Overview
- Astronomers report the first detection of a double helium tail from an exoplanet, observed around the hot Jupiter WASP-121b.
- JWST’s NIRISS instrument tracked the planet continuously for about 37 hours, covering more than one full orbit.
- Helium absorption remained detectable across roughly 60% of the orbit, indicating sustained mass loss.
- The combined outflows span about 107 times the planet’s diameter, with a trailing tail driven by radiation and stellar wind and a denser leading tail shaped by stellar gravity.
- The findings, published in Nature Communications, prompt calls for 3D escape models and follow-up observations to determine how common this behavior is.