A University of Toronto team working on the Gemini North telescope on Mauna Kea have released a picture of what appears to be a large planetary body close to the star 1RXS J160929.1-21052, a member of a very new (~5 million years old) star group known as the Upper Scorpius association, about 150 parsecs from the Sun. Although it is unlikely to be a chance alignment, it may take years to establish that the body and the star are moving together through space.
The team relied on the telescope’s high resolution advanced adaptive optics to see the body, light from which would normally be drowned out by the effects of earth’s atmosphere. They also looked at young stars “so that any planetary mass object they hosted would not have had time to cool, and thus would still be relatively bright,”says Marten van Kerkwijk, a member of the Canadian team. Most orbiting planetary bodies discovered to date have been associated with brown dwarfs, whose dimness makes it easier to spot orbiting bodies.
The object is estimated to be 330 AU from the star (2.22″ of arc). This is a surprising distance, and suggests that our current models of solar system formation need revision. Neptune, the most distant planet in our own solar system, is only 30 AU from the sun. The body is also much hotter than any planet in our solar system which is consistent with the very young age of the star. From the spectrum it appears to be 1800 Kelvin.
The team estimates the mass of the body from its temperature, using the AMES-DUSTY atmosphere model, as about 8 times the mass of Jupiter–which would make it by far the least massive planetary body ever spotted.
- First Picture of Likely Planet around Sun-like Star -press release, September 15, 2008. Gemini Observatory website
- Direct Imaging and Spectroscopy of a Planetary Mass Candidate to a Young Solar Analog – abstract of paper submitted to The Astrophysical Journal Letters. Draft paper can be downloaded.
- Astronomers image planet around sun-like star -New Scientist, September 15, 2008