In a landmark achievement for astronomy, scientists using NASA’s James Webb Space Telescope (JWST) have uncovered compelling evidence of a gas giant planet orbiting Alpha Centauri A — one of the closest Sun-like stars to Earth. This discovery marks a significant milestone in the search for exoplanets and deepens our understanding of planetary systems beyond our own.
Located just four light-years away, the Alpha Centauri system is the nearest stellar neighborhood to our solar system. It consists of three stars: Alpha Centauri A and B, which are similar to our Sun, and Proxima Centauri, a faint red dwarf already known to host three confirmed planets. Until now, however, the brighter pair — Alpha Centauri A and B — had eluded planet hunters due to their intense luminosity and close proximity to each other.
The newly detected planet candidate, designated S1, was observed using JWST’s Mid-Infrared Instrument (MIRI), which employs a coronagraphic mask to block out the overwhelming glare of Alpha Centauri A. This allowed astronomers to spot a faint object approximately 186 million miles (300 million kilometers) from the star — about twice the distance between Earth and the Sun.
Initial observations were made in August 2024, with follow-up attempts in early 2025. Although the object was not visible in subsequent observations, researchers used advanced computer simulations to model millions of possible orbits. These simulations suggest that the planet may have moved too close to its host star to be detected during later scans, reinforcing the likelihood of its existence.
If confirmed, this gas giant would be the closest planet to Earth orbiting within the habitable zone of a Sun-like star. However, due to its gaseous composition — estimated to be similar in mass to Saturn — it is unlikely to support life as we know it. Still, its presence in such a nearby system offers an unprecedented opportunity to study planetary formation and dynamics in environments similar to our own.
“This is the most promising evidence yet of a planet around Alpha Centauri A,” said Charles Beichman, co-lead author of the studies and executive director of the NASA Exoplanet Science Institute. “With this system being so close to us, any exoplanets found here offer our best chance to collect detailed data on worlds beyond our solar system.”
The discovery also challenges existing models of planetary formation. The Alpha Centauri system’s binary nature — with two bright stars in close orbit — was previously thought to hinder planet formation due to gravitational disruptions. The presence of a gas giant in this environment suggests that planets may be more resilient and adaptable than previously believed.
While the planet’s potential habitability remains unlikely, its detection is a testament to the capabilities of the JWST and the ingenuity of the scientific teams behind it. As follow-up observations continue, astronomers hope to confirm the planet’s existence and learn more about its characteristics, including its atmosphere, orbit, and potential moons.
This discovery reignites excitement about the possibility of finding Earth-like worlds in our cosmic backyard and brings us one step closer to answering the age-old question: Are we alone in the universe?