An artistic impression of the new system - the two 'new
planets' are second and third from the left.

University of Tasmania astronomers have played an important role in the discovery of the first planetary system with similarities to our Solar System.

Dr John Greenhill and Dr Stefan Dieters, from the UTAS School of Mathematics and Physics, are the Australian contributors to an international collaboration, led by Dr Scott Gaudi of Ohio State University, which uncovered the system and reported its results on 15 February 2008 in the prestigious international journal, Science.

The collaboration used a technique known as gravitational microlensing with photometric data (brightness measurements) from telescopes in Chile, USA, New Zealand, Israel, the Canary Islands and Tasmania.

The Tasmanian observations were made by Dr Greenhill and Dr Dieters from April 4-8, 2006, using the UTAS Mt Canopus 1 metre telescope, based near Hobart.

The newly discovered system, which is code-named OGLE-2006-BLG-109L, contains two planets orbiting a cooler star half the mass of our Sun, about 5000 light years from Earth.

It resembles a scaled down version of our Solar System with the two planets having mass ratios (as compared with their star), orbital separations and surface temperatures similar to those of Jupiter and Saturn.

Dr Greenhill said the discovery was particularly important because it demonstrated that, using microlensing, we will be able to estimate how many Solar System analogues there are in the Galaxy.

“The technique used does not necessarily detect all planets in the system, so it is possible that OGLE-2006-BLG-109L may contain other planets – even ones like Earth,” he said.

Dr Dieters said hunting for planets in this way was exciting: “On each night, with each observation, there is the chance to discover a whole new world’’.