Discovery | |
---|---|
Discovered by | Cameron et al. (SuperWASP) |
Discovery site | SAAO |
Discovery date | April 1, 2008 [1] |
Transit | |
Orbital characteristics | |
0.0234+0.00056 −0.00050 AU | |
Eccentricity | 0.049 ± 0.015 |
1.091423±0.000003 d | |
Inclination | 83.37°+0.72° −0.64° |
−74°+13° −10° | |
Star | WASP-12 |
Physical characteristics | |
Mean radius | 1.900+0.057 −0.055, [2] RJ |
Mass | 1.47+0.076 −0.069 [2] MJ |
Mean density | 266 kg/m3 (448 lb/cu yd) [2] |
3.004±0.015 g [2] | |
Temperature | 3128+64 −68 K (2885+64 −68 °C, 5225+147 −155 °F) [3] |
WASP-12b is a hot Jupiter [4] (a class of extrasolar planets) orbiting the star WASP-12, discovered on April 1, 2008, by the SuperWASP planetary transit survey. [1] The planet takes only a little over one Earth day to orbit its star, in contrast to about 365.25 days for the Earth to orbit the Sun. Its distance from the star (approximately 3.5 million kilometers [2.2 million miles ; 0.023 astronomical units ]) is only the Earth's distance from the Sun, with an eccentricity the same as Jupiter's. Consequently, it has one of the lowest densities for exoplanets ("inflated" by the flux of energy from the star). On December 3, 2013, scientists working with the Hubble Space Telescope (HST) reported detecting water in the atmosphere of the exoplanet. [5] [6] In July 2014, NASA announced finding very dry atmospheres on three exoplanets (HD 189733b, HD 209458b, WASP-12b) orbiting sun-like stars. [7]
In September 2017, researchers working on the HST announced that WASP-12b reflects just 6% of the light that shines on its surface. As a result, the exoplanet has been described as "black as asphalt" and as "pitch black." [8]
Since hot Jupiter exoplanets are tidally locked (i. e. the same side always faces the host star, just as the same side of the Moon always faces the Earth), there is a large flow of heat from the highly irradiated illuminated side to the cooler dark side. This is thought to result in 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. 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 its star that its tidal forces are distorting it into an egg shape and pulling away its atmosphere at a rate of about 10−7 MJ (about 189 quadrillion tons) per year. [10] The so-called "tidal heating", and the proximity of the planet to its star, combine to bring the surface temperature to more than 2,500 K (2,200 °C).
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. [11]
The Hubble Space Telescope observed the planet by using its Cosmic Origins Spectrograph (COS). 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.
A study in 2012, utilizing the Rossiter–McLaughlin effect, determined that WASP-12b's orbit is strongly misaligned with the equatorial plane of its star by 59+15
−20°. [12]
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 value was updated in 2020 to 32.53±1.62 msec/year, giving WASP-12b an estimated lifetime of 2.90±0.14 million years. [13] 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. The decay is much faster than the decay of WASP-19b, which does not show a decay with current data. [14] [15] In 2022, the decay rate was further refined to 29.81±0.94 msec/year, which corresponds to an estimated lifetime of 3.16±0.10 Ma . [16]
Evidence reported in a 2010 study 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. [17] 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". [18]
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." [17] These remarks have led the media to pick up on the story, [19] some even calling WASP-12b a "diamond planet". [20]
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 . [21]
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. [22] This is not expected, as hot Jupiter-type planets are expected to lose large moons within geologically short timescales. [23] The satellite in question could instead be a Trojan body. [24]
HD 209458 b, which is also nicknamed Osiris after the Egyptian god, is an exoplanet that orbits the solar analog HD 209458 in the constellation Pegasus, some 159 light-years from the Solar System. The radius of the planet's orbit is 0.047 AU, or one-eighth the radius of Mercury's orbit. This small radius results in a year that is 3.5 Earth-days long and an estimated surface temperature of about 1,000 °C. Its mass is 220 times that of Earth and its volume is some 2.5 times greater than that of Jupiter. The high mass and volume of HD 209458 b indicate that it is a gas giant.
Hot Jupiters are a class of gas giant exoplanets that are inferred to be physically similar to Jupiter but that have very short orbital periods. The close proximity to their stars and high surface-atmosphere temperatures resulted in their informal name "hot Jupiters".
An exomoon or extrasolar moon is a natural satellite that orbits an exoplanet or other non-stellar extrasolar body.
HD 189733, also catalogued as V452 Vulpeculae, is a binary star system approximately 64.5 light-years away in the constellation of Vulpecula. The primary star is suspected to be an orange dwarf star, while the secondary star is a red dwarf star. Given that this system has the same visual magnitude as HD 209458, it promises much for the study of close transiting extrasolar planets. The star can be found with binoculars 0.3 degrees east of the Dumbbell Nebula (M27).
XO-1b is an extrasolar planet approximately 536 light-years away from Earth.
The study of extraterrestrial atmospheres is an active field of research, both as an aspect of astronomy and to gain insight into Earth's atmosphere. In addition to Earth, many of the other astronomical objects in the Solar System have atmospheres. These include all the gas giants, as well as Mars, Venus and Titan. Several moons and other bodies also have atmospheres, as do comets and the Sun. There is evidence that extrasolar planets can have an atmosphere. Comparisons of these atmospheres to one another and to Earth's atmosphere broaden our basic understanding of atmospheric processes such as the greenhouse effect, aerosol and cloud physics, and atmospheric chemistry and dynamics.
