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IC 10

October 8, 2012

The things we see in the night sky aren’t always what they seem. An example is an object that was discovered 125 years ago today.

Lewis Swift found it during a night of observing at Warner Observatory in New York. He described it as a faint star surrounded by nebulosity — in other words, a cloud of gas and dust.

But a half-century later, another astronomer realized that it’s not a star at all — it’s a small galaxy. Cataloged as IC 10, it turns out that it’s a member of our own galactic neighborhood, the Local Group.

IC 10 is unique among the group’s members because it’s been undergoing intense bouts of starbirth.

Astronomers see evidence of these waves of starbirth in the large number of massive stars that are ending their lives. These stars are much heavier than the Sun, so they live much shorter lives. Since they’re all in the same stage of life now, they must have been born at about the same time.

IC 10 is about two-and-a-half million light-years away, which makes it one of our closer galactic neighbors. But it’s only a few percent as massive as the Milky Way, so it’s small and faint. And it’s hidden behind clouds of dust in the Milky Way, so it’s tough to study — adding to the uncertainty about this small but busy star factory.

IC 10 is in the constellation Cassiopeia, which wheels high across the north on October nights. Its brightest stars form a letter M or W, twinkling through the hazy band of the Milky Way.


Script by Damond Benningfield, Copyright 2012

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