WASP-5b: A dense, very hot Jupiter transiting a 12th-mag Southern-hemisphere star

We report the discovery of WASP-5b, a Jupiter-mass planet orbiting a 12th-mag G-type star in the Southern hemisphere. The 1.6-d orbital period places WASP-5b in the class of very hot Jupiters and leads to a predicted equilibrium temperature of 1750 K. WASP-5b is the densest of any known Jovian-mass planet, being a factor of 7 denser than TrES-4, which is subject to similar stellar insolation, and a factor of 3 denser than WASP-4b, which has a similar orbital period. We present transit photometry and radial velocity measurements of WASP-5 (= USNO-B1 0487-0799749), from which we derive the mass, radius and density of the planet: MP= 1.58+0.13−0.08 MJ, RP= 1.090+0.094−0.058 RJ and ρP= 1.22+0.19−0.24 ρJ. The orbital period is P= 1.6284296+0.0000048−0.0000037 d and the mid-transit epoch is TC (HJD) = 245 4375.62466+0.00026−0.00025.