HIP 41378 f

HIP 41378 f is an exoplanet orbiting around the F-type [main sequence star|F-type] star HIP 41378. It is the outermost planet of its system and notable for the possibility that the planet may host circumplanetary debris rings. It is located within the Circumstellar [habitable zone|optimistic habitable zone] of its parent star.
A 2023 study analyzed the orbital stability and detectability of a hypothetical Mars-sized exomoon orbiting HIP 41378 f, finding that the existence of such a moon is feasible but is currently unlikely to be detectable.

Potential ring system

HIP 41378 f has an anomalously large radius for a planet of its size and temperature. This radius, combined with its measured mass of, suggest that its core has a maximum mass of 3 and subsequently the planet has an envelope fraction of 75% or greater. This envelope fraction is larger than would be possible in the core accretion model of planet formation for a planet with its core mass, which is consistent with the hypothesis that the planet's radius may be observed to be larger than it actually is due to an optically thick ring system. Said ring system would have a density roughly equivalent to that of water, indicating that if it exists it is composed of porous rocky material. One proposed origin for such a ring system is an exomoon, which migrated outwards and had its eccentricity raised until it got tidally disrupted. No atmospheric signatures were found as of 2022, further reinforcing the hypothesis of opaque circumplanetary rings.