Astronomers have uncovered a planetary system around the red dwarf star LHS 1903, situated 116 light-years from Earth, that challenges established theories of planet formation due to its unconventional ‘inside out’ configuration. This discovery, made using NASA’s Transiting Exoplanet Survey Satellite (TESS) and the European Space Agency’s CHaracterising ExOPlanet Satellite (Cheops), suggests that planetary systems may form in more diverse ways than previously thought, with implications for our understanding of the universe.
The system comprises four planets orbiting LHS 1903, with the innermost being rocky, the next two gaseous, and the outermost also rocky—a sequence that contradicts the common pattern observed in our solar system and across the galaxy, where rocky planets like Earth orbit closer to their star. Researchers, led by Thomas Wilson of the University of Warwick, detailed these findings in a study published on February 12, 2026, in the journal Science, highlighting how this arrangement defies expectations based on temperature gradients during planet formation.
Typically, planets form from a disk of gas and dust around a young star, with rocky bodies emerging in hotter inner regions where volatile materials vaporize, while gas giants develop farther out beyond the ‘snow line’ where ice can condense. In the LHS 1903 system, however, the presence of a rocky super-Earth, designated LHS 1903 e, at the outer edge after two gas-rich planets upends this model, prompting scientists to investigate alternative formation mechanisms.
To explain this anomaly, the team conducted extensive dynamical analyses, testing hypotheses such as planetary collisions or atmospheric loss, but found these scenarios inadequate. Instead, they propose a ‘gas-depleted’ formation process where the planets formed sequentially from the inside out, with the outermost rocky planet developing millions of years later when the disk had insufficient gas for it to become a gas giant.
This theory suggests that the order of planet formation can vary, with LHS 1903 e’s rocky nature resulting from its late formation in a resource-scarce environment. Sara Seager, a coauthor from MIT, noted that this discovery offers some of the first evidence for flipping the script on how planets form around red dwarfs, the most common stars in the galaxy, though she emphasized that the interpretation remains open to debate.
External experts, such as Heather Knutson of Caltech, expressed intrigue, noting that LHS 1903 e could host diverse atmospheres and might be cool enough for water condensation, making it a prime target for future observations with the James Webb Space Telescope. Ana Glidden of MIT’s Kavli Institute added that the system serves as a natural laboratory for studying planet formation around stars different from our sun, potentially refining models of planetary evolution.
The findings underscore the complexity of planet formation, with Néstor Espinoza of the Space Telescope Science Institute warning that while exciting, the hypothesis requires further validation. As astronomers continue to explore exoplanetary systems, LHS 1903 provides a critical datapoint that could reshape theories, encouraging more nuanced approaches to understanding how celestial bodies assemble in diverse cosmic environments.
Ultimately, this discovery not only highlights the unpredictability of planetary systems but also opens new avenues for research, particularly in characterizing atmospheres of distant worlds and refining formation models, with the James Webb Space Telescope poised to offer deeper insights in the coming years.
