Wasp-19b is an exoplanet slightly larger than Jupiter (1.1 times the mass, 1.31 times the radius) orbiting a G-type star 815 light years from the Earth in the constellation of Vela. It was discovered in 2009 by the WASP-South Telescope near Sutherland in Northern Cape Province, South Africa, and its discovery reported in a paper in The Astrophysical Journal by a team lead by Leslie Hebb of the School of Physics and Astronomy at the University of St. Andrews in Scotland.
Wasp-19b has the shortest year of any known planet, orbiting its star in slightly under 19 hours, at a distance of 1.65% of that at which the Earth orbits the Sun. This comfortably places Wasp-19b in the 'Hot Jupiter' category of planets, large planets orbiting close to their stars. But Wasp-19b is hot even for a Hot Jupiter, since the star it orbits is not a cool Red Dwarf, like most Hot Jupiters, but a G-type star with a mass 95% of that of the Sun, a radius 93% of that of the Sun (which is 7.15 times that of Wasp-19b), and a luminosity 71% of that of the Sun. Wasp-19b has an almost circular orbit, with an eccentricity of just 6000 km (that is to say when it is at its closest to its star it is only 6000 km closer than when it is at its furthest).
A simple model of the Wasp-19 system.
This month a team lead by David Anderson of the Astrophysics Group at Keele University published a paper on the arXiv online Database at Cornell University Library detailing the results of a spectrographic study of the atmosphere of Wasp-19b using the Spitzer Space Telescope; this paper has also been accepted for publication in the Monthly Notices of the Royal Astronomical Society.
Most Hot Jupiters appear dark due to Titanium and Vanadium Oxides (TiO and VO) trapped it warm layers of the upper stratosphere, but Wasp-19b appears bright, suggesting that it lacks these dark-molecule trapping layers. The most likely explanation for that is that it lacks a stratified atmosphere due to the high energy input it receives from it's star. Thus it is likely to have both Titanium and Vanadium Oxide in its atmosphere, just not trapped in a discreet layer where they can act as a dark layer.
The precise makeup of the atmosphere of Wasp-19b could not be determined by this study, but the team were able to narrow it down to two possible models. The first, the 'carbon rich' model has an atmosphere comprised primarily of Carbon Monoxide (CO) and Methane (CH₄); the second, or 'oxygen rich', model has an atmosphere composed mostly of Carbon Monoxide, Carbon Dioxide (CO₂) and Water (H₂O).
See also The Atmosphere of GJ1214b, TrES-2b, the black planet and Exoplanets on Sciency Thoughts YouTube.