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Escaped Star

November 29, 2013

The V-shaped face of Taurus, the bull, gazes down upon us on November and December evenings. The brightest star in the V is Aldebaran, the bull’s orange eye. All of the other stars in the V are members of a big stellar family — a star cluster known as the Hyades. It’s about 150 light-years away.

Astronomers have recently found evidence that one member of the Hyades family ran away. It’s moved so far that it appears in a different constellation — Horologium, the pendulum clock, which is so far south that it’s not visible from most of the United States.

The escapee is Iota Horologii. It’s known to have at least one planet — a giant that’s comparable to Jupiter, the giant of our own solar system.

The system is just 56 light-years away — only about a third as far as the Hyades. Even so, astronomers have several reasons to think the star escaped from the Hyades.

First, Iota Horologii has the same chemical composition as the stars of the Hyades. And second, it moves through space in the same direction and at the same speed.

Finally, astronomers measured “jiggles” on the star’s surface that probe its internal structure, just as earthquakes probe Earth’s interior. They indicated that the star is the same age as the Hyades — about 600 million years old. All of these factors indicate that Iota Horologii was born in the Hyades but somehow escaped — perhaps kicked out of its nest by a close encounter with one of its stellar siblings.


Script by Ken Croswell, Copyright 2013

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