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First-Ever Observation of WASP-121b's Atmospheric Escape

1/22/2026

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Summary

Story summary

Astronomers from the University of Geneva and the University of Montreal used the James Webb Space Telescope to observe WASP-121b shedding its atmosphere.
Two helium tails extend behind and ahead of the planet, trailing and leading over half its orbit.
This is the first continuous observation of atmospheric escape over an entire orbit.
The findings, published in Nature Communications, call for improved models of gravity, radiation, and stellar winds.

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Story summary

Astronomers from the University of Geneva and the University of Montreal used the James Webb Space Telescope to observe WASP-121b shedding its atmosphere.
Two helium tails extend behind and ahead of the planet, trailing and leading over half its orbit.
This is the first continuous observation of atmospheric escape over an entire orbit.
The findings, published in Nature Communications, call for improved models of gravity, radiation, and stellar winds.