A new examination of Jupiter’s intense northern lights using the James Webb Space Telescope has unveiled previously unseen features, simultaneously presenting scientists with an intriguing puzzle to unravel.
On December 25th, 2023, a group of astronomers pointed the advanced James Webb Space Telescope towards Jupiter, the biggest planet in our solar system. This observation was not novel; however, their focus was distinct—specifically targeting the vibrant auroras near the giant planet’s powerful northern magnetic region.
Although these auroras near Jupiter’s poles were previously captured by the Hubble Space Telescope, Webb offered an unparalleled perspective, revealing intricate details of this spectacle as never seen before.
The auroras of Jupiter (on the left) were captured using the Near-Infrared Camera (NIRCam) aboard NASA’s James Webb Space Telescope on December 25, 2023. To help locate these observed auroras, an image of Jupiter itself is shown on the right side; this image was first released in 2023. This work involved contributions from organizations such as NASA, ESA, CSA, STScI along with scientists including Ricardo Hueso (from UPV), Imke de Pater (of UC Berkeley), Thierry Fouchet (at Observatory of Paris), Leigh Fletcher (University of Leicester), Michael H. Wong (also at UC Berkeley), Joseph DePasquale (working for STScI), Jonathan Nichols (again University of Leicester), and Mahdi Zamani (representing ESA/Webb).
"What an incredible Christmas gift it was — I was completely blown away!" stated Jonathan Nichols, the principal investigator of this research at the University of Leicester, in a NASA press statement.
The Aurora Borealis and Aurora Australis seen on our planet happen when energetic particles from the Sun travel around Earth. These particles come either directly via the solar wind or through significant outbursts of solar material called coronal mass ejections (CMEs) passing near our world.
These particles get trapped by Earth’s geomagnetic field and guided towards the upper atmosphere. Upon reaching this region, they interact with oxygen and nitrogen atoms and molecules in the air, transferring their energy. This transferred energy causes the oxygen and nitrogen to emit colored lights—green and red hues come from oxygen, while primarily blues originate from nitrogen.
The Aurora Borealis observed close to Guelph, Ontario, on September 16, 2024. (Stormtracker Mark Robinson)
The same procedure happens on Jupiter as well, but it includes another source of high-energy charged particles.
As the planet's powerful magnetic field traps particles from the solar wind and coronal mass ejections, it simultaneously gathers ionized particles from its closest major moon.
Io stands out as the most volcanically active body within our solar system. Its surface is scattered with numerous volcanoes, driven by the intense tidal forces caused by Io’s orbital dance around Jupiter and its periodic closeness to neighboring moons Europa and Ganymede, leading to constant gravitational pulling and pushing.
Captured by NASA's Juno spacecraft during its 57th orbit around Jupiter, this image shows Io with its surface marked by both rugged and smooth terrains, a result of ongoing frequent volcanic eruptions. (NASA/JPL-Caltech/SwRI/MSSS/Kevin M. Gill)
Jupiter’s magnetic field functions akin to a particle accelerator, propelling a mix of solar and volcanic ions downward towards the planet’s upper atmosphere. These particles collide with atmospheric atoms and molecules at incredibly high velocities as a consequence, causing Jupiter’s auroras to shine very brightly.
As the mechanism behind the formation of auroras produces heat, known as infrared radiation, Jupiter’s auroras appear exceptionally vivid to Webb due to its specialized design for detecting this particular wavelength of light. This enabled scientists to obtain an intricate look at these phenomena and observe their evolution over time.
What they witnessed during their observations left them astonished.
Nichols stated, "We anticipated observing the auroras slowly brightening and dimming, maybe taking around 15 minutes or so for these changes. However, what we witnessed was quite different: the entire aurora zone flickering rapidly with luminosity, altering within just seconds at times."
Here are three distinct images of Jupiter’s auroras captured on December 25, 2023, overlaid onto a previous JWST picture of the planet. (NASA, ESA, CSA, STScI, Ricardo Hueso (UPV), Imke de Pater (UC Berkeley), Thierry Fouchet (Paris Observatory), Leigh Fletcher (University of Leicester), Michael H. Wong (UC Berkeley), Joseph DePasquale (STScI), Jonathan Nichols (University of Leicester), Mahdi Zamani (ESA/Webb))
The auroras on Jupiter can generate an unusual form of hydrogen called the trihydrogen cation. Typically, molecular hydrogen consists of two hydrogen atoms, featuring a pair of protons encircled by a couple of electrons. Conversely, within a trihydrogen cation, you'll find three protons enclosed by just two electrons, resulting in a positive charge.
It was this very specific molecule that Nichols and his team were able to focus Webb onto, to gather the data for their study.
NASA states that identifying the emissions from these trihydrogen cations will assist scientists in comprehending the heating and cooling processes in Jupiter’s upper atmosphere.
A mystery revealed
One peculiar observation caught the attention of Nichols' team during their study.
Auroras show up in various colours across the spectrum of visible light, such as green, red, and blue. However, when we use telescopes to see auroras on Jupiter, we only see them in infrared and ultraviolet wavelengths. In this case, JWST handled the infrared observations, while another telescope provided the ultraviolet view.
"The uniqueness of these observations was further enhanced because we concurrently captured images in the ultraviolet using NASA’s Hubble Space Telescope," Nichols pointed out.
A puzzle emerged when comparing images from opposite ends of the spectrum. It was expected that the brightest areas visible in both ultraviolet and infrared light would align. Instead, they did not coincide.
Oddly enough, the most luminous emission detected by Webb didn’t correspond with anything visible in Hubble’s images," Nichols stated. "This has really puzzled us. To produce the level of brightness recorded by both Webb and Hubble, there needs to be an abundance of extremely low-energy particles interacting with the atmosphere, something that was considered unlikely before. The mechanism behind this remains unclear.
The discrepancy could stem from the varying amounts of solar particles compared to the volcanic debris from Io. Alternatively, there might be another factor at play that they have not yet considered.
NASA reports that the research team intends to conduct a more thorough analysis of the comparisons between the Webb and Hubble data they have gathered. Additionally, they aim to carry out further observations using Webb, which will then be contrasted with information provided by the Juno probe as it continues its orbit around Jupiter.
