Astronomers have discovered a planetary system 116 light-years from Earth that challenges conventional understanding of planetary formation. The system, designated LHS 1903, features an unusual configuration: rocky planets both near and far from its host star, a modest, cool red dwarf.
The discovery, detailed in a study published in Science, centers on LHS 1903, observed using data from the European Space Agency’s (ESA) CHEOPS satellite. Initial observations revealed a system resembling our own, with inner rocky planets and outer gas giants. However, CHEOPS data confirmed that the outermost planet in the system is also rocky, a configuration that deviates from established planetary formation theories.
“This strange arrangement makes it a unique system,” said Thomas Wilson, the lead author of the study, from the University of Warwick. “Rocky planets are not usually formed far from their star, outside of the gas giants.”
Current theories suggest that planets close to a star tend to be rocky because stellar radiation strips away their atmospheres. Gas giants, conversely, form further out where lower temperatures allow them to retain gas. The existence of a rocky planet so distant from LHS 1903 suggests that planetary formation can occur even in gas-poor environments, or that the planet may have lost its atmosphere.
Researchers initially considered several hypotheses to explain the system’s unusual structure, including the possibility that planets had migrated from their original positions or that the outermost rocky planet had lost its atmosphere through collision. However, evidence indicated that the four planets formed sequentially, from the inside out. This stepwise formation suggests that each planet evolved in a different environment and by the time the outermost rocky planet formed, the system may have been depleted of gas, hindering the formation of gas giants.
“When this last outer planet formed, the solar system may have run out of gas, which is considered crucial for planet formation,” Wilson explained. “We have found the first evidence of a planet formed in a gas-poor environment.”
The discovery prompts a reevaluation of existing planetary formation models, which have historically been based on observations of our own solar system. “Historically, our theories about planet formation have been based on what we see and know about our own Solar System,” said Isabel Rebollido, a researcher at the ESA. “As we observe more exoplanetary systems, we are beginning to revise our theories based solely on it.”
In February 2026, NASA confirmed the passage of an interstellar comet through the solar system, a separate but contemporaneous observation highlighting the diversity of celestial bodies and systems beyond our own. Astronomers continue to refine methods for detecting exoplanets, relying on observing stellar wobbles, blueshifts, and transits, as even the most powerful telescopes cannot directly image these distant worlds. In late 2025, Elon Musk’s Tesla Roadster, carrying the mannequin “Starman,” completed its deep-space journey, offering a unique, if unconventional, marker of human exploration beyond Earth.
Jupiter’s existence has been credited with protecting Earth from extinction-level events, a factor that underscores the importance of understanding planetary system dynamics. A recent study also suggested that a small asteroid that visited Earth may be a fragment of lunar rock, further demonstrating the complex interactions within our solar system.
Further research is planned to investigate the atmospheric composition of the planets in the LHS 1903 system, which may provide additional clues about their formation, and evolution.
