Kiwis Help Discover Giant Planet

Kiwis Help Discover Giant Planet
24/05/2005 06:27 PM -


Amateur and professional New Zealand astronomers have contributed significantly to the discovery of a planet several times larger than Jupiter, the largest planet in our solar system.

Using a new technique, university researchers working as part of the MOA (Microlensing Observations in Astrophysics) Japan/NZ Collaboration made key contributions, together with amateur astronomers at Auckland´s Stardome Observatory.

MOA Project Leader Associate Professor Phil Yock of The University of Auckland´s Faculty of Science says the planet was discovered using a new variation of a fairly old technique called gravitational microlensing.

"The original gravitational microlensing technique was proposed by Professor Bohdan Paczynski of Princeton University and his then student Shude Mao. Following Einstein´s ideas, the technique uses the gravitational fields of stars to magnify more distant stars.

"Subsequent workers refined the technique and in 1998 Professor Kim Griest and Dr Neda Safizadeh of the University of California showed that planets would be more likely to be detected when the magnification caused by a gravitational lens was high, an intuitively reasonable result," says Associate Professor Yock.

In the past three years Associate Professor Yock, together with Dr Ian Bond of Massey University and Dr Nicholas Rattenbury of Jodrell Bank Observatory in the UK, both former PhD physics students of The University of Auckland, have developed a strategy for searching for planets in very high magnifications events, for example when the magnification is about 100 or more. Using data gained by the MOA Collaboration at Canterbury´s Mt John Observatory, they showed the technique was feasible, and that planets as small as Earth could be detected this way.

"Gradually, other observatories focussed their attentions on microlensing events of very high magnification, and the recent planet discovery provides stunning confirmation of the predictions," says Associate Professor Yock.

The lead observations in the event were made by OGLE, a Polish group based in Chile, and the event is currently referred to as OGLE 2005-BLG-71.

"Most of the OGLE observations were made by their principal investigator, Professor Andrzej Udalski, a remarkable achievement. Many other observatories around the globe made contributing observations that assisted to pin down the parameters of the new planet.

"In New Zealand, observations were made over several nights by Paul Tristram of the MOA Collaboration from Mt John Observatory, and by Dr Grant Christie and Jennie McCormick of Auckland´s Stardome Observatory," says Associate Professor Yock.

Amateur First

The Stardome observations are notable because they are the first observations of a planet carried out by amateurs using microlensing, made possible by the very high magnification of the event. These observations were analysed by Dr Bond using advanced image analysis software at Massey University.

Located 15,000 light years away from the Earth, the new planet is one of the most distant ever discovered. It has about twice the mass of Jupiter and is twice as far from its solar-type star as the Earth is from the Sun.

The scientific paper describing the event includes 33 authors from 11 countries and has been submitted to the US journal Astrophysical Journal Letters.

The MOA team has recently installed a new 1.8m telescope at Mt John Observatory, which will soon become the world´s largest telescope dedicated to detecting gravitational microlensing events.

"The new telescope will substantially increase the research capability in this area by providing additional alerts of microlensing events and increasing the density of survey coverage," says Associate Professor Yock.

About MOA

MOA is a NZ/Japan collaboration that includes researchers from Auckland, Massey, Canterbury and Victoria Universities in New Zealand and Nagoya University in Japan. The group makes observations on dark matter, extra-solar planets, stellar atmospheres and stellar shapes using the gravitational microlensing technique at the Mt John Observatory in New Zealand. Mt John Observatory is operated by the University of Canterbury.

[link to xtramsn.co.nz]