Astronomers probe star wrapped in comets

Tau Ceti dubbed 'Asteroid Alley'

A group of professional UK star gazers says that huge numbers of comets and asteroids encircle our nearest sun-like star, Tau Ceti, making it extremely unlikely that life has had a chance to evolve on any planets in the system.

Tau Ceti is a mere 12 light years away - the astronomical equivalent of just round the corner.. It is also the first star astronomers have seen with a disk of dust, comets and asteroids similar to that surrounding our own Sun.

Jane Greaves, Royal Astronomical Society Norman Lockyer Fellow and lead scientist, said: "Tau Ceti has more than ten times the number of comets and asteroids that there are in our Solar System." Because of this, the team has nicknamed the system Asteroid Alley. Any planets orbiting the star would suffer huge numbers of devastating impacts, similar in size to those that wiped out the dinosaurs, making it nearly impossible for life (as we know it) to gain a foothold.

Greaves suggests the findings mean we will have to rethink where we look for extra-solar life. "It may be that hostile systems like Tau Ceti are just as common as suitable ones like the Sun", she added.

The team bases its findings on observations taken with the James Clark Maxwell telescope, and SCUBA, the world's most sensitive submillimetre camera. The images reveal a disk of freezing dust (-210 ºC) in orbit around the star. This is most likely formed by countless collisions of asteroids and comets, gradually breaking into smaller pieces, impact by impact.

Team member Mark Wyatt says the reasons for the huge number of comets orbiting Tau Ceti are not fully understood. He suggests that our Sun could have passed close to another star at some point in its history, an encounter which could have stripped most of the comets and asteroids away.

The Particle Physics and Astronomy Research Council website has an artist's impression of what the view might be like from the surface of a planet orbiting Tau Ceti. ®

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