WASP-31b is a
low-density (puffy) "
hot Jupiter"
exoplanet with a mass about 0.48 times that of
Jupiter and a radius about 1.55 times that of Jupiter.[2][1] The planetary atmosphere has indeed the largest
scale height, equal to 1150km, among exoplanets with measurable atmospheres as at 2021.[5]
The exoplanet orbits WASP-31, its host star, every 3.4 days.[2]
In 2012, it was found from the
Rossiter–McLaughlin effect that WASP-31b is orbiting the parent star in a prograde direction, with the WASP-31 star rotational axis inclined to the planetary orbit by 2.8±3.1 degrees.[6] The spectroscopic study in 2014 revealed that WASP-31b has a dense cloud deck overlaid by a hazy atmosphere.[7] WASP-31b was also reported to have significant amounts of
potassium in its upper atmosphere, but the detection of potassium was refuted in 2015.[8] The potassium detection discrepancy was resolved in 2020 with the improved cloud deck model,[9] with the best fit being a very small amount of water over clouds and no potassium at all.[10]
Reanalysis of planetary spectroscopic data in 2020 has revealed the presence of
chromium monohydride besides water.[11]
^Baxter, Claire; Désert, Jean-Michel; Tsai, Shang-Min; Todorov, Kamen O.; Bean, Jacob L.; Deming, Drake; Parmentier, Vivien; Fortney, Jonathan J.; Line, Michael; Thorngren, Daniel; Pierrehumbert, Raymond T.; Burrows, Adam; Showman, Adam P. (2021), "Evidence for disequilibrium chemistry from vertical mixing in hot Jupiter atmospheres", Astronomy & Astrophysics, 648: A127,
arXiv:2103.07185,
doi:
10.1051/0004-6361/202039708,
S2CID232222174
^Brown, D. J. A.; Cameron, A. Collier; Anderson, D. R.; Enoch, B.; Hellier, C.; Maxted, P. F. L.; Miller, G. R. M.; Pollacco, D.; Queloz, D.; Simpson, E.; Smalley, B.; Triaud, A. H. M. J.; Boisse, I.; Bouchy, F.; Gillon, M.; Hébrard, G. (2012). "Rossiter-Mc Laughlin effect measurements for WASP-16, WASP-25 and WASP-31★". Monthly Notices of the Royal Astronomical Society. 423 (2): 1503–1520.
arXiv:1203.4971.
Bibcode:
2012MNRAS.423.1503B.
doi:
10.1111/j.1365-2966.2012.20973.x.
S2CID53445367.
^Gibson, Neale P.; De Mooij, Ernst J W.; Evans, Thomas M.; Merritt, Stephanie; Nikolov, Nikolay; Sing, David K.; Watson, Chris (2019). "Revisiting the potassium feature of WASP-31b at high resolution". Monthly Notices of the Royal Astronomical Society. 482 (1): 606–615.
arXiv:1810.03693.
Bibcode:
2019MNRAS.482..606G.
doi:
10.1093/mnras/sty2722.