An international team of astronomers has announced an astonishing discovery - three Earth-sized planets orbiting within a rare double-star system located about 190 light-years from Earth.

The findings, published in Astronomy & Astrophysics, provide fresh insight into how planets can form and remain stable in binary systems - environments once thought too gravitationally chaotic for complex planetary systems to exist.

"Our analysis shows a unique planetary arrangement: two planets are transiting one star, and the third is transiting its companion star," said Sebastián Zúñiga-Fernández, researcher and member of the ExoTIC group at the University of Liège (ULiège) and first author of the study. "This makes TOI-2267 the first binary system known to host transiting planets around both of its stars."

The system, known as TOI-2267, is described as a compact binary - two stars locked in a tight orbit around one another, creating what is typically an unstable environment for planet formation. Yet, researchers identified three Earth-sized planets in short orbits, defying existing theories about how planets form in such dynamic conditions.

"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," explained Francisco J. Pozuelos, a former member of the ExoTIC group, now at the Instituto de Astrofísica de Andalucía (IAA-CSIC), and co-leader of the study.

"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."

Pozuelos added, "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."

The discovery raises new questions about how planets form and evolve in binary systems. Astronomers plan to conduct follow-up observations with the James Webb Space Telescope (JWST) and future generations of ground-based observatories, which could determine the planets' masses, densities, and potentially even their atmospheric compositions.