Two articles, one published in the journal “Nature” and one in the journal “Astronomy & Astrophysics” (links to the files in PDF format), report the results of two studies of the exoplanet WASP-121b, officially named Tylos, which describe different aspects of its very turbulent atmosphere. Two teams of researchers with several members in common used the ESPRESSO instrument mounted on ESO’s VLT (Very Large Telescope) in Chile exploiting the combination of the four telescopes to examine the atmosphere of Tylos during a complete transit in front of its star. The result was a mapping of the layers of the atmosphere and the detection of traces of various chemical elements including sodium, iron, and titanium.
About 900 light-years from Earth, the exoplanet Tylos has a mass slightly greater than that of Jupiter but its size is almost twice as Jupiter’s due to the very high temperatures that heat the gas that forms it expanding them. That’s because it’s so close to its star that a year lasts about 30 hours.
The extreme conditions that exist in the atmosphere of what is classified as an ultra-hot Jupiter have been studied since its discovery was announced in March 2016. An article published in February 2022 in the journal “Nature Astronomy” suggested that perhaps on Tylos it rains rubies and sapphires.
The study of Tylos continued and the researchers who conducted these new exams found three distinct layers in its atmosphere in ESPRESSO’s detections, indicated in the image (ESO/M. Kornmesser). The lower layer is characterized by iron winds, the middle layer has fast jets of sodium, and the upper layer has hydrogen winds. This is a mapping that reached an unprecedented level for a planet outside the solar system. Julia Victoria Seidel of ESO, lead author of the study published in “Nature”, commented that the behaviors of Tylos’ atmosphere challenge our understanding of how weather works, and not just on Earth, to the point of being something out of science fiction.
The new measurements confirmed that the winds in Tylos’ atmosphere are fiercer than any found in the Solar System. This is due to its proximity to its star and the fact that it’s tidally locked, meaning it always shows the same face to its star. The resulting mapping indicates that materials are being redistributed in the atmosphere by winds that go from this exoplanet’s dayside to its nightside.
Not everything is clear about the processes at work in the atmosphere of the exoplanet Tylos and the various mechanisms behind them. For example, the roles of possible magnetic fields and the loss of atmosphere due to the star’s action are unclear. These processes are common to other gas giant exoplanets close to their stars as well but further studies are needed to have a clearer picture that can lead to explanations and precise models.
The presence of titanium in the atmosphere of the exoplanet Tylos was confirmed, although it seems limited to the equatorial regions. This could be due to limits in the mixing of materials present in the atmosphere. The identification of titanium and its compounds is a step forward in understanding the condensation mechanisms in the atmosphere of extremely hot planets.
The greatest interest in the atmospheres of exoplanets concerns potentially habitable ones but extreme environments such as those of ultra-hot Jupiters are interesting from the scientific point of view of their characteristics impossible to find in the solar system. For this reason, the exoplanet Tylos will continue to be studied, also with other very advanced instruments.
