Chemical Traces in the HR 8799 System: Core Accretion vs. Gravitational Instability A UC San Diego led team used JWST spectral data to detect hydrogen sulfide (H2S) in the atmosphere of HR 8799c. These gas giants are 5-10x the mass of Jupiter. The presence of sulfur is strong evidence that objects of this mass can still form via "core accretion." Traditional planet formation models are being redefined.