Webb finds a surprising atmosphere on a scorching lava world
The James Webb Space Telescope has found strong evidence that the rocky lava world HD 3167 b has an atmosphere, despite circling its star every 24 hours under extreme heat. The surprising discovery could help scientists understand how rocky planets retain atmospheres and what the young, molten Earth may once have looked like.
Key points
- Researchers led by University of Chicago scientist Brandon Park Coy found evidence of an atmosphere on HD 3167 b, a rocky super-Earth 154 light-years away in Pisces.
- The planet, a lava world orbiting its star in one Earth day, is the coldest such world with an atmosphere detected so far.
- The team used the James Webb Space Telescope's secondary eclipse method to measure the planet's heat and infer an atmosphere.
A team led by University of Chicago scientist Brandon Park Coy has reported evidence of an atmosphere around HD 3167 b, a rocky super-Earth located 154 light-years away in the constellation Pisces. The intensely hot planet, classified as a lava world, completes an orbit around its star in only one Earth day. The study was published in The Astrophysical Journal Letters.
The finding adds another world to the short list of known rocky planets that appear to possess atmospheres. According to the article, only a small number of cataloged exoplanets are rocky, and even fewer are known to have atmospheres.
What researchers said
Edwin Kite, UChicago associate professor of geophysical sciences and co-author of the study, said it is surprising that lava worlds can have atmospheres despite being bombarded by stellar wind and high-energy photons. He noted that these planets are too hot for life, but studying them can reveal processes relevant to other rocky worlds.
Coy, a graduate student in Kite's group and first author, explained that the James Webb Space Telescope is being used to determine whether planets orbiting stars much smaller than the sun have atmospheres. He said most terrestrial planets appear to be bare rock, but evidence suggests the majority of lava worlds might have atmospheres.
We're interested in studying these kinds of planets because we think early Earth might have looked a lot like a lava world.
— Brandon Park Coy
How the atmosphere was detected
The researchers used the secondary eclipse method, measuring the mid-infrared light lost when the planet passes behind its star. This difference indicates how hot the planet is. If a planet has no atmosphere, its star-facing day side should be as hot as theoretically possible; an atmosphere would redistribute heat to the night side and could also form clouds that reflect starlight.
HD 3167 b is noticeably cooler than its expected maximum, providing strong evidence that it has an atmosphere. The study is the first from a program led by Megan Weiner Mansfield, now at the University of Maryland, which is examining 10 ultra-hot lava worlds to find a possible critical temperature for atmospheres.
