WASP-121b

WASP-121b is an extrasolar planet orbiting the star WASP-121.[3][4] WASP-121b is the first exoplanet found to contain water in an extrasolar planetary stratosphere (i.e., an atmospheric layer in which temperatures increase as the altitude increases).[3][4] WASP-121b is in the constellation Puppis,[5] and is about 850 light-years from Earth.[6][3][7]

WASP-121b
Artist's impression of WASP-121b and its host star
Discovery
Discovery date2015[1]
Primary Transit[1]
Orbital characteristics
0.02544 AU (3,806,000 km)
Eccentricity0.0[1]
1.275[1] d
Inclination87.6°[1]
StarWASP-121
Physical characteristics
Mean radius
1.81[2] RJ
Mass1.184[1][2] MJ

    Characteristics
    WASP-121b - computer simulated views (August 2018)

    WASP-121b is a "hot Jupiter" exoplanet with a mass about 1.18 times that of Jupiter and a radius about 1.81 times that of Jupiter.[2][3] The exoplanet orbits WASP-121, its host star, every 1.27 days.[2][3]

    In 2019 a work by Hellard et al. discussed the possibility to measure the Love number of transiting hot Jupiters using HST/STIS. A tentative measurement of for WASP-121b was published in the same work.[8][9]

    Atmospheric composition

    Spectral survey in 2015 have attributed 2,500 °C (4,530 °F), hot[3] stratosphere absorption bands to water molecules, titanium(II) oxide (TiO) and vanadium(II) oxide (VO).[1] The neutral iron was also detected in stratosphere of WASP-121b in 2020,[10][11] along with the neutral chromium and vanadium.[12] The detection claims of titanium(II) oxide (TiO) and vanadium(II) oxide (VO) were disproved in 2018 and 2020, respectively.[13]

    Reanalysis of aggregated spectral data was published in June 2020. Neutral magnesium, calcium, vanadium, chromium, iron, and nickel, along with ionized sodium atoms, were detected. The low quality of available data do preclude a positive identification of any molecular species, including water. The atmosphere appears to be significantly out of chemical equilibrium and possibly escaping.[14]

    See also

    References
    1. Staff (2015). "Planet WASP-121 b". exoplanet.eu. Retrieved 3 August 2017.
    2. Staff (2017). "WASP Planets". wasp-planets.net. Retrieved 3 August 2017.
    3. Landau, Elizabeth; Villard, Ray (2 August 2017). "Hubble Detects Exoplanet with Glowing Water Atmosphere". NASA. Retrieved 2 August 2017.
    4. Evans, Thomas M.; et al. (2 August 2017). "An ultrahot gas-giant exoplanet with a stratosphere". Nature. 548 (7665): 58–61. arXiv:1708.01076. Bibcode:2017Natur.548...58E. doi:10.1038/nature23266. PMID 28770846.
    5. Staff. "Finding the constellation which contains given sky coordinates". djm.cc. Retrieved 3 August 2017.
    6. Brown, A. G. A; et al. (2016). "Gaia Data Release 1. Summary of the astrometric, photometric, and survey properties". Astronomy and Astrophysics. 595. A2. arXiv:1609.04172. Bibcode:2016A&A...595A...2G. doi:10.1051/0004-6361/201629512. hdl:2445/125903.Gaia Data Release 1 catalog entry
    7. Greicius, Tony (7 August 2018). "Water Is Destroyed, Then Reborn in Ultrahot Jupiters". NASA. Retrieved 15 November 2018.
    8. Hellard, Hugo; Csizmadia, Szilárd; Padovan, Sebastiano; Sohl, Frank; Rauer, Heike (2020). "HST/STIS capability for Love number measurement of WASP-121b". The Astrophysical Journal. 889 (1): 66. arXiv:1912.05889. Bibcode:2020ApJ...889...66H. doi:10.3847/1538-4357/ab616e.
    9. waspplanets (19 December 2019). "The tidal shape of the exoplanet WASP-121b". WASP Planets. Retrieved 20 January 2020.
    10. Gibson, Neale P.; Merritt, Stephanie; Nugroho, Stevanus K.; Cubillos, Patricio E.; de Mooij, Ernst J. W.; Mikal-Evans, Thomas; Fossati, Luca; Lothringer, Joshua; Nikolov, Nikolay; Sing, David K.; Spake, Jessica J.; Watson, Chris A.; Wilson, Jamie (2020). "Detection of Fe I in the atmosphere of the ultra-hot Jupiter WASP-121b, and a new likelihood-based approach for Doppler-resolved spectroscopy". Monthly Notices of the Royal Astronomical Society. 493 (2): 2215. arXiv:2001.06430. Bibcode:2020MNRAS.493.2215G. doi:10.1093/mnras/staa228.
    11. Cabot, Samuel H. C.; Madhusudhan, Nikku; Welbanks, Luis; Piette, Anjali; Gandhi, Siddharth (2020). "Detection of neutral atomic species in the ultra-hot jupiter WASP-121b". Monthly Notices of the Royal Astronomical Society. 494 (1): 363–377. arXiv:2001.07196. Bibcode:2020MNRAS.494..363C. doi:10.1093/mnras/staa748.
    12. A bot will complete this citation soon. Click here to jump the queue arXiv:2006.05995.
    13. Mikal-Evans, Thomas; Sing, David K.; Kataria, Tiffany; Wakeford, Hannah R.; Mayne, Nathan J.; Lewis, Nikole K.; Barstow, Joanna K.; Spake, Jessica J. (2020). "Confirmation of water emission in the dayside spectrum of the ultrahot Jupiter WASP-121b". arXiv:2005.09631 [astro-ph.EP].
    14. Hot Exoplanet Atmospheres Resolved with Transit Spectroscopy (HEARTS) IV. A spectral inventory of atoms and molecules in the high-resolution transmission spectrum of WASP-121 b, 2020, arXiv:2006.11308

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