The Andromeda Galaxy, also known as Messier 31 or M31, is a large spiral galaxy located about 2.537 million light-years away from the Milky Way. It is the closest spiral galaxy to our own.
Regarding its motion, observations have shown that the Andromeda Galaxy is moving towards the Milky Way. Both galaxies are part of the Local Group, a collection of galaxies that includes several smaller galaxies as well. The motion of the Andromeda Galaxy towards the Milky Way is primarily due to the gravitational attraction between the two galaxies.
In fact, current scientific understanding suggests that the Andromeda Galaxy and the Milky Way are on a collision course. They are expected to collide in the distant future, around 4 to 6 billion years from now. The collision will result in a merger of the two galaxies, forming a new elliptical galaxy. This event is often referred to as the "Andromeda-Milky Way collision" or "Milkomeda."
The reduction in distance between the Andromeda Galaxy and the Milky Way is attributed to their mutual gravitational interaction. As both galaxies possess immense masses, their gravitational pull affects each other, causing them to move closer over time. The exact rate of convergence can vary, but estimates suggest they are approaching each other at a speed of about 110 kilometers per second (68 miles per second).
It's important to note that on human timescales, the relative motion between the Andromeda Galaxy and the Milky Way is incredibly slow and not noticeable. The collision is an event that will occur on a much larger cosmic timescale.