from neezy - Thursday, October 30, 2008
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Taken from: http://ukpress.google.com/article/ALeqM5jFyGqA4IYJxiv1HFw_flQkbPn9kg
'Twin' solar system 'like ours'
2 days ago
Undiscovered planets may lie hidden in a "twin" solar system 10.5 light years from the Earth, scientists believe.
Epsilon Eridani looks very like a much younger version of our own star system, say astronomers in the latest edition of the Astrophyiscal Journal.
It possesses a rocky asteroid belt identical to the one that lies between Mars and Jupiter, and an outer ring of icy material similar to the Kuiper Belt at the edge of our Solar System. In addition it has a second outer belt of asteroids containing 20 times more space rock than the inner one.
Astronomers think unseen planets must have confined and shaped the three rings of material surrounding Epsilon Eridani. Three planets with masses between those of Neptune and Jupiter would neatly explain the observations.
One candidate planet near the innermost asteroid belt has already been detected from the "wobble" effect of its gravity on the star. A second planet is thought to lurk near the second asteroid belt and a third near the inner edge of Epsilon Eridani's "Kuiper Belt".
Epsilon Eridani, which is visible to the naked eye, is slightly smaller and cooler than the Sun but much younger. Whereas the Sun formed around 4.57 billion years ago, Epsilon Eridani is only around 850 million years old. The star's asteroid belts were found using the Spitzer space telescope.
Dr Massimo Marengo, from the Harvard-Smithsonian Centre for Astrophysics in Cambridge, Massachusetts, one of the US astronomers who made the discovery, said: "Studying Epsilon Eridani is like having a time machine to look at our solar system when it was young."
Co-author Dr Dana Backman, from the SETI (Search for Extra Terrestrial Intelligence) Institute, said: "This system probably looks a lot like ours did when life first took root on Earth."
Although Epsilon Eridani's "Kuiper Belt" is about 100 times more packed with icy debris than our own, scientists think that when our solar system was 850 million years old, its Kuiper Belt must have looked very similar.
Since then, much of the material has been swept out of the Solar System or sent plunging into the inner planets in an event known as the Late Heavy Bombardment. The Moon's heavily cratered surface is the result of this violent episode in the Solar System's history. Epsilon Eridani's star system might undergo a similar episode of dramatic upheaval in the future, the astronomers believe.