WASP-121b


WASP-121b is an extrasolar planet orbiting the star WASP-121. WASP-121b is the first exoplanet found to contain water in an extrasolar planetary stratosphere. WASP-121b is in the constellation Puppis, and is about 850 light-years from Earth.

Characteristics

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. The exoplanet orbits WASP-121, its host star, every 1.27 days.
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.

Atmospheric composition

Spectral survey in 2015 have attributed, hot stratosphere absorption bands to water molecules, titanium oxide and vanadium oxide. The neutral iron was also detected in stratosphere of WASP-121b in 2020, along with the neutral chromium and vanadium.
The detection claims of titanium oxide and vanadium oxide were disproved in 2018 and 2020, respectively.
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.