Milky Way Has The Mass Of 800 Billion Suns, Study Finds

Weighty matters

As Seen From Earth

Science@NASA, Space Telescope Science Institute (STScI) and NASA's Goddard Space Flight Center

Astronomers have performed yet another checkup on our home galaxy, this time asking it to step on a scale. The Milky Way has a mass equal to 800 billion suns, according to the team of researchers from Europe, Canada and the U.S. The team also found there's a 95 percent chance that the Milky Way is smaller than Andromeda, which is the closest spiral galaxy to our own whorled home, and a sky-watchers' favorite. (You can spot Andromeda with your naked eye.)

Over the past ten years or so, different teams of astronomers have periodically measured the mass of the Milky Way and its neighbors–some saying it's similar to the new measurement, and some saying it's greater. Teams have also variously found that the Milky Way is more massive than Andromeda, that Andromeda is more massive than the Milky Way, and that the two are about the same in mass. There's ongoing debate about how much matter is in each, including how much dark matter, which is of intense interest to astronomers today.

In a statement, one of the study's authors, Matthew Walker, explained what made his team's measurements the latest and greatest. "By studying two massive galaxies that are close to each other and the galaxies that surround them, we can take what we know about gravity and pair that with what we know about expansion to get an accurate account of the mass contained in each galaxy," he said. "This is the first time we've been able to measure these two things simultaneously."

Walker and his colleagues published their work in the journal Monthly Notices of the Royal Astronomical Society. Now, go see if you can incorporate the phrase "the mass of 800 billion suns" into daily conversation somehow.