A view of the Andromeda galaxy, also known as M31, with measurements of the motions of stars within the galaxy. This spiral galaxy is the nearest large neighbor of our Milky Way.
The background image, obtained with NASA's Galex satellite at near-ultraviolet wavelengths, highlights regions within the galaxy where stars are forming.
Blue symbols mark the locations of bright young stars that were used to measure the motion of the galaxy, and yellow arrows indicate the average stellar motions at various locations, based on data from the second release of ESA’s Gaia satellite. A counter-clockwise rotation of the spiral galaxy’s disc is evident.
The precision of these measurements is expected to improve with the future Gaia data releases.