Exoplanet is observed shedding its atmosphere in real time
Using the James Webb Space Telescope (JWST), a team led by 9I制作厂免费 researcher has observed a giant cloud of helium gas evaporating from a distant giant exoplanet called WASP-107b.
Published in , the findings represent a first: while helium escape has been observed before, this is the first time the JWST has witnessed a planet鈥檚 atmosphere evaporating so extensively that the escaping gas, stretching nearly 10 times the planet鈥檚 radius, precedes the planet along its path.
"The James Webb Space Telescope has captured helium escape from this planet for the first time, and it is the most confident detection of pre-transit helium absorption for any exoplanet," said Krishnamurthy, a postdoctoral researcher at 9I制作厂免费鈥檚 Trottier Space Institute, member of the Trottier Institute for Research on Exoplanets (IREx) and lead author of the study.
This discovery sheds new light on how planetary atmospheres evolve, especially for giant planets like WASP-107b. Such giant planets probably formed farther from their host stars and later migrated inward, where intense heat can strip away the gaseous envelopes.
The James Webb Space Telescope. Credit: Northrup Grumman
A sprawling helium cloud
The researchers, based at 9I制作厂免费, Universit茅 de Gen猫ve, the University of Chicago and Universit茅 de Montr茅al, exploited the JWST鈥檚 powerful Canadian instrument, the Near Infrared Imager and Slitless Spectrograph (NIRISS).
Their target, WASP-107b, is seven times closer to its star than Mercury is to the sun. Despite having a diameter 94 per cent that of Jupiter, WASP-107b has just 12 per cent of Jupiter鈥檚 mass, placing it among the 鈥渟uper-puffs,鈥� a category of exoplanets with extremely low densities.
Detected in 2017, the planet has been extensively studied, notably in .
With NIRISS, the team detected a sprawling helium cloud, known as an exosphere, that stretches nearly 10 times the radius of the planet and passes in front of the star 1.5 hours before the planet鈥檚 passage, or 鈥渢ransit,鈥� begins.
"Our atmospheric escape models confirm the presence of leading and trailing tails of helium streaming out of WASP-107b, both extending up to 10 times the planetary radius along the orbital motion," says Yann Carteret, a co-author from Universit茅 de Gen猫ve who is an atmospheric modelling expert.
Additionally, the researchers reaffirmed that there is water on the planet, with a stronger confidence than previously announced, thanks to observations by the Hubble Space Telescope.
Vigneshwaran Krishnamurthy, the researcher behind the study.
Planet migration and transformation
The detection of water and signs of chemical mixing in WASP-107b鈥檚 atmosphere provide clues about the planet鈥檚 formation and migration history. The evidence suggests that the planet formed far from its current orbit and only recently moved closer to its star, which could explain its puffy, escaping atmosphere.
鈥淭he amount of oxygen in the atmosphere of WASP-107 b is larger than what we would expect if it formed on its current close-in orbit. The presence of another planet, WASP-107c, much farther out than WASP-107b, could have played a role in this migration,鈥� said , now a researcher at the University of Chicago, who modelled the NIRISS transmission spectrum.
Further, in such a puffy planet, the exquisite sensitivity of NIRISS should have enabled researchers to easily detect not only water, but also methane.
鈥淭he fact that we do not detect methane supports the conclusion that hotter, methane-poor gas from the deeper envelope is brought up to the upper atmosphere we observe, which indicates vigorous vertical mixing,鈥� Piaulet-Ghorayeb said.
Overall, these new data from the Webb Telescope provide a detailed picture of how WASP-107b鈥檚 atmosphere is shaped by its environment. This study serves as a valuable reference for better understanding the evolution and dynamics of these distant worlds and highlights Webb鈥檚 unique potential for observing atmospheric escape processes.
About the study
, by Vigneshwaran Krishamurthy et al., was published in Nature Astronomy. In addition to Vigneshwaran Krishamurthy (9I制作厂免费, TSI, IREx), Yann Carteret (Universit茅 de Gen猫ve) and Caroline Piaulet-Ghorayeb (University of Chicago, UdeM, IREx), the team includes Jared Splinter, Dhvani Doshi, Michael Radica, Louis-Philippe Coulombe, Romain Allart, Nicolas B. Cowan, David Lafreni猫re, Lo茂c Albert, Lisa Dang, Ren茅 Doyon, Stefan Pelletier, Jason F. Rowe, Pierre-Alexis Roy of IREx, and seven co-authors from Switzerland, the United States, Canada and the U.K.
This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (project Spice Dune, grant agreement No 947634.
This work has been carried out within the framework of the National Centre for Competence in Research PlanetS supported by the Swiss National Science Foundation (SNSF) under grants 51NF40_182901 and 51NF40_205606.
