June 25, 2024

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

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

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Gliese 12 b, which orbits a cool red dwarf star located just 40 light-years away, promises to tell astronomers more about how planets close to their stars retain or lose their atmospheres. In this concept art, Gliese 12 b is shown maintaining a thin atmosphere. Image source: NASA/JPL-Caltech/R. Hurt (California Institute of Technology-IPAC)

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Gliese 12 b, which orbits a cool red dwarf star located just 40 light-years away, promises to tell astronomers more about how planets close to their stars retain or lose their atmospheres. In this concept art, Gliese 12 b is shown maintaining a thin atmosphere. Image source: NASA/JPL-Caltech/R. Hurt (California Institute of Technology-IPAC)

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

The potentially habitable planet, called Gliese 12 b, orbits its host star every 12.8 days. It is similar in size to Venus – slightly smaller than Earth – and its surface temperature is estimated at 42 degrees Celsius (107 degrees Fahrenheit), which is much lower. Of the 5,000 exoplanets confirmed so far.

This is assuming it has no atmosphere, which is the next crucial step to determining whether it is habitable. It may have an Earth-like atmosphere, which is closer to Venus — which has experienced runaway global warming that has made it a 400°C (752°F) hellhole — and no atmosphere, or perhaps a different type of atmosphere than Earth. Found in our sun. System.

Obtaining an answer is vital because it will reveal whether Gliese 12 b is able to maintain temperatures suitable for the presence of liquid water – and perhaps life – on its surface, while also unlocking answers about how and why Earth and Venus evolved so differently.

Gliese 12 b is by no means the first exoplanet to be discovered, but as NASA said, there are only a few worlds like it that are worth a closer look.

It has been described as “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 to us – and perhaps the most famous – is Proxima Centauri b, which is only four light-years away. However, since it is not a transient 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 the planet passes in front of its star from our view, causing the host star to decrease in brightness.

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

Gliese 12 b could also be important because it may help reveal whether the majority of 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 about 40 light-years from Earth in the constellation Pisces.

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

He co-led a 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 star.

However, the distance between Gliese 12 and the new planet is only 7% of the distance between Earth and the Sun. Thus, Gliese 12 b receives 1.6 times more energy from its star than Earth receives from the Sun, and about 85% of what Venus receives.


The estimated size of Gliese 12 b could be as large as Earth or slightly smaller, comparable to Venus in our solar system. This artist’s concept compares Earth to different possible interpretations of Gliese 12 b, from one with no atmosphere to one with a thick, Venus-like atmosphere. Image source: NASA/JPL-Caltech/R. Hurt (California Institute of Technology-IPAC)

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The estimated size of Gliese 12 b could be as large as Earth or slightly smaller, comparable to Venus in our solar system. This artist’s concept compares Earth to different possible interpretations of Gliese 12 b, from one with no atmosphere to one with a thick, Venus-like atmosphere. Image source: NASA/JPL-Caltech/R. Hurt (California Institute of Technology-IPAC)

This difference in solar radiation is important because it means that the planet’s surface temperature depends greatly on weather conditions. Compared to Gliese 12 b’s estimated surface temperature of 42 °C (107 °F), Earth’s average surface temperature is 15 °C (59 °F).

“The atmosphere traps heat, and can change the actual surface temperature dramatically, depending on the species,” Dholakia explained. “We’re quoting the equilibrium temperature of the planet, which is the temperature the planet would be if it didn’t have an atmosphere.

“A big part of the scientific value of this planet is understanding what kind of atmosphere it could have. Since Gliese 12 b falls between the amount of light that Earth and Venus get from the Sun, this will be valuable for 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 stripped away and then replenished by the release of volcanic gases and the bombardment of remaining material in the solar system.

“Earth is habitable, but Venus is not due to its complete loss of water. Because Gliese 12 b is between Earth and Venus in terms of temperature, its atmosphere can teach us a lot about the habitability paths that planets take as they evolve.”

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

“We have found the closest, transiting, temperate, Earth-sized planet to date,” said Masayuki Kuzuhara, an assistant professor at the Center for Astrobiology in Tokyo, who co-led a research team with Akihiko Fukui, a project assistant. Professor at the University of Tokyo.

“Although we don’t yet know if it has an atmosphere, we’ve been thinking of it as an exoplanet, with the same size and energy it receives from its star as our planetary neighbor in the solar system.”

An important factor in maintaining the atmosphere is the storminess of its star. Red dwarfs tend to be magnetically active, giving rise to frequent and powerful X-ray flares.

However, analyzes by both teams concluded that Gliese 12 shows no signs of such extreme behavior, raising hopes that Gliese 12 b’s atmosphere may still be intact.

“We only know of a few temperate Earth-like planets that are close enough to us that they meet the other criteria needed for this type of study, called transmission spectroscopy, using existing facilities,” said Michael McElwain, an astrophysicist at NASA’s Goddard Center. . Space Flight Center in Greenbelt, Maryland, and co-author of the Kuzuhara and Fukui paper.

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

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

It consists of seven planets, almost all in the Earth-sized range and likely rocky, orbiting a red dwarf star.

Three of them are located in the habitable zone, but at least two of them – and perhaps all of them – have no atmosphere and are likely barren, dashing hopes when they were first discovered eight years ago that they could be watery worlds hosting life.

more information:
Shishir Dholakia et al., Gliese 12 b, a temperate Earth-sized planet at 12 parsecs discovered using TESS and CHEOPS, Monthly Notices of the Royal Astronomical Society (2024). doi: 10.1093/mnras/stae1152

Magazine information:
Monthly Notices of the Royal Astronomical Society


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