James Webb Telescope Reveals Alien World With Two Completely Different Twilights: Fierce Winds Separate Day and Night

[Tracey99]

NASA's James Webb Space Telescope published dramatic findings this week about exoplanet WASP-121 b, a gas giant about 880 light years from Earth that is tidally locked to its star, meaning one side permanently faces its star in blistering day and the other faces permanently into space in deep cold night. Webb's infrared instruments measured the chemistry and temperature of the planet's dawn and dusk regions separately for the first time, revealing that the morning and evening terminator zones are surprisingly different from each other. The morning side shows cooler chemistry with molecules that have had time to form in the cold night hemisphere being dragged around to face the star, while the evening side shows hotter, more processed gases from the permanent dayside being swept around by winds.

The winds transporting heat around WASP-121 b blow at speeds estimated to exceed 5,000 kilometres per hour, faster than the speed of sound and far faster than any weather phenomenon on Earth. The morning terminator shows water vapour, carbon dioxide and other molecules; the evening terminator shows atomic gases and dissociated molecules that have been broken apart by heat. This difference tells astronomers that the winds are not simply averaging the temperature across the planet but are creating distinct chemical environments at each boundary.

WASP-121 b is a so-called hot Jupiter, a class of gas giant that orbits extremely close to its host star and is not believed to support life. But it is one of the most studied exoplanets because its extreme conditions make atmospheric signals particularly clear to observe. The findings were published in Nature and represent one of the most detailed characterisations of any exoplanet atmosphere ever achieved.

News - NASA Sciencescience.nasa.gov