Companion to the stars

The saying everyone needs a friend has taken on cosmic proportions with new research showing that even stars like companions.

University of Canterbury astronomers Dr Michael Albrow and Dr Karen Pollard are part of an international team that has just released its findings that, on average, every star in the Milky Way has at least one companion planet

Published this week in the prestigious international journal Nature, the research suggests the existence of planets orbiting stars in our Galaxy is the rule, rather than the exception.

Drs Albrow and Pollard, together with scientists in Europe, USA, Chile, South Africa, Japan and Australia, performed the analysis using data gathered from a gravitational microlensing experiment they have conducted over the last decade. Gravitational microlensing occurs when the gravitational field of a star acts like a lens, magnifying the light of a distant background star. Because all stars in our galaxy are moving, each microlensing event lasts for typically a few days or weeks.

Dr Albrow said that using a global network of telescopes, the researchers had detected brief additional magnification due to planets in orbit around some of the “lens stars”.

“Through a careful analysis of the sensitivity of our experiment we have uncovered the fraction of star-bound planets orbiting at a distance of 0.5 to 10 times the Sun–Earth distance. We have found that around 17 per cent of stars host Jupiter-mass planets, around 52 per cent accommodate Neptune-like planets, and ‘super-Earths’ are the most abundant, being associated with around 62 per cent of stars.”

Dr Pollard said the research “shows that solar systems similar to ours are likely to be very common throughout the universe”.

The research was partly supported by a grant from the Marsden Fund.