Astronomers Detect Hydrogen Sulfide in Distant Exoplanets

Discovery provides clues about how gas giants form and could aid search for Earth-like exoplanets

Published on Feb. 12, 2026

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UCLA and UC San Diego astronomers have detected hydrogen sulfide gas in the atmospheres of four distant, Jupiter-like exoplanets orbiting the star HR 8799, located about 133 light-years away. The presence of this sulfur-containing gas provides insights into how these massive gas giants formed, as the sulfur had to have come from solid matter in the disk around the star. The new detection technique used by the researchers will also help improve the search for Earth-like exoplanets in the future.

Why it matters

The discovery of hydrogen sulfide in these distant exoplanets solves a mystery about how some gas giants form, as the sulfur had to have come from solid matter in the disk around the star rather than just gas. Additionally, the new detection method used by the researchers will aid the search for Earth-like exoplanets by allowing astronomers to study distant planets in clear detail.

The details

The four exoplanets orbiting HR 8799 are each between 5 and 10 times more massive than Jupiter. Using spectral data from the James Webb Space Telescope, the researchers were able to identify the presence of hydrogen sulfide in the planets' atmospheres. This indicates that the sulfur was accreted from solid matter in the disk around the star, rather than just gas, as the sulfur could not have been present as a gas at the planets' distance from the star. The researchers also developed new data analysis techniques to extract the weak signal of the planets from the much brighter host star.

  • The research paper announcing these discoveries was published in Nature Astronomy on February 12, 2026.

The players

Jerry Xuan

A postdoctoral researcher at UCLA and first co-author of the paper.

Jean-Baptiste Ruffio

A research scientist at UC San Diego and first co-author of the paper.

HR 8799

The star around which the four exoplanets orbit, located approximately 133 light-years away in the constellation Pegasus.

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What they’re saying

“The boundary between star formation and planet formation is quite fuzzy at these middle mass ranges. The definition that says a brown dwarf is an object more massive than 13 Jupiter masses is fairly arbitrary. It's not based on knowledge of how planets and stars form.”

— Jerry Xuan, Postdoctoral researcher at UCLA (Nature Astronomy)

“Finding an Earth analog is the holy grail for exoplanet search, but we're probably decades away from achieving that. But maybe in 20-30 years, we'll get the first spectrum of an Earth-like planet and search for biosignatures like oxygen and ozone in its atmosphere.”

— Jerry Xuan, Postdoctoral researcher at UCLA (Nature Astronomy)

What’s next

The researchers plan to continue using the new detection technique to study other distant exoplanet systems in order to better understand planet formation and identify potential Earth-like worlds.

The takeaway

This discovery of hydrogen sulfide in distant exoplanets not only provides insights into how gas giants form, but also demonstrates a powerful new technique that will aid the search for Earth-like exoplanets in the coming decades.