Hydrogen sulfide detected in distant gas giant exoplanets for the first time

Using JWST spectra and new analysis techniques, astronomers identified hydrogen sulfide in the atmospheres of four gas giants orbiting HR 8799, and concluded the sulfur was delivered as solid material during planet formation.

Astronomers report the first detection of hydrogen sulfide in the atmospheres of four distant gas giant exoplanets. The planets orbit the star HR 8799, about 133 light-years from Earth, and span roughly five to ten times the mass of Jupiter. The team used spectral data from the James Webb Space Telescope alongside new data-analysis methods to isolate the faint planetary signals from the much brighter host star. The finding offers new evidence about how these large planets collected heavy elements during their formation. Key findings: - Hydrogen sulfide (H2S) was identified in the atmospheres of four gas giants around HR 8799 using JWST spectra. - The planets are about 5–10 times the mass of Jupiter and orbit far from their star; the closest lies near 15 times Earth’s orbital distance. - Researchers developed analysis techniques to extract signals that are roughly 10,000 times fainter than the host star. - The team infers the sulfur was accreted as solids in the protoplanetary disk and later evaporated into gas as the young planets heated. - The pattern of heavy-element enrichment (carbon, oxygen, sulfur, nitrogen) resembles that seen in Jupiter and Saturn. Summary: The detection supports a formation pathway in which these gas giants accumulated solid material that released sulfur into their atmospheres as they heated. Researchers say the spectral separation method will improve detailed studies of distant exoplanets and could be applied to smaller, terrestrial worlds as telescopes and instruments advance.