Smelly exoplanets are rotten eggs

According to a new study of data from the James Webb Space Telescope, an exoplanet infamous for its deadly weather hides another strange feature—it’s dripping with rotten eggs.

The atmosphere of HD 189733 b, a Jupiter-sized gas giant, contains a molecule called hydrogen sulfide that not only emits a foul odor, but also provides scientists with new clues about how sulfur, the planet’s building block, affects interiors. and the atmospheres of gaseous worlds beyond the Solar System.

„Hydrogen sulfide is a big molecule, and we didn’t know it was there. We predicted it would be there, we knew it was on Jupiter, but we haven’t really detected it outside the Solar System,” says Guangwei Fu, an astrophysicist at Johns Hopkins University who led the research.

„We’re not looking for life on this planet because it’s too hot, but finding hydrogen sulfide is a step toward finding this molecule on other planets and gaining a better understanding of how different types of planets form.”

In addition to detecting hydrogen sulfide and measuring total sulfur in HD 189733 b’s atmosphere, Fu’s team precisely measured water, carbon dioxide, and carbon monoxide, the planet’s main sources of oxygen and carbon.

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

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At 64 light-years from Earth, HD 189733 b is a „hot Jupiter” astronomers can see passing in front of its star, making it a key planet for detailed studies of exoplanet atmospheres since its discovery in 2005, Fu says.

Mercury is 13 times closer to its star than the Sun and takes only two Earth days to complete one orbit. It has temperatures as hot as 1,700 degrees Fahrenheit and is notorious for inclement weather, including rain glass blown sideways by 5,000 mph winds.

By detecting water, carbon dioxide, methane and other important molecules on other exoplanets, Webb gives scientists another new tool to track hydrogen sulfide and measure sulfur on gas planets outside the Solar System.

„We’re studying another 100 hot Jupiters, all of them enhanced by sulfur. What does that mean for how they were born and how they differ compared to our own Jupiter?” Fu says.

The new data rule out the presence of methane in HD 189733 b, with unprecedented precision and near-infrared wavelength observations from the Webb telescope, challenging previous claims about the abundance of that molecule in the atmosphere.

„We thought the planet was too hot to have high concentrations of methane, and now we know it’s not,” Fu says.

The team also measured the amount of heavy metals similar to those on Jupiter, a finding that could help scientists answer questions about how a planet’s metallicity relates to its mass, Fu says.

The less massive ice giant planets like Neptune and Uranus contain more metals than the gas giants like Jupiter and Saturn, the largest planets in the Solar System. High metals suggest that Neptune and Uranus accumulated more ice, rock, and other heavier elements compared to gases like hydrogen and helium during the early stages of their formation. Scientists are testing whether that connection holds true for exoplanets, Fu says.

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“This Jupiter-mass planet is the closest to Earth and the most well-studied. „Now we have this new measurement to show that metal concentrations provide a very important anchor point for this study of how a planet’s composition varies with its mass and radius,” says Fu. „The findings support our understanding of how planets form by building up more solid material after initial core formation. , and then they are naturally enriched with heavy metals.”

In the coming months, Fu’s team plans to monitor sulfur in more exoplanets and detect high levels of the compound the closer they form to their parent stars.

„We want to know how these types of planets got there, and understanding their atmospheric composition can help answer that question,” Fu says.

Research shows Nature.

Additional co-authors are from Johns Hopkins, Arizona State University, University of Maryland, California Institute of Technology, University of Chicago, Utah Valley University, Tennessee State University, University of Arizona, and NASA Ames Research Center.

This research was supported by NASA through the JWST GO program.

Source: Johns Hopkins University

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