WASHINGTON—HD 189733b, a planet discovered in 2005, is known for its extreme conditions. This scorching hot gas giant, slightly larger than Jupiter, is a vivid cobalt blue color with sideways blowing molten glass rain in its intense atmospheric winds. But now, researchers have found a way to top that.
By adding hydrogen sulfide—the compound responsible for the smell of rotten eggs. Data from the James Webb Space Telescope has revealed new insights into HD 189733b, one of the most extensively studied exoplanets (planets outside our solar system). For the first time, a trace amount of hydrogen sulfide has been detected in its atmosphere.
“The addition of the stinky smell would certainly enhance its already notorious reputation. While it may not be a planet fit for human exploration, it is a valuable asset for advancing our knowledge of planetary science,” said astrophysicist Guangwei Fu of Johns Hopkins University, the lead author of the study published in the journal Nature.
HD 189733b is classified as a “hot Jupiter”—gas giants similar to Jupiter but much hotter due to their close proximity to their host stars. This particular planet orbits its host star 170 times closer than Jupiter does to the sun, completing one orbit every two days compared to Jupiter’s 12-year orbit.
Its orbit is even closer to its host star than Mercury is to the sun, resulting in temperatures reaching about 1,700 degrees Fahrenheit (930 degrees Celsius) on the side facing the star.
“Hot Jupiters are quite rare, with less than one in 100 star systems having them,” Mr. Fu explained.
Located 64 light-years from Earth in the constellation Vulpecula within the Milky Way galaxy, this planet is considered relatively close for detailed studies. The star it orbits is smaller and cooler than the sun and is part of a binary system.
The James Webb Space Telescope, operational since 2022, has enabled researchers to conduct more thorough examinations of exoplanet atmospheres by observing a wider range of wavelengths.
“Our research indicates that HD 189733b is more similar to Jupiter than previously thought. Despite the similarities, this planet is hotter than Jupiter,” said Luis Welbanks, an astrophysicist at Arizona State University and co-author of the study.
In addition to hydrogen sulfide, the Webb observations also detected water and carbon dioxide in the planet’s atmosphere, confirming earlier data.
“By analyzing these molecules, we can determine the amounts of oxygen, carbon, and sulfur present on the planet, providing insights into its formation and differences from planets in our solar system,” Mr. Welbanks explained.
Furthermore, the observations ruled out the presence of methane in the planet’s atmosphere.
“Understanding the composition of exoplanets like HD 189733b helps us appreciate the uniqueness of our solar system and contextualize our existence,” Mr. Welbanks added.
“While we are not actively searching for life on HD 189733b due to its extreme conditions, studying its atmosphere allows us to explore the behavior of physics and chemistry in diverse environments and piece together the ‘recipe’ for planet formation,” he concluded.
By Will Dunham