Exoplanet HD 189733 b Exhibits Rotten Egg Odor Due to Hydrogen Sulfide
Exoplanet HD 189733 b, notorious for its extreme weather conditions such as rain composed of glass and scorching temperatures exceeding 900 degrees Celsius, has revealed another peculiar trait: it reeks of rotten eggs. This discovery was made by scientists at Johns Hopkins University.
The gas giant, comparable in size to Jupiter, possesses an atmosphere containing traces of hydrogen sulfide. This compound not only exudes a foul smell but also offers scientists valuable insights into the role of sulfur, a fundamental element for life, in shaping the atmospheres of gas planets beyond our solar system.
Insights from Hydrogen Sulfide
“Hydrogen sulfide is an essential gas that we had suspected to be present on this exoplanet, especially since it’s found on Jupiter as well,” explained Guangwei Fu, the lead researcher and an astrophysicist at Johns Hopkins University. “Although we are not looking for life on this planet due to its extreme heat, the detection of hydrogen sulfide sets a precedent for identifying this gas on other planets, enhancing our understanding of planetary formation.”
Utilizing the James Webb Space Telescope, scientists were able to detect hydrogen sulfide and measure the total sulfur content in the atmosphere. They also identified primary sources of oxygen and carbon, including water, carbon dioxide, and carbon monoxide. “Sulfur is crucial for creating complex molecules and, like carbon, nitrogen, oxygen, and phosphate, needs to be studied thoroughly to understand planet formation and composition,” added Fu. The study was published in the journal Nature.
A Close Neighbor
Located just 64 light-years away from Earth, HD 189733 b is the nearest example of a “hot Jupiter.” Astronomers have been observing it since its discovery in 2005, particularly as it transits in front of its star. This proximity makes it an essential reference for atmospheric studies of exoplanets.
The planet orbits its star at a distance 13 times closer than Mercury is to the Sun, completing an orbit in just two days. Conditions on HD 189733 b are harsh, with temperatures surpassing 900 degrees Celsius and winds traveling sideways at speeds over 8,000 kilometers per hour. The weather is further complicated by glass rain driven by these ferocious winds.
Advanced Observations with James Webb
The James Webb Space Telescope has significantly aided astronomers in measuring hydrogen sulfide and sulfur on gas planets. “If we were to study a hundred hot Jupiters and found all to be sulfur-rich, it would provide essential clues about their formation and differentiation from our own Jupiter,” pondered Fu. The recent measurements also ruled out the presence of methane, affirming theories that the planet’s extreme heat precludes high concentrations of methane.
Searching for Heavy Metals
Additionally, the team searched for heavy metals similar to those found on Jupiter. This investigation can help determine the relationship between the presence of such metals and a planet’s mass.
Less massive ice planets like Neptune and Uranus contain more metals compared to gas giants like Jupiter and Saturn. This difference suggests that Neptune and Uranus accumulated a higher proportion of ice, rock, and other heavy elements compared to gases like hydrogen during their formation. Scientists are testing if this holds true for exoplanets as well, Fu explained.
A Treat for Science
“This exoplanet’s proximity to Earth and its extensive study history make it an excellent subject. The new measurements highlight the importance of metal concentrations as a crucial factor in varying planetary compositions based on mass and diameter,” confirmed Fu. “Our findings support the idea that planets form from an increasing accumulation of solid materials around an initial core, which naturally enriches with heavy metals.”
In the coming months, scientists plan to measure sulfur on more exoplanets to understand how high sulfur levels could affect their proximity to their parent stars. “We aim to uncover the formation history of these planets, and understanding their atmospheric composition is key to answering this question,” concluded Fu.
