Wasp-43b was identified as a likely planet by the SuperWASP extra-solar planet detection program's WASP-South Observatory in South Africa in 2009 and confirmed by further observations by WASP-South and WASP-North at the Isaac Newton Group of Telescopes on La Palma. Its discovery was announced in 2011 in a paper in the journal Astronomy & Astrophysics by a team lead by Coel Hellier of the Astrophysics Group at Keele University.
Wasp-43b is a Hot-Jupiter type planet orbiting Wasp-43, a K-type Red Dwarf star roughly 260 light years from the Earth in the constellation of Sextans. Wasp-43 was identified as the lowest mass star then discovered to host a Hot-Jupiter type planet. Wasp-43 orbited this star every 374.4 hours at a distance of 0.014 AU (1.4% of the distance between the Earth and the Sun), making it the closest known Hot Jupiter to its star. The planet was calculated to have a mass of 1.8 times that of Jupiter, and 90% of Jupiter's radius.
An artist's impression of Wasp-43b.
On 13 January 2012 a paper was published on the online arXiv database at Cornell University Library by a team lead by Michael Gillon of the Université de Liège detailing a revised study of the Wasp-43 system combining the original WASP data with new data gathered by the TRAPPIST Telescope, at the European Southern Observatory's La Silla Observatory in Chille, and the Very Large Telescope, also at La Silla.
This more refined view of the system gives the star, Wasp-43A, a radius of 72% of that of our sun and a mass of 2.5% the sun's. Wasp-43b orbits this star at a distance of 0.015 AU (1.5% of the distance between the Earth and the sun) making it the closest known Hot Jupiter to its host star. Wasp-43b has a mass of 2.04 times that of Jupiter, and 1.04 times its radius. Despite being the closest known Hot Jupiter to its star, Wasp-43b is not thought to be highly irradiated for this type of planet. Indeed with a cool star, a high density implying a large core and a very stable orbit it is quite likely that Wasp-43b has sat in its current configuration quite happily for several billion years.
A comparison of the size of Wasp-43b and the planets of our own solar system.
See also A planet disintegrating in the heat of its own sun, KOI-961, a mini planetary system with a star not much bigger than Jupiter, Wasp-19b: a highly irradiated Hot Jupiter and Exoplanets on Sciency Thoughts YouTube.