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The largest member of the Local Group is Andromeda, a spiral galaxy like ours. Andromeda is about 2.2 million light-years away and about one and a half times larger than the Milky Way?150,000 light-years across.

With about 300 billion stars, its gravitational pull causes several smaller satellite galaxies to orbit around it. Two of these elliptical satellites can be seen with a small telescope.

The Andromeda galaxy is moving toward the Milky Way at about 186 miles per second. It would take about 2 billion years, but it is possible that the two galaxies could collide or merge into each other.

Like the Milky Way, the spiral galaxy Andromeda revolves around a central ?bulge.? Scientists believe this center contains a massive black hole.

Answers From the Expert
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Frank Summers, American Museum of Natural History
? What will happen when the Andromeda galaxy and the Milky Way galaxy collide?

Click here for Frank's answer.

? What happens when two galaxies collide?

Click here for Frank's answer.

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