Two international teams of astronomers have discovered a planet between the sizes of Earth and Venus only 40 light-years away, using observations by NASA’s TESS and other facilities. The planet, named Gliese 12 b, is located in the constellation Pisces around a cool red dwarf star called Gliese 12. The star is 27% of the size of the Sun and has a surface temperature of around 60% of the Sun’s. Gliese 12 b is Earth’s size or slightly smaller, with a surface temperature of approximately 107 degrees Fahrenheit assuming it has no atmosphere.
The discovery of Gliese 12 b is significant because it represents one of the best targets to study whether Earth-size planets orbiting cool stars can retain their atmospheres, which is crucial to understanding habitability on planets in our galaxy. The planet is in a perfect location to help unlock aspects of Earth’s and Venus’s evolution, as it is in between the two in terms of temperature. Researchers hope to learn more about the habitability pathways planets take as they develop by studying the atmosphere of Gliese 12 b.
The dimunitive sizes and masses of red dwarf stars make them ideal for finding Earth-size planets, as a smaller star results in greater dimming for each transit and a lower mass allows an orbiting planet to produce a greater wobble, known as “reflex motion,” of the star. This makes smaller planets easier to detect. The habitable zones around red dwarf stars are closer to these stars than others, making it easier to detect transiting planets within habitable zones around them. This proximity also allows for the study of whether Earth-size planets can retain their atmospheres.
Despite the storminess typically associated with red dwarf stars, analyses by both research teams found that Gliese 12 shows no signs of extreme behavior. During a transit, the host star’s light passes through any atmosphere of the planet, providing a set of chemical fingerprints that can be detected by telescopes like NASA’s James Webb Space Telescope. The transit spectroscopy can help better understand the diversity of atmospheres and evolutionary outcomes for planets like Gliese 12 b, which are close enough to us and meet the criteria necessary for this kind of study.
With the discovery of Gliese 12 b, researchers hope to advance understanding of habitability on planets in our galaxy by studying the atmosphere of this Earth-size planet. By studying planets like Gliese 12 b, which are temperate and close enough to us, astronomers can gain insight into the evolution of our own solar system and the pathways planets take to develop habitable environments. The findings of the two international research teams suggest that Gliese 12 b is a promising target for further study using NASA’s James Webb Space Telescope to unlock more mysteries about the atmospheres and habitability of planets across our galaxy.