Gliese 12 b: A New Temperate Exoplanet Found Just 40 Light-Years Away

Astronomers using NASA’s Transiting Exoplanet Survey Satellite (TESS) has discovered a new planet that lies between the sizes of Earth and Venus, located only 40 light-years away. This intriguing find, named Gliese 12 b, presents a promising candidate for further study using NASA’s James Webb Space Telescope.

TESS, which observes large sections of the sky for about a month at a time, tracks the brightness of tens of thousands of stars, aiming to capture transits—brief, regular dimmings caused by orbiting planets. This mission’s primary goal is to identify these transits and learn more about the exoplanets that cause them.

“We’ve found the nearest, transiting, temperate, Earth-size world located to date,” said Masayuki Kuzuhara, a project assistant professor at the Astrobiology Center in Tokyo. Kuzuhara co-led the research team with Akihiko Fukui, a project assistant professor at the University of Tokyo. Although the planet’s atmosphere is still unknown, the team is considering it as an “exo-Venus,” due to its similar size and energy reception from its star.

The host star, Gliese 12, is a cool red dwarf in the constellation Pisces. It is about 27% the size of our Sun and has roughly 60% of the Sun’s surface temperature. Gliese 12 b orbits this star every 12.8 days and is comparable to Earth or slightly smaller, with an estimated surface temperature of around 107 degrees Fahrenheit (42 degrees Celsius), assuming it has no atmosphere.

Red dwarf stars like Gliese 12 are ideal for finding Earth-size planets because their smaller size and mass make the detection of planetary transits and reflex motions easier. The lower luminosity of these stars also means that their habitable zones are closer, facilitating the discovery of potentially habitable planets.

The distance between Gliese 12 and its new planet is just 7% of the distance between Earth and the Sun. The planet receives 1.6 times more energy from its star than Earth does from the Sun and about 85% of what Venus experiences. Shishir Dholakia, a doctoral student at the Centre for Astrophysics at the University of Southern Queensland, Australia, highlighted the significance of this discovery, stating, “Gliese 12 b represents one of the best targets to study whether Earth-size planets orbiting cool stars can retain their atmospheres, a crucial step to advance our understanding of habitability on planets across our galaxy.”

Studying Gliese 12 b could also provide insights into our solar system’s evolution. Larissa Palethorpe, a doctoral student at the University of Edinburgh and University College London, explained, “It is thought that Earth’s and Venus’s first atmospheres were stripped away and then replenished by volcanic outgassing and bombardments from residual material in the solar system. Because Gliese 12 b is between Earth and Venus in temperature, its atmosphere could teach us a lot about the habitability pathways planets take as they develop.”

One key factor in retaining an atmosphere is the star’s activity level. Red dwarfs are often magnetically active, producing powerful X-ray flares. However, analyses by both research teams indicate that Gliese 12 shows no signs of extreme behavior, making it an even more intriguing target for study.

The findings by Kuzuhara and Fukui’s team were published in The Astrophysical Journal Letters, while Dholakia and Palethorpe’s research appeared in Monthly Notices of the Royal Astronomical Society. These studies highlight the potential of using transmission spectroscopy to analyze the atmospheres of temperate planets like Gliese 12 b. Michael McElwain, a research astrophysicist at NASA’s Goddard Space Flight Center, emphasized, “To better understand the diversity of atmospheres and evolutionary outcomes for these planets, we need more examples like Gliese 12 b.”

TESS, a NASA Astrophysics Explorer mission, is managed by NASA Goddard and operated by MIT. The mission involves multiple partners, including Northrop Grumman, NASA’s Ames Research Center, the Center for Astrophysics | Harvard & Smithsonian, MIT’s Lincoln Laboratory, and the Space Telescope Science Institute, along with more than a dozen universities, research institutes, and observatories worldwide.

The discovery of Gliese 12 b opens new avenues for understanding the potential for habitability on planets beyond our solar system, marking another significant achievement for NASA’s TESS mission.

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