Astronomers have examined Gliese 367 b, a neighboring sub-Earth exoplanet,
with the James Webb Space Telescope (JWST). The data collected suggest that
this extraterrestrial globe is hot, black, and devoid of any discernible
atmosphere. The updated results were made available on the pre-print service
arXiv on
January 2.
Known by the Tahay name, Gliese 367 b (or GJ 367 b) was found in December
2021 using NASA's Transiting Exoplanet Survey Satellite (TESS). It revolves
around Gliese 367, sometimes called Añañuca—an M-dwarf of spectral type
M1.0V that is around 31 light years distant and has a mass and size that is
over half that of the sun. At least two more planets, situated farther out
from the host, are also present in the system.
Gliese 367 b's mass is estimated to be 0.67 Earth masses, meaning it is
around 30% smaller than Earth, according to earlier measurements. At 1,367
K, its equilibrium temperature, it orbits its parent star once every 7.7
hours.
The atmosphere of Gliese 367 b has now been studied by a group of
astronomers led by Michael Zhang of the University of Chicago using JWST's
Mid-Infrared Instrument (MIRI). Further information about this exoplanet's
characteristics and nature was provided by the observations.
"We monitored GJ 367 b for 12.7 h, corresponding to 1.6 planetary orbits,
using the Mid-Infrared Instrument on JWST," the researchers stated in their
report.
Based on the data, Gliese 367 b is a planet with a blackbody emission
spectra in the MIRI bandpass, a dark surface, and no discernible atmosphere
or heat redistribution. Gliese 367 b was discovered to have a daytime
temperature of 1,728 K and an estimated nighttime temperature of less than
847 K.
The findings, as reported in the publication, rule out the likelihood that
Gliese 367 b contains an atmosphere of carbon dioxide at a pressure higher
than one bar. Additionally, it does not include an outgassed atmosphere
under severely oxidizing circumstances or one that is expelled under heavily
reducing conditions with a pressure of more than 10 millibar.
Based on the available information, Gliese 367 b is expected to have a
mostly molten dayside. As a result, any volatiles in this planet's silicate
mantle ought presumably be distributed among the atmosphere. Because of
this, the paper's authors came to the conclusion that, barring a
volatile-free mass, Gliese 367 b must not have an atmosphere.
Based on the findings, the scientists further hypothesize that Gliese 367
b's apparent absence of atmosphere suggests that the planet contains a lot
less volatiles overall than Earth. They speculate that the absence of
atmosphere may result from strong star irradiation eliminating the early
volatiles.
