An infrared image of Saturn with an aurora visible at its south pole, taken by the Cassini … [+]
NASA, Cassini, VIMS Team, University of Arizona, University of Leicester, JPL, ASI
Saturn, the large ringed planet of our solar system, has a kind of aurora powered by wind.
The dancing lights (known as the northern lights or southern lights on Earth) happen when energized solar particles flow along magnetic field lines of a planet, creating a glow as the particles strike parts of the upper atmosphere. At big planets like Saturn, the vast magnetosphere (magnetized part of the atmosphere) can also help generate auroras.
But the newly found ones are of a different sort, and have a different suspected origin story: energy in one part of the atmosphere (known as the thermosphere), together with winds in the ionosphere, create auroras in the magnetosphere just above.
“It’s absolutely thrilling to be able to provide an answer to one of the longest standing questions in our field. This is likely to initiate some rethinking about how local atmospheric weather effects on a planet impact the creation of aurorae, not just in our own solar system but farther afield too,” said lead author and PhD researcher Nahid Chowdhury, a planetary scientist at the University of Leicester, in a statement.
Northern lights (aurora borealis) illuminate the sky over Reinfjorden in Norway, on September 8, … [+]
AFP via Getty Images
The researchers found the auroras using the W. M. Keck Observatory on Mauna Kea, Hawaiʻi Island. The observatory’s Near-Infrared Spectrograph (NIRSPEC) peers at objects in infrared, which was helpful at Saturn to look at wind currents.
Besides pretty lights, another application of the study could be to figure out why the length of the day varies at Saturn. The planet has variable rotation rates over extremely short periods of time, for reasons that are poorly understood, creating different measurements through missions over the decades ranging from Voyager to Cassini. It may be that the winds also cause this variability, the researchers said. Cassini researchers, the study added, have fixed the day of Saturn at 10 hours, 33 minutes and 38 seconds based on gravitational perturbations in Saturn’s rings.
“Our understanding of the physics of planetary interiors tells us the true rotation rate of the planet can’t change this quickly, so something unique and strange must be happening at Saturn,” Chowdury added.
A study based on the research was published in Geophysical Research Letters.
