Astronomers have uncovered the secrets of an alien atmosphere on an exoplanet far beyond our Solar System, and it’s unlike anything we’ve ever seen before.
In a scientific first, an international team of astronomers has 3D mapped the atmosphere of planet WASP-121b, also known as Tylos. Using the European Southern Observatory’s Very Large Telescope (yes, that’s really what it’s called), they identified complex weather patterns and a surprising chemical composition. Their study, published in an early unedited version on Tuesday in the journal Nature, paves the way for future research into extraterrestrial atmospheres.
“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,” Julia Victoria Seidel, a physicist at the European Southern Observatory (ESO) in Chile and lead author of the study, said in an ESO statement. It’s worth mentioning that, since the official definition of “planet” remains limited to celestial bodies within our solar system (some astronomers are proposing to change this), Tylos is technically an exoplanet—but astronomers sometimes stick to “planet” for simplicity’s sake.
The exoplanet in question is a gas giant (a large planet primarily made of helium and/or hydrogen) roughly 900 light years away from Earth. It closely orbits its star in just around 30 hours—so close, in fact, that Tylos is also classified as an ultra-hot Jupiter: an extremely large and hot planet with a very tight orbit. The time it takes Tylos to complete one orbit is the same time it takes the gas giant to complete one rotation, meaning that one of Tylos’ sides permanently faces its star and is much hotter than the other (i.e. it’s tidally locked).
Seidel and her colleagues analyzed the exoplanet’s atmosphere using all four telescope units of the ESO’s VLT. By tracing iron, sodium, and hydrogen, they were able to investigate the planet’s distinct deep, mid, and upper atmospheric layers.
“The VLT enabled us to probe three different layers of the exoplanet’s atmosphere in one fell swoop,” said Leonardo A. dos Santos, an assistant astronomer at the Space Telescope Science Institute in Baltimore who participated in the study. “It’s the kind of observation that is very challenging to do with space telescopes, highlighting the importance of ground-based observations of exoplanets,” he added.
The team then created a 3D map of their observations, unveiling an alien atmosphere outside of our Solar System in unprecedented detail.
“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. In comparison to the size and speed of Tylos’ jet stream, “even the strongest hurricanes in the Solar System seem calm in comparison,” she added.
Additionally, a companion study—published earlier this week in the journal Astronomy & Astrophysics by some of the same researchers—notes the discovery of titanium below the jet stream. Previous research had not spotted this chemical presence, perhaps because of its depth within the atmosphere.
“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 in astronomy and astrophysics at Lund University. “This experience makes me feel like we’re on the verge of uncovering incredible things we can only dream about now.” Prinoth co-authored the Nature paper and led the companion piece.
Prinoth’s excitement is well placed. Future telescopes—such as ESO’s forthcoming Extremely Large Telescope (ELT)—will allow researchers to conduct similar atmospheric analyses of smaller Earth-like planets. “The ELT will be a game-changer for studying exoplanet atmospheres,” Prinoth concluded.