Researchers have discovered HD 3167 b, an unusually cold lava world located 154 light-years away that retains an atmosphere despite orbiting close enough to its host star to complete a full year in just one Earth day. Spotted using the James Webb Space Telescope, this rocky super-Earth challenges existing models of planetary atmospheric survival under intense stellar winds.
Observing HD 3167 b with the James Webb Space Telescope
Astronomers used the James Webb Space Telescope’s mid-infrared instrument (MIRI) to observe HD 3167 b during a secondary eclipse. By measuring mid-infrared light fluctuations as the planet passed behind its host star, researchers estimated surface temperatures and detected the presence of an atmosphere. Co-author Edwin Kite, an associate professor of geophysical sciences at the University of Chicago, noted that proximity to a star normally strips away a rocky planet’s atmosphere through high-energy photons and stellar wind bombardment.
This tidally locked world features a permanent dayside and nightside. Lead author Brandon Park Coy, a graduate student in Kite’s research group, explained that without an insulating or heat-redistributing gas layer, the dayside would reach the maximum theoretical temperature for its orbital distance. Instead, the team recorded a dayside temperature noticeably cooler than expected maximums.
| Planet Property | Observed Detail |
|---|---|
| Distance from Earth | 154 light-years |
| Orbital Period (Year) | 1 Earth day |
| Instrument Used | JWST MIRI (Mid-Infrared Instrument) |
| Key Characteristic | Coldest lava world known with an atmosphere |
Atmospheric Heat Redistribution on Super-Earths
Data indicates that HD 3167 b possesses an atmosphere capable of cooling its dayside by reflecting stellar light and redirecting thermal energy toward the perpetually dark nightside. While astronomers have previously identified atmospheres on ultra-hot lava worlds, finding one on a comparatively cool rocky body raises new questions about how and at what temperatures these volatile envelopes form and persist.
Did you know? Since the confirmation of the first exoplanet over 30 years ago, scientists have cataloged more than 6,300 planets outside our solar system, ranging from hot gas giants to rocky super-Earths.
This observation forms part of a broader observational program led by astronomer Megan Weiner Mansfield at the University of Maryland. The research initiative targets a sample of 10 different lava worlds to establish the temperature thresholds required for rocky planets to retain atmospheres.
Insights Into Early Earth and Magma Ocean Stages
Investigating extreme exoplanets provides planetary scientists with empirical models to study conditions that existed during the formation of our own solar system. Brandon Park Coy pointed out that early Earth likely experienced a magma ocean stage with a completely liquid surface driven by intense planetesimal collisions.
Edwin Kite emphasized that while these burning worlds are entirely inhospitable to life, analyzing their atmospheric dynamics clarifies the geological and atmospheric processes governing rocky worlds across the galaxy. The findings are detailed in a study published in The Astrophysical Journal Letters.
Atmosphere and characteristics of lava world HD 3167 b
How close is HD 3167 b to its host star?
HD 3167 b orbits closely enough that one complete revolution around its star takes just one Earth day.
What instrument discovered the atmosphere on HD 3167 b?
Researchers utilized the mid-infrared instrument (MIRI) aboard the James Webb Space Telescope during a secondary eclipse.
Why is HD 3167 b considered unique among lava worlds?
It is the smallest and coldest lava world discovered to date that still manages to maintain an atmosphere.
What does this discovery reveal about early Earth?
By studying how rocky lava worlds handle extreme heat and maintain atmospheres, scientists gain a window into Earth’s initial magma ocean phase during its first couple of million years.
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