Astronomers have observed for the first time an aurora driven by swirling winds in the atmosphere of Saturn.
Auroras are typically created by the interaction of energetic particles flowing from the planet’s magnetosphere into its atmosphere. On Earth, these particles originate from the Sun, while on Jupiter and Saturn, they come from volcanic eruptions on the moons of these planets.
However, in a new study published in the journal Geophysical Research Letters, astronomers led by Nahid Chowdhury from the University of Leicester in the UK have discovered a new type of aurora on Saturn caused by swirling winds in the planet’s atmosphere, a phenomenon that has never been observed before.
Infrared image showing auroras at the south pole of Saturn. (Photo: NASA/University of Leicester).
This new discovery was not serendipitous but based on “some initial theories about auroras.” The research team utilized the Near Infrared Spectrograph (NIRSPEC) at the Keck Observatory on Mauna Kea, Hawaii, to observe the swirling winds around Saturn’s atmosphere and measure the infrared emissions from this area, which were then used to map the planet’s weather patterns.
The study indicates that Saturn’s weather system is driven by energy from the atmosphere, with winds in the ionosphere (located beneath the magnetosphere) generating auroras on the planet. These swirling winds also appear to be responsible for the changing rotation speed of Saturn, making it difficult for researchers to determine how long a day lasts on this ringed planet.
Various spacecraft—including NASA’s Voyager and Cassini probes—have attempted to measure Saturn’s rotation speed by tracking radio emission pulses from the atmosphere, which can be used to determine the length of the planet’s day. However, the speed of these pulses has varied over decades between observations by different spacecraft.
“Understanding the physics of the planet tells us that Saturn’s actual rotation speed cannot produce rapid changes, so something unique and strange must be happening. Several theories have been proposed since NASA’s Cassini mission attempted to explain the mechanisms behind these observed cycles. The new study represents the first discovery of the fundamental engine located in Saturn’s upper atmosphere, which continues to generate both auroras and the observable cycles of the planet,” Chowdhury stated in a press release.
The lead author of the study added that this result will prompt astronomers to reconsider theories about local atmospheric weather patterns and their potential relationship with auroras, not just on the planets of our Solar System but also on worlds orbiting other stars in our galaxy.
