Astronomers discover new families of comets


An artist's impression of the comets around Beta Pictoris.
ESO

With comets in the news, from Rosetta's mission to land on one and the close fly-by of Mars by another this week, French astronomers have added to the excitement with the discovery of two new families of comets orbiting the star Beta Pictoris, some 63 light years away.

They used the HARPS instrument at ESO’s La Silla Observatory in Chile to make the most complete census of comets around another star ever created, studying nearly 500 individual comets orbiting the star.

They can be broken down into two distinct groups – old exocomets that have made multiple passages near the star, and younger exocomets that probably came from the recent breakup of one or more larger objects.

The new results appear in the journal Nature.

Beta Pictoris and its neighbourhood.
ESO

Beta Pictoris is a young star – only about 20 million years old – and is surrounded by a huge disc of material, an active young planetary system where gas and dust are produced by the evaporation of comets and the collisions of asteroids.

Flavien Kiefer, lead author of the new study explained the significance, saying the research gives us clues to help understand what processes occur in this kind of young planetary system.

“For the first time a statistical study has determined the physics and orbits for a large number of exocomets. 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," he said.

The exocomets of the first family have a variety of orbits and show a rather weak activity with low production rates of gas and dust. This suggests that these comets have exhausted their supplies of ices during their multiple passages close to Beta Pictoris.

The second family members are much more active and are also on nearly identical orbits, suggesting that they all arise from the same origin: probably the breakdown of a larger object the fragments of which are on an orbit grazing the star Beta Pictoris.

  1. http://www.eso.org/public/news/eso1432/
  2. http://en.wikipedia.org/wiki/Exocomet
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