An international group of astronomers led by Dr. Jean-Philippe Beaulieu
(Institut d’Astrophysique de Paris) and Dr. Martin Dominik (University of
St Andrews) are about to continue their hunt for extrasolar planets with an
enhanced world-wide telescope network in May this year. They are hoping to
secure the firm evidence for the existence of Earth-mass planets orbiting
stars other than the Sun, which has so far eluded astronomers. Dr Dominik
will describe the project, known as PLANET (Probing Lensing Anomalies
NETwork), at the Royal Astronomical Society National Astronomy Meeting at
the Open University on Thursday 1 April.

Recent scientific research shows that the existence of life on other worlds
is a realistic scenario. By measuring the periodic variation of the radial
velocity of stars induced by an orbiting planet, astronomers have so far
detected over 100 planets but all of them are large, similar to Jupiter and
Saturn in our solar system, and environmental conditions suitable for life
do not exist on such gas giant planets.

The only technique currently capable of detecting planets similar to Earth
makes use of the phenomenon called “galactic microlensing.” In a
microlensing event, a star temporarily appears brighter than it really is
because another astronomical body is passing between it and observers on
Earth; the gravitational field of the intervening object affects the
starlight in a way similar to a lens.

If the intervening object is a star, it causes a characteristic signal that
lasts about a month. Any planets orbiting this star can produce significant
deviations in the signal, lasting days for giant planets down to hours for
Earth-mass planets. The probability of this happening is between 1.5% and
20% depending on the mass of the planet.

The PLANET campaign performs nearly-continuous round-the-clock
high-precision monitoring of ongoing microlensing events, sampling the
lightcurve at intervals that may be as little as few minutes with a
world-wide network of telescopes. The backbone of the network is formed by
the Danish 1.54-m telescope at the European Southern Observatory at La
Silla
(Chile), the Canopus Observatory 1.0-m telescope (Tasmania, Australia), the
Perth 0.6-m telescope (Western Australia), and the Boyden 1.5-m telescope
(South Africa), which is supplemented by some other telescopes.

PLANET will share information and some resources with the microlensing
campaign performed with RoboNet, a UK robotic telescope network comprised
of the Liverpool 2.0-m (Canary Islands, Spain) and the two Faulkes 2.0-m
telescopes (Hawaii and Australia).

>From the 500-700 microlensing events announced annually by the survey
campaigns OGLE and MOA that monitor tens of millions of stars on a daily
basis, PLANET focuses on up to 75 events that are selected as most suitable
candidates for the detection of planets around the intervening lens star.
“If 20% of these stars are surrounded by planets, 10-15 giant planets and 1
or 2 terrestrial planets are expected to reveal their existence over three
years of operation”, Dr. Dominik said.

While PLANET might detect a second Earth, its typical expected distance
would be 20,000 light years – much too far to think of establishing any
contact!

CONTACTS

Dr. Martin Dominik University of St Andrews School of Physics & Astronomy
North Haugh St Andrews KY16 9SS United Kingdom Phone: (+44)-(0)1334-463066
Fax: (+44)-(0)1334-463104 e-mail: md35@st-andrews.ac.uk

Dr. Jean-Philippe Beaulieu Institut d’Astrophysique de Paris 98bis
Boulevard d’Arago 75014 Paris France Phone: +33-1-44-328119
Fax: +33-1-44-328001 e-mail: beaulieu@iap.fr

NOTES

1. The PLANET Collaboration e-mail: planet@iap.fr

2. Other authors/PLANET members:
University of St Andrews (St Andrews, United Kingdom): Prof. Keith D.
Horne, Dr. Stephen R. Kane

Institut d’Astrophysique de Paris (Paris, France): Arnaud Cassan, Dr.
Christian Coutures

Observatoire Midi-Pyr’en’ees (Toulouse, France): Dr. Pascal Fouqu’e

TU Wien (Vienna, Austria): Jadzia Donatowicz

Universit”at Potsdam (Potsdam, Germany): Dijana Dominis, Daniel Kubas,
Prof. Joachim Wambsganss

Niels Bohr Institute (Copenhagen, Denmark): Dr. Uffe G. J/orgensen

European Southern Observatory (Santiago de Chile, Chile): Dr. Stephane
Brillant

Space Telescope Science Institute (Baltimore, MD, USA): Dr. John A. R.
Caldwell, Dr. Kailash C. Sahu

University of Notre Dame (Notre Dame, IN, USA): Prof. David P. Bennett

Lawrence Livermore National Laboratory (Livermore, CA, USA):
Dr. Kem H. Cook

University of Washington (Seattle, WA, USA): Chris Laws

University of Canterbury (Christchurch, New Zealand):
Dr. Michael D. Albrow, Dr. Karen R. Pollard

Canopus Observatory (Hobart, Australia): Dr. John Greenhill, Dr. Kym Hill,
Dr. Robert Watson

Perth Observatory (Bickley, Australia): Dr. Ralph Martin, Dr. Andrew
Williams

University of the Free State (Bloemfontein, South Africa): Hannes Calitz,
Dr. Matie Hoffman, Prof. Pieter Meintjes

South African Astronomical Observatory (Cape Town, South Africa): Dr. John
W. Menzies

3. LINKS: