Orbiting a cool red dwarf just 40 light-years away, Gliese 12b promises to tell astronomers more about how planets close to their stars retain or lose atmospheres. In this artist’s concept, Gliese 12 b is shown maintaining a thin atmosphere. Credit: NASA/JPL-Caltech/R. Hurt (Caltech-IPAC)
Scientists discovered Gliese 12 b, an exoplanet similar in size Venus and only 40 light-years away, with ongoing research to determine its atmosphere and potential to support life.
In a rare and exciting discovery, astronomers have found an Earth-like exoplanet 40 light-years away that may be only slightly warmer than our own world.
The potentially habitable planet, named Gliese 12b, orbits its host star every 12.8 days, is comparable in size to Venus – slightly smaller than Earth – and has an estimated surface temperature of 42 °C (107 °F), which is lower than most of the 5,000 exoplanets confirmed so far.
That’s assuming it has no atmosphere, which is another crucial step to determining whether it’s habitable.
The Atmospheric Mystery of Gliese 12 b
Gliese 12b’s atmosphere could resemble Earth’s. It could reflect Venus experiencing a greenhouse effect that turned it into a 400 °C (752 °F) hellhole. It could also have no atmosphere, or perhaps another type of atmosphere not found in our solar system.
Getting the answer is vital because it would reveal whether Gliese 12b can maintain temperatures suitable for the existence of liquid water—and possibly life—on its surface, while also unlocking answers about how and why Earth and Venus evolved so differently.
Gliese 12b is by no means the first Earth-like exoplanet to be discovered, but as NASA he said that there are only a handful of similar worlds that deserve a closer look.
The estimated size of Gliese 12 b may be Earth-sized or slightly smaller – comparable to Venus in our solar system. This artist’s concept compares Earth to various possible interpretations of Gliese 12b, from one without an atmosphere to one with a thick Venus. Credit: NASA/JPL-Caltech/R. Hurt (Caltech-IPAC)
Gliese 12 b: Primary target for the James Webb Space Telescope
It was considered “the closest, transiting, temperate Earth-sized world found to date” and a potential target for further investigation by the US space agency’s $10 billion. The James Webb Space Telescope.
The closest Earth-like exoplanet – and perhaps the most famous – is Proxima Centauri b, which is just 4 light-years away. However, since it is not a transiting world, we still have a lot to learn about it, including whether it has an atmosphere and the potential to harbor life.
Most exoplanets are discovered using the transit method, where a planet passes in front of its star from our point of view, causing the host star to dim in brightness.
During the transit, the starlight also passes through the exoplanet’s atmosphere and some wavelengths are absorbed. Different gas molecules absorb different colors, so the transit provides a set of chemical fingerprints that can be detected by telescopes like Webb.
The importance of Gliese 12b in the study of exoplanets
Gliese 12b could also be significant because it may help reveal whether most of the stars in our planet Milky Way galaxies – i.e. cool stars – are capable of hosting temperate planets that have atmospheres and are therefore habitable.
The discovery of an “exo-Venus” by two international teams of astronomers was published today (May 23) in Monthly Notices of the Royal Astronomical Society.
It orbits a cool red dwarf star called Gliese 12, which is nearly 40 light-years from Earth in the constellation Pisces.
Insights from researchers
“Gliese 12b represents one of the best targets for studying whether Earth-sized planets orbiting cool stars can retain atmospheres, a crucial step toward advancing our understanding of planetary habitability throughout our galaxy,” said Shishir Dholakia, a doctoral student at the university. Center for Astrophysics at the University of Southern Queensland, Australia.
He co-led the research team with Larissa Palethorpe, a PhD student at the University of Edinburgh and University College London.
The exoplanet’s host star is about 27 percent the size of our Sun, and its surface temperature is about 60 percent that of our own star.
However, the distance between Gliese 12 and the new planet is just 7 percent of the distance between Earth and the Sun. Gliese 12b therefore receives 1.6 times more energy from its star than Earth does from the Sun, and about 85 percent of what Venus experiences.
Understanding atmospheric influences
This difference in solar radiation is important because it means that the planet’s surface temperature is highly dependent on its atmospheric conditions. Compared to Gliese 12b’s estimated surface temperature of 42 °C (107 °F), Earth has an average surface temperature of 15 °C (59 °F).
“The atmosphere traps heat and – depending on the type – can substantially change the actual surface temperature,” Dholakia explained. “We give the ‘equilibrium temperature’ of the planet, which is the temperature the planet would have if it had no atmosphere.
“Most of the scientific value of this planet lies in understanding what kind of atmosphere it might have. Since Gliese 12b will fall between the amount of light that Earth and Venus receive from the Sun, it will be valuable in bridging the gap between the two planets in our solar system.
Palethorpe added: “The first atmospheres of Earth and Venus are thought to have been stripped away and then replenished by volcanic outgassing and bombardment from leftover material in the solar system.
“Earth is habitable, but Venus is not due to the complete loss of water. Since Gliese 12b is between Earth and Venus in temperature, its atmosphere could teach us a lot about the ways in which planets develop habitability.”
The scientists, along with another team in Tokyo, used NASA’s Transiting Exoplanet Survey Satellite (TESS) observations to help make their discovery.
“We found the closest, transiting, temperate Earth-sized world we’ve found so far,” said Masayuki Kuzuhara, a project assistant at the Astrobiology Center in Tokyo, who led the research team with Akihiko Fukui, a project assistant. a professor at the University of Tokyo.
“Although we don’t yet know if it has an atmosphere, we thought of it as an exo-Venus with a similar size and energy that it receives from its star as our planetary neighbor in the Solar System.”
An important factor in maintaining the atmosphere is the turbulence of its star. Red dwarfs tend to be magnetically active, resulting in frequent, strong X-ray bursts.
However, the two teams’ analyzes concluded that Gliese 12 shows no signs of such extreme behavior, raising hopes that Gliese 12 b’s atmosphere may still be intact.
“We know of only a handful of Earth-like temperate planets that are close enough to us that meet the other criteria needed for this kind of study, called transmission spectroscopy, using current equipment,” said Michael McElwain, an astrophysicist at NASA Goddard. Space Flight Center in Greenbelt, Maryland, and co-authored the article with Kuzuhara and Fukui.
“To better understand the diversity of atmospheres and evolutionary outcomes of these planets, we need more examples like Gliese 12b.”
At 40 light years from Earth, Gliese 12b is about the same distance as the TRAPPIST-1 system.
It consists of seven planets, all roughly in the Earth-sized range and probably rocky, orbiting a red dwarf.
Three of them are in the habitable zone, but at least two – and probably all – have no atmosphere and are likely barren, dashing hopes that they might be life-hosting water worlds when they were first discovered eight years ago.
Link: “Gliese 12b, Earth-sized temperate planet at 12 parsecs discovered with TESS and CHEOPS” by Shishir Dholakia and Larissa Palethorpe et al. 23 May 204, Monthly Notices of the Royal Astronomical Society.
DOI: 10.1093/mnras/stae1152