Nasa has announced the discovery of a “super Earth” that orbits an M-type star. The exoplanet, codenamed “Gliese 12 b”, is potentially habitable.
It’s not just Nasa that made the discovery. In a groundbreaking study, two teams of scientists have identified Gliese 12b, a theoretically habitable exoplanet – it’s smaller than Earth but larger than Venus.
Its mass is 3.87 Earths, it takes 12.8 days to complete one orbit of its star, and is 0.0668 astronomical unit (AU) from its star. Its discovery was announced in 2024. (an AU a unit of length effectively equal to the mean distance between Earth and the Sun – 149.6 million km).
Discovery of Gliese 12b
This intriguing planet orbits a small star about 40 light-years away in the constellation Pisces.
The star, a cool red dwarf, is approximately 27 per cent the size of our Sun and has 60 per cent of its temperature, according to studies published in The Astrophysical Journal Letters and Monthly Notices of the Royal Astronomical Society.
Despite its rapid orbit of 12.8 days, Gliese 12b resides in the habitable zone — the optimal distance from its star where liquid water can exist.
Without an atmosphere, scientists estimate its surface temperature to be around 107 degrees Fahrenheit (42 degrees Celsius).
Announcement
“We’ve found the nearest, transiting, temperate, Earth-size world located to date,” announced Masayuki Kuzuhara, a project assistant professor at the Astrobiology Center in Tokyo, who co-led one of the research teams with Akihiko Fukui from the University of Tokyo.
Identifying temperate, Earth-sized planets is a significant step towards analyzing their atmospheres for life-sustaining elements, such as water. Larissa Palethorpe, a doctoral student at the University of Edinburgh and University College London, who co-led the other study, emphasised the rarity and significance of this discovery, stating: “This is our nearest, and so that’s quite a major discovery.”
Unveiling Gliese 12b
The discovery of Gliese 12b was facilitated by data from NASA’s Transiting Exoplanet Survey Satellite (TESS), which monitors thousands of stars monthly, tracking brightness changes indicative of orbiting exoplanets.
Red dwarf stars, like the one Gliese 12b orbits, are easier targets for exoplanet detection due to their small size, which causes a more noticeable dimming effect during transits.
Currently, scientists are uncertain about the planet's atmosphere and the presence of water.
Palethorpe told CNN: “There could be no water, and then we know a runaway greenhouse effect has already happened on this planet and it’s more like Venus. There could be water, in which case it’s more like us…”
The next phase involves using the James Webb Space Telescope for spectroscopy analysis to identify atmospheric molecules by observing which wavelengths of starlight are absorbed. This research could also provide insights into why Earth remained habitable while Venus did not, offering valuable lessons on planetary development.
Challenges and prospects
Despite its potential for habitability, visiting Gliese 12b remains a distant dream. “It’s not reachable, it’s 12 parsecs away,” explained Palethorpe, noting that it would take approximately 225,000 years to reach the planet with current spacecraft technology.
Nevertheless, the discovery of Gliese 12b not only advances our understanding of exoplanets but also promises to illuminate the evolutionary pathways that determine planetary habitability.
