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NASA's James Webb Space Telescope has revealed enormous swirling auroras on Jupiter for the first time. Hundreds of times more intense and brighter than those seen on Earth, they're caused both by high-energy particles from the sun but also from Jupiter's moon, Io -- the most volcanic body in the solar system.
The stunning images below reveal how the gas giant's magnetic field and atmospheric dynamics combine to produce something truly unique in the solar system.
All auroras occur when high-energy particles enter a planet's atmosphere near its magnetic poles. The particles, which travel to a planet from the sun as the solar wind, then collide with gas atoms in a planet's atmosphere to produce photons of light. That's a textbook explanation for Earth and Jupiter, but the gas giant planet has something extra that makes its auroras significantly more intense.
Captured on December 25, 2023, using its Near-Infrared Camera (NIRCam), the Webb Telescope's images of Jupiter's auroral emissions were possible because it can detect emissions from trihydrogen cation, a molecule formed when high-energy electrons strike molecular hydrogen. The resulting emission -- high up in Jupiter's atmosphere -- is bright in infrared light, which Webb is uniquely sensitive to.
It's thought that Jupiter's strong magnetic field grabs charged particles from its surroundings -- not only those from the solar wind but also those thrown into space by the large volcanoes on its moon Io.
Although Webb saw the auroras on Jupiter in 2023, the Hubble Space Telescope did not -- despite the same observations being made simultaneously in the ultraviolet light by both space observatories. "Bizarrely, the brightest light observed by Webb had no real counterpart in Hubble's pictures," said Jonathan Nichols from the University of Leicester in the U.K., who led the research. "This has left us scratching our heads. In order to cause the combination of brightness seen by both Webb and Hubble, we need to have a combination of high quantities of very low-energy particles hitting the atmosphere, which was previously thought to be impossible. We still don't understand how this happens."
Hubble photographed aurora around Jupiter's poles in 2016, which were also overseen by Nichols.
Arguably, one of the most spectacular images of Jupiter ever taken was one from the Webb Telescope in 2022, as part of the Early Release Science program shortly after it began science operations. The image above, of Jupiter on July 27, 2022, was taken using Webb's NIRCam infrared instrument and showed the giant planet's mighty storms (including its "Great Red Spot," an Earth-sized anticyclonic storm), cloud bands, rings and unprecedented views of the planet's auroras over its north and south poles. The jaw-dropping image can be downloaded from the European Space Agency website.
Webb is the most ambitious and complex space science telescope ever constructed, with a massive 6.5-meter primary mirror that will be able to detect the faint light of far-away stars and galaxies. It's designed to detect infrared light emitted by distant stars, planets and clouds of gas and dust. During its initial 10-year mission, which began in 2022, Webb will study the solar system, directly image exoplanets, photograph the first galaxies, and explore the mysteries of the origins of the Universe.