Webb Discovers Evidence of Giant ‘Disappearing’ Planet Nearby

Key Takeaways

1. Alpha Centauri is a triple star system located four light-years from Earth, consisting of stars Alpha Centauri A, B, and Proxima Centauri.
2. The Webb Space Telescope detected a potential gas giant planet orbiting Alpha Centauri A, likely similar in mass to Saturn.
3. The planet is believed to have an elliptical orbit, varying in distance from one to two times that of Earth to the Sun.
4. Initial detection of the planet occurred in August 2024, but subsequent searches in early 2025 were unsuccessful, possibly due to the planet’s proximity to the star at those times.
5. Future observations, including data from the upcoming Nancy Grace Roman Space Telescope, may provide more insights into the planet’s existence and characteristics.

Alpha Centauri is a triple star system located just four light-years from Earth, which has captured the attention of astronomers searching for exoplanets. The system consists of three stars: Alpha Centauri A and B, both resembling our Sun, and Proxima Centauri, a dim red dwarf star. Studies have confirmed that there are three planets orbiting Proxima Centauri. However, detecting planets around Alpha Centauri A and B has proven difficult due to their brightness.

Webb’s Discovery

Recently, the Mid-Infrared Instrument on the Webb Space Telescope has detected signs of a planet orbiting Alpha Centauri A. The image captured by Webb, along with analysis from a research team and computer simulations, indicates that this planet may be a gas giant similar in mass to Saturn. It is thought to travel in an elliptical orbit, with distances ranging from one to two times that of the Earth to the Sun.

To identify this planet, Webb used a coronagraphic mask with its MIRI to block the light from Alpha Centauri A. Additional work by the research team helped to filter the light from Alpha Centauri B, uncovering an object that is 10,000 times dimmer than Alpha Centauri A and is believed to be a planet.

Challenges and Future Prospects

The first detection of this planet occurred in August 2024. However, subsequent attempts in February and April 2025 were unsuccessful in finding similar objects. “It’s like we’re dealing with a vanishing planet,” stated Aniket Sanghi, a PhD student at Caltech and co-first author of two papers detailing the research. Simulations have indicated that the planet’s closeness to the star during the observations in February and April may explain why Webb couldn’t locate it.

Looking ahead, future observations, which may include data from the upcoming Nancy Grace Roman Space Telescope, might shed more light on this mysterious planet.

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