The James Webb Space Telescope has captured new details of the auroras on our solar system’s largest planet. The dancing lights observed on Jupiter are hundreds of times brighter than those seen on Earth. Using Webb’s advanced sensitivity, astronomers have studied the phenomena to better understand Jupiter’s magnetosphere.
The nature of the auroras
The auroras are produced when energetic particles enter a planet’s atmosphere near its magnetic poles and collide with gas atoms. Jupiter’s auroras are not only huge, they are hundreds of times more energetic than Earth’s. Here, auroras are caused by solar storms – when charged particles rain down on the upper atmosphere, exciting gases and causing them to glow in red, green and purple colors.
Meanwhile, Jupiter has an additional source for its auroras; the gas giant’s strong magnetic field traps charged particles from its surroundings. This includes not only the charged particles in the solar wind, but also the particles ejected into space by its orbiting moon Io, known for its numerous and large volcanoes. Io’s volcanoes spew particles that, remarkably, escape the moon’s gravity and orbit Jupiter. A barrage of charged particles unleashed by the Sun during solar storms also reaches the planet.
Jupiter’s large and powerful magnetic field traps the charged particles and accelerates them to tremendous speeds. These high-speed particles slam into the planet’s atmosphere at high energies, exciting the gas and causing it to glow.
Credit:
NASA, ESA, CSA, STScI, Ricardo Hueso (UPV), Imke de Pater (UC Berkeley), Thierry Fouchet (Observatory of Paris), Leigh Fletcher (University of Leicester), Michael H. Wong (UC Berkeley), Joseph DePasquale (STScI), J. Nichols (University of Leicester), M. Zamani (ESA/Webb)
Webb reveals secrets
Now, Webb’s unique capabilities are providing new insights into Jupiter’s auroras. The telescope’s sensitivity allows astronomers to increase the shutter speed to capture rapidly changing auroral features. The new data was captured on Christmas Day 2023 with Webb’s Near-InfraRed Camera (NIRCam) by a team of scientists led by Jonathan Nichols of the University of Leicester in the United Kingdom.
“What a Christmas present this was – it just blew me away!” said Nichols. “We wanted to see how quickly the auroras change, expecting them to fade in and out slowly, perhaps over a quarter of an hour or so. Instead, we observed the whole auroral region fizzing and popping with light, sometimes changing by the second.”
The team’s data revealed that the emission of the trihydrogen ion, known as H3+, is much more variable than previously thought. The observations will help scientists better understand how Jupiter’s upper atmosphere is heated and cooled.
Mysterious observations
The team also uncovered some unexplained observations in their data.
“What makes these observations even more special is that we also took simultaneous ultraviolet images with the NASA/ESA Hubble Space Telescope,” added Nichols. “Bizarrely, the brightest light observed by Webb had no real counterpart in Hubble’s images. This left us scratching our heads. To cause the combination of brightness seen by both Webb and Hubble, we need a seemingly impossible combination of large amounts of very low energy particles hitting the atmosphere – like a storm of drizzle! We still don’t understand how this happens.
The team now plans to study this discrepancy between the Hubble and Webb data and explore the broader implications for Jupiter’s atmosphere and space environment. They also plan to follow up this research with more Webb observations, which they can compare with data from NASA’s Juno spacecraft to better understand the cause of the puzzling bright emission.
These findings may also aid the European Space Agency’s Jupiter Icy Moons Explorer, Juice, which is en route to Jupiter to make detailed observations of the giant gas planet and its three large, ocean-bearing moons – Ganymede, Callisto and Europa. Juice will use seven unique scientific instruments, including two imagers, to study Jupiter’s auroras.
These close-up measurements will help us understand how the planet’s magnetic field and atmosphere interact, and how charged particles from Io and the other moons affect Jupiter’s atmosphere.
These results were obtained using data from Webb’s Cycle 2 observing program #4566 and Hubble’s observing program #17471. The results are published today in the journal Nature Communications.
