A laser-like spot of light could predict the eventual collision of the Milky Way with the Andromeda Galaxy. Loránt Sjouwerman of the National Radio Astronomy Observatory in Socorro, New Mexico, and colleagues have glimpsed a bright, laser-like spot of microwave radiation, called a maser, in Andromeda that could help measure its sideways movement. The speed at which Andromeda is moving towards the Milky Way can be determined from the Doppler shift of the light it emits. But the galaxy is too spread out for its subtle sideways motion in the sky to be detected. If it moves sideways fast enough it may miss colliding the Milky Way altogether.
"Measuring the proper motion of Andromeda is key to determining the fate of the Milky Way," says Mark Reid of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts. "Such a measurement is best done with a compact, bright source such as a maser, but until now no maser strong enough for current telescopes to measure has been detected."
The Daily Galaxy via newscientist.com and Astrophysical Journal Letters, DOI: 10.1088/2041-8205/724/2/L158