By combining years of observations from NASA’s Hubble Space Telescope with computer simulations, astronomers have found evidence of violent hurricanes and other dynamic weather activity on a hot Jupiter-sized planet 880 light-years away.

The planet named WASP-121 b is uninhabitable. But the result is an important early step in studying weather conditions on distant worlds and perhaps eventually in the search for potentially habitable exoplanets with stable, long-term climates.

Over the past few decades, detailed observations of neighboring planets in our solar system using telescopes and spacecraft have shown that the turbulent atmospheres of these planets are not static but constantly changing, like the weather on Earth. This variability should also apply to planets around other stars. But actually measuring such changes requires a lot of detailed observations and computational modelling.

To make this discovery, an international team of astronomers collected and reprocessed Hubble observations of WASP-121 b from 2016, 2018, and 2019.

They found that the planet has a dynamic atmosphere that changes over time. The team used complex modeling techniques to show that these dramatic temporal changes could be explained by weather conditions in the exoplanet’s atmosphere.

The team found that WASP-121 b’s atmosphere varies markedly between observations. Most dramatically, powerful weather fronts, storms and massive hurricanes can occur, constantly created and destroyed by the large temperature difference between the side facing the star and the dark side of the exoplanet. They also found a clear balance between the hottest part of the exoplanet and the point on the planet closest to the star, as well as variability in the chemistry of the exoplanet’s atmosphere (as measured by spectroscopy).

The team reached these results using computational models to help explain observed changes in the exoplanet’s atmosphere. “The exquisite detail of our exoplanet atmosphere simulations allows us to accurately model weather on superhot planets like WASP-121 b,” said Jack Skinner, a postdoctoral researcher at the Cal Institute of Technology in Pasadena, California, and one of the leaders. . of this study. “Here we take an important step forward by combining observational constraints with atmospheric modeling to understand changing weather on these planets.”

“This is an extremely exciting result as we progress in observing the weather of exoplanets,” said Quentin Changet, one of the team’s principal investigators and a European Space Agency scientist at the Space Telescope Science Institute in Baltimore, Maryland. “Studying exoplanet weather is vital to understanding the complexity of exoplanet atmospheres on other worlds, especially in the search for exoplanets with conditions suitable for life.”

WASP-121 b is so close to its parent star that its orbital period is only 1.27 days. This proximity means that the planet is tidally locked, so that the same hemisphere is always facing the star, just as one side of our Moon is always facing the Earth. Daytime temperatures approach 3,450 degrees Fahrenheit (2,150 degrees Kelvin) on the side of the planet facing the star.

The team used four sets of archival Hubble observations of WASP-121 b. The full data set included observations of WASP-121 b (taken in June 2016) passing in front of its star; WASP-121 b, also known as a secondary eclipse, passes behind its star (viewed in November 2016); and WASP-121 b’s brightness as a function of its phase angle to the star (the varying amount of light Earth receives from an exoplanet as it orbits its parent star, similar to the phase cycle of our Moon). These data were taken in March 2018 and February 2019, respectively.

“The collected data set represents a significant amount of observation time for a single planet and is currently the only consistent set of such repeated observations,” Changet said. said. The information we obtained from these observations was used to understand the chemical composition, temperature, and turbidity of WASP-121 b’s atmosphere at different times. “This gave us an excellent picture of the planet changing over time.”

Hubble’s capabilities are also evident in the wide range of science programs it will enable with its 31st observing cycle, which begins December 1. About two-thirds of Hubble’s time will be devoted to imaging studies, with the remainder devoted to spectroscopic studies such as those used for WASP-121 b. You can find more details about the science of Cycle 31 in a recent announcement.