In August 2022, this planet and its host star were included among 20 systems to be named by the third
NameExoWorlds project.[10] The approved names, proposed by a team from
Bahrain, were announced in June 2023. WASP-121b is named Tylos after the
ancient Greek name for Bahrain, and its host star is named Dilmun after the
ancient civilization.[2]
Characteristics
WASP-121b is a
hot Jupiterexoplanet with a mass about 1.16 times that of
Jupiter and a radius about 1.75 times that of Jupiter. The exoplanet orbits
WASP-121, its host star, every 1.27 days.[3]
In 2019 a work by Hellard et al. discussed the possibility of measuring the
Love number of transiting hot Jupiters using HST/
STIS. A tentative measurement of for WASP-121b was published in the same work.[11][12]
The planetary orbit is inclined to the equatorial plane of the star by 8.1°.[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 preclude a positive identification of any molecular species, including water. The atmosphere appears to be significantly out of chemical equilibrium and possibly escaping.[21] The strong atmospheric flows beyond the
Roche lobe, indicating ongoing atmosphere loss, were confirmed in late 2020.[13]
In 2021, the planetary atmosphere turned out to be slightly more blue and less absorbing, which may be an indication of planetary weather patterns.[22] By mid-2021, the presence of ions of
iron,
chromium,
vanadium and
calcium in the planetary atmosphere was confirmed.[23] In 2022, barium was also detected.[24] By 2022, an absence of titanium in the planetary atmosphere was confirmed and attributed to the nightside condensation of highly refractory
titanium dioxide.[25]
Observations by the
Hubble Space Telescope from 2016-2019, published in 2024, confirm variability in the atmosphere of WASP-121b.[26][27]
^Delrez, L.; Santerne, A.; Almenara, J.-M.; Anderson, D. R.; Collier-Cameron, A.; Díaz, R. F.; Gillon, M.; Hellier, C.; Jehin, E.; Lendl, M.; Maxted, P. F. L.; Neveu-Vanmalle, M.; Pepe, F.; Pollacco, D.; Queloz, D.; Ségransan, D.; Smalley, B.; Smith, A. M. S.; Triaud, A. H. M. J.; Udry, S.; Van Grootel, V.; West, R. G. (2015), "WASP-121 b: A hot Jupiter close to tidal disruption transiting an active F star", Monthly Notices of the Royal Astronomical Society, 458 (4): 4025–4043,
arXiv:1506.02471,
Bibcode:
2016MNRAS.458.4025D,
doi:
10.1093/mnras/stw522
^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.
S2CID210714233.
^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.
S2CID210838889.
^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". Monthly Notices of the Royal Astronomical Society. 496 (2): 1638–1644.
arXiv:2005.09631.
Bibcode:
2020MNRAS.496.1638M.
doi:
10.1093/mnras/staa1628.
S2CID218684532.
^
abHoeijmakers, H.J.; Seidel, J.V.; Pino, L.; Kitzmann, D.; Sindel, J.P.; Ehrenreich, D.; Oza, A.V.; Bourrier, V.; Allart, R.; Gebek, A.; Lovis, C.; Yurchenko, S.N.; Astudillo-Defru, N.; Bayliss, D.; Cegla, H.; Lavie, B.; Lendl, M.; Melo, C.; Murgas, F.; Nascimbeni, V.; Pepe, F.; Segransan, D.; Udry, S.; Wyttenbach, A.; Heng, K. (18 September 2020). "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". Astronomy & Astrophysics. 641: A123.
arXiv:2006.11308.
Bibcode:
2020A&A...641A.123H.
doi:
10.1051/0004-6361/202038365.
S2CID219966241.
^Wilson, Jamie; Gibson, Neale P.; Lothringer, Joshua D.; Sing, David K.; Mikal-Evans, Thomas; De Mooij, Ernst J W.; Nikolov, Nikolay; Watson, Chris A. (2021), "Gemini/GMOS optical transmission spectroscopy of WASP-121b: Signs of variability in an ultra-hot Jupiter?", Monthly Notices of the Royal Astronomical Society, 503 (4): 4787–4801,
arXiv:2103.05698,
doi:
10.1093/mnras/stab797
^Merritt, Stephanie R.; Gibson, Neale P.; Nugroho, Stevanus K.; De Mooij, Ernst J W.; Hooton, Matthew J.; Lothringer, Joshua D.; Matthews, Shannon M.; Mikal-Evans, Thomas; Nikolov, Nikolay; Sing, David K.; Watson, Chris A. (2021), "An inventory of atomic species in the atmosphere of WASP-121b using UVES high-resolution spectroscopy", Monthly Notices of the Royal Astronomical Society, 506 (3): 3853–3871,
arXiv:2106.15394,
doi:
10.1093/mnras/stab1878
^Hoeijmakers, H. J.; Kitzmann, D.; Morris, B. M.; Prinoth, B.; Borsato, N.; Pino, L.; Lee, E. K. H.; Akın, C.; Heng, K. (2022), The Mantis Network III: A titanium cold-trap on the ultra-hot Jupiter WASP-121 b.,
arXiv:2210.12847