The new planet, which has a mass about that of Jupiter, circles its star Tau1 Gruis about every four years. Tau1 Gruis can be found in the constellation Grus (the crane) and is about 100 light years away from Earth. The planet is three times as far from its star as the Earth is from the Sun.

'Now our searches have become precise enough to find many planets in orbits like those in our Solar System, we are seeing clues which may help us understand how planets are formed.' said UK team leader Hugh Jones of Liverpool John Moores University. 'We are seeing a pattern for these planets to be of two types, those very close-in and another set with orbits further out. This Tau1 Gruis planet builds this second group. Why are there these two groups? We hope the theorists will be able to explain this.'

The long-term goal of this programme is the detection of true analogues to the Solar System. This discovery of a companion planet to the Tau1 Gruis star with a relatively long-period orbit and mass similar to that of Jupiter is a step toward this goal. The discovery of other such planets and planetary satellites within the next decade will help astronomers assess the Solar System's place in the galaxy and whether planetary systems like our own are common or rare.

'The Anglo-Australian Telescope is providing the most accurate planet-search observations in the Southern Hemisphere', said Dr Alan Penny, the other UK team member from the Rutherford Appleton Laboratory.

The researchers have found that as they probe for planets in larger orbits, the distribution of planets around stars is quite different from that of binary stars orbiting one another, where there is a smooth distribution of orbits. In contrast to the early discoveries of exoplanets, we now find that less than 1 in 5 exoplanets are to be found very close to their stars, a few orbiting with a period of 5 to 50 days but most giant planets are orbiting at large distances from their host stars. This supports the idea that they are formed at Jupiter-like distances from their host star. Dependent on the details of the early solar system, most giant planets probably spiral inwards towards their star until they reach a point where a lack of frictional forces stops their further migration.

To find evidence of planets, the astronomers use a high-precision technique developed by Paul Butler of the Carnegie Institute of Washington and Geoff Marcy of the University of California at Berkeley to measure how much a star "wobbles" in space as it is affected by a planet's gravity. As an unseen planet orbits a distant star, the gravitational pull causes the star to move back and forth in space. That wobble can be detected by the 'Doppler shifting' it causes in the star's light. The AAT team measure the Doppler shift of stars to an accuracy of 3 metres per second - bicycling speed. This very high precision allows the team to find planets.

Notes for Editors:

The team are supported by the UK Particle Physics and Astronomy Research Council, the Australian government, the US National Science Foundation and NASA.

Dr Alan Penny will be giving a presentation at the second European Workshop on Astrobiology in Graz, Austria. The paper describing the new planet has been submitted for publication the Monthly Notices of the Royal Astronomical Society.

The members of the Anglo-Australian Planet Search team are:

From the UK; Dr Hugh R. A. Jones (Liverpool John Moores University) and Dr Alan J. Penny (Rutherford Appleton Laboratory).

From Australia; Dr Chris G. Tinney (Anglo-Australian Observatory) and Dr Brad Carter (University of Southern Queensland).

From the US; Dr R. Paul Butler (Carnegie Institution of Washington), Dr Geoffrey W. Marcy (University of California Berkeley and San Francisco State University) and Dr Chris McCarthy (Carnegie Institution of Washington).

For more information please contact:

UK
Liverpool John Moores University
Dr Hugh Jones
Tel: 0151 231 2909 / 2919
Mobile: 07956 945276 (Friday)
Email: hraj@astro.livjm.ac.uk
Homepage: http://www.astro.livjm.ac.uk/~hraj

Rutherford Appleton Laboratory
Dr Alan Penny
Email: alan.penny@rl.ac.uk
Homepage: http://ast.star.rl.ac.uk/penny

PPARC
Julia Maddock
PPARC Press Office
Tel: 01793 442094
Email: Julia.Maddock@pparc.ac.uk

AUSTRALIA
Anglo Australian Observatory
Dr Chris Tinney
Tel: +61 2 9372 4849
Mobile: +61 0416 092 117
Email: cgt@aaoepp.aao.gov.au

Anglo Australian Observatory
Helen Sim
Communications Manager
Tel: +61 2 9372 4251
Email: hsim@atnf.csiro.au
University of Southern Queensland
Brad Carter
Mobile +61 0401 337 319
Email: carterb@usq.edu.au

USA
Carnegie Institution of Washington
Dr R. Paul Butler
Tel: +1 202 478 8866
Email: paul@dtm.ciw.edu

University of California, Berkeley
Dr Geoff Marcy
Tel: +1 510 642 1952
Email: gmarcy@etoile.berkeley.edu

The Anglo-Australian Planet Search Home Page - http://www.aao.gov.au/local/www/cgt/planet/aat.html

Exoplanets Home Page - http://exoplanets.org/

The Extra-solar Planets Encyclopaedia - http://www.obspm.fr/encycl/encycl.html

The Particle Physics and Astronomy Research Council (PPARC) is the UK's strategic science investment agency. It funds research, education and public understanding in four broad areas of science - particle physics, astronomy, cosmology and space science.

PPARC is government funded and provides research grants and studentships to scientists in British universities, gives researchers access to world-class facilities and funds the UK membership of international bodies such as the European Laboratory for Particle Physics, CERN, the European Southern Observatory and the European Space Agency. It also contributes money for the UK telescopes overseas on La Palma, Hawaii, Australia and in Chile, the UK Astronomy Technology Centre at the Royal Observatory, Edinburgh and the MERLIN/VLBI National Facility.

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