Universality of delayed methane onset in low-gravity objects

Determine whether the 3.4 micrometer hydrocarbon feature is common among low-luminosity star-forming regions and whether delayed methane onset is universal in low-surface-gravity objects.

Background

After masking the unknown 3.4 micrometer hydrocarbon feature, the IC 348 objects show little or no methane absorption down to effective temperatures of approximately 890 K. This behavior is consistent with the gravity-dependent methane delay inferred for transiting planets and young directly imaged companions.

The available IC 348 sample cannot establish whether this behavior is a general property of low-gravity atmospheres or whether the hydrocarbon contaminant occurs broadly in comparable star-forming regions. The authors identify further spectroscopic observations as necessary to resolve both questions.

References

Additional spectroscopic observations of low-luminosity star-forming regions will be highly informative on whether the hydrocarbon feature is common and if the delayed methane onset is universal in low surface gravity objects.

— JWST color sequence of transiting exoplanets and directly imaged substellar objects  (2608.25993 - Fu et al., 26 Aug 2026) in Section 3.4, subsection “IC 348 star forming region objects”