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WASP-12b

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WASP-12b is a hot Jupiter[5] (a class of extrasolar planets) orbiting the star WASP-12, discovered in April of 2008, by the SuperWASP planetary transit survey.[6][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.[7][8] In July 2014, NASA announced finding very dry atmospheres on three exoplanets (HD 189733b, HD 209458b, WASP-12b) orbiting sun-like stars.[9]

WASP-12b
Size comparison of WASP-12b (right) with Jupiter
Discovery
Discovered byCameron et al. (SuperWASP)
Discovery siteSAAO
Discovery dateApril 2008[1]
Transit
Orbital characteristics
0.0234+0.00056
−0.00050 AU
Eccentricity0.049 ± 0.015
1.0914199±0.0000002 d[2]
Inclination81.92°±1.51°[2]
−74°+13°
−10°
StarWASP-12
Physical characteristics
1.819±0.142[2] RJ
Mass1.47+0.076
−0.069[3] MJ
Mean density
0.266 g/cm3[3]
3.004±0.015 g[3]
Temperature3128+64
−68 K (2885+64
−68 °C, 5225+147
−155 °F)[4]

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."[10]

Characteristics

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Artist's depiction of WASP-12b's atmosphere being tidally stripped by its parent star

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.[11] 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.[12]

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.

Orbit

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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°.[13]

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.[14] 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.[15][16] 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.[17]

Carbon content

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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.[18] 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".[19]

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."[18] These remarks have led the media to pick up on the story,[20] some even calling WASP-12b a "diamond planet".[21]

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.[22]

 
Comparison of "hot Jupiter" exoplanets - from top left to lower right: WASP-12b, WASP-6b, WASP-31b, WASP-39b, HD 189733b, HAT-P-12b, WASP-17b, WASP-19b, HAT-P-1b and HD 209458b.
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    WASP-12b and its host star, WASP-12 (artist conception).
  •  
    Hot, carbon-rich planet WASP-12b and its host star. (Exoplanet color was unknown at the time of this artist conception).
  •  
    WASP-12b and its host star, WASP-12 − with IR spectra noting the presence of various chemical molecules.

Candidate satellite

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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.[23] This is not expected, as hot Jupiter-type planets are expected to lose large moons within geologically short timescales.[24] The satellite in question could instead be a Trojan body.[25]

