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Palomar 1

December 4, 2010

Our home galaxy, the Milky Way, is a killer. It's far larger, brighter, and more massive than most other galaxies. Its great heft gives it such a strong gravitational pull that it can snare wandering star clusters and even entire galaxies.

The latest victim to be identified is a faint globular star cluster called Palomar 1. It's 36,000 light-years away in the constellation Cepheus, the king, which is high in the north at nightfall and wheels around the North Star during the night.

Palomar 1 probably was part of a small galaxy that strayed too close and crashed into the Milky Way half a billion years ago.

The cluster itself is shaped like a globe -- hence the term "globular" cluster. But images from Hubble Space Telescope reveal that the Milky Way has pulled strands of stars from the cluster.

That's because the Milky Way's gravity creates a tide, just as the Moon creates tides on Earth: It pulls more strongly on the side of the cluster that faces the Milky Way, ripping the cluster apart and pulling its stars into the galaxy. In fact, the Hubble images reveal that some stars have been yanked more than a thousand light-years from their home. No match for the mighty Milky Way, the cluster will ultimately disintegrate.

But the Milky Way is a gentle killer. Although the cluster will cease to exist, its stars will keep on shining. They will simply switch addresses -- from the globular cluster to the great disk of the Milky Way.


Script by Ken Croswell, Copyright 2010


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