Astronomers have unveiled the discovery of a remarkable new exoplanet — Gliese 12 b — a world roughly the size of Earth located a mere 40 light-years from our Solar System. The finding, first identified by data from Transiting Exoplanet Survey Satellite (TESS) in May 2024, suggests that Gliese 12 b sits inside the habitable zone of its host star — a region where conditions might allow liquid water — and therefore raises the possibility that it could harbor life. ScienceAlert+2iac.es+2

The planet circles a cool red-dwarf star known as Gliese 12, which is only about 27 % the size of our Sun. Despite the close orbital distance — just 7 % of the distance between Earth and the Sun — Gliese 12’s lower luminosity means Gliese 12 b receives roughly 1.6 times the energy Earth receives from the Sun, placing it at a surprisingly temperate energy budget for a planet so near to its star. ScienceDaily+2Earth.com+2

According to the peer-reviewed study published in the journal Monthly Notices of the Royal Astronomical Society (MNRAS), Gliese 12 b has an orbital period of approximately 12.76 days, and a measured radius about equal to Earth’s (~1.0 R⊕), indicating a rocky composition — a strong hint it might be a terrestrial planet rather than a gas giant. arXiv+2ScienceAlert+2

What makes this world especially intriguing is its placement in what astronomers call the "Goldilocks zone" — neither too hot nor too cold — where temperatures could allow for the existence of liquid water. On Gliese 12 b, assuming it has no atmosphere, scientists estimate a “surface equilibrium temperature” of about 315 K (~42 °C / 107 °F). ScienceDaily+2phys.org+2 This temperature is hotter than Earth’s average, but far milder than for most known exoplanets, and leaves open the possibility that with the right atmospheric conditions, the planet could support temperate climates. Science Focus+1

Still, whether Gliese 12 b is truly habitable depends critically on one key unknown: whether it possesses an atmosphere. As of the 2024 discovery, there is no confirmed evidence of a gaseous envelope, water vapor, or surface pressure necessary to sustain oceans. Live Science+2Live Science+2

Even so, astronomers are cautiously optimistic. One reason: Gliese 12 appears to be unusually inactive compared with typical red dwarfs. High stellar activity — frequent flares and intense X-ray emissions — can strip away atmospheres of nearby planets. In this case, analyses conclude that Gliese 12 exhibits minimal signs of such violent behavior, thereby increasing the chances that its planet could retain whatever atmosphere it may have. ScienceDaily+2iac.es+2

Because of these favorable factors — Earth-like size, temperate energy input, and a quiet host star — Gliese 12 b is being hailed as among the most promising nearby exoplanet candidates for studying planetary habitability. Scientists argue that it may offer one of the clearest opportunities to explore whether Earth-sized planets around cool stars can sustain climates suitable for liquid water and possibly life. iac.es+2ScienceAlert+2

To pursue that possibility, astronomers are preparing follow-up observations — especially atmospheric studies. The clarity of the transit (when the planet passes in front of its star) and the planet’s relative proximity make Gliese 12 b an excellent target for transmission spectroscopy, a technique that can reveal the presence of gases such as water vapor, oxygen, carbon dioxide, or other potential biosignatures — using instruments like the James Webb Space Telescope (JWST) and other powerful ground-based facilities. ScienceDaily+2iac.es+2

If future observations confirm a stable, temperate atmosphere on Gliese 12 b, the implications could be profound. The planet might end up resembling a milder, more temperate cousin of Venus — or even a second Earth. At only 40 light-years, Gliese 12 b would grant scientists a nearby “laboratory” for testing long-standing theories about how atmospheres form, evolve, and permit life on rocky planets. It could also help us understand the range of possible climates on exoplanets orbiting red dwarfs — the most common type of star in our galaxy.

That said, some caution remains. As the discovery team themselves note, without confirmed atmospheric data, it is premature to label Gliese 12 b a “second Earth.” Many previously discovered exoplanets once considered promising have disappointed when deeper study revealed barren surfaces, extreme radiation, or no atmosphere at all. phys.org+2iac.es+2

In summary: Gliese 12 b is a stunning and exciting find — one of the nearest Earth-size planets in the habitable zone ever discovered. Its characteristics make it a prime target for further study, and it could dramatically advance our understanding of planetary habitability beyond our Solar System. But for now, it remains a candidate — a world full of promise, yet still awaiting confirmation that it truly could support life.