More analysis needed to see if exoplanet Gliese 12 b has an atmosphere & maintains temperatures that allows liquid water
Artist’s concept of Gliese 12 b retaining a thin atmosphere. Photo: NASA / JPL-Caltech / R Hurt (Caltech-IPAC) Astronomers have discovered a potentially habitable exoplanet about 40 light-years away from Earth — one of the closest ones so far. The exciting discovery of Gliese 12 b was detailed in a new study published in journal Monthly Notices of the Royal Astronomical Society.
According to the study, the exoplanet's average surface temperature is 42 degrees Celsius, which is lower than the majority of the 5,000 or so exoplanets discovered thus far. Its size is comparable to Venus and is slightly smaller than Earth.
Gliese 12 b, however, is warmer than the Earth’s average surface temperature of 15°C. Still, the researchers argue for more investigation of the exoplanet, including its atmosphere, which is essential for habitable conditions.
Read more: Water vapour discovered on potentially ‘habitable’ planet
“We have found the nearest, transiting, temperate, Earth-size world located to date,” said Masayuki Kuzuhara, a project assistant professor at the Astrobiology Center in Tokyo, who co-led a research team with Akihiko Fukui, a project assistant professor at the University of Tokyo, said in a statement.
“Investigating Earth-sized planets is important as we continue forwards to try and infer the number of true-Earth analogues, to cement how we understand our own place in the Universe,” Larissa Palethorpe, a PhD student from the University of Edinburgh, told Down To Earth.
National Aeronautics and Space Administration’s (NASA) Transiting Exoplanet Survey Satellite (TESS) had earlier identified Gliese 12 b as a possible planet candidate.
The team used observations from TESS and the European Space Agency’s CHaracterising ExOPlanet Satellite or CHEOPS to validate Gliese 12 b.
The scientists discovered that Gliese 12 b orbits Gliese 12, a M dwarf star (a type of low-mass star), every 12.8 days. This star has seven planets orbiting it, all of which are roughly the size of Earth and are most likely rocky.
Of these planets, three fall within the habitable zone. The habitable zone is the distance from a star at which liquid water can exist on the surfaces of planets orbiting it.
Read more: NASA’s TESS confirms 3 new exoplanets
Furthermore, the star is metal-poor, which suggests that it may have weaker magnetic fields and more volcanism than Earth. Because the host star has low magnetic activity, the researchers believe that Gliese 12 b may have an atmosphere.
There’s a possibility the exoplanet could have an atmosphere similar to Earth, but it could be a different type too, according to the team.
Further analysis could also reveal if Gliese 12 b is habitable. “We tend to define habitability in terms of liquid water, rather than where humanity would be able to maintain life. So while this temperature would be a bit on the hot side for humans to live comfortably, it doesn’t necessarily mean other forms of life wouldn’t be able to thrive in these conditions,” Palethorpe explained.
It could also shed light on the evolution of Earth and Venus and why they appear so different.
Read more: How did James Webb telescope detect CO2 in a giant Jupiter-like planet? Experts tell us
Earth retained its water, whereas Venus’ runaway greenhouse effect caused it to escape. Researchers might be able to spot signatures of whether the exoplanet is witnessing a runaway greenhouse effect. If they find no water in the future, it could indicate that such a process has already occurred, like on Venus.
Gliese 12 b, according to the paper, is a potential target for NASA’s James Webb Space Telescope (JWST) as it can detect atmospheric features of planets.
The team hasn’t currently submitted a JWST proposal for this target yet. For now, they are trying to calculate its mass, bulk density, and radius estimates to understand the exoplanet’s internal structure.
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