Just next door in cosmic terms, astronomers may have spotted a new planetary neighbour – a gas giant circling Alpha Centauri A, the closest Sun-like star to Earth.
Located a mere four light-years away, this possible Saturn-sized world was detected by the James Webb Space Telescope in its most challenging exoplanet hunt yet.
If confirmed, it would be the closest planet ever found in the habitable zone of a Sun-like star, offering an unprecedented glimpse into a nearby solar system.
Alpha Centauri: Our closest cosmic neighbour
Visible from Earth’s Southern Hemisphere, the Alpha Centauri system consists of three stars: the Sun-like pair Alpha Centauri A and Alpha Centauri B, plus the faint red dwarf Proxima Centauri.
Proxima is already known to host three confirmed planets, but finding worlds around the brighter A and B stars has proven far more challenging.
Alpha Centauri A is the third-brightest star in our night sky, and its close companion B makes observations complex. Any planetary discovery here would offer an unprecedented opportunity to study a nearby solar system in detail.
Cutting-edge observations with Webb
The breakthrough came from Webb’s Mid-Infrared Instrument (MIRI), which used a coronagraphic mask to block the glare of Alpha Centauri A.
In August 2024, astronomers detected a faint object over 10,000 times dimmer than the star located at about twice the Earth-Sun distance.
Because Alpha Centauri B sits nearby, its extra light complicated the analysis. Careful subtraction of both stars’ glow revealed the mysterious candidate, sparking excitement among the team.
The mystery of the disappearing planet
Follow-up observations in February and April 2025, using Webb’s Director’s Discretionary Time, failed to spot the object again.
Rather than dismissing the find, scientists ran millions of computer simulations to model potential orbits.
Results showed that in nearly half the scenarios, the planet would have moved too close to Alpha Centauri A during those later observations, hiding it from Webb’s view.
The models suggest a gas giant roughly the mass of Saturn, travelling in an elliptical path that ranges from one to two times Earth’s orbital distance from the Sun.
This is not the first time Alpha Centauri A has teased astronomers. In 2019, the European Southern Observatory’s Very Large Telescope recorded a potential exoplanet in the system.
The new Webb data, combined with that earlier hint, strengthens the case for a genuine planetary companion.
Why this potential gas giant matters
If the detection holds, this would be the closest directly imaged planet to a Sun-like star and the most similar in temperature and age to our own gas giant planets. It would also be the nearest such world to Earth, making it an ideal candidate for future study.
Its presence in a binary system would also challenge existing models of planet formation, survival, and stability in dynamic environments.
The find underscores how the James Webb Space Telescope is expanding our ability to image exoplanets directly – something that was once nearly impossible, especially around bright and nearby stars.
Further observations will be needed to confirm the gas giant’s existence and refine its orbit. If verified, the discovery could reshape the next decade of exoplanet science, offering the closest and clearest look yet at a planetary system beyond our own.