Astronomers using the James Webb Space Telescope (JWST) have identified compelling evidence of a gas giant planet orbiting Alpha Centauri A, the closest Sun-like star to Earth. This significant discovery, detailed in two papers accepted by The Astrophysical Journal Letters, marks a crucial step in the search for exoplanets in our immediate cosmic neighborhood.
The Alpha Centauri system, located just 4 light-years away, comprises three stars: Alpha Centauri A and B, both Sun-like, and the red dwarf Proxima Centauri. While planets have been confirmed around Proxima Centauri, detecting celestial bodies around Alpha Centauri A and B has been challenging due to the stars' brightness and proximity. The JWST's Mid-Infrared Instrument (MIRI), equipped with a coronagraphic mask, was instrumental in overcoming these obstacles by blocking the intense glare of Alpha Centauri A. Initial observations in August 2024 revealed an object over 10,000 times fainter than its host star, located approximately 1.5 arcseconds away. Subsequent observations in February and April 2025 did not confirm the object's presence, leading researchers to employ sophisticated computer modeling. These simulations suggest the planet may follow an elliptical orbit with a period of two to three years around Alpha Centauri A. The planet is estimated to be roughly the mass of Saturn and orbits at a distance comparable to that between the Sun and Earth, approximately one to two times that distance.
Although this potential exoplanet is a gas giant, rendering it unsuitable for life as we understand it, its discovery is immensely valuable. It opens new avenues for research and offers an unparalleled opportunity to study planetary systems beyond our own. The proximity of Alpha Centauri makes any discovered planets prime candidates for detailed characterization by JWST and other observatories, fueling optimism for the possibility of smaller, potentially habitable worlds in this nearby stellar neighborhood. The detection process itself highlights the advanced capabilities of the JWST and the ingenuity of the scientific teams involved, particularly the MIRI instrument's ability to perform coronagraphic imaging in a challenging multi-star system.