Newly discovered exoplanet could have temperatures similar to Earth, astronomers suggest

A newly discovered exoplanet, estimated to have a remarkably moderate surface temperature, is suddenly one of the most intriguing objects in our immediate sky. This Venus-sized rocky world passes by a red dwarf star, offering astronomers a rare opportunity to investigate whether such planets can maintain their atmospheres and possibly support life.

Gliese 12 b, similar in size to Venus but slightly smaller than Earth, orbits its cool red dwarf host star, Gliese 12, just 7% of the distance between Earth and the Sun. This unnerving proximity results in a year that lasts just 12.8 days and the planet receives 1.6 times more energy from its star than Earth does from the Sun. Despite this, Gliese 12 b maintains an estimated surface temperature of 42 degrees Celsius, making it a temperate world and one of the cooler exoplanets discovered so far, according to new sources. research published today in the Monthly Notices of the Royal Astronomical Society. By comparison, Earth has one average surface temperature of 59 degrees F (15 degrees C), but it is rising due to human-induced climate change.

The next big steps are for astronomers to find out whether Gilese 12 b, located 40 light-years from Earth, harbors an atmosphere, and if so, what type, and whether this planet is capable of harboring stable liquid water – the prerequisite for life if we know it – on the surface. “Gliese 12 b represents one of the best targets to investigate whether Earth-sized planets orbiting cool stars can maintain their atmospheres, a crucial step in advancing our understanding of the habitability of planets in our Milky Way,” says Shishir Dholakia, a PhD candidate at the Centre. in astrophysics at the University of Southern Queensland in Australia, explained in an emailed statement.

Gliese 12 b is estimated to be about the same size as Earth, or slightly smaller, comparable to Venus.  This artist's concept compares Earth to several possible interpretations of Gliese 12 b, ranging from one with no atmosphere to one with a thick, Venus-like atmosphere.

Gliese 12 b is estimated to be about the same size as Earth, or slightly smaller, comparable to Venus. This artist’s concept compares Earth to several possible interpretations of Gliese 12 b, ranging from one with no atmosphere to one with a thick, Venus-like atmosphere.
Image: NASA/JPL-Caltech/R. Pain (Caltech-IPAC)

The host star, Gliese 12, is about 27% the size of our Sun and has a surface temperature about 60% that of our host star. Unlike many red dwarfs, which are known for their magnetic activity and frequent, powerful X-ray flares, Gliese 12 shows no signs of such extreme behaviorThis raises hopes that Gliese 12 b’s atmosphere is still intact, the astronomers said.

The exoplanet’s atmosphere (which may or may not exist) will be a primary focus of future studies, especially with the James Webb Telescope, which is well suited for analyzing the chemical composition of planetary atmospheres thanks to its advanced infrared capabilities. Gliese 12 b, a transiting exoplanet, regularly passes by its host star from our perspective on Earth, allowing detailed observations via transit spectroscopy. This method allows astronomers to study the light filtered through the planet’s atmosphere, revealing the presence of various gases and potential indicators of habitability.

“Although we don’t yet know if it has an atmosphere, we have seen it as an exo-Venus, with a similar size and energy received from its star as our planetary neighbor in the Solar System,” says Masayuki Kuzuhara. a project assistant professor at the Astrobiology Center in Tokyo. To which he added: “We have found the closest, continuous, temperate world the size of Earth known yet.”

The planet’s location and characteristics may provide insight into why Earth and Venus, despite their similarities, have vastly different atmospheres. As Dholakia explained: “Atmospheres retain heat and – depending on the type [of atmosphere]– can significantly change the actual surface temperature.”

In the study, the researchers refer to the exoplanet’s ‘equilibrium temperature’, i.e. how hot it would be without an atmosphere. The main scientific interest in Gliese 12 b is to understand what kind of atmosphere it might have; Ideally, it would have an atmosphere like Earth’s, and not the thick, toxic clouds of sulfuric acid found on Venus, where surface temperatures soar above 450 degrees Celsius. Because it receives a similar amount of light as Earth and Venus, studying it can help us learn more about the differences between these two planets in our solar system, Dholakia said.

The researchers used NASA’s Transiting Exoplanet Survey Satellite (TESS) and the European Space Agency’s CHEOPS (CHaracterising ExOPlanets Satellite) to estimate the equilibrium temperature of Gliese 12 b. TESS initially discovered the planet by observing its transits. These are periodic dips in starlight caused by the planet passing in front of its host star. These observations were then followed by more precise measurements from CHEOPS, which helped refine the planet’s orbital period and radius. The combined data from TESS and CHEOPS allowed the researchers to calculate the equilibrium temperature by assessing the amount of starlight the planet receives and its distance from the star. The project was a joint effort between teams from the University of Southern Queensland, the University of Edinburgh and the University of Tokyo Astrobiology Centre.

The significance of this discovery extends beyond our solar system. It could help show whether most of the stars in our Milky Way, which are cool red dwarfs, could host temperate planets with atmospheres, making them potentially habitable. Research from 2013 suggested that as many as 4.5 billion potentially habitable planets in our Milky Way could orbit red dwarfs, but evidence to support this is scant to non-existent.

Related article: How life could survive on exoplanet Proxima b

The discovery of Gliese 12 b highlights the progress astronomers are making in the search for habitable worlds. While Proxima Centauri b, the closest Earth-like exoplanet just four light-years away, remains less understood due to its non-transiting nature, the transit behavior of Gliese 12 b provides a clearer path for atmospheric studies. This advantage will hopefully allow scientists to better understand its potential habitability.

As research continues, Gliese 12 b could play a crucial role in our quest to understand the conditions necessary for life beyond our solar system.

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