HD 189733 b is an exoplanet approximately 64.5 light-years (19.8 pc) away from the Solar System in the constellation of Vulpecula. Astronomers in France discovered the planet orbiting the star HD 189733 on October 5, 2005, by observing its transit across the star's face. With a mass 16.2% higher than that of Jupiter and a radius 13.8% greater, HD 189733 b orbits its host star once every 2.2 days at an orbital speed of 152.5 kilometers per second, making it a hot Jupiter with poor prospects for extraterrestrial life.
WASP-6b is an extrasolar planet approximately 600 light years away in the constellation Aquarius. It was discovered in 2008, by the WASP survey, by astronomical transit across its parent star WASP-6. This planet orbits only 4% that of Earth-Sun distance. The planet has mass half that of Jupiter, but its insolation has forced a thermal expansion of its radius over that of Jupiter. The planet is an inflated Hot Jupiter. Starspots on the host star WASP-6 helped to refine the measurements of the mass and the radius of the planet.
WASP-17b is an exoplanet in the constellation Scorpius that is orbiting the star WASP-17. Its discovery was announced on 11 August 2009. It is the first planet discovered to have a retrograde orbit, meaning it orbits in a direction counter to the rotation of its host star. This discovery challenged traditional planetary formation theory. In terms of diameter, WASP-17b is one of the largest exoplanets discovered and at half Jupiter's mass, this made it the most puffy planet known in 2010. On 3 December 2013, scientists working with the Hubble Space Telescope reported detecting water in the exoplanet's atmosphere.
WASP-18 is a magnitude 9 star located in the Phoenix constellation of the southern hemisphere. It has a mass of 1.25 solar masses.
WASP-19b is an extrasolar planet, notable for possessing one of the shortest orbital periods of any known planetary body: 0.7888399 days or approximately 18.932 hours. It has a mass close to that of Jupiter, but by comparison has a much larger radius ; making it nearly the size of a low-mass star. It orbits the star WASP-19 in the Vela constellation. At the time of discovery it was the shortest period hot Jupiter discovered as planets with shorter orbital periods had a rocky, or metallic composition.
WASP-33b is an extrasolar planet orbiting the star HD 15082. It was the first planet discovered to orbit a Delta Scuti variable star. With a semimajor axis of 0.026 AU and a mass likely greater than Jupiter's, it belongs to the hot Jupiter class of planets.
An exoplanet is a planet located outside the Solar System. The first evidence of an exoplanet was noted as early as 1917, but was not recognized as such until 2016; no planet discovery has yet come from that evidence. What turned out to be the first detection of an exoplanet was published among a list of possible candidates in 1988, though not confirmed until 2003. The first confirmed detection came in 1992, with the discovery of terrestrial-mass planets orbiting the pulsar PSR B1257+12. The first confirmation of an exoplanet orbiting a main-sequence star was made in 1995, when a giant planet was found in a four-day orbit around the nearby star 51 Pegasi. Some exoplanets have been imaged directly by telescopes, but the vast majority have been detected through indirect methods, such as the transit method and the radial-velocity method. As of 1 June 2023, there are 5,388 confirmed exoplanets in 3,979 planetary systems, with 859 systems having more than one planet. This is a list of the most notable discoveries.
WASP-43b is a transiting planet in orbit around the young, active, and low-mass star WASP-43 in the constellation Sextans. The planet is a hot Jupiter with a mass twice that of Jupiter, but with a roughly equal radius. WASP-43b was flagged as a candidate by the SuperWASP program, before they conducted follow-ups using instruments at La Silla Observatory in Chile, which confirmed its existence and provided orbital and physical characteristics. The planet's discovery was published on April 14, 2011.
WASP-121b is an extrasolar planet orbiting the star WASP-121. WASP-121b is the first exoplanet found to contain water in an extrasolar planetary stratosphere. WASP-121b is in the constellation Puppis, and is about 850 light-years from Earth.
WASP-121, also known as CD-38 3220, is a magnitude 10.4 star located approximately 850 light-years away in the constellation Puppis. WASP-121 has a mass and radius similar to the Sun's.
WASP-107b is a super-Neptune exoplanet that orbits the star WASP-107. It lies 200 light-years away from Earth in the constellation Virgo. Its discovery was announced in 2017 by a team led by D. R. Anderson via the WASP-South.
HD 146389, is a star with a yellow-white hue in the northern constellation of Hercules. The star was given the formal name Irena by the International Astronomical Union in January 2020. It is invisible to the naked eye with an apparent visual magnitude of 9.4 The star is located at a distance of approximately 446 light years from the Sun based on parallax, but is drifting closer with a radial velocity of −9 km/s. The star is known to host one exoplanet, designated WASP-38b or formally named 'Iztok'.
WASP-72 is the primary of a binary star system. It is an F7 class dwarf star, with an internal structure just on the verge of the Kraft break. It is orbited by a planet WASP-72b. The age of WASP-72 is younger than the Sun at 3.55±0.82 billion years.
Exometeorology is the study of atmospheric conditions of exoplanets and other non-stellar celestial bodies outside the Solar System, such as brown dwarfs. The diversity of possible sizes, compositions, and temperatures for exoplanets leads to a similar diversity of theorized atmospheric conditions. However, exoplanet detection technology has only recently developed enough to allow direct observation of exoplanet atmospheres, so there is currently very little observational data about meteorological variations in those atmospheres.
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