British and Australian astronomers have discovered four new extrasolar
planets, in collaboration with American colleagues who also today announce
their discovery of another eleven more planets, including one only forty
times heavier than the Earth and another which has an orbit just like that
of Jupiter.

‘Most of the planets found previously are like distant cousins to the
planets in our own Solar System, but now we are finding ones much more like
ours. We are getting closer to our brothers and sisters.’, said UK team
leader Dr Hugh Jones of Liverpool John Moores University.

The image shows an artist’s impression of a planet like those discovered by
the Anglo-Australian Telescope team. This particular image is the one
announced today by the US team – the planet orbiting the star 55 Cancri. As
distant from it’s star as Jupiter is from our Sun, it takes thirteen years
to go round, compared with the twelve of Jupiter. Although four times the
mass of Jupiter, it is thus really like Jupiter. The four Anglo-Australian
planets are Jupiter-like in orbits of up to five years – sort of first
cousins to our own planets. The Anglo-Australian discoveries are filling up
the planetary zoo.

‘Following these planets over many years is hard work, and the investment by
the Particle Physics and Astronomy Research Council (the UK funding agency)
of a large amount of time on the truly excellent Anglo-Australian Telescope
is really paying off.’ commented UK team member Dr Alan Penny of the
Rutherford Appleton Laboratory.

The British, Australian and US astronomers work together on a collaborative
programme looking at 1200 stars. The very light planet announced by the US
team of only 40 Earth masses is the lightest extrasolar planet yet found.
The planet orbits the star HD49674 in the constellation of Auriga with a
period of 5 days. How such a relatively light planet can get so close to
it’s star is a real problem for the current theories of how planets form.

‘Although this planet is probably a gas giant like Neptune and not a rocky
planet, it really shows we are working our way down.’ Said Dr Jones.

‘I’m particularly excited about this, as I’m also involved in the European
Space Agency’s Eddington mission, recently announced for a 2007/2008 launch.
It will use a different to search for planets like the Earth. Together the
two techniques will tell us how common Solar Systems are.’ Enthused Dr
Penny.

The US team’s discovery of their planets was revealed today by Geoff Marcy,
University of California and Paul Butler, Carnegie Institution of Washington
[5 pm GMT, Thursday] at a news conference at NASA headquarters, Washington,
DC.

The Anglo-Australian-US discoveries used the 3.9m Anglo-Australian Telescope
[AAT] in the Warumbungles, New South Wales, Australia. The US team
discoveries used the 10m Keck Telescope in Hawaii, and the 3m Lick telescope
in California.

Together the 15 new planets announced by the joint teams range in mass from
0.12 to 10 times the mass of Jupiter, the largest planet in the Solar
System. They have orbital periods between 5 days and 13 years. They orbit
their stars at distances ranging from about 0.05 to 5.7 times the Earth-Sun
distance.

The 4 Anglo-Australian planets announced are HD73526, HD196050, HD216437 and
HD30177. The later three of these are interesting because they add to the
growing number of mildly eccentric longer-period planets whose orbital
parameters bear some likeness to those of the Solar System. In addition, the
signal of a previously announced planet around HD160691 now indicates
several planets, such multiple planets systems are still comparatively rare
and this is the first such system found by the Anglo-Australian planet
search team. The HD numbers refer to a catalogue of bright stars known as
the Henry Draper catalogue produced at the beginning of 20th century.

The long-term goal of these programmes is the detection of true analogues to
the Solar System. 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 discovery of a ‘real Jupiter’ is a major step toward
this goal.

To find evidence of planets, the astronomers use a high-precision version of
the radial velocity 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. Some planet-hunting groups can pick up the Doppler shift in light
from a star moving at 10 metres/sec – the speed of a world-class sprinter.
But the search technique used by the team is three times as precise making
it sensitive to the effects of smaller planets.

The first extrasolar planet ever discovered was found by a Swiss team in
1995. With the new planets announced today more than 90 extrasolar planets
have now been discovered.

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

Notes to Editors

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

UK: Dr Hugh R. A. Jones (Liverpool John Moores University), Dr Alan J. Penny
(Rutherford Appleton Laboratory).

Australia: Dr Chris G. Tinney (Anglo-Australian Observatory), Dr Brad Carter
(University of Southern Queensland)

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

The members of the Keck and Lick Planet Search teams are:

US: Dr Steven S. Vogt (UCO/Lick Observatory), Dr R. Paul Butler (Carnegie
Institution of Washington), Dr Geoffrey W. Marcy (University of California
Berkeley and San Francisco State University), Dr Debra A. Fischer
(University of California Berkeley), Dr Gregory Laughlin (University of
California Santa Cruz), Dr Gregory Henry (Tennessee State University), Dr
Jason Wright (University of California Berkeley).

Images

An image showing an impression of the possible scene from a moon orbiting
the extrasolar planet in orbit around the star 55 Cnc, is available from the
PPARC web site:- www.pparc.ac.uk or by contacting Gill Ormrod at the PPARC
Press Office on 01793 442012 or email gill.ormrod@pparc.ac.uk

This figure may be reproduced, but acknowledgement must be made to the
artist, Lynette Cook, who retains the copyright.

Further information for the caption:- The planet is about four times the
mass of Jupiter and orbits the star in around 13 years which is rather close
to the 12 year orbital period of Jupiter around the Sun. The star 55 Cancri
is a 6th magnitude star in the constellation of Cancer, and is slightly
cooler than our own Sun. The similarity of the appearance of the extrasolar
planet to that of Jupiter is deduced because it has a similar mass. The
possible existence of the moon has been inferred from our knowledge of the
planets in our own Solar System and from theories of planetary formation –
it has not actually been detected.

An image of the Anglo Australian Telescope at Siding Springs in Australia
can be found at http://www.aao.gov.au/htdocs/images/captions/aat001.html

Graphics and images for the new planets from the Keck and Lick telescopes
can be found at the US team website at http://exoplanets.org

For more information please contact:

UK

Dr Hugh Jones

Liverpool John Moores University

Tel: 0151 231 2909 / 2919

Mobile: 07956 945276

Email: hraj@astro.livjm.ac.uk

Homepage: http://www.astro.livjm.ac.uk/~hraj

Dr Alan Penny

Rutherford Appleton Laboratory

Tel: 01865 723668

Email: alan.penny@rl.ac.uk

Homepage: http://ast.star.rl.ac.uk/penny

Gill Ormrod – PPARC Press Office

Tel: 01793 442012

Email: gill.ormrod@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

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

US

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@etiole.berkeley.edu

National Aeronautical Space Administration (NASA)

Donald Savage

Tel: +1 202 358 1600

Email: dsavage@hq.nasa.gov

Links:

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

Keck and Lick Planet Search Home Page – http://exoplanets.org/

The Extra-solar Planets Encyclopedia –
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, 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.

PPARC’s Public Understanding of Science and Technology Awards Scheme
provides funding to both small local projects and national initiatives aimed
at improving public understanding of its areas of science.