Potentially habitable ‘exo-Venus’ with Earth-like temperature discovered

Astronomers have made the rare and exciting discovery of an Earth-like exoplanet 40 light-years away that may be only slightly warmer than our own world. A new paper, “Gliese 12b, an Earth-sized planet at 12 parsecs discovered with TESS and CHEOPS” was published in Monthly Notices of the Royal Astronomical Society.

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 less. 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. It may have an Earth-like atmosphere, similar to Venus, which experienced a greenhouse effect that turned it into a 400°C (752°F) hellhole—no atmosphere, or perhaps a different kind of atmosphere not found in our solar system. 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 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 said, there are only a handful of similar worlds that deserve a closer look.

It was considered “the closest, transiting, temperate Earth-sized world yet found” and a potential target for further investigation by the James Webb Space Telescope.

The closest Earth-like exoplanet—and perhaps the most famous—is Proxima Centauri b, just four 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.

Gliese 12b could also be significant because it may help reveal whether most of the stars in our Milky Way galaxy—that is, cool stars—are capable of hosting temperate planets that have atmospheres and are therefore habitable.

It orbits a cool red dwarf star called Gliese 12, which is nearly 40 light-years from Earth in the constellation Pisces.

“Gliese 12b represents one of the best targets for studying whether Earth-sized planets orbiting cool stars can retain their atmospheres, a crucial step toward advancing our understanding of planetary habitability throughout our galaxy,” said Shishir Dholakia, a Ph.D. 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% the size of our Sun, and its surface temperature is about 60% that of our own star.

However, the distance between Gliese 12 and the new planet is only 7% 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% of what Venus experiences.

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 state the ‘equilibrium temperature of the planet’, which is the temperature the planet would have if it had no atmosphere.

“Much of the scientific value of this planet lies in understanding what kind of atmosphere it might have. Since Gliese 12b will fall within 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 because of its complete loss of water. Because Gliese 12b is between Earth and Venus in temperature, its atmosphere could teach us a lot about the habitability pathways that planets take.”

The scientists, along with another team in Tokyo, used NASA’s Transiting Exoplanet Survey Satellite (TESS) observations to help make their discovery.

“We have found the closest, transiting, temperate Earth-sized world to date,” said Masayuki Kuzuhara, a project assistant professor 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 received 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 when they were first discovered eight years ago that they could be water worlds hosting life.