Andromeda galaxy smaller than anticipated

The Milky Way’s ‘bigger’ brother may be more of a twin The Andromeda Galaxy might not be as large as we thought, as a new method of measuring its size suggests that it is roughly the same mass as the Milky Way. The team behind the discovery measured the speeds of stars in Andromeda to find the escape velocity of the galaxy, which is determined by its mass.

“By examining the orbits of high-speed stars, we discovered that this galaxy has far less dark matter than was previously thought, and only a third of that uncovered in previous observations,” says Dr Prajwal R Kafle from the University of Western Australia who led the study.

Andromeda and the Milky Way are the two most prominent members of the Local Group of galaxies, and this finding will have big implications for our ideas about our nearest neighbours.

“It’s really exciting that we’ve been able to come up with a new method and suddenly 50 years of collective understanding of the Local Group has been turned on its head,” says Kafle.

With Andromeda no longer considered the Milky Way’s big brother, new simulations are required to predict what will happen when the two galaxies collide Andromeda

Milky Way