Exoplanets · Space Codex
WASP-76 b
An ultra-hot Jupiter whose 2,000+ K dayside vaporises iron.
Where it may rain iron
Artist's concept. No telescope has seen WASP-76 b as more than a point of light, and most exoplanets not even that. What we know comes from how a planet dims or tugs its star. Any picture of its surface, colour or sky, anywhere, is an illustration, not an observation.
At a glance
Key points
Iron vapour seen on only the evening edge suggests it condenses and rains out on the night side.
- Dayside hot enough to vaporise iron
- Iron may rain out on the night side
- A possible 'glory' halo, still tentative
How it was found
SuperWASP picked up its 1.8-day transits, reported in 2016. Radial-velocity follow-up showed a planet just under Jupiter's mass but 1.85 times as wide, puffed up by a hot F-type star only 0.033 AU away. Its low gravity and huge atmosphere quickly made it a favourite for high-resolution spectrographs on large telescopes.
A periodic table in the air
In 2023 a team measured 14 rock-forming elements in its atmosphere. Those that condense below about 1,550 K appear in roughly solar proportions; those that condense at higher temperatures are strongly depleted, as if they freeze out into clouds on the cooler night side and never return. Vanadium oxide, long proposed as a driver of hot upper layers, was detected outright. Nickel looks enriched, possibly from the iron-rich core of a body the planet once absorbed.
Iron rain
ESPRESSO spectra in 2020 showed iron vapour on the evening terminator but not the morning one. The leading explanation is that iron evaporates on the dayside, winds carry it to the cooler night side, and it condenses into droplets. Temperature asymmetries could also explain part of the signal.
What we still don't know
Whether the CHEOPS 'glory' is real, which would require spherical droplets, possibly of iron. JWST phase-curve results are not yet published.
Missions
- 2021–
Infrared observatory at Sun–Earth L2, about 1.5 million km from Earth.
Related entries
- WASP-12 bA pitch-black planet spiralling into its star
- HD 189733 bA cobalt-blue world that smells of rotten eggs
Sources
- NASA Exoplanet Archive: WASP-76 overview (opens in a new tab)
- May et al. 2021 (arXiv) (opens in a new tab)
- Demangeon et al. 2024, A&A (Chalmers record) (opens in a new tab)
- Pelletier et al. 2023, Nature (arXiv) (opens in a new tab)
Last reviewed against these sources. Built from public NASA, ESA and JPL data; not affiliated with or endorsed by any agency.