Way, Two Galaxies on a Collision Course
The two large spiral galaxies will eventually collide in five billion years or so, according to calculations based on data published in the second release of the Gaia astrometric satellite catalog. But it won’t be a head-on collision
Our galaxy, the Milky Way, together with about seventy other galaxies, is part of a cluster called the Local Group, which extends for about 10 million light-years. The two largest and most massive galaxies of the Local Group are Andromeda (M31) and the Milky Way, followed by another spiral, the Triangle Galaxy (M33). The fourth galaxy of the group by mass and size is the Large Magellanic Cloud, which is considered a minor galaxy, as it is a Milky Way’s satellite.
The glue that holds the Local Group together is the mutual gravitational attraction between the several galaxies that are part of it. The major centers of this attraction are obviously the three main galaxies — Andromeda, the Milky Way, and the Triangle. For many years, astronomers have been studying the motions of stars in these galaxies to try to calculate as accurately as possible the route they are following under the pull of mutual attraction. It has been known for…
