Tuesday 21 February 2012

Wasp-12b; slowly boiling away...

Wasp-12b is a super-Jovian Hot Jupiter type planet (a planet larger than Jupiter orbiting very close to its parent star) 871 light years from Earth in the constellation of Auriga. It orbits Wasp-12A, a G-type yellow dwarf star slightly bigger and hotter than our sun (1.35 × the Sun's mass, with a surface temperature of 6300 K, as opposed to 5770 K for our sun), every 26 hours at a distance of 0.229 AU (2.29 % of the distance at which the Earth orbit's the Sun more than ten times as close to its star as Mercury). Wasp-12b is 1.39 as massive as Jupiter but has 28.3 times its volume, being inflated by the heat of the star, with an average surface temperature of 2525 K. It was discovered in 2008 by the SuperWASP planetary survey, and its discovery announced in a paper in The Astrophysical Journal in 2009, by a team of scientists led by Leslie Hebb of the School of Physics and Astronomy at the University of St. Andrews.

In a paper published on 26 January 2012 in the online arXiv database at Cornell University Library a team of scientists led by Nicolas Cowan of the Center for Interdisciplinary Exploration and Research in Astrophysics and the Department of Physics & Astronomy at Northwestern University describe a new study of Wasp-12b, based upon data from the Spitzer Space Telescope.

Cowan et al. came to the conclusion that Wasp-12b is probably elliptical in shape, and tidally locked, with one face (end) pointing permanently to the star. This face of the planet would reach temperatures in excess of 3000 K, hot enough for the atmosphere to slowly boil away into space. The material lost in this way probably forms an accretionary disk about the star, which will slowly be drawing mass from the planet.

An artist's impression of Wasp 12b, by Greg Bacon of The Space Telescope Science Institute.