Discovery of 'Inside-Out' Planetary System Challenges Formation Theories

Astronomers have discovered a planetary system around the red dwarf star LHS 1903, located approximately 116 light-years from Earth, that challenges existing theories of planet formation. The system comprises four planets with an unusual configuration: a rocky planet closest to the star, followed by two gas-rich planets, and another rocky planet in the outermost orbit.

This arrangement contrasts with the conventional model observed in our solar system, where rocky planets are situated near the star and gas giants occupy more distant orbits. The unexpected positioning of the outermost rocky planet, LHS 1903 e, suggests that it formed after the inner planets, during a period when the protoplanetary disk had already lost much of its gas. This scenario, termed 'inside-out' formation, implies that planets can form sequentially from the inside outward, leading to diverse planetary architectures.

The discovery was made using data from NASA's Transiting Exoplanet Survey Satellite (TESS) and the European Space Agency's CHaracterising ExOPlanet Satellite (Cheops). The findings suggest that planet formation processes may be more varied than previously thought, particularly around red dwarf stars, which are the most common type in the universe.