From: Royal Astronomical Society
Posted: Tuesday, July 6, 2004
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 submillimetre 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. (Details of the media preview are given in the notes.)
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.'
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.
Images are available from http://www.pparc.ac.uk/Nw/tc_images.asp and can be accessed using username tcMedia and password ngc247. (The password will be taken off once the embargo expires.)
1. Artist's impression: For any planets orbiting Tau Ceti, the skies will be criss-crossed with comets and meteors will frequently strike the surface. Credit: David Hardy.
2. SCUBA Image: Image of the disc of dust particles around the star Tau Ceti, taken with the submillimetre-wavelength camera SCUBA. The false colours show the brightness of the disc. Its diameter is slightly larger than the Solar System. Credit: James Clerk Maxwell Telescope.
3. The James Clerk Maxwell Telescope (JCMT) was used to take the image of the Tau Ceti dust disk. It is the world's largest single-dish submillimetre telescope. It collects faint submillimetre signals with its 15 metre diameter dish. It is situated near the summit of Mauna Kea on the Big Island of Hawaii, at an altitude of approximately 4000 metres (14000 feet) above sea level. Credit: Nik Szymanek.
Dr Jane Greaves, Astronomer, University of St Andrew
Phone: (+44) (0)7745 127391
Peter Barratt, Head of Communications, PPARC
Phone (+44) (0)1793 442025
Eleanor Gilchrist, Public Relations Officer,
Royal Observatory Edinburgh
Phone (mobile): (+44) (0)771 873 6971
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Douglas Pierce Price, James Clerk Maxwell Telescope
Phone: (+1) 808 969 6524
1. Royal Society Summer Exhibition The Royal Society Summer Exhibition runs from 5 to 8 July and is open to the general public on Monday 5 July 6 p.m. - 9 p.m.; Tuesday 6 July 11a.m. - 4.30 p.m.;=20 Wednesday 7 and Thursday 8 July 10 a.m. - 4.30 p.m.
There is a media preview on Tuesday 5 July 10 a.m. - 11 a.m. To pre-register please email email@example.com.
2. Observing Tau Ceti
Tau Ceti is in the constellation Cetus. Although it is visible without a telescope, at this time of year it rises in the South East at about 3 a.m. - just before the Sun, so is very hard to spot.
3. The James Clerk Maxwell Telescope (JCMT)
The JCMT is the world's largest single-dish submillimetre telescope. It is situated near the summit of Mauna Kea on the Big Island of Hawaii, at an altitude of approximately 4000 metres (14000 feet) above sea level. It is operated by the Joint Astronomy Centre, on behalf of the UK Particle Physics and Astronomy Research Council, the Canadian National Research Council, and the Netherlands Organisation for Scientific Research.
SCUBA (the Submillimetre Common-User Bolometer Array) is the world's most powerful submillimetre camera. It is attached to the James Clerk Maxwell Telescope, and contains sensitive detectors called bolometers, which are cooled to 60 milliKelvin, 0.06 degrees above absolute zero (60 milliKelvin is about -273.1 degrees Celsius or -459.6 degrees Fahrenheit). SCUBA was built in the UK by the Royal Observatory, Edinburgh, at what is now the UK Astronomy Technology Centre.
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