An international team has discovered vast helium clouds migrating away from the exoplanet WASP-107b.
An international collaboration, including astronomers from the University of Geneva and the Swiss National Center for Research Excellence PlanetS, has detected huge helium streams escaping from the exoplanet WASP-107b.
The observations were collected using the James Webb Space Telescope and then analyzed using modeling tools developed at the University of Geneva. The findings, published in the journal Nature Astronomy, provide important insights into atmospheric escape and how it affects the long-term evolution of exoplanets and some of their salient features.
Planetary atmospheres can sometimes leak into space. Earth also experiences this phenomenon, losing a little over three kilograms of material every second—mostly hydrogen—a loss that is irreversible. The process, known as atmospheric escape, is especially significant on worlds orbiting very close to their star, where the intense heating greatly amplifies the effect. Understanding this process is crucial because it can shape the way planets change over time.
Using the James Webb Space Telescope, researchers from the University of Geneva Observatory, together with colleagues from the Universities of McGill, Chicago and Montreal, have detected extensive streams of helium gas escaping from WASP-107b, a dwarf planet orbiting a star more than 210 light-years from our solar system. This is the first detection of helium on an extrasolar planet using the James Webb Space Telescope, and it allows us to study the process of atmospheric escape in extraordinary detail.
The James Webb Space Telescope is NASA's most advanced observatory, designed to explore the universe in infrared light and reveal the earliest galaxies, stars, and planetary systems. Credit: Northrop Grumman
WASP-107b, discovered in 2017, orbits its parent star at a distance of only one-seventh the distance between Mercury and the Sun. The planet is about the size of Jupiter, but its mass is only one-tenth that of Jupiter, making it unusually low in density. This places it in the category of “super-puff” planets—extrasolar planets known for their extremely light and puffy atmospheres.
The huge helium stream was discovered in the outer layer of the atmosphere, known as the exosphere. This cloud blocks some of the star's light even before the planet itself passes in front of it. "Our atmospheric escape models confirm the presence of helium streams, both in front of and behind the planet, extending along the direction of the planet's orbit and reaching almost ten planetary radii," explains Yann Carteret, a doctoral student in the Department of Astronomy at the Faculty of Sciences of the University of Geneva and co-author of the study.
Beyond helium, astronomers were also able to confirm the presence of water and traces of other chemical compounds – including carbon monoxide, carbon dioxide and ammonia – in the planet’s atmosphere. At the same time, they noted the absence of methane, which the James Webb Space Telescope can detect. These are important clues used to reconstruct the formation and migration history of WASP-107b. The planet likely formed far from its current orbit, and then migrated closer to its star. This process could explain its puffy atmosphere and loss of gas.
The study of WASP-107b is a key reference point for understanding (an important point for understanding or a turning point in understanding) the evolution and dynamics of such distant worlds. “Observations and modeling of atmospheric escape are a key research area in the Department of Astronomy at the University of Geneva, because they are thought to be responsible for some of the features we see in the exoplanet population,” explains Dr. Vincent Bourrier, Senior Lecturer and Researcher in the Department of Astronomy at the Faculty of Sciences at the University of Geneva and co-author of the study.
"On Earth, atmospheric escape is too weak to change our planet dramatically. But it is probably responsible for the absence of water on our close neighbor Venus. It is therefore essential to deeply understand the mechanisms at work in this phenomenon, which could erode the atmospheres of certain rocky planets outside the solar system," he concludes.
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