"This planet's atmosphere behaves in ways that challenge our understanding of how weather works - not just on Earth, but on all planets. It feels like something out of science fiction," said Julia Victoria Seidel, lead author of the study and researcher at the European Southern Observatory (ESO) in Chile. The findings have been published in *Nature*.
Situated approximately 900 light-years away in the constellation Puppis, Tylos is an ultra-hot Jupiter orbiting its star so closely that a full year lasts only about 30 Earth hours. The planet is tidally locked, meaning one hemisphere is constantly exposed to its host star's intense radiation while the other remains much cooler.
Through advanced observations, scientists have unveiled complex atmospheric movements, forming a 3D wind map. "What we found was surprising: a jet stream rotates material around the planet's equator, while a separate flow at lower levels of the atmosphere moves gas from the hot side to the cooler side. This kind of climate has never been seen before on any planet," Seidel explained. The jet stream, spanning half the planet, intensifies as it crosses Tylos's scorching hemisphere, creating turbulent atmospheric conditions. "Even the strongest hurricanes in the Solar System seem calm in comparison," she added.
To achieve this groundbreaking observation, researchers employed ESO's VLT and its ESPRESSO instrument, which merges light from all four of the VLT's telescopes into a single signal. This approach enhances sensitivity, allowing scientists to detect faint spectral signatures. Observing the planet as it transited its host star, ESPRESSO identified multiple chemical elements at different altitudes, revealing a vertical atmospheric profile.
"The VLT enabled us to probe three different layers of the exoplanet's atmosphere in one fell swoop," noted study co-author Leonardo A. dos Santos, an assistant astronomer at the Space Telescope Science Institute in Baltimore, United States. The team tracked iron, sodium, and hydrogen across various atmospheric depths, providing an unprecedented view of the planet's climate. "It's the kind of observation that is very challenging to do with space telescopes, highlighting the importance of ground-based observations of exoplanets," dos Santos added.
Further observations, detailed in a companion study in *Astronomy and Astrophysics*, revealed unexpected titanium signatures just beneath the jet stream, contradicting earlier findings that suggested the element was absent. Researchers believe this discrepancy arises from titanium being deeply embedded in the atmospheric layers.
"It's truly mind-blowing that we're able to study details like the chemical makeup and weather patterns of a planet at such a vast distance," said Bibiana Prinoth, a PhD student at Lund University, Sweden, and ESO, who led the companion study and co-authored the *Nature* paper.
While these findings mark a major step in understanding exoplanet atmospheres, future research will require even more advanced telescopes. The upcoming ESO Extremely Large Telescope (ELT) and its ANDES instrument will provide even deeper insights into the atmospheres of smaller, Earth-like worlds. "The ELT will be a game-changer for studying exoplanet atmospheres," Prinoth stated. "This experience makes me feel like we're on the verge of uncovering incredible things we can only dream about now."
Research Report:Vertical structure of an exoplanet's atmospheric jet stream
Research Report:Titanium chemistry of WASP-121b with ESPRESSO in 4-UT mode
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