#^TESS finds three Earth-sized exoplanets orbiting binary stars
Through international collaboration, a team of astronomers has confirmed two exoplanets and found hints of a third exoplanet at a binary star system known as TOI-2267. The planets were first found by NASA’s Transiting Exoplanet Survey Satellite (TESS), using the team’s own exoplanet detection software. This tantalizing find might provide new insights into planet formation in binary systems.
TESS launched atop a SpaceX Falcon 9 in 2018 to study exoplanets that transit their star from our perspective, meaning they pass between their star and the TESS. These transits slightly dim the starlight that reaches the telescope, allowing astronomers to detect these planets through the changing light signal.
“Our analysis shows a unique planetary arrangement: two planets are transiting one star, and the third is transiting its companion star,” said the study’s first author, Sebastián Zúñiga-Fernández of the University of Liège (ULiège), Belgium. “This makes TOI-2267 the first binary system known to host transiting planets around both of its stars.”
The TOI-2267 system, located about 72 light-years from Earth, consists of two red dwarf stars, separated by 8 astronomical units (AU), or eight times the distance between Earth and the Sun.
TESS observed the system multiple times in 2019 and 2020. Originally, these observations resulted in the discovery of one exoplanet in the system, with an orbital period of roughly 3.5 Earth days. The team used its own software, named SHERLOCK to reprocess TESS’s observations and found two additional planets with orbital periods of 2.03 and 2.28 days. However, the astronomers could not fully confirm the existence of the latter.
To investigate the binary system’s layout, the team ran simulations that suggested the system can only be stable if the three planets do not all orbit the same star.
See Also
“Our discovery breaks several records, as it is the most compact and coldest pair of stars with planets known, and it is also the first in which planets have been recorded transiting around both components,” said co-lead Francisco J. Pozuelos, of the Instituto de Astrofísica de Andalucía (IAA-CSIC) in Granada, Spain.
Following their discovery of the two additional planets, the astronomers returned to TESS for confirmation. The telescope had also visited the system during its extended mission and observed it eight more times from 2021 through 2024. The team reanalyzed the original findings and five new observations with the software that originally detected only one exoplanet. This time, the results matched SHERLOCK’s findings.
While TESS indicated the presence of planets at TOI-2267, the telescope’s findings alone were not sufficient to confirm the planets. This follows from TESS’s limited ability to resolve fine details. The telescope’s pixels cover a large area of the sky, which increases the risk of signal contamination from nearby stars.
To further confirm the existence of these exoplanets, the team used ground-based telescopes, including the Search for habitable Planets EClipsing ULtra-cOOl Stars (SPECULOOS) North Observatory at the Teide Observatory in Tenerife and the Transiting Planets and Planetesimals Small Telescope (TRAPPIST) North at the Oukaïmeden Observatory in Morocco.
Archival images for TOI-2267. The red circle indicates the system’s position on Nov. 9, 2022. (Credit: Zúñiga-Fernández et al.)
Moreover, the team analyzed archival imagery, dating back as far as 1955, to exclude contamination from background objects in the system’s current position.
These additional observations corroborated TESS’s findings of two exoplanets at the TOI-2267 system but failed to confirm the presence of a third. The team had a further opportunity to search for the third exoplanet but could not find it due to suboptimal instruments and exposure time. With insufficient data to verify the final planet, the team instead used the observations to search for potential objects that could have caused incorrect TESS readings, but found none.
Although confident in the uncontaminated nature of TESS’s findings, the astronomers refuse to claim a third planet exists without further research.
If a follow-up study confirms TESS’s findings, the TOI-2267 system is rather unique. The team’s simulations suggest that the two already confirmed planets must orbit the same star, while the third, currently unconfirmed, planet would orbit the other. Any other configuration was unstable and could not exist for a long time.
Comparison between several binary systems with confirmed exoplanets, arranged by distance between the stars. (Credit: Zúñiga-Fernández et al.)
Moreover, the binary stars are close together, challenging earlier studies suggesting close stellar companions may stop planets from forming or prevent their survival. Instead, the newly discovered planets hint that rocky planets could be common in such systems than previously thought.
“This system is a true natural laboratory for understanding how rocky planets can emerge and survive under extreme dynamical conditions, where we previously thought their stability would be compromised,” said Pozuelos.
The astronomers want to further study the TOI-2267 system with space telescopes, including Hubble and the James Webb Space Telescope. Not only could these follow-up studies confirm the existence of the third planet, but they could also help identify which planets orbit each star.
“Discovering three Earth-sized planets in such a compact binary system is a unique opportunity,” said Zúñiga-Fernández. “It allows us to test the limits of planet formation models in complex environments and to better understand the diversity of possible planetary architectures in our galaxy.”
Zúñiga-Fernández et al.’s findings were published in the journal Astronomy & Astrophysics on Oct. 24, 2025.(Lead image: Illustration of the TOI-2267 system, depicting its two binary red dwarfs and three exoplanets in the most probable configuration. Credit: Mario Sucerquia (University of Grenoble Alpes))The post
TESS finds three Earth-sized exoplanets orbiting binary stars appeared first on
NASASpaceFlight.com.
