Massey scientist's software finds 'orphan' planets

Software developed by a Massey University computer scientist and astrophysicist is being used to discover extrasolar planets.

A major development has been the discovery of free-floating ‘orphan’ planets.

Associate Professor Dr Ian Bond, based at the Institute of Natural and Mathematical Sciences in Auckland, says the discovery has major implications for understanding the dynamics of solar systems.

“It’s a big deal. It’s like finding a needle in a haystack – the sense of discovery is hugely exciting,” Dr Bond says. 

Published in Nature

The study found evidence of 10 Jupiter-sized free floating gas giant planets, also described as “orphan” or “rogue” planets, because they are not believed to be orbiting stars. A report on the work, entitled Unbound or distant planetary mass population detected by gravitational microlensing was published in Nature online science journal in 2011.

The discovery was made by analysing data from telescopic camera recordings which captured variations in the brightness of some 50 million stars in the Milky Way galaxy.

As principal investigator in the Microlensing Observations in Astrophysics (MOA) international study, Dr Bond leads researchers from Massey, Auckland, Canterbury and Victoria universities, as well as participants from Japan and the United States.

Gravitational microlensing

Gravitational microlensing is an astronomical phenomenon which allows the study of planetary bodies that emit little or no light, and refers to the bending of light, first discussed by Albert Einstein in 1915, that occurs when a distant star gets aligned with a massive foreground object.

“The microlensing effect is very recognisable,” says Dr Bond. “The time scale of a lensing effect depends on the mass of the lens [planetary body]. If the ‘lens’ is a star, it takes 10 to 20 days to pass in front of the star, and if it's a planet, it’s a much shorter time.”

He has detected around 5000 microlensing events since 2006, and analysed 500 of them. The MOA study focuses on a segment of roughly 50 million stars at the centre of the Milky Way, which are 25,000 light years away and are a fragment of the estimated 100-400 billion stars and 50 billion planets in the galaxy. 

The discovery has led to speculation that smaller, Earth-sized free-floating planets – yet to be detected –may be more common than stars, and that Earth may have a long-lost ‘sibling’ that was once part of our solar system. Such small planets will be very hard to detect but work is continuing to try and discover evidence of these. “These may already be hidden in the MOA data” says Dr Bond. “MOA has accumulated more than 50 TB of imaging data. We are now working on new computational techniques to analyse this large and growing data set”.