Webb Telescope Finds Saturn-Sized Planet Around Our Nearest Solar Twin - But It Keeps Disappearing

**Astronomers using NASA's James Webb Space Telescope have discovered strong evidence of a Saturn-sized gas giant orbiting Alpha Centauri A**, our closest Sun-like star at just **4.3 light-years away**. But there's a cosmic mystery: **the planet keeps vanishing from subsequent observations**. This discovery represents potentially **the closest directly imaged exoplanet** to its host star ever detected—and could become a touchstone object for exoplanet science. Yet the disappearing act has scientists both excited and puzzled about what they're actually seeing. The breakthrough demonstrates how space telescope technology is revealing [impossible worlds that challenge our understanding](/space/toi-2431-b-impossible-planet-defies-physics-nasa-discovery), while AI systems help us [predict cosmic phenomena with unprecedented accuracy](/technology/ai-solar-storm-prediction-nyuad-breakthrough-45-percent-accuracy). ## The Hunt at Our Cosmic Doorstep **Alpha Centauri A** is effectively our Sun's twin—nearly identical in size, mass, and temperature. Using **Webb's Mid-Infrared Instrument (MIRI)** with its coronographic mask, astronomers can block the star's intense glare to hunt for much fainter planetary companions. The initial detection came in **August 2024**, when Webb spotted what appeared to be **a gas giant roughly Saturn's mass** orbiting at **1-2 times Earth's distance from the Sun**. This placed the potential planet squarely within Alpha Centauri A's habitable zone—the region where liquid water could theoretically exist. > "With this system being so close to us, any exoplanets found would offer our best opportunity to collect data on planetary systems other than our own." > > — **Dr. Charles Beichman**, Co-first author, Caltech/JPL The discovery required **extraordinarily challenging observations**. Even with the world's most powerful space telescope, detecting planets around such bright, close stars that move rapidly across the sky pushes Webb to its absolute limits. ## The Vanishing Planet Mystery Here's where the story gets strange. **Follow-up observations in February and April 2025** using Webb's Director's Discretionary Time—reserved for the most urgent discoveries—**failed to detect the planet**. > "We are faced with the case of a disappearing planet!" > > — **Aniket Sanghi**, Ph.D. student, Caltech/JPL Computer simulations suggest a solution to this cosmic hide-and-seek game. The planet likely follows **a highly elliptical orbit** that periodically brings it too close to Alpha Centauri A for Webb to distinguish from the star's glare. In roughly **half of the simulated orbital scenarios**, the planet would be invisible during the February and April observation windows. This orbital behavior—if confirmed—would challenge our understanding of planetary formation in binary star systems. The **Alpha Centauri system contains three stars**, with the red dwarf **Proxima Centauri** and **Alpha Centauri B** potentially influencing any planetary orbits through gravitational interactions. ## Breaking the Cosmic Distance Barrier The significance extends far beyond a single planet discovery. **Alpha Centauri** represents **humanity's best laboratory** for studying exoplanetary systems in detail. At **4.3 light-years away**, it's close enough for unprecedented observational precision. Any confirmed planets here would be prime targets for future interstellar missions—whether robotic probes or, eventually, crewed exploration. > "This would become a touchstone object for exoplanet science." > > — **Dr. Charles Beichman**, Caltech/JPL **Webb was originally designed to find the most distant galaxies** in the universe, not hunt for planets around nearby stars. That it can detect such objects demonstrates **revolutionary observational capabilities** that are opening entirely new frontiers in astronomy—much like how [NASA's Parker Solar Probe achieved the closest approach to any star](/space/parker-solar-probe-christmas-eve-historic-flyby) at **430,000 MPH** on Christmas Eve. The potential gas giant, while not habitable itself, could indicate additional rocky planets in the system. Many gas giants act as gravitational shepherds, protecting inner rocky worlds from asteroid impacts—exactly the configuration that may have allowed life to develop on Earth. ## The Future of Nearby Planet Hunting **NASA's Nancy Grace Roman Space Telescope**, launching **between fall 2026 and May 2027**, will conduct dedicated follow-up observations. Roman carries specialized hardware designed specifically for binary star system observations like Alpha Centauri. These next-generation observations should **definitively confirm or rule out** the planet's existence. If confirmed, it would represent a new class of detectable exoplanets—worlds orbiting our immediate stellar neighbors that were previously beyond our observational reach. The discovery methodology also opens possibilities for detecting smaller, potentially habitable rocky planets around Alpha Centauri A and other nearby Sun-like stars. Such worlds could become priority targets for the search for extraterrestrial life—research that has taken on new urgency since [NASA's emergency announcement about potential biosignatures discovered on Mars](/space/nasa-mars-emergency-discovery-biosignature). **Two peer-reviewed papers** detailing the findings have been accepted in **The Astrophysical Journal Letters**, marking the rigorous scientific validation required for such extraordinary claims. ## Rewriting Planetary Science Whether the **Alpha Centauri A planet** is ultimately confirmed or not, this detection pushes planetary science into uncharted territory. It demonstrates that habitable-zone planets around nearby Sun-like stars are within our technological reach to study. The **disappearing planet phenomenon** also highlights how much we still don't understand about planetary orbital dynamics in complex stellar systems. Real exoplanets may behave in ways that challenge our theoretical models, much like [how TOI-2431 b defies physics with its impossible 5.4-hour orbit](/space/toi-2431-b-impossible-planet-defies-physics-nasa-discovery). As Webb continues its observations and Roman Space Telescope prepares for launch, our cosmic neighborhood is about to become much more familiar—and much more interesting. ## Sources 1. [NASA's Webb Finds New Evidence for Planet Around Closest Solar Twin](https://science.nasa.gov/missions/webb/nasas-webb-finds-new-evidence-for-planet-around-closest-solar-twin/) - NASA Science 2. [NASA's Webb Finds New Evidence for Planet Around Closest Solar Twin](https://www.jpl.nasa.gov/news/nasas-webb-finds-new-evidence-for-planet-around-closest-solar-twin/) - NASA JPL 3. [James Webb Space Telescope spots a potential new exoplanet just 4 light-years away from Earth](https://www.space.com/astronomy/exoplanets/james-webb-space-telescope-spots-a-potential-new-exoplanet-just-4-light-years-away-from-earth) - Space.com 4. [Alpha Centauri Might Have a Planet, Webb Telescope Finds](https://skyandtelescope.org/astronomy-news/alpha-centauri-might-have-a-planet-webb-telescope-finds/) - Sky & Telescope 5. [The most significant JWST finding to date: James Webb telescope spots giant planet in the habitable zone](https://www.livescience.com/space/astronomy/the-most-significant-jwst-finding-to-date-james-webb-spots-then-loses-a-giant-planet-orbiting-in-the-habitable-zone-of-our-closest-sun-like-star) - Live Science