The closest galaxy to our own is the majestic Andromeda galaxy, a collection of a trillion stars located a “mere” 2 million light years away. New research suggests that, contrary to previous estimates, this galaxy isn’t much bigger than the Milky Way, and is practically our twin. This means our galaxy won’t be completely devoured when the two galaxies collide in five billion years.
Astronomer Heidi Newberg of the Rensselaer Polytechnic Institute, who wasn’t involved with the new study, told Gizmodo that the method used by Kafle “seems to be at least as good as any other method for determining the mass of a galaxy.... They claim to have smaller errors that pin it down to a smaller total mass.”
Newberg says it’s important to know the mass of galaxies to better than a factor a three [the margin of error], in part because that changes the amount of dark matter required to explain the mass. “Dark matter is expected to dominate the mass of galaxies (and the Universe), but has not yet been successfully observed,” she said.