Wednesday, April 6, 2011

Is This an Alien Planet

Most methods for finding extra-solar planets favor worlds very close to their stars. Direct imaging, on the other hand, favors those far away - at least when it looks for an object's own infrared heat glow, rather than reflected starlight. Young giant planets should still be glowing from the heat of their formation. This Gemini Observatory infrared image shows the young star 1RXS J160929.1-210524 and a suspected planet-mass object 2.2 arc seconds from it. This separation amounts to at least330 astronomical units (8 times Pluto's average distance from the Sun) at the star's distance of 500 light-years.

David Lafrenière and two University of Toronto colleagues estimate, based on the star’s age and the object's spectrum and temperature, that it probably has only about 8 times the mass of Jupiter.But it’s highly unlikely that so massive a "planet" would have formed so far from its star. It's probably more accurate to call it a "brown dwarf" - or perhaps a new name for objects in between.

"This is the first time we have directly seen a planetary mass object in a likely orbit around a star like our Sun," said David Lafrenière, lead author of a paper submitted to the Astrophysical Journal Letters and also posted online. "If we confirm that this object is indeed gravitationally tied to the star, it will be a major step forward."Until now, the only planet-like bodies that have been directly imaged outside of the solar system are either free-floating in space (i.e. not found around a star), or orbit brown dwarfs, which are dim and make it easier to detect planetary-mass companions.

The existence of a planetary-mass companion so far from its parent star comes as a surprise, and poses a challenge to theoretical models of star and planet formation. "This discovery is yet another reminder of the truly remarkable diversity of worlds out there, and it's a strong hint that nature may have more than one mechanism for producing planetary mass companions to normal stars," said Ray Jayawardhana, team member and author of a forthcoming book on extra-solar planets entitled Worlds Beyond.

Gemini adaptive optics image of 1RSX J160929.1-210524 and its likely ~8 Jupiter-mass companion (within red circle). The image is a composite of J-, H- and K-band near-infrared images. All images obtained with the Gemini Altair adaptive optics system and the Near-Infrared Imager (NIRI) on the Gemini North telescope. Photo Credit: Gemini Observatory.

The Gemini Observatory is an astronomical observatory consisting of two 8.1-metre (27 ft) telescopes at different sites in Hawaii and Chile. Together, the twin Gemini telescopes provide almost complete coverage of both the northern and southern skies. They are currently among the largest and most advanced optical/infrared telescopes available to astronomers.

Southern Observatory located at 2,722 m (8,930 ft)
above sea level, in Cerro Pachón, Chile

Sources: Sky & Telescope Magazine, Wikipedia, NASA, Google Maps, and various

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