[meteorite-list] Death Down Asteroid Alley

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Fri Jul 2 18:45:15 2004
Message-ID: <200407022245.PAA24159_at_zagami.jpl.nasa.gov>


Death Down Asteroid Alley
Astrobiology Magazine
July 2, 2004

The nearest sun-like star, Tau Ceti, has been a candidate that might
harbor life. At 12 light-years, the star has the right location and
luminosity, but according to recent observation, Tau Ceti hosts ten
times the flux of meteors and comets. Any potentially life-threatening
encounter on Tau Ceti's inner planets might have cut short evolution
before it could even start.

Death Down Asteroid Alley

based on PPARC <http://www.pparc.ac.uk/> report

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.

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.

The astronomers' 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 realized.

Though the star Tau Ceti is similar to the Sun, any planets it has are
unlikely to be havens for life, say a team of UK astronomers. Using
submillimeter images of the disk of material surrounding Tau Ceti, they
found that it must contain more than ten times as many comets and
asteroids than there are in the Solar System.

With so many more space rocks hurtling around the star, devastating
collisions of the sort that could lead to the destruction of life would
be much more likely in the Tau Ceti system than in our own planetary system.

Publication of the result in Monthly Notices of the Royal Astronomical
Society coincides with an exhibit 'Hunting for Planets in Stardust' at
the Royal Society Summer Exhibition by the same science team from the UK
Astronomy Technology Centre in Edinburgh and the University of St. Andrews.

The similarity between Tau Ceti and our own sun ends with their
comparable sizes and luminosities, 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 civilizations 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.'

The reason for the larger number of comets is not fully understood
explains Mark Wyatt, another member of the team: 'It could be that the
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 degrees
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.
Received on Fri 02 Jul 2004 06:45:10 PM PDT

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