See also

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References

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  1. ^ a b Moskowitz, Clara (October 16, 2008). "Astronomers find hottest planet ever discovered". NBC news. Archived from the original on April 4, 2024. Retrieved April 4, 2024.
  2. ^ a b c Öztürk, Oğuz; Erdem, Ahmet (March 14, 2019). "New photometric analysis of five exoplanets: CoRoT-2b, HAT-P-12b, TrES-2b, WASP-12b, and WASP-52b". Monthly Notices of the Royal Astronomical Society. 486 (2): 2290–2307. doi:10.1093/mnras/stz747. ISSN 0035-8711.
  3. ^ a b c Collins, Karen A; Kielkopf, John F; Stassun, Keivan G (2017). "Transit Timing Variation Measurements of WASP-12b and Qatar-1b: No Evidence for Additional Planets". The Astronomical Journal. 153 (2): 78. arXiv:1512.00464. Bibcode:2017AJ....153...78C. doi:10.3847/1538-3881/153/2/78. S2CID 55191644.
  4. ^ Owens, Niall; De Mooij, E J W.; Watson, C. A.; Hooton, M. J. (2021), "Phase curve and variability analysis of WASP-12b using TESS photometry", Monthly Notices of the Royal Astronomical Society: Letters, 503: L38–L46, arXiv:2102.00052, doi:10.1093/mnrasl/slab014
  5. ^ Starr, Michelle (April 23, 2018). "Astronomers Just Found a 'Hot Jupiter' So Dark, It Absorbs Nearly 99% of Light". ScienceAlert.
  6. ^ "WASP Planets". SuperWASP. December 5, 2013. Retrieved January 26, 2016.
  7. ^ Staff (December 3, 2013). "Hubble Traces Subtle Signals of Water on Hazy Worlds". NASA. Retrieved December 4, 2013.
  8. ^ Mandell, Avi M.; Haynes, Korey; Sinukoff, Evan; Madhusudhan, Nikku; Burrows, Adam; Deming, Drake (December 3, 2013). "Exoplanet Transit Spectroscopy Using WFC3: WASP-12 b, WASP-17 b, and WASP-19 b". Astrophysical Journal. 779 (2): 128. arXiv:1310.2949. Bibcode:2013ApJ...779..128M. doi:10.1088/0004-637X/779/2/128. S2CID 52997396.
  9. ^ Harrington, J.D.; Villard, Ray (July 24, 2014). "RELEASE 14-197 - Hubble Finds Three Surprisingly Dry Exoplanets". NASA. Retrieved July 25, 2014.
  10. ^ Wall, Mike (September 18, 2017). "The hellish world WASP-12b is darker than fresh asphalt in visible light, but glows red-hot in infrared". Scientific American. Retrieved September 19, 2017.
  11. ^ Li, Shu-lin; Miller, N.; Lin, Douglas N. C. & Fortney, Jonathan J. (2010). "WASP-12b as a prolate, inflated and disrupting planet from tidal dissipation". Nature. 463 (7284): 1054–1056. arXiv:1002.4608. Bibcode:2010Natur.463.1054L. doi:10.1038/nature08715. PMID 20182506. S2CID 4414948.
  12. ^ Hubble Finds a Star Eating a Planet nasa.gov. 2010-05-20. Retrieved on 2010-12-10.
  13. ^ Albrecht, Simon; Winn, Joshua N.; Johnson, John A.; Howard, Andrew W.; Marcy, Geoffrey W.; Butler, R. Paul; Arriagada, Pamela; Crane, Jeffrey D.; Shectman, Stephen A.; Thompson, Ian B.; Hirano, Teruyuki; Bakos, Gaspar; Hartman, Joel D. (2012), "Obliquities of Hot Jupiter host stars: Evidence for tidal interactions and primordial misalignments", The Astrophysical Journal, 757 (1): 18, arXiv:1206.6105, Bibcode:2012ApJ...757...18A, doi:10.1088/0004-637X/757/1/18, S2CID 17174530
  14. ^ Turner, Jake D.; Ridden-Harper, Andrew; Jayawardhana, Ray (2021), "Decaying Orbit of the Hot Jupiter WASP-12b: Confirmation with TESS Observations", The Astronomical Journal, 161 (2): 72, arXiv:2012.02211, Bibcode:2021AJ....161...72T, doi:10.3847/1538-3881/abd178, S2CID 227305717
  15. ^ waspplanets (November 26, 2019). "The orbit of WASP-12b is decaying". WASP Planets. Retrieved January 1, 2020.
  16. ^ Yee, Samuel W.; Winn, Joshua N.; Knutson, Heather A.; Patra, Kishore C.; Vissapragada, Shreyas; Zhang, Michael M.; Holman, Matthew J.; Shporer, Avi; Wright, Jason T. (November 20, 2019). "The Orbit of WASP-12b is Decaying". The Astrophysical Journal. 888: L5. arXiv:1911.09131. doi:10.3847/2041-8213/ab5c16. S2CID 208202070.
  17. ^ Wong, Ian; Shporer, Avi; Vissapragada, Shreyas; Greklek-McKeon, Michael; Knutson, Heather A.; Winn, Joshua N.; Benneke, Björn (January 20, 2022). "TESS Revisits WASP-12: Updated Orbital Decay Rate and Constraints on Atmospheric Variability". The Astronomical Journal. 163 (4): 175. arXiv:2201.08370. Bibcode:2022AJ....163..175W. doi:10.3847/1538-3881/ac5680. S2CID 246063389.
  18. ^ a b Madhusudhan, N.; Harrington, J.; Stevenson, K. B.; Nymeyer, S.; Campo, C. J.; Wheatley, P. J.; Deming, D.; Blecic, J.; Hardy, R. A.; Lust, N. B.; Anderson, D. R.; Collier-Cameron, A.; Britt, C. B. T.; Bowman, W. C.; Hebb, L.; Hellier, C.; Maxted, P. F. L.; Pollacco, D.; West, R. G. (2010). "A high C/O ratio and weak thermal inversion in the atmosphere of exoplanet WASP-12b". Nature. 469 (7328): 64–67. arXiv:1012.1603. Bibcode:2011Natur.469...64M. doi:10.1038/nature09602. PMID 21150901. S2CID 4415171.
  19. ^ "Carbon-Rich Planet: A Girl's Best Friend?". U.S. News & World Report. December 10, 2010.
  20. ^ Lorianna De Giorgio (December 10, 2010). "Carbon-rich planet could house diamonds". Toronto Star.
  21. ^ "Diamond planet found by Keele University astronomers". BBC News Online. December 9, 2010.
  22. ^ Intagliata, Christopher (December 9, 2010). "Exoplanet Strikes Carbon Pay Dirt". Scientific American.
  23. ^ Российские астрономы впервые открыли луну возле экзопланеты (in Russian) - "Studying of a curve of change of shine of WASP-12b has brought to the Russian astronomers unusual result: regular splashes were found out.<...> Though stains on a star surface also can cause similar changes of shine, observable splashes are very similar on duration, a profile and amplitude that testifies for benefit of exomoon existence."
  24. ^ Barnes, Jason W.; O'Brien, D. P. (2002). "Stability of Satellites around Close-in Extrasolar Giant Planets". The Astrophysical Journal. 575 (2): 1087–1093. arXiv:astro-ph/0205035. Bibcode:2002ApJ...575.1087B. doi:10.1086/341477. S2CID 14508244.
  25. ^ Kislyakova, K. G.; Pilat-Lohinger, E.; Funk, B.; Lammer, H.; Fossati, L.; Eggl, S.; Schwarz, R.; Boudjada, M. Y.; Erkaev, N. V. (2016), "On the ultraviolet anomalies of the WASP-12 and HD 189733 systems: Trojan satellites as a plasma source", Monthly Notices of the Royal Astronomical Society, 461 (1): 988–999, arXiv:1605.02507, Bibcode:2016MNRAS.461..988K, doi:10.1093/mnras/stw1110, S2CID 119205132
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