The planetary candidate, Alpha Centauri AB, may be a gas giant orbiting at a distance of one to two times that of the Earth from the Sun, as indicated in two research papers. Astrophysics Journal Letter. If verified, this planet would be the closest known to Earth within the habitable zone of a Sun-like star. Nonetheless, since it is a gas giant, astronomers do not believe it could support life as we understand it.
Artist’s rendering of the gas giant Alpha Centauri A. Image credits: NASA/ESA/CSA/STSCI/Robert L. Hurt, Caltech & IPAC.
Alpha Centauri resides in the Centaurus constellation and represents the nearest star system to Earth.
Also referred to as Rigil Centaurus, Rigil Kent, and Griese 559, this system includes a bright binary star pair, Alpha Centauri A and Alpha Centauri B, alongside a fainter red star known as Alpha Centauri C.
The two prominent stars are approximately 4.35 light-years away, while Alpha Centauri C, commonly called Proxima Centauri, is slightly nearer at about 4.23 light-years.
In comparison to the Sun, Alpha Centauri A is a G2-type star similar in nature, but slightly larger (1.1 times the size of the Sun and around 1.5 times its luminosity).
Alpha Centauri B, classified as a K1-type star, is slightly smaller and less luminous (approximately 0.9 times the mass of the Sun, with about 45% of its visual brightness).
These two stars orbit around a common center of gravity approximately every 80 years, maintaining a minimum distance of about 11 times that of the Earth-Sun distance.
Astronomers study these stars closely along with our nearest interstellar neighbor, Proxima Centauri, making them prime targets in the search for potentially habitable planets.
“This proximity offers the best chance to gather data on planetary systems beyond our own,” stated Dr. Charles Beichman from NASA’s Jet Propulsion Laboratory and the Exoplanet Science Institute at IPAC Astronomy Center in California.
“However, the brightness and swift motion of these stars present significant challenges in observation, even for the world’s most advanced space telescopes.”
The Alpha Centauri star system captured by different terrestrial and space-based observatories: DSS, Hubble Space Telescope, and James Webb Space Telescope. While the DSS shows the triple system as one light source, Hubble distinguishes between Alpha Centauri A and B. Webb’s Milimask image mitigates glare from Alpha Centauri A via a coronagraphic mask. Image credits: NASA/ESA/CSA/ANIKET SANGHI, CALTECH/CHAS BEICHMAN, NEXSCI, NASA & JPL-CALTECH/DIMITRI MAWET, CALTECH/JOSEPH DEPASQUALE, STSCI.
The first observations of this system occurred in August 2024, employing a Coronagraphic Mask with Webb’s Mid-Infrared Instrument (MIRI) to reduce the brightness of Alpha Centauri A.
The presence of nearby companion star Alpha Centauri B added complexity to the analysis, but astronomers successfully subtracted the light from both stars, uncovering objects that were more than 10,000 times dimmer than Alpha Centauri A.
On the other hand, an initial detection was promising, but further data was required for a definitive conclusion.
However, subsequent observations in February and April of 2025 did not unveil any objects akin to those detected in August 2024.
“We are facing a case of disappearing planets,” remarked Dr. Aniket Sangi from Caltech.
“To unravel this mystery, we employed computer models simulating millions of potential orbits, taking into account the insights gained from observing planets and their absence.”
In the simulations, the team incorporated the 2019 sightings of potential exoplanet candidates reported by the ESO’s Very Large Telescope, alongside new data from Webb, considering the gravitational stability of orbits influenced by Alpha Centauri B.
“The non-detections in the second and third rounds with Webb were not unexpected,” stated Sangi.
“In many simulated orbits, the planet was positioned too close to the star, rendering it invisible to Webb during both February and April 2025.”
“Based on mid-infrared observations of planetary brightness and orbital simulations, this gas giant could have a mass similar to Saturn, orbiting Alpha Centauri A at a distance one to two times greater than that between the Sun and Earth.”
“If confirmed, the potential planets identified in Webb’s Alpha Centauri images will represent a significant milestone in exoplanet imaging efforts,” Sangi added.
“Of all directly imaged planets, this would be the closest star we have ever observed.”
“Moreover, it would be the nearest to our home, with gas giants in our solar system that are similar in temperature and age to Earth.”
“The mere existence of two closely separated star systems poses intriguing challenges to our understanding of planetary formation, survival, and evolution within chaotic environments.”
If substantiated by further observations, these findings could reshape the field of exoplanet science.
“This will become a pivotal object in exoplanet research, offering multiple opportunities for detailed characterization by Webb and other observatories,” Dr. Beichman concluded.
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Charles Beichman et al. 2025. The Neighbor World: Imaging a giant planet candidate, orbital and physical properties of CEN A, and habitable zones at the exozodiacal upper limit. ApJL in press; Arxiv: 2508.03814
Aniket Sangi et al. 2025. The Neighbor World: Imaging a giant planet candidate in the habitable zone of Cen A. II. Binary Star Modeling, Planetary and Exozodiacal Search, and Sensitivity Analysis. ApJL in press; Arxiv: 2508.03812
Source: www.sci.news
