Amazing stuff!
Why "stars much smaller than the sun"?
"... a scorching world that may resemble early Earth and offer clues about how young planets hold onto their gaseous envelopes."
"... Researchers spotted HD 3167 b, a rocky super-Earth covered in lava, orbiting a star 154 light-years away. This planet orbits so closely to its star that a "year" on the world (one revolution around its star) takes only one Earth day. But it's not just a lava-covered rock — it's the smallest lava world researchers have ever found. And yet, it has managed to hang onto its atmosphere. ...
One of the driving questions that the James Webb Space Telescope is being used to answer is whether planets orbiting stars much smaller than the sun have atmospheres. It appears that most of those terrestrial planets don’t—they’re just bare rock. ..."
From the abstract:
"“Lava worlds”, Earth-sized planets hot enough (Teq ≳ 1100 K) to melt their dayside silicate surfaces, have emerged as promising candidates for atmospheric detection and characterization.
Thermal emission observations show an apparent dichotomy: The hottest lava worlds have colder daysides than the temperature of a maximally emitting bare rock, indicating the likely presence of thick and/or reflective atmospheres, while the coldest ones do not.
However, where in instellation flux this potential bifurcation occurs is uncertain. We present a JWST/MIRI Low Resolution Spectrometer eclipse of the ultra-short-period (USP) lava world HD 3167 b (Teq = 1786 K, R = 1.6 R⊕, P = 0.96 day) that helps bridge this gap.
We measure the white-light eclipse depth to be 38 ± 11 ppm, more than 5σ lower than the expected eclipse depth of a dark, maximally hot bare rock. We use this to derive a dayside brightness temperature that is best explained by the presence of an atmosphere that cools the dayside by reflecting incoming starlight and/or efficiently redistributing heat to the planet’s nightside.
An atmosphere is further compatible with the planet’s slight underdensity compared to an Earth-like composition. The corresponding dayside emission spectrum is not precise enough to constrain atmospheric composition, motivating follow-up spectroscopic observations with JWST/NIRSpec.
Lastly, we use our observation and existing data to refine key planetary parameters of the HD 3167 system. HD 3167 b is currently the least irradiated USP super-Earth with evidence for an atmosphere."
Astronomers discover a cold lava planet that may resemble early Earth ""We think early Earth might have looked a lot like a lava world.""
Study led by UChicago scientists finds atmosphere on the coldest lava world to date (original news release) "Studying the atmospheres of lava worlds offers window to Earth’s earliest history, pathway to habitable worlds"
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