The Sydney University Stellar Interferometer, courtesy the University of Sydney

Astronomers using the Sydney University Stellar Interferometer at Narrabri in NSW have recently observed the fascinating double star Gamma 2 Velorum, that was briefly mentioned recently on this blog. This system consists of a hot and massive star being circled by another hot star that is at a very late stage of its lifecycle and hence is a candidate to explode as a supernova.

The two stars are so closely together that they cannot be seen separately by an optical telescope, not even by the sharp vision of the Hubble Space Telescope. However, the system can be separated with SUSI which uses the interference of light to resolve extremely tiny angles in the sky.

The team of astronomers led by Julian North obtained full details of the system including the masses of the two stars, their brightnesses and the separation between them. They found that the double star is at a distance of 1095 light years from us. Other teams using different techniques have generally found a closer distance. Interestingly, the distance obtained in 1970 from a previous Sydney University instrument, the legendary Narrabri Intensity Interferometer, was comparable though with much larger errors.

This work is a great example of what can be done with the help of an interferometer. Well done SUSI, Julian and the others in the team!