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On the Move

February 13, 2018

Our home galaxy, the Milky Way, is on the move. It’s being pulled by the gravity of other galaxies, which are tugging in several directions.

The most immediate tug is toward M31, the Andromeda Galaxy. Like the Milky Way, it’s a cosmic pinwheel known as a spiral galaxy. It’s two-and-a-half million light-years away. But M31 and the Milky Way are quite heavy, so they exert a strong gravitational pull on each other. So in a few billion years they’ll merge, forming a galactic behemoth.

At the same time, the two galaxies are moving toward the Virgo Cluster of galaxies. It’s about 50 million light-years away, and contains more than a thousand galaxies. Many other galaxies will join the cluster. But a recent study says the Milky Way and M31 won’t — they’re about 12 million light-years too far away to be captured.

The same study shows that almost every galaxy in our region is flowing toward a flat sheet of galaxies known as the Local Sheet. And finally, everything including the Virgo Cluster is moving toward a region known as the Great Attractor, which is the core of a supercluster of galaxies. It contains tens of thousands of times the mass of the Milky Way. It’s the ultimate destination for a galaxy on the move.

And under a dark sky, you can see the outline of the Milky Way’s disk on February evenings. It arcs from the brilliant Dog Star, Sirius, in the southeast, directly overhead, and down to Deneb, the tail of the swan, in the northwest.

Script by Damond Benningfield


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