Webb Captures Auroras on Jupiter 100 Times Brighter Than Those on Earth

The NASA/ESA/CSA James Webb Space Telescope (JWST) captured brilliant new details of the auroras on Jupiter, the Solar System’s largest planet. The auroras observed on Jupiter are a staggering 100 times brighter than the auroral displays observed on Earth.

Thanks to Webb’s extreme sensitivity across a wide range of wavelengths, including near-infrared and infrared, scientists have learned new details about Jupiter’s enigmatic magnetosphere. Webb recently observed auroras on Neptune for the first time as well.

Like on Earth, auroras on Jupiter arise when high-energy particles enter the planet’s atmosphere near its magnetic poles and interact with atoms of gas in the atmosphere. However, the auroras in Jupiter are not only huge, the European Space Agency (ESA) explains that the auroras are hundreds of times more energetic than they are on Earth.

On Earth, auroras result from solar storms sending highly charged particles raining down on the atmosphere, exciting certain gases and causing them to glow in various colors, commonly green, purple, and red. Jupiter has an additional auroral source, its strong magnetic field. The gas giant’s magnetic field “grabs charged particles from its surroundings,” including the particles within the solar wind that cause auroras on Earth and the particles that Jupiter’s moon, Io, puts into space. Io is known for its many large volcanoes, which are strong enough to erupt particles outside Io’s orbit and then orbit Jupiter.

Jupiter’s powerful magnetic field captures these charged particles, alongside those riding the solar wind, and accelerates them “to tremendous speeds.” These super-swift particles “slam into the planet’s atmosphere at high energies, which excites the gas and causes it to glow.”

This has been historically challenging to observe, which is where Webb’s unique imaging capabilities come into play. The space telescope is very sensitive to many wavelengths of light, for starters, but its imaging performance is also good enough that scientists can significantly increase its shutter speed, enabling it to observe rapidly-changing auroral features on Jupiter.

The new results were initially captured on Christmas Day in 2023 by a scientific team led by Jonathan Nichols from the University of Leicester in the United Kingdom.

“What a Christmas present it was — it just blew me away!” Nichols says. “We wanted to see how quickly the auroras change, expecting it to fade in and out ponderously, perhaps over a quarter of an hour or so. Instead we observed the whole auroral region fizzing and popping with light, sometimes varying by the second.”

Nichols and his team discovered that the emission from the trihydrogen ion, H3+, is much more variable than scientists previously believed. The observations help explain how Jupiter’s upper atmosphere heats and cools.

The team also performed simultaneous observations using the Hubble Space Telescope, and something unexpected happened.

“What made these observations even more special is that we also took pictures simultaneously in the ultraviolet with the NASA/ESA Hubble Space Telescope,” Nichols explains. 

“Bizarrely, the brightest light observed by Webb had no real counterpart in Hubble’s pictures. 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 an apparently impossible combination of high quantities of very low energy particles hitting the atmosphere — like a tempest of drizzle! We still don’t understand how this happens.”

The team is working now to understand the discrepancy between the two space telescopes and what the differences in observations mean for Jupiter’s atmosphere and surrounding cosmic environment.

Image credits: ESA/Webb, NASA, CSA, J. Nichols (University of Leicester), M. Zamani (ESA/Webb)