---

SA astronomers in 'extraordinary' find

20 June 2011

Stephen Potter and Encarni Romero-Colmenero from the South African Astronomical Observatory (SAAO), along with other collaborators, have found evidence for the existence of an extraordinary planetary system where two giant planets are orbiting a close pair of "suns".

If confirmed, this would be an example of a very strange planetary system, given the nature of the stellar pair.

The discovery was made possible by new SAAO and Southern African Large Telescope (SALT) observations combined with archival data spanning 27 years, gathered from multiple observatories and satellites.

White and red dwarf

The two stars, referred to as a "white dwarf" and a "red dwarf", are each smaller than our Sun and are so close that they take only a couple of hours to orbit each other – the pair of them would actually fit comfortably within our Sun.

By chance, the system is oriented in such a way that the stars appear to eclipse each other once every orbit as viewed from Earth.

"Potter and his collaborators noticed that the eclipses were not occurring on time, but were sometimes too early or too late," the SAAO said in a statement last week. "This led them to hypothesise the presence of two giant planets whose gravitational effect would cause the stars' orbit to wobble and consequently slightly alter the measured time between eclipses."

Constantly 'stealing' material

The astronomers were also able to infer that the masses of the two planets must be at least 6 and 8 times that of Jupiter and take 16 and 5 years respectively to orbit the two stars, the SAAO said. The system is too far away from us to be imaged directly.

This binary star system (known as UZ For) would be an extremely inhospitable environment. Due to their close proximity, the gravity of the white dwarf is constantly "stealing" material from the surface of the red dwarf in a continuous stream.

This stream crashes onto the white dwarf, where it gets super-heated to millions of degrees and subsequently floods the entire planetary system with enormous amounts of deadly X-rays.

SAinfo reporter