James Webb Telescope Finds Gas Giant Orbiting Alpha Centauri A

Updated on: August 8, 2025 | By: Jameswebb Discovery Editorial Team

The James Webb Space Telescope (JWST), NASA’s most advanced space observatory, has made a groundbreaking discovery: strong evidence of a gas giant planet, roughly the mass of Saturn, orbiting Alpha Centauri A, the closest Sun-like star to Earth at just 4 light-years away. This finding, announced on August 7, 2025, marks a significant milestone in the search for exoplanets and could reshape our understanding of planetary systems beyond our own. At JamesWebbDiscovery.com, we’re dedicated to tracking every awe-inspiring discovery from the JWST, and this potential planet in the Alpha Centauri system is one of the most exciting yet.

A Historic Discovery in Our Cosmic Backyard

The Alpha Centauri system, located in the southern constellation Centaurus, is the closest stellar system to our Sun. It consists of three stars: Alpha Centauri A, a Sun-like star and the third brightest in the night sky; Alpha Centauri B, another Sun-like star; and Proxima Centauri, a faint red dwarf known to host three confirmed planets. While Proxima Centauri has been a focal point for exoplanet discoveries, detecting planets around the brighter Alpha Centauri A and B has proven challenging due to their intense brightness and rapid movement across the sky. Using its Mid-Infrared Instrument (MIRI), the JWST has provided the strongest evidence to date of a gas giant orbiting Alpha Centauri A. This planet candidate, if confirmed, would be the closest exoplanet to Earth orbiting in the habitable zone of a Sun-like star. However, as a gas giant similar to Jupiter or Saturn, it is unlikely to support life as we know it. The discovery, detailed in two papers accepted by The Astrophysical Journal Letters, highlights the JWST’s unparalleled ability to observe faint objects near bright stars.

How Webb Uncovered the Planet Candidate

Detecting a planet around a star as bright as Alpha Centauri A required innovative techniques and meticulous planning. In August 2024, the JWST team used MIRI’s coronagraphic mask to block the star’s intense glare, revealing an object over 10,000 times fainter than Alpha Centauri A. This object, labeled “S1,” is separated from the star by approximately twice the distance between Earth and the Sun. The team conducted additional observations in February and April 2025, but the object was not detected in these follow-ups, leading to the intriguing case of a “disappearing planet.”To investigate, researchers led by Charles Beichman of NASA’s Jet Propulsion Laboratory and PhD student Aniket Sanghi of Caltech ran millions of orbital simulations. These models incorporated a 2019 sighting by the European Southern Observatory’s Very Large Telescope, the JWST data, and gravitational stability in the presence of Alpha Centauri B. The simulations suggest that the planet follows an elliptical orbit, varying between 1 to 2 times the Earth-Sun distance, and was likely too close to the star to be visible during the later observations. This explains the non-detections and strengthens the case for a real planetary object.

What Makes This Discovery Significant?

This potential gas giant is a game-changer for exoplanet science for several reasons:

1. Proximity to Earth: At just 4 light-years away, this planet would be the closest directly imaged exoplanet to Earth, offering unprecedented opportunities for detailed study.

2. Orbiting a Sun-like Star: Unlike most directly imaged exoplanets, which orbit far from their stars, this candidate is relatively close to Alpha Centauri A, making it more comparable to the giant planets in our solar system.

3. Challenging Planet Formation Theories: The presence of a planet in a binary star system like Alpha Centauri, with two closely separated stars, challenges existing models of how planets form and survive in such dynamic environments.

4. Future Observations: If confirmed, this planet could become a prime target for further study by the JWST and upcoming observatories like NASA’s Nancy Grace Roman Space Telescope, set to launch by May 2027. The Roman Telescope’s visible light observations could complement Webb’s infrared data, providing insights into the planet’s size, reflectivity, and atmospheric composition.

The Role of JWST’s Advanced Technology

The JWST’s ability to detect this faint planet candidate is a testament to its cutting-edge technology. The MIRI instrument, equipped with a coronagraphic mask, was critical in blocking Alpha Centauri A’s light to reveal the faint signal of the potential planet. However, the nearby Alpha Centauri B and the telescope’s optics created complex light patterns, making the detection challenging. The team used reference images and algorithms to subtract these patterns, isolating the planet candidate in the August 2024 observation.The Space Telescope Science Institute developed a custom observing sequence to account for the brightness and rapid motion of the Alpha Centauri system. This precision underscores why the JWST is the world’s premier space science observatory, capable of probing not only distant galaxies but also nearby planetary systems.

What’s Next for the Alpha Centauri Planet Candidate?

While the evidence is compelling, the planet’s existence requires confirmation through additional observations. The research team plans to continue monitoring the Alpha Centauri system with the JWST to track the planet’s orbit and confirm its presence. The Nancy Grace Roman Space Telescope, with its advanced coronagraphic capabilities, will also play a key role in future studies, potentially providing a clearer picture of this intriguing world.If confirmed, this gas giant could become a “touchstone object” for exoplanet science, offering a unique opportunity to study a planet in a system so close to our own. Its discovery would also highlight the chaotic yet fascinating nature of planet formation in binary star systems, paving the way for new theories and discoveries.

Why Follow James Webb Telescope Discoveries?

The discovery of a potential gas giant in the Alpha Centauri system is just one of many remarkable findings from the JWST. At JamesWebbDiscovery.com, we’re committed to bringing you the latest updates on all JWST discoveries, from exoplanets to distant galaxies. By following our site, you’ll stay informed about the telescope’s mission to unravel the mysteries of the universe, including:

• New exoplanet discoveries and their implications for life beyond Earth.

• Insights into the formation of stars, planets, and galaxies.

• Stunning images and data that reveal the beauty and complexity of the cosmos.

Stay Updated with JamesWebbDiscovery.com

The James Webb Space Telescope is transforming our understanding of the universe, and JamesWebbDiscovery.com is your go-to source for tracking its discoveries. Visit our site regularly for detailed articles, updates, and insights into the JWST’s mission. Whether you’re an astronomy enthusiast or a curious explorer, our content is designed to inspire and inform.