Astronomers using the James Webb Space Telescope have discovered a potential planet in Alpha Centauri, the closest star system to Earth. If confirmed, this gas giant would be the closest exoplanet to Earth located in the habitable zone of a Sun-like star. This is considered a significant step in the search for life outside the Solar System.
New Planet Discovered
The Alpha Centauri system consists of three stars located just 4.34 light-years from the Sun: the Sun-like stars Alpha Centauri A and Alpha Centauri B, and the red dwarf star Proxima Centauri. Until now, planets had only been discovered orbiting Proxima Centauri.
Observations with Webb’s MIRI instrument changed this. In the first observation in August 2024, the telescope’s coronagraph mask blocked the brightness of Alpha Centauri A, revealing an object 10,000 times fainter than the star.
However, subsequent observations in February and April 2025 failed to detect the same object. To clarify this, scientists simulated millions of possible orbital scenarios. The resulting model suggests that the planet has an elliptical orbit and was not detected by Webb when it approached its star.
According to the models, this planet has a mass similar to Saturn. It orbits Alpha Centauri A at a distance between 1 and 2 times the Sun-Earth distance. Its estimated surface temperature is calculated as -48°C. While the planet itself is unlikely to harbor life, potentially habitable moons around it or other planets in the system may have suitable conditions for life.
Alpha Centauri A’s close resemblance to the Sun makes this system special for scientists. The discovery of a habitable planet around this star could provide unique data that will help understand our own solar system and identify other habitable worlds.
