Exoplanet's Winds 'Challenge Our Understanding of How Weather Works'

The first-ever three-dimensional observations of the atmosphere of a planet outside our solar system have proven "surprising" in a way that may shake up our understanding of weather. This is the conclusion of a study, published in the journal Nature, undertaken using the European Southern Observatory (ESO)'s Very Large Telescope (VLT), in Chile's Atacama Desert. The planet—WASP-121b, also known as "Tylos"—is a gas giant that lies some 900 light-years away from Earth, in the constellation Puppis. Tylos orbits so close to its host star that not only does its year last just 30 Earth hours, but one side of the planet always faces its star, making it seething hot (at temperatures of around 4,600 degrees Fahrenheit), while the colder side always faces away. "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 lead author and astrophysicist Julia Victoria Seidel in a statement. She elaborated to Newsweek: "Basically, our models in the field—so-called 'Global Circulation Models—come from the meteorology and climate community here on Earth. They were then adapted to also handle circulation, based on fluid mechanics, for other worlds. "However, now that we look at the extreme cases of atmosphere, like for Tylos, we see that likely there is some physics missing in how we describe atmospheric flows in general." Scientists will now need to see what aspects of physics need to be added to current Global Circulation Models to make them more like reality. This, Seidel said, is "likely wither the impact from energy deposit from the star, or even magnetic fields, both aspects which we largely neglected so far for simplicity."

In their study, Seidel and colleagues were able to probe the three-dimensional structure of Tylos' atmosphere by combining the signals from all four telescope units in the VLT, enabling the team to reveal fainter details. The researchers observed Tylos as it passed in front of its host star, revealing the signatures of various chemical elements—including hydrogen, iron and sodium—blowing around at different depths in its atmosphere. "The VLT enabled us to probe three different layers of the exoplanet's atmosphere in one fell swoop," said paper co-author and astrophysicist Leonardo dos Santos, of the Space Telescope Science Institute in Baltimore, in a statement. By tracking the movements of hydrogen, iron and sodium specifically, the team were able to trace out the winds in Tylos' shallow, deep and mid atmospheric layers, respectively.

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This, dos Santos explained, is "the kind of observation that is very challenging to do with space telescopes, highlighting the importance of ground-based observations of exoplanets." "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," explained Seidel. The jet stream on Tylos spans half of the world—gaining speed and ferocity as it crosses the hot, star-facing side of the planet, the researchers report. "Even the strongest hurricanes in the Solar System seem calm in comparison," Seidel added.

Another surprise came via the detection of titanium on Tylos, just beneath the jet stream. Previous observations of the exoplanet had suggested that this element was absent; it may be that it was so deep in the atmosphere it was hidden to us before. The findings of the study are described in a companion paper in the journal Astronomy & Astrophysics. Astrophysicist Bibiana Prinoth of Sweden's Lund University is the lead author of this study, and a co-author on the Nature paper. "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," Prinoth said in a statement. In the future, astronomers may be able to undertake similar studies of smaller, more Earth-like planets—although larger and more powerful telescopes will be needed first. One such project is the ESO's "Extremely Large Telescope" (ELT), which is currently under construction in the Atacama Desert, just some 13 miles from the VLT. "The ELT will be a game-changer for studying exoplanet atmospheres," said Prinoth. "This experience makes me feel like we're on the verge of uncovering incredible things we can only dream about now." "This larger telescope will allow us to 'switch on the microscope' even more than we did in this study," added Seidel. The ELT, she concluded, "will hopefully allow us to do similar studies to the one shown here for planets more the size and temperature of Earth." Do you have a tip on a science story that Newsweek should be covering? Do you have a question about space? Let us know via science@newsweek.com. Update 03/02/25, 1:24 p.m. ET: This article was updated with additional information and comments from Julia Victoria Seidel.

References

Prinoth, B., Seidel, J. V., Hoeijmakers, H. J., Morris, B. M., Baratella, M., Borsato, N. W., Damasceno, Y. C., Parmentier, V., Kitzmann, D., Sedaghati, E., Pino, L., Borsa, F., Allart, R., Santos, N., Steiner, M., Suárez Mascareño, A., Tabernero, H., & Zapatero Osorio, M. R. (2025). Titanium chemistry of WASP-121 b with ESPRESSO in 4-UT mode. Astronomy & Astrophysics. http://dx.doi.org/10.1051/0004-6361/202452405 Seidel, J. V., Prinoth, B., Pino, L., dos Santos, L. A., Chakraborty, H., Parmentier, V., Sedaghati, E., Wardenier, J. P., Jentink, C. F., Zapatero Osorio, M. R., Allart, R., Ehrenreich, D., Lendl, M., Roccetti, G., Damasceno, Y., Bourrier, V., Lillo-Box, J., Hoeijmakers, H. J., Pallé, E., Santos, N., Suárez Mascareño, A., Sousa, S. G., Tabernero, H. M., & Pepe, F. A. (2025). Vertical structure of an exoplanet's atmospheric jet stream. Nature. http://dx.doi.org/10.1038/s41586-025-08664-1