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Health & Science2h 50m ago

Astronomers watched the ultrahot Jupiter WASP-121 b cross its star and detected, for the first time, that its evening terminator is hotter than its morning one, by measuring how the planet's silhouette changed as it rotated during the transit.

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WASP-121 b (exoplanet)

Who
Astronomers, James Webb Space Telescope, Cyril Gapp
What
Astronomers watched the ultrahot Jupiter WASP-121 b cross its star and detected, for the first time, that its evening terminator is hotter than its morning one, by measuring how the planet's silhouette changed as it rotated during the transit.
When
Tue, 16 Jun 2026 08:08:23 GMT · 2h 50m ago
Where
WASP-121 b (exoplanet) ·
Why
On WASP-121 b, the edge of the planet where evening is setting runs hotter than the edge where morning is breaking, and on the hotter side the air is fierce enough to tear water molecules into their separate atoms.
The Frontline Impact

How this affects you

This observation provides a new method for studying exoplanet atmospheres and their weather patterns, allowing astronomers to understand dynamic processes on distant worlds by observing their rotation during transits. It opens possibilities for similar studies on other fast-rotating exoplanets.

Story chain

4 events in this thread
  1. Health & Science2h 50m ago
    Astronomers detected that the evening terminator of the exoplanet WASP-121 b is hotter than its morning one, a first-time measurement achieved by observing the planet's rotation during a single transit with the James Webb Space Telescope.
    Open article
  2. Currently Reading2h 50m ago
    Astronomers watched the ultrahot Jupiter WASP-121 b cross its star and detected, for the first time, that its evening terminator is hotter than its morning one, by measuring how the planet's silhouette changed as it rotated during the transit.
  3. Health & Science5h 30m ago
    James Webb Space Telescope observations suggest that the two day-night boundary zones on the gas exoplanet WASP-121 b are chemically different from each other.
    Open article
  4. Health & Science5h 30m ago
    JWST observations suggest that the two day-night boundary zones on the gas exoplanet WASP-121 b are chemically different from each other.
    Open article

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