Using the James Webb Space Telescope a research team at Johns Hopkins University discovered that an exoplanet, notorious for its extreme weather, has a surprising feature—it smells like rotten eggs. Interestingly, the presence of this foul odour is more than just a curious fact.
An artist’s impression of exoplanet HD 189733 b - (Image Credit: Roberto Molar Candanosa/Johns Hopkins Univeristy)
The Stench of Rotten Eggs
In their publication in the peer-reviewed science journal Nature, the team explains that HD 189733 b, a Jupiter-sized exoplanet, has trace amounts of hydrogen sulphide in its atmosphere. This molecule, known for its characteristic foul odour similar to that of rotten eggs, provides new insights into the role of sulphur, a crucial element in planetary formation.
According to Guangwei Fu, the lead astrophysicist on the study, “Hydrogen sulphide 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.”
At only 64 light-years away, HD 189733 b is the closest "hot Jupiter" to Earth that can be observed passing in front of its star. This proximity makes it a valuable subject for studying exoplanetary atmospheres. Fu's team also measured the planet's oxygen and carbon sources, including water, carbon dioxide, and carbon monoxide, offering a more comprehensive understanding of its atmospheric composition.
Heavy metals
The researchers also observed levels of heavy metals similar to those found on Jupiter, a discovery that could help scientists understand how a planet’s metallicity correlates with its mass.
Less massive giant icy planets, such as Neptune and Uranus, have higher metal content compared to gas giants like Jupiter and Saturn, the largest planets in our solar system. This higher metallicity indicates that Neptune and Uranus accumulated more ice, rock, and other heavy elements relative to gases like hydrogen and helium during their early formation. Scientists are now investigating whether this correlation also applies to exoplanets
A closeup of Neptune’s atmosphere, as taken by the Voyager 2 spacecraft - (Image Credit: NASA/Jet Propulsion Lab)
Implications for Planetary Formation
“Say we study another 100 hot Jupiter’s and they're all sulphur enhanced. What does that mean about how they were born and how they form differently compared to our own Jupiter?” Fu said
The detection of hydrogen sulphide and the measurement of heavy metals in HD 189733 b’s atmosphere have broader implications for understanding planetary formation. “Sulphur is a vital element for building more complex molecules,” Fu explained. The study also ruled out the presence of methane with high precision, challenging previous assumptions about the planet’s atmospheric composition.
The findings on HD 189733 b add a piece to the puzzle of how gas giants form and evolve, helping scientists understand the differences in planetary formation within and beyond our solar system. Fu and his team plan to continue tracking sulphur in other exoplanets to explore how this element influences their formation and characteristics.
If you are interested in more details about this discovery be sure to check out the article published in Nature, listed below.
Sources and further reading:
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