Glass rain, supersonic winds, and Eau de Rotten Egg – just another day on HD 189733 b

Sounds better than a British summer

At the time of year when thoughts naturally turn to a much-earned vacation, news arrives of a planet with temperatures of 920°C (1,688°F), raining glass blown horizontal by 5,000 mph (8,047 kph) winds, and the constant smell of rotten eggs.

According to a new Johns Hopkins University study of data from the James Webb Space Telescope, HD 189733 b shows signs of hydrogen sulfide, which would be responsible for an eggy smell were any human able to survive there for more than a second.

The Jupiter-sized gas giant planet orbits its star at a distance 13 times closer than Mercury's orbit around the Sun, and takes about two Earth days to complete an orbit. At just 64 light-years from Earth, HD 189733 b is the nearest "hot Jupiter" astronomers can observe passing in front of its star.

This transit, as experts call it, has made it the target of a study of exoplanet atmospheres since its discovery in 2005. Prior studies of HD 189733 b have detected carbon monoxide and water molecules in the atmosphere, but the presence of other gases has been more difficult to pin down.

A paper published in Nature this week describes how hydrogen sulfide has been discovered on the distant planet.

Guangwei Fu, the assistant research scientist at Johns Hopkins who led the research, said: "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 detected it outside the solar system."

Fu explained that finding hydrogen sulfide on such a distant orb could be seen as a bridge to finding it elsewhere in the universe.

"This Jupiter-mass planet is very close to Earth and has been very well studied," Fu said in a statement. "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.

"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."

The Johns Hopkins team plans to conduct further studies on the presence of sulfur on other planets outside the solar system. They aim to set out how high levels of the compound can affect how close they form to their host stars. They are just thankful they can do it without experiencing the smell. ®

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