Tau Ceti: Asteroid Heaven

UK astronomers studying the Tau Ceti system have discovered that it
contains ten times as much material in the form of asteroids and comets
as our own solar system.

Their discovery, being published in Monthly
Notices of the Royal Astronomical Society, suggests that even though
Tau Ceti is the nearest Sun-like star, any planets that may orbit it
would not support life as we know it due to the inevitable large number
of devastating collisions. It also suggests that the tranquil space
environment around the Earth may be more unusual than previously
realised.

Tau Ceti, only 12 light years away, is the nearest Sun-like star
and is easily visible without a telescope. It is the first star to be
found to have a disk of dust and comets around it similar in size and
shape to the disk of comets and asteroids that orbits the Sun.

But the similarity ends there explains Jane Greaves, Royal Astronomical Society Norman Lockyer Fellow and lead scientist: "Tau Ceti has more than ten
times the number of comets and asteroids that there are in our Solar
System. We don't yet know whether there are any planets orbiting Tau
Ceti, but if there are, it is likely that they will experience constant
bombardment from asteroids of the kind that is believed to have wiped
out the dinosaurs. It is likely that with so many large impacts life
would not have the opportunity to evolve."

The discovery means that scientists are going to have to
rethink where they look for civilisations outside our Solar System.
Jane Greaves continues "We will have to look for stars which are even
more like the Sun, in other words, ones which have only a small number
of comets and asteroids. It may be that hostile systems like Tau Ceti
are just as common as suitable ones like the Sun."

Tau Ceti has more than ten
times the number of comets and asteroids that there are in our Solar
System.The reason for the larger number of comets orbiting Tau Ceti is
not fully understood, explains Mark Wyatt, another member of the team:
"It could be that our Sun passed relatively close to another star at
some point in its history and that the close encounter stripped most of
the comets and asteroids from around the Sun."

The new results are based on observations taken with the
world's most sensitive submillimetre camera, SCUBA. The camera, built
by the Royal Observatory, Edinburgh, is operated on the James Clerk
Maxwell Telescope in Hawaii. The SCUBA image shows a disk of very cold
dust (-210 C) in orbit around the star. The dust is produced by
collisions between larger comets and asteroids that break them down
into smaller and smaller pieces.

UK participation in the James Clerk Maxwell Telescope is
provided by the Particle Physics and Astronomy Research Council
(PPARC). Professor Ian Halliday, PPARC Chief Executive said "SCUBA
continues to unveil the mysteries of planetary systems, in this case
the "asteroid alley" that is Tau Ceti; - clearly a place you would not
wish to be."

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