Exoplanet circles 'normal star'

From the BBC

Monday, 15 September 2008

A planet has been pictured outside our Solar System which appears to be circling a star like our own Sun - a first in astronomy. Most of the potential exoplanets imaged to date have been seen orbiting brown dwarfs, which are dim - making it easier to detect companion objects. The new planet is huge, with a mass about eight times that of Jupiter. The Canadian team that obtained the picture says the parent star is similar to the Sun but somewhat younger.

Three astronomers from the University of Toronto used the Gemini North telescope on Mauna Kea in Hawaii to take images of the young star 1RXS J160929.1-210524 and the planetary candidate. The star and its companion lie about 500 light-years from Earth. "This is the first time we have directly seen a planetary mass object in a likely orbit around a star like our Sun," said lead author David Lafreniere. "If we confirm that this object is indeed gravitationally tied to the star, it will be a major step forward."

The planet itself lies out at a great distance from its parent star: about 330 times the distance between the Earth and the Sun. By comparison, the most distant planet in our Solar System, Neptune, orbits at about 30 times the distance between the Earth and the Sun.

Dr Matt Burleigh, from the University of Leicester, UK, commented: "This is a very good candidate for a first picture of a planet orbiting a normal star. Now the team needs to make more observations to hopefully confirm that the two are moving together through space," he told BBC News. Finding a planetary-mass companion so far from its parent star came as a surprise to the astronomers, and poses a challenge to theories of star and planet formation.

The astronomers used adaptive optics technology to reduce the distortions to the image caused by turbulence in the Earth's atmosphere. The near-infrared images and spectra of the planetary candidate indicate that it is too cool to be a star or a brown dwarf - a failed star. It may take about two years to confirm that the star and its probable planet are moving through space together. The object is about 1,500C (1,800 Kelvin) - much hotter than Jupiter, which it resembles in terms of size. The work that led to this discovery is part of a survey of more than 85 stars in the Upper Scorpius association - a group of young stars formed about five million years ago.

[It sounds like a rather bizarre planet but there might be smaller planets closer in and somewhat cooler… maybe with liquid water and blue skies….. Maybe……]