Milky Way Is a 'Galactic Lightweight'

Same-sized neighbor Andromeda has twice the mass

By Rob Quinn,  Newser Staff

Posted Jul 30, 2014 3:45 AM CDT

(Newser) – If our galaxy were a boxer, it would have just slipped down a few weight classes—and would be no match for our neighbor Andromeda. New research has revealed that the Milky Way, while still mind-bogglingly vast, is only around half the weight of the Andromeda galaxy, which is about 2.6 million light years from us, the BBC reports. Scientists who calculated the amount of invisible matter in the outer regions of both galaxies believe invisible "dark matter" explains the huge difference in mass between the two.

"We always suspected that Andromeda is more massive than the Milky Way, but weighting both galaxies simultaneously proved to be extremely challenging," the lead researcher says. ''Our study combined recent measurements of the relative motion between our galaxy and Andromeda with the largest catalog of nearby galaxies ever compiled to make this possible.'' This is one of the best times of year to get a good look at our lightweight galaxy in the night sky, especially with the moon in a new phase this week, National Geographic notes. (But you've only got 4 billion years left to see the Milky Way before Andromeda crashes into it, forming a gigantic combined galaxy.)

This image made by the Hubble Space Telescope shows the Andromeda Galaxy.
This image made by the Hubble Space Telescope shows the Andromeda Galaxy.   (AP Photo/University of Utah)
This photo provided by the European Southern Observatory shows the Milky Way above the La Silla Observatory in Chile.
This photo provided by the European Southern Observatory shows the Milky Way above the La Silla Observatory in Chile.   (AP Photo/Zdenek Bardon/ProjectSoft, European Southern Observatory)
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