Two teams of astronomers used NASA's Transiting Exoplanet Survey Satellite (TESS) and a number of other telescopes to discover a warm, Earth-sized exoplanet orbiting a cool red dwarf star called Gliese 12. The planet, named Gliese 12b, could have an atmosphere like Earth's, an atmosphere similar to Venus', no atmosphere at all, or a different kind of atmosphere not found in our solar system.
Artist's impression of Gliese 12b and its host star. Image courtesy of NASA / JPL-Caltech / R. Hurt, Caltech-IPAC.
Gliese 12 It is an M3 dwarf star located 12.2 parsecs (40 light years) from Earth in the constellation Pisces.
Also known as TOI-6251 or GJ 12, the star is about 27% of the size of the Sun and has a surface temperature about 60% of the Sun's.
The newly discovered planet, Gliese 12b, is about the same size as Earth, or slightly smaller, and comparable in size to Venus.
“We have discovered the closest transiting, temperate, Earth-sized planet ever discovered,” said astronomer David Schneider of the Astrobiology Center in Tokyo. paper Published in Astrophysical Journal Letters.
“While we don't yet know if it has an atmosphere, it has been thought to be an extrasolar Venus, with a size similar to our solar system's neighbors and receiving a similar amount of energy from their stars.”
“Gliese 12b is one of the best targets to study whether Earth-sized planets orbiting cool stars can retain atmospheres, and is an important step towards improving our understanding of planetary habitability in our galaxy,” said Dr. paper Published in Monthly Bulletin of the Royal Astronomical Society.
Gliese 12b has an orbital period of 12.76 days and an equilibrium temperature of about 42 °C (107 °F). By comparison, Earth's average surface temperature is 15 °C (59 °F).
The alien world receives 1.6 times the energy from its star that Earth receives from the Sun, or about 85% of the energy that Venus receives.
“The atmosphere traps heat and, depending on the type, can dramatically change the actual surface temperature,” Dholakia said.
“What we're quoting is the planet's equilibrium temperature, meaning the temperature of the planet if it didn't have an atmosphere.”
“Much of the scientific value of this planet is in understanding what kind of atmosphere it may have.”
“Gliese 12b lies between the amount of light Earth and Venus receive from the Sun, making it a valuable resource for bridging the gap between these two planets in our solar system.”
Astronomers suggest that studying Gliese 12b may help shed light on some aspects of our solar system's evolution.
“The initial atmospheres of Earth and Venus are thought to have been stripped away and then replenished by volcanic outgassing and bombardment from remnant material in the solar system,” said Larissa Palethorpe, a doctoral student at the University of Edinburgh and University College London.
“Earth is habitable, but Venus is not habitable because it has completely lost all water.”
“Gliese 12b has temperatures intermediate between Earth and Venus, so its atmosphere could tell us a lot about the habitability trajectory that planets follow as they develop.”
One of the key factors in maintaining an atmosphere is the strength of its stellar storms: red dwarfs tend to be magnetically active, which results in frequent, powerful X-ray flares.
However, their analysis concluded that Gliese 12 showed no signs of extreme behaviour.
During a transit, the host star's light passes through the atmosphere, and because different gas molecules absorb different colors, the transit leaves a series of chemical fingerprints that can be detected by telescopes like Webb.
“There are only a handful of known temperate planets that are Earth-like, close enough to Earth, and meet the other criteria needed for this type of study, called transmission spectroscopy, with current equipment,” said Dr. Michael McElwain, an astrophysicist at NASA's Goddard Space Flight Center.
“We need more examples like Gliese 12b to better understand the diversity and evolutionary consequences of the atmospheres of these planets.”
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Masayuki Kuzuhara others2024, Gliese 12b: Earth-sized temperate planet, 12 parsecs from Earth, ideal for atmospheric transmission spectroscopy. Apu JL 967, L21; doi: 10.3847/2041-8213/ad3642
Shishir Dholakia others2024. Gliese 12b, a temperate planet the size of Earth, measuring 12 parsecs, discovered by TESS and CHEOPS. MNRAS 531(1):1276-1293; doi:10.1093/mnras/stae1152
Source: www.sci.news
