Astronomers have mapped the atmospheres of exoplanets for a while, but a good look at their night sides has proven to be elusive — until today. A study led by MIT provided the first detailed look at the dark side of a “hot Jupiter” exoplanet mapping temperatures based on WASP-121b’s altitude and water presence levels. As the distant planet (850 light-years away) is tethered to its host star, the differences on the bright side couldn’t be more stark.
The dark side of the planet contributes to an extremely violent water cycle. Where the dayside rips through the water with temperatures above 4,940F, the night is cool enough (‘only’ 2,780F max) to recombine them in water. The result hurls water atoms around the planet at over 11,000 MPH. This dark side is also cool enough to have clouds of iron and corundum (a mineral in rubies and sapphires), and you can see rain made of liquid gemstones and titanium as the steam on the day side cools.
The researchers collected the data using Hubble Space Telescope spectroscopy for two orbits in 2018 and 2019. Many scientists used this method to study the bright sides of exoplanets, but observations of the dark side required detecting tiny shifts in the spectral line indicating carbon vapor. Water . That line helped scientists create temperature maps, and the team sent those maps through models to help identify likely chemicals.
This represents the first detailed study of an exoplanet’s global atmosphere, according to MIT. This comprehensive view should help explain where hot Jupiters like WASP-121b can form. And while a Jovian world like this is clearly too dangerous for humans, more thorough examinations of exoplanet atmospheres could help in the search for truly habitable planets.
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