A Scorching Planet Grew Two Tails express

Original: "A complex structure of escaping helium spanning more than half the orbit of the ultra-hot Jupiter WASP-121\,b"
arXiv:2510.09809 · 2025-10-10 · CC BY 4.0 · 1 min
The James Webb Telescope caught a scorching planet turning into a comet for the first time: its atmosphere boils off, creating two giant helium tails.

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Planet WASP-121b orbits so near its star that the fierce heat boils its atmosphere away, streaming like a comet's tails. With the James Webb Space Telescope, astronomers continuously watched this process for the first time. They found that helium from the atmosphere is pulled into two enormous plumes, stretching across 60% of the orbit — hundreds of millions of kilometers. One tail, pushed by stellar radiation, surges ahead of the planet and falls onto the star. The other trails behind and escapes into space. The planet is morphing into a comet-like body, shedding its gaseous envelope. Such twin tails had never been seen in their full extent before. This helps us understand how swiftly gas worlds perish under alien suns. The observations relied on a special glow from helium, allowing light analysis to detect even the thinnest layers of the atmosphere, like peering deep into space weather.

The unique glow of helium lets us peek into the uppermost, bloated layers of exoplanet atmospheres — regions where ordinary light can't reach.

Scientists
Adam RiessBrian SchmidtEdwin HubbleGeorges LemaîtreMaarten SchmidtSaul Perlmutter
Concepts
jwst exoplanet atmospheres hot jupiter atmospheres helium star water vapor planetary atmospheric loss hydrogen envelope jupiter exoplanet atmosphere gas giant trappist 1 europa tidal migration james webb space telescope helium 3 wolf rayet star escape velocity heat shield hydrogen atmosphere tess comet tail