A Moon is Born?

StarDate: December 23, 2009

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Young solar systems never quite seem to have enough elbow room for their newborn planets. In our own solar system, for example, the Moon most likely was born after a collision between Earth and another planet. Other impacts may have knocked Uranus on its side, and stripped Mercury of its crust.

A similar collision took place fairly recently in another star system, known as HD 172555.

Spitzer Space Telescope discovered glass, rock, and other debris around the star. A team of astronomers deduced that the material was produced by a violent collision that took place just a few thousand years ago.

One of the two colliding worlds was about the size of Mercury, the smallest planet in our own solar system. The other was about the size of the Moon. They rammed into each other at more than 22,000 miles an hour. The collision probably blasted the smaller world apart, and stripped the larger one of its outer layers, spewing gas and molten rock into space. Much of the rock has cooled to form a type of glass.

There's no indication that the debris is coalescing to create a moon -- but it could. Our moon most likely formed from just such a cloud of debris after the young Earth was hit by a planet as big as Mars. The Moon probably formed in just a few thousand years. If so, then future generations of Earthlings may be able to watch as a moon is born from the aftermath of a planetary collision.

We'll talk about another planetary system tomorrow.

Script by Damond Benningfield, Copyright 2009

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