Astronomers involved in planet discovery

26 January 2006

Canterbury astronomers involved in ground-breaking

University of Canterbury astronomers have helped discover a new planet, significantly more Earth-like than any other.

They say the discovery, which will be reported this week in leading scientific journal Nature, marks a ground-breaking result in the search for planets that could support life.

The planet, which is designated by the unglamorous identifier of OGLE-2005-BLG-390Lb, orbits a red star five times less massive than the Sun and is located at a distance of nearly 25 000 light years, not far from the centre of the Milky Way galaxy.

The newly-discovered planet has a calculated surface temperature of 220°C below zero. Because of its low mass and low temperature, it is most likely to be solid with an icy or rocky surface.

The planet was discovered using a technique known as gravitational microlensing, which is more sensitive to smaller mass planets than other methods.

The Probing Lensing Anomalies NETwork (PLANET) collaboration involves scientists from a dozen countries including New Zealand.

University of Canterbury husband-and-wife astronomers, Dr Michael Albrow and Dr Karen Pollard, are founding members of the PLANET team.

“We began our planet-hunting research in 1995. It has taken ten years of hard work and patience, but we are delighted to be part of the team that has discovered this planet,” says Dr Albrow.

Dr Pollard explains what the team has been looking for over the past 10 years.

“With this method, we let the gravity of a dim nearby star act as a giant natural lens for us, magnifying a distant, bright star. The extra brightening due to the presence of an orbiting planet around the lens star is the signature we are looking for – we don't directly see the planet, or even the star that it's orbiting, we just see the effect of their gravity.”

The Microlensing Observations in Astrophysics (MOA) collaboration, a joint venture between New Zealand and Japan based at UC’s Mt John Observatory, has also played an important role in verifying the discovery.

Discovering the new planet has been the result of round-the-clock monitoring of images collected at PLANET telescopes around the world. Astronomers hope the discovery of this new planet will encourage the intensification of microlensing planet searches, using current and additional facilities.

Dr Albrow says the discovery hints there are further low-mass planets waiting to be detected, raising hope that microlensing will soon lead to the discovery of a twin Earth.

“The search for a second Earth is the driving force behind our research and this discovery constitutes a major leap forward since it is the most Earth-like planet discovered to date.

“If such planets are much more common than Jupiter-like planets, as this result implies, then the chances of there being habitable planets in our galaxy is a very real and exciting possibility.”

ENDS

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