We report on the discovery of WASP-12b, a new transiting extrasolar planet with R pl = 1.79 +0.09 −0.09 R J and M pl = 1.41 +0.10 −0.10 M J . The planet and host star properties were derived from a Monte Carlo Markov chain analysis of the transit photometry and radial velocity data. Furthermore, by comparing the stellar spectrum with theoretical spectra and stellar evolution models, we determined that the host star is a supersolar metallicity ([M/H]= 0.3 +0.05 −0.15 ), late-F (T eff = 6300 +200 −100 K) star which is evolving off the zero-age main sequence. The planet has an equilibrium temperature of T eq = 2516 K caused by its very short period orbit (P = 1.09 days) around the hot, twelfth magnitude host star. WASP-12b has the largest radius of any transiting planet yet detected. It is also the most heavily irradiated and the shortest period planet in the literature.

We derive the fundamental parameters (temperature and luminosity) of 107 619 Hipparcos stars and place these stars on a true Hertzsprung–Russell diagram. This is achieved by comparing bt‐settl model atmospheres to spectral energy distributions (SEDs) created from Hipparcos, Tycho, Sloan Digital Sky Survey, DENIS, Two Micron All Sky Survey, MSX, AKARI, IRAS and Wide‐field Infrared Survey Explorer data. We also identify and quantify from these SEDs any infrared excesses attributable to circumstellar matter. We compare our results to known types of objects, focusing on the giant branch stars. Giant star dust production (as traced by infrared excess) is found to start in earnest around 680 L⊙.

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We report the discovery of WASP‐3b, the third transiting exoplanet to be discovered by the WASP and SOPHIE collaboration. WASP‐3b transits its host star USNO‐B1.0 1256−0285133 every 1.846 834 ± 0.000 002 d. Our high‐precision radial velocity measurements present a variation with amplitude characteristic of a planetary‐mass companion and in phase with the light curve. Adaptive optics imaging shows no evidence for nearby stellar companions, and line‐bisector analysis excludes faint, unresolved binarity and stellar activity as the cause of the radial velocity variations. We make a preliminary spectroscopic analysis of the host star and find it to have Teff= 6400 ± 100 K and log  g= 4.25 ± 0.05 which suggests it is most likely an unevolved main‐sequence star of spectral type F7‐8V. Our simultaneous modelling of the transit photometry and reflex motion of the host leads us to derive a mass of 1.76+0.08−0.14MJ and radius 1.31+0.07−0.14RJ for WASP‐3b. The proximity and relative temperature of the host star suggests that WASP‐3b is one of the hottest exoplanets known, and thus has the potential to place stringent constraints on exoplanet atmospheric models.

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