Sunday 21 August 2011

New Exoplanet: TrES-5.

On the 17 August 2011 a team from the Trans-Atlantic Exoplanet Survey reported the discovery of a new 'Hot Jupiter' type exoplanet in a paper on the online arXiv forum, hosted by Cornell University Library. The planet orbits the star GSC 03949-00967, a G-type dwarf (the same sort of star as our sun) slightly under 90% of the mass and radius of our sun, roughly 1175 light years from our solar system in the constellation Cygnus, the faintest star about which is the faintest star about which an exoplanet has been discovered using Earth-based telescopes.

An artist's impression of a Hot Jupiter type planet.

The team was lead by Georgi Mandushev of the Lowell Observatory in Arizona, and first observed the planetary candidate in 2007 using the Planet Search Survey Telescope at Lowell Observatory and the STARE Telescope (STellar Astrophysics and Research on Exoplanets) in the Canary Islands. In order to confirm this was an exoplanet, and not a dim binary star or some sort of sunspot, follow up observations were made using the Hall and Perkins Telescopes at Lowell Observatory, and the Tillinghast Reflector Echelle Spectograph at Fred Lawrence Whipple Observatory in Arizona.

The paper refers to the planet as TrES-5 and the star as GSC 03949-00967 (GSC stands for 'Guide Star Catalogue', the numbers are co-ordinates in the sky), though strictly speaking the star should be referred to as either TrES-5A or GSC 03949-00967A and the planet as TrES-5b or GSC 03949-00967b if conventions on the naming of astronomical objects are followed.

Mandushev et al. calculate that TrES-5 has a mass of 1.8 times that of Jupiter and a radius 1.2 time that of Jupiter. This is roughly the radius we would expect for a planet of this mass, which is surprising as most 'Hot Jupiter' type planets have anomalously large radiuses; Mandushev et al. attribute this to the age of the system; the GSC 03949-00967 system is 7.38 billion years old, which may have allowed the planet to reach an equilibrium temperature distribution not seen in younger 'Hot Jupiter' planets. The planet takes 35 hours and 30 minutes to orbit its star, and does not show any appreciable eccentricity in its orbit.

See also TrES-2b, the black planet, The discovery of Kepler 17-b and Exoplanets on Sciency Thoughts YouTube.