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Upsilon Andromedae

February 9, 2011

Andromeda descends the northeastern sky this evening, well to the right of the Moon. Among its many wonders is a misaligned planetary system -- one that could have implications for the evolution of all planetary systems.

Upsilon Andromedae consists of two stars -- a white star that's bright enough to see with the unaided eye, and a distant companion that's a faint cosmic ember.

The system also contains at least three giant planets in orbit around the bright star. They're similar to Jupiter, the giant of our own solar system. But they're closer to the star, so they're hotter.

A long-term study found that the system is a little out of whack. The study was led by Texas astronomer Barbara McArthur, and used observations from Hubble Space Telescope and the Hobby-Eberly Telescope at McDonald Observatory. It showed that the planets don't orbit the star in the same plane, as the stars of our solar system do. Instead, the orbit of one of the three is tilted at a jaunty angle relative to the other two.

It's unclear just why that's the case. It's possible that the gravity of the smaller star kicked the out-of-whack planet into its odd orbit. Or perhaps the planet and another staged a gravitational dance that kicked one of them completely out of the system.

No matter how it happened, though, Upsilon Andromedae shows that there's more than one way to lay out a solar system.

More about planets beyond the solar system tomorrow.


Script by Damond Benningfield, Copyright 2010


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