Tassie's key science role

The Mercury, Friday 24 May 2005 By MARGARETTA POS

THE discovery of a huge planet by a team of Tasmanian scientists will be announced to the world this morning.

The odds of the discovery were one in 10 million, said Stefan Dieters of the Canopus Observatory team at Cambridge, which found the planet.

On three nights in April, Dr Dieters and Kym Hill were in the right place at the right time to identify the planet, which is 1000 times the size of Earth.

The news will be posted at 10am on the NASA-sponsored website of Harvard University's Centre for Astrophysics.

The University of Tasmania team is part of an international collaborative project co-ordinated by the Paris Institute for Astrophysics, which is pioneering the use of gravitational microlensing to look for new planets.

The massive, gaseous planet, called OB-05-071, is in the Milky Way between Earth and the centre of the galaxy, about 25,000 light years away.

The project group has telescopes ringing the southern hemisphere -- in Hobart, Perth, Chile and South Africa -- enabling members to continuously keep watch at night.

Dr Dieters and Dr Hill were at Canopus when they were alerted by a New Zealand group that was not part of the project.

Their observations were monitored by the Paris Institute as they made them.

"There had been data coverage from many telescopes but we filled in the gaps on three important nights -- April 20, 21 and 26," Dr Hill said.

Another planet was identified by the project group two years ago but scientists were not convinced the data was unassailable.

The university's head of physics, John Dickey, said: "This is the first confirmed planet discovered using this technique.

"There is no ambiguity in the interpretation. It is very exciting."

Gravitational microlensing has its origins in Einstein's general theory of relativity.

He argued that the gravitational field of a massive object could slightly bend rays of light that happened to pass close to its surface.

In principle, the gravitational field of a star could act as a lens and focus the light from an object much further away.

But the stellar alignment must be close to perfect for this effect to be seen.

And until the mid-1990s, scientists lacked the computing power to continuously measure hundreds of millions of stars and record their brightness in data bases.

"Survey teams measure hundreds of millions of stars every night to look for one that starts to brighten, indicating a microlensing event," Dr Hill said.

"And now we've done it."

The project team in Hobart comprises Dr Hill, research associate in the School of Maths and Physics, Dr Dieters, lecturer in astronomy and physics, and honorary research associate John Greenhill.

Others include Prof Dickey and honorary research associate David Warren.

Professor Dickey said the success of the project would lead to further discoveries.

"We are confident we will detect an Earth-like planet using gravitational microlensing, that could harbour life on it," he said.

The original article can be found here

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URL: http://www.phys.utas.edu.au/physics/optastr/merc010705.htm
16th December 1998