In an awakening study, astronomers have discovered an Earth-like exoplanet named Gliese 12 b, located just 40 light-years away in the constellation Pisces. This new find, orbiting a cool red dwarf star, could be one of the most promising candidates for future studies on habitability and the search for extraterrestrial life.
The planet is unique for several reasons. It’s comparable in size to Venus, slightly smaller than Earth, and has an estimated surface temperature of 107 Fahrenheit (42 Celsius). This temperature is notably cooler than many of the over 5,000 exoplanets discovered so far.
“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,” said Shishir Dholakia, a doctoral student at the Centre for Astrophysics at the University of Southern Queensland in Australia.
The planet orbits its star, Gliese 12, every 12.8 days at a distance of just 7% of the Earth-Sun distance. As a result, it receives approximately 60% more energy from its star compared to what Earth receives from the Sun. On the flipside, the host star is about 27% the size of our Sun and has a surface temperature of roughly 60% of it. This balances things out to make Gliese 12 potentially habitable despite the close proximity to its star.
Determining whether Gliese 12 b has an atmosphere is crucial for understanding its potential to support life. The planet’s surface conditions could vary dramatically based on its atmospheric composition. It could have an Earth-like atmosphere, maintaining temperatures supporting liquid water and life. Alternatively, a Venus-like atmosphere could result in a runaway greenhouse effect, making the planet inhospitable. If the planet has no atmosphere, its conditions would be vastly different from both Earth and Venus.
“Atmospheres trap heat and — depending on the type — can change the actual surface temperature substantially,” Dholakia said. “We are quoting the planet’s ‘equilibrium temperature’, which is the temperature the planet would be if it had no atmosphere. Much of this planet’s scientific value is understanding what kind of atmosphere it could have. Since Gliese 12 b gets in between the amount of light as Earth and Venus get from the Sun, it will be valuable for bridging the gap between these two planets in our solar system.”
Gliese 12 b was discovered using the transit method, which involves detecting dips in a star’s brightness as a planet passes in front of it. This method not only helps in identifying planets but also provides a way to study their atmospheres. During a transit, if the planet has an atmosphere, some of the star’s light passes through it, leaving unique chemical markers that telescopes like the James Webb Space Telescope (JWST) can examine.
The discovery offers a unique opportunity to study whether Earth-like planets orbiting cool stars can retain their atmospheres and remain habitable.
This new find is among the few temperate, Earth-sized planets close enough for detailed study. It is described as “the nearest, transiting, temperate, Earth-size world located to date” and is a significant target for NASA’s $7.5 billion JWST. This discovery raises hopes for a deeper understanding of how planets like Earth and Venus evolved so differently and whether Gliese 12 b might support life.
“Gliese 12 b represents one of the best targets to study whether Earth-size planets orbiting cool stars can retain their atmospheres,” said Larissa Palethorpe, a doctoral student at the University of Edinburgh and University College London, who also co-led the research. “This is a crucial step to advance our understanding of habitability on planets across our galaxy.”
Further studies and observations, particularly using JWST, will focus on detecting and analyzing the atmosphere. These efforts will help determine if the planet can maintain conditions suitable for liquid water and possibly life. The discovery also underscores the importance of studying planets around cool stars, the most common type of stars in our galaxy.
“We know of only a handful of temperate planets similar to Earth that are both close enough to us and meet other criteria needed for this kind of study, called transmission spectroscopy, using current facilities,” said Michael McElwain, a research astrophysicist at NASA’s Goddard Space Flight Center, and a paper co-author. “To better understand the diversity of atmospheres and evolutionary outcomes for these planets, we need more examples like Gliese 12 b.”
The study was published in the Monthly Notices of the Royal Astronomical Society.
