A newly discovered exoplanet whose surface temperature is estimated to be remarkably mild is suddenly one of the most intriguing objects in our immediate celestial neighborhood. This rocky Venus-sized world is orbiting a red dwarf, offering astronomers a rare opportunity to investigate whether such planets can retain their atmospheres and potentially support life.
Gliese 12 b, comparable in size to Venus but slightly smaller than Earth, orbits its cool red dwarf host star Gliese 12 at a distance of just 7% of the distance from Earth to the Sun. This alarmingly close proximity results in a year lasting just 12.8 days, and the planet receiving 1.6 times more energy from its star than Earth does from the Sun. Despite this, Gliese 12b maintains an estimated surface temperature of 107 degrees F (42 degrees C), making it a temperate world and one of the cooler exoplanets yet discovered. research published today in the Monthly Notices of the Royal Astronomical Society. By comparison, Earth has average surface temperature 59 degrees F (15 degrees C), but is increasing due to human-induced climate change.
The next big step is for astronomers to determine whether Giles 12b, located 40 light-years from Earth, hosts an atmosphere, and if so, what type, and whether the planet is capable of hosting stable liquid water—a prerequisite for life as we know it—on surface. “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,” Shishir Dholakia, a Ph.D. student at the Center. for astrophysics at the University of Southern Queensland in Australia, he explained in an emailed statement.
The host star, Gliese 12, is about 27% the size of our Sun, and its surface temperature is about 60% that of our host star. Unlike many red dwarfs, which are known for their magnetic activity and frequent, strong X-ray flares, Gliese 12 shows no signs of such extreme behaviorwhich astronomers say raises hopes that Gliese 12b’s atmosphere may still be intact.
The exoplanet’s atmosphere (which may or may not exist) will be a major focus of future studies, particularly with the James Webb Telescope, which is well-suited to analyzing the chemical composition of planetary atmospheres thanks to its advanced infrared capabilities. A transiting exoplanet, Gliese 12b often passes in front of its host star from our perspective on Earth, allowing for detailed observations through transit spectroscopy. This method allows astronomers to study light filtered by the planet’s atmosphere and reveal the presence of various gases and potential indicators of habitability.
“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,” said Masayuki Kuzuhara. project assistant at the Astrobiology Center in Tokyo. He added: “We have found the closest transiting temperate Earth-sized world yet.”
The planet’s location and characteristics could provide insight into why Earth and Venus, despite their similarities, have vastly different atmospheres. As Dholakia explained, “Atmospheres trap heat and—depending on the type [of atmosphere]-can substantially change the actual surface temperature.”
In the study, the researchers refer to the exoplanet’s “equilibrium temperature,” which is how hot it would be without an atmosphere. The main scientific interest in Gliese 12b is to understand what kind of atmosphere it might have; ideally, it would have an atmosphere like Earth’s, rather than the thick toxic sulfuric acid clouds of Venus, where surface temperatures reach over 450 degrees C (860 degrees F). Because it receives a similar amount of light to Earth and Venus, studying it can help us learn more about the differences between the two planets in our solar system, Dholakia says.
Scientists used NASA’s Transiting Exoplanet Survey Satellite (TESS) and the European Space Agency’s CHAracterising ExOPlanets Satellite (CHEOPS) to estimate the equilibrium temperature of Gliese 12b. TESS first detected the planet by observing its transits, which are periodic dips in starlight caused by a planet passing in front of its host star. These observations were then followed up by more precise measurements from CHEOPS, which helped to refine the orbital period and radius of the planet. 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 collaboration between teams from the University of Southern Queensland, the University of Edinburgh and the Astrobiology Center at the University of Tokyo.
The significance of this discovery goes beyond our solar system. It may help show whether most of the stars in our Milky Way, which are cool red dwarfs, can host temperate planets with atmospheres, making them potentially habitable. 2013 research suggested that there may be as many as 4.5 billion potentially habitable planets orbiting red dwarfs in our galaxy, but there was little to no evidence to support this.
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The discovery of Gliese 12 b highlights the progress astronomers are making in the search for habitable worlds. While Proxima Centauri b, the nearest Earth-like exoplanet at a distance of only 4 light-years, remains less understood due to its non-transiting nature, the transiting behavior of Gliese 12b provides a clearer path for atmospheric studies. This advantage will hopefully give scientists a better insight into its potential habitability.
As research continues, Gliese 12b could play a key role in our quest to understand the conditions necessary for life outside our solar system.
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