Potentially habitable “Exo-Venus” with Earth-like temperatures discovered

Astronomers have made the rare and exciting discovery of an Earth-like exoplanet 40 light-years away that may be just a little warmer than our own world. The new article “Gliese 12 b, a temperate 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, called Gliese 12 b, orbits its parent 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 roughly 5,000 exoplanets confirmed to date.

However, this assumes there is no atmosphere, which is the crucial next step in determining whether it is habitable. It could have an Earth-like atmosphere more similar to that of Venus – which experienced a runaway greenhouse effect that turned it into a 400 °C (752 °F) hellhole – no atmosphere, or perhaps a different type of atmosphere There is no system in our solar system.

Getting an answer to this is crucial, as it would shed light on whether Gliese 12 b can maintain temperatures suitable for the existence of liquid water – and possibly life – on its surface. At the same time, it would provide answers to the question of how and why Earth and Venus evolved so differently.

Gliese 12 b is by no means the first Earth-like exoplanet discovered, but as NASA said, there are only a handful of such worlds that warrant a closer look.

It is considered “the closest transient temperate world the size of Earth to date” and a potential target for further study by the James Webb Space Telescope.

The closest Earth-like exoplanet to us – and possibly the most famous – is Proxima Centauri b, which is just four light-years away. However, because it is not a transiting planet, we still have a lot to learn about it, including whether it has an atmosphere and whether it can support life.

Most exoplanets are discovered using the transit method, in which a planet passes in front of its star from our perspective, thereby dimming the brightness of the parent star.

During a transit, the star’s light also passes through an exoplanet’s atmosphere and some wavelengths are absorbed. Different gas molecules absorb different colors, so the transit provides a series of chemical fingerprints that can be detected by telescopes like the Webb Telescope.

Gliese 12 b could also be important because it could shed light on whether the majority of stars in our Milky Way – the cool stars – are capable of hosting temperate planets that have an atmosphere and are therefore habitable .

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

“Gliese 12 b is one of the best targets for studying whether Earth-sized planets orbiting cool stars can retain their atmospheres. This is a crucial step in advancing our understanding of the habitability of planets in our galaxy,” said Shishir Dholakia, a PhD student at the Centre for Astrophysics at the University of Southern Queensland in Australia.

He led a research team with Larissa Palethorpe, a PhD student at the University of Edinburgh and University College London.

The exoplanet’s parent 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 12 b therefore receives 1.6 times more energy from its star than Earth receives from the Sun and about 85% of the energy that Venus experiences.

This difference in solar radiation is important because it means that the planet’s surface temperature depends strongly on its atmospheric conditions. For comparison, the estimated surface temperature of Gliese 12 b is 42 °C (107 °F), while the average surface temperature of Earth is 15 °C (59 °F).

“Atmospheres trap heat and, depending on the type, can significantly change the actual surface temperature,” Dholakia explained. “We are referring to the planet’s ‘equilibrium temperature’, which is the temperature the planet would be if it had no atmosphere.

“Much of the scientific value of this planet is understanding what kind of atmosphere it might have. Since Gliese 12 b lies between the amount of light that Earth and Venus receive from the Sun, it will be valuable in bridging the gap between these two planets in our solar system.

Palethorpe added: “The first atmospheres of Earth and Venus are thought to have been destroyed by volcanic outgassing and bombardment from leftover material in the solar system and then refilled.”

“Earth is habitable, but Venus is not because it has completely lost water. Since Gliese 12 b is between Earth and Venus in temperature, its atmosphere could teach us a lot about the habitability paths that planets take as they evolve.”

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

“We have found the closest temperate transiting space the size of Earth to date,” said Masayuki Kuzuhara, a project assistant at the Astrobiology Center in Tokyo, who led a research team with Akihiko Fukui, a project assistant at the University of Tokyo.

“Although we don’t yet know whether it has an atmosphere, we have considered it to be an exo-Venus, with a similar size and energy received from its star as our neighboring planet in the solar system.”

An important factor in maintaining an atmosphere is the storms of its star. Red dwarfs tend to be magnetically active, which leads to frequent, powerful X-ray flares.

However, analyses by both teams conclude 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 planets in temperate climates that are close enough to us and meet other criteria needed to do this type of study, called transmission spectroscopy, with current facilities,” said Michael McElwain, a research astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and co-author of the Kuzuhara and Fukui paper.

“To better understand the diversity of atmospheres and evolutionary outcomes of these planets, we need more examples like Gliese 12 b.”

Gliese 12 b is 40 light-years from Earth, about the same distance as the TRAPPIST-1 system.

It consists of seven planets, all roughly the same size as Earth, probably rocky and orbiting a red dwarf star.

Three of them lie in the habitable zone, but at least two – and probably all – have no atmosphere and are thought to be barren, dashing any hopes that they might be watery worlds with life when they were first discovered eight years ago.