Scientists Create Large Census Yet of Comets Around Another Star, Revealing Two Families

First Posted: Oct 23, 2014 06:08 AM EDT
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Using the HARPS instrument at ESO's La Silla Observatory, scientists have created the most complete census of comets yet around another star. The findings reveal information about 500 individual comets orbiting the star Beta Pictoris and show that they belong to two distinct families of exocomets: old exocomets and younger exocomets.

Beta Pictoris is a relatively young star located about 63 light-years from the sun.  Only about 20 million years old, the star is surrounded by a huge disc of material that represents a very active young planetary system where gas and dust are produced by the evaporation of comets and the collisions of asteroids.

"Beta Pictoris is a very exciting target!" said Flavien Kiefer, lead author of the new study, in a news release. "The detailed observations of its exocomets give us clues to help understand what processes occur in this kind of young planetary system."

In order to better study this star's exocomets, the scientists analyzed more than 1,000 observations obtained between 2003 and 2011 with the HARPS instrument. Then, the researchers selected a sample of 493 different exocomets. Careful analysis revealed the speed as size of the gas clouds, and some of the orbital properties of the exocomets. In the end, they found that there two distinct families of exocomet.

One family of old exocomet had orbits that were controlled by a massive planet. The other family probably arose from the recent breakdown of one or a few bigger objects. The older exocomets had a variety of orbits and actually showed rather weak activity with low production rates of gas and dust. This, in particular, seems to indicate that these comets have exhausted their supplies of ices during their multiple passages close to Beta Pictoris.

"For the first time a statistical study has determined the physics and orbits for a large number of exocomets," said Kiefer. "This work provides a remarkable look at the mechanisms that were at work in the solar system just after its formation 4.5 billion years ago."

The findings are published in the journal Nature.

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