WASP-12b is an extrasolar planet orbiting the starWASP-12, discovered by the SuperWASPplanetary transit survey. Its discovery was announced on April 1, 2008. Due to its extremely close orbit to its star, it has one of the lowest densities for exoplanets. The planet takes only a little over a day to orbit the star, in contrast to 365 days for the Earth to orbitthe Sun. Its distance from the star is only 1/44 the Earth's distance from the Sun, with an eccentricity the same as Jupiter's. On 3 December 2013, scientists working with the Hubble Space Telescope reported detecting water in the atmosphere of the exoplanet. In July 2014, NASA announced finding very dry atmospheres on three exoplanets orbiting sun-like stars. In September 2017, researchers, working on the HST, announced that WASP-12b absorbs, instead of reflects, at least 94% of the light that shines on its surface. As a result, the exoplanet has been described as "black as asphalt", and as "pitch black" and is a type of planet known as a hot Jupiter.
Characteristics
Since hot Jupiter exoplanets are “phase locked” by tidal interactions, there will be a large flow of heat from the highly irradiated “day side” to the cooler “night side”. This is thought to result in very strong winds rushing around the planet's atmosphere. Taylor Bell and Nicolas Cowan have pointed out that hydrogen will tend to be ionised on the day-side face. After flowing to the cooler face in a wind, it will then tend to recombine into neutral atoms, and thus will enhance the transport of heat. The planet is so close to WASP-12 that the star's tidal forces are distorting it into an egg shape and pulling away its atmosphere at a rate of about 10−7 per year. The so-called "tidal heating", and the proximity of the planet to its star, combine to bring the surface temperature to more than. On May 20, 2010, the Hubble Space Telescope spotted WASP-12b being "consumed" by its star. Scientists had been aware that stars could consume planets; however, this was the first time such an event had been observed so clearly. NASA has estimated that the planet has 10 million years left of its life. The Hubble Space Telescope observed the planet by using its Cosmic Origins Spectrograph. The observations have confirmed predictions published in Nature in February 2009 by Peking University's Shu-lin Li. The planet's atmosphere has ballooned to be nearly three times the radius of Jupiter, while the planet itself has 40% more mass than Jupiter.
Orbit
The study in 2012, utilizing a Rossiter–McLaughlin effect, have determined the planetary orbit is strongly misaligned with the equatorial plane of the star, misalignment equal to 59°. A study from 2019 found that the time interval between two transits has decreased by 29 ± 2 msec/year since the discovery in 2008. The study came to the conclusion that the orbit of WASP-12b is decaying as a result of tidal interactions between the planet and the host star WASP-12. Due to this decay, the orbital period will get shorter and the planet will get closer to the host star, until it will become part of the star. This process might take a few million years. The decay is much faster than the decay of WASP-19b, which does not show a decay with current data.
Carbon content
Recent evidence indicates that WASP-12b has an enhanced carbon-to-oxygen ratio, significantly higher than that of the Sun, indicating that it is a carbon-rich gas giant. The C/O ratio compatible with observations is about 1, while the solar value is 0.54. The C/O ratios suggest that carbon-rich planets may have formed in the star system. One of the researchers behind that study commented that "with more carbon than oxygen, you would get rocks of pure carbon, such as diamond or graphite". The published study states: "Although carbon-rich giant planets like WASP-12b have not been observed, theory predicts myriad compositions for carbon-dominated solid planets. Terrestrial-sized carbon planets, for instance, could be dominated by graphite or diamond interiors, as opposed to the silicate composition of Earth." These remarks have led the media to pick up on the story, some even calling WASP-12b a "diamond planet". The carbon content of the planet is located within its atmosphere, in the form of carbon monoxide and methane. The study appears in the journal Nature.
Candidate satellite
Russian astronomers studying a curve of change of shine of the planet observed regular variation of light that may arise from plasma torus surrounding at least one exomoon in orbit around WASP-12b. This is not expected, as hot Jupiter-type planets are expected to lose large moons within geologically short timescales. Alternative plasma sources for observed variations of spectra may be the troyan stellite sharing the same orbit with WASP-12b but not orbiting it.
