WASP-76b

WASP-76b is an exoplanet classified as a Hot Jupiter. It is located in the constellation Pisces and orbits its host star, WASP-76, at a distance of approximately 0.033 astronomical units (AU). The orbital period of WASP-76b is approximately 1.8 days. Its mass is about 0.92 times that of Jupiter.[4][5][6] The discovery of WASP-76b took place on October 21, 2013, and it is currently the only known planet in the WASP-76 system as of 2022. The equilibrium temperature of WASP-76b is estimated to be around 2,190 K (1,920 °C; 3,480 °F), However, the measured daytime temperature is higher, reaching approximately 2,500 ± 200 K (2,227 ± 200 °C; 4,040 ± 360 °F).[3]

WASP-76b
Artistic image of WASP-76b (based on 2020 data)
Discovery
Discovered byR.G. West et al. (SuperWASP)[1]
Discovery dateOctober 21, 2013
Transit (including secondary eclipses)
Orbital characteristics[2]
0.033±0.0005 AU
Eccentricity0
1.809886±0.000001 d
Inclination88.0°±1.6°
StarWASP-76
Physical characteristics
Mean radius
1.83±0.06 RJ
Mass0.92±0.03 MJ
Temperature2500±200 K[3]

    An artist's illustration showing WASP-76b during its night hours.

    Atmospheric composition

    Data collected from the Hubble and Spitzer Space Telescopes have provided evidence of titanium oxide and small amounts of water within the atmosphere of WASP-76b.[7] Further analysis using higher-resolution spectra has revealed the presence of ionized elements such as lithium, sodium, magnesium, calcium, manganese, potassium, and iron.[8] The existence of calcium (Ca) was confirmed by the Gemini North Observatory in 2021,[9][10][11] and in 2022, the element barium (Ba) was also detected.[12]

    The atmosphere of WASP-76b is characterized as cloudy, predominantly grey, and exhibits significant thermal incandescence.[13]

    Iron rain

    In March 2020, an initial spectroscopic analysis revealed the presence of neutral iron in the atmosphere of WASP-76b. The conditions required for the vaporization and condensation of neutral iron were determined to be a temperature of 2,400 °C (2,700 K; 4,400 °F) and a lower temperature of 1,400 °C (1,700 K; 2,600 °F) for condensation. Under these specific temperature conditions, neutral iron could potentially precipitate like liquid rain.[14]

    In May 2020, the Hubble Space Telescope discovered that the previous spectrum of WASP-76b had been distorted by the light from a companion star. Subsequently, an updated atmospheric model was developed using the most recent spectrum data. The revised model indicates the presence of a cloudy hydrogen-helium envelope and suggests the absence of previously reported neutral iron, including "iron rain."[15] Additionally, only upper limits on the presence of titanium and vanadium oxides were detected.[13] By 2021, the controversy surrounding the presence of iron condensation had been resolved by demonstrating that the observed signal may also be due to temperature variations between different parts of the planet. However, existing data is insufficient to definitively distinguish between these two scenarios.[16]

    Based on planetary atmospheric circulation models for WASP-76b, it is suggested that dense cloud layers composed of aluminum oxide, neutral iron, or magnesium orthosilicate may form. However, significant condensation of iron on the night side of the planet is not indicated by the available data.[17]

