Researchers discovered hydrogen sulfide in its atmosphere which smells of rotten eggs, making it similar to Jupiter.


Researchers have uncovered evidence that an exoplanet could smell of rotten eggs to the human nose in the first discovery of its kind outside our solar system.

Exoplanet HD 189733 b, which is located around 65 light-years away from Earth, was discovered in 2005. 

It’s part of the Hot Jupiter class which includes the giant planets made of gas, making them physically similar to Jupiter.

The team of researchers from Johns Hopkins University in the US determined that the exoplanet’s atmosphere contained hydrogen sulfide using data from James Webb Space Telescope, a powerful tool for studying exoplanets.

Jupiter’s atmosphere also contains trace amounts of hydrogen sulfide.

Researchers used the near-infrared camera of the telescope which analyses the transit, the moment when an exoplanet passes directly in front of its host star by looking at the starlight that filters through the exoplanet’s atmosphere. 

Different gases within the atmosphere absorb specific wavelengths of light, leaving dips in the overall spectrum, revealing the composition of the exoplanet’s atmosphere.

The team published their findings in Nature

“Hydrogen sulfide is a major molecule that we didn’t know was there. We predicted it would be, and we know it’s in Jupiter, but we hadn’t really detected it outside the solar system,” Guangwei Fu, an astrophysicist at Johns Hopkins and one of the study’s authors said in a statement

“We’re not looking for life on this planet because it’s way too hot, but finding hydrogen sulfide is a stepping stone for finding this molecule on other planets and gaining more understanding of how different types of planets form,” he added.

The team also measured the main sources of the planet’s key oxygen and carbon compounds: water, carbon dioxide, and carbon monoxide.

“Sulfur is a vital element for building more complex molecules, and – like carbon, nitrogen, oxygen, and phosphate – scientists need to study it more to fully understand how planets are made and what they’re made of,” Fu said.

New information about how planets form

The team also found levels of heavy metals similar to those on Jupiter. 

Scientists are studying the connection between a planet’s mass and the amount of heavy metals it contains.

Smaller icy giants like Neptune and Uranus have more metals than larger gas giants like Jupiter and Saturn. 

This suggests they incorporated more ice, rock, and other heavy elements during their formation.

“This Jupiter-mass planet is very close to Earth and has been very well studied. Now we have this new measurement to show that indeed the metal concentrations it has provide a very important anchor point to this study of how a planet’s composition varies with its mass and radius,” Fu said. 

“The findings support our understanding of how planets form through creating more solid material after initial core formation and then are naturally enhanced with heavy metals”.


Researchers plan to investigate sulfur in more exoplanets and see how it might influence how close they form to their stars.

“We want to know how these kinds of planets got there, and understanding their atmospheric composition will help us answer that question,” Fu added.

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