CHEOPS Finds Rocky Planet in LHS 1903
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- CHEOPS detected a fourth planet, LHS 1903e, in the LHS 1903 system in 2026, adding to three inner planets previously found by TESS between 2019‑2023.
- LHS 1903e is a rocky world orbiting at 0.15 AU with a 29‑day period, placing it beyond two mini‑Neptune gas dwarfs (c and d) and within Mercury’s orbital distance.
- Gaia astrometry data ruled out additional gas giants farther out, confirming the compact architecture of the system.
- Monika Lendl (UNIGE) said the planet’s existence “completely overturns our theories” because rocky planets are not expected to form beyond gas giants.
- Yann Alibert (UNIBE) proposed the planet formed after the protoplanetary disk’s gas had vanished, leaving it gas‑depleted and explaining its rocky composition.
- Science published the study (Thomas G. Wilson et al., 2026) reporting that the LHS 1903 system’s architecture challenges traditional models that place gas giants only beyond rocky worlds.
Why it matters: The discovery overturns the prevailing view that rocky planets form only interior to gas giants, compelling planetary scientists to revise formation models that assume a temperature‑driven separation of rock and gas. This reshapes how researchers interpret compact exoplanetary systems and guides future observational strategies.