    See also

    References
    1. West, R. G.; Hellier, C.; et al. (January 8, 2016). "Three irradiated and bloated hot Jupiters". Astronomy & Astrophysics. 585: A126. arXiv:1310.5607. doi:10.1051/0004-6361/201527276. S2CID 54746373.
    2. "Planet WASP-76 b". exoplanet.eu. March 7, 2022. Archived from the original on April 30, 2022. Retrieved August 28, 2022.
    3. Zhou, G.; Bayliss, D. D. R.; et al. (December 11, 2015) [October 16, 2015]. "Secondary eclipse observations for seven hot-Jupiters from the Anglo-Australian Telescope". Monthly Notices of the Royal Astronomical Society. 454 (3): 3002–3019. arXiv:1509.04147. Bibcode:2015MNRAS.454.3002Z. doi:10.1093/mnras/stv2138. S2CID 84835437. Retrieved March 21, 2022.
    4. "WASP-76 b". Exoplanet Exploration: Planets Beyond our Solar System. NASA. n.d. Retrieved March 21, 2022.
    5. Ehrenreich, David; et al. (March 11, 2020). "ESO Telescope Observes Exoplanet Where It Rains Iron". European Southern Observatory. Retrieved March 21, 2022.
    6. Reuters (March 11, 2020). "On a faraway planet, it's cloudy with a chance of liquid iron rain". NBC News. Retrieved May 3, 2020. {{cite news}}: |last= has generic name (help)
    7. Fu, Guangwei; Deming, Drake; et al. (August 17, 2021). "The Hubble PanCET Program: Transit and Eclipse Spectroscopy of the Strongly Irradiated Giant Exoplanet WASP-76b". The Astronomical Journal. 162 (3): 108. arXiv:2005.02568. Bibcode:2021AJ....162..108F. doi:10.3847/1538-3881/ac1200. ISSN 0004-6256. S2CID 218517004.
    8. Tabernero, H. M.; Osorio, M. R. Zapatero; et al. (February 19, 2021). "ESPRESSO high resolution transmission spectroscopy of WASP-76b". Astronomy & Astrophysics. 646. 17. arXiv:2011.12197. Bibcode:2021A&A...646A.158T. doi:10.1051/0004-6361/202039511. ISSN 0004-6361. S2CID 227151361. Retrieved May 24, 2022.
    9. Casasayas-Barris, N.; Orell-Miquel, J.; et al. (October 27, 2021). "CARMENES detection of the Ca II infrared triplet and possible evidence of He I in the atmosphere of WASP-76b". Astronomy & Astrophysics. 654. 20. arXiv:2109.00059. doi:10.1051/0004-6361/202141669. ISSN 0004-6361. S2CID 237376656. Retrieved May 24, 2022.
    10. Deibert, Emily K.; de Mooij, Ernst J. W.; et al. (September 28, 2021). "Detection of Ionized Calcium in the Atmosphere of the Ultra-hot Jupiter WASP-76b". The Astrophysical Journal Letters. 919 (2): L15. arXiv:2109.04373. Bibcode:2021ApJ...919L..15D. doi:10.3847/2041-8213/ac2513. ISSN 2041-8205. S2CID 237452713.
    11. Source, News Staff / (October 13, 2022). "Barium Detected in Atmospheres of Two Ultrahot Jupiters | Sci.News". Sci.News: Breaking Science News. Retrieved October 15, 2022.
    12. Azevedo Silva, T.; et al. (2022), "Detection of barium in the atmospheres of the ultra-hot gas giants WASP-76b and WASP-121b", Astronomy & Astrophysics, 666: L10, arXiv:2210.06892, doi:10.1051/0004-6361/202244489, S2CID 252873126
    13. Edwards, Billy; Changeat, Quentin; et al. (June 9, 2020). "ARES I: WASP-76 b, A Tale of Two HST Spectra*". The Astronomical Journal. 160 (1): 8. arXiv:2005.02374. Bibcode:2020AJ....160....8E. doi:10.3847/1538-3881/ab9225. S2CID 218502668.
    14. Amos, Jonathan (March 11, 2020). "Wasp-76b: The exotic inferno planet where it 'rains iron'". BBC News. Retrieved May 3, 2020.
    15. Lothringer, Joshua D.; Fu, Guangwei; et al. (July 21, 2020). "UV Exoplanet Transmission Spectral Features as Probes of Metals and Rainout". The Astrophysical Journal. 898 (1): L14. arXiv:2005.02528. Bibcode:2020ApJ...898L..14L. doi:10.3847/2041-8213/aba265. S2CID 218516764.
    16. Wardenier, Joost P; Parmentier, Vivien; et al. (June 26, 2021). "Decomposing the iron cross-correlation signal of the ultra-hot Jupiter WASP-76b in transmission using 3D Monte Carlo radiative transfer". Monthly Notices of the Royal Astronomical Society. 506 (1): 1258–1283. arXiv:2105.11034. doi:10.1093/mnras/stab1797. ISSN 0035-8711. Retrieved May 24, 2022.
    17. Savel, Arjun B.; Kempton, Eliza M.-R.; et al. (February 15, 2022). "No Umbrella Needed: Confronting the Hypothesis of Iron Rain on WASP-76b with Post-processed General Circulation Models". The Astrophysical Journal. 926 (1): 85. arXiv:2109.00163. Bibcode:2022ApJ...926...85S. doi:10.3847/1538-4357/ac423f. ISSN 0004-637X. S2CID 237372235.
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