Watch Saturn’s Auroras Flash And Dance In New Hubble Photos

This image is a composite of photos of Saturn made in 2018 in visible light and in ultraviolet light in 2017 that features auroras in Saturn’s north pole region.  In contrast to the auroras on Earth the auroras on Saturn are only visible in the ultraviolet. ESA/Hubble, NASA, A. Simon (GSFC) and the OPAL Team, J. DePasquale (STScI), L. Lamy (Observatoire de Paris)

Auroras aren’t unique to Earth. They occur on every planet except Mercury. Venus and Mars have minor, patchy auroras compared to Earth’s, but Jupiter’s and Saturn’s displays are massive befitting their physical size and enormous magnetic fields.

In 2017, over a period of seven months, scientists used the Hubble Space Telescope to take photos of Saturn’s north pole region in ultraviolet light. While the still images clearly show an oval crown of aurora just like the northern oval, be sure to check out the video. The time lapse shows that the aurora is a shape-shifting creature no matter the planet.


Saturn’s northern auroras — Watch ’em go!

On both Earth and Saturn, auroras are mainly created by electrons and protons — particles that make up hydrogen atoms — blown into space in the form of the solar wind. When this stream of electrically charged particles arrives at our planet, it normally gets swept aside by Earth’s magnetic field, which acts as a gigantic shield. Occasionally the particles link up with the field and follow the magnetic field lines down to the magnetic poles, located on Ellesmere Island in Canada and off the coast of Antarctica. Crashing into the upper atmosphere at extremely high speeds, the they interact with the oxygen and nitrogen atoms to make the shimmering displays of northern and southern lights.*

The image, observed with the Space Telescope Imaging Spectrograph in the ultraviolet, shows the auroras surrounding Saturn’s north pole region. ESA/Hubble, NASA & L. Lamy (Observatoire de Paris)

Field lines are invisible lines of magnetic force exactly like those around a common bar magnet. Bits of iron sprinkled around the magnet will reveal the lines. Auroras act a little like those iron filings to reveal structure in Earth’s magnetic field.

Because Saturn’s atmosphere is dominated by hydrogen, auroras don’t glow green and red there. Matter of fact we wouldn’t see them at all because they shine in ultraviolet light, which lies just beyond the visible spectrum. To see UV you either need to be a bee or study the phenomenon from outer space with an orbiting telescope like the Hubble. Earth’s atmosphere blocks most UV light except for a couple narrow windows that allow a sliver through — just enough to give us a painful sunburn if we’re not careful.

Saturn and Mars dominate the southern sky in early September. Mars is considerably brighter, but Saturn’s no slouch either. Stellarium

The images show a rich variety of auroral emissions. The variability of Saturn’s auroras is influenced by both the solar wind and the rapid rotation of Saturn, which lasts only about 11 hours. On top of this, the northern aurora displays two distinct peaks in brightness — at dawn and just before midnight. The latter peak, unreported before, seems to occur when the solar wind hooks into Saturn’s magnetic field at the planet’s solstice.

You can always see Saturn for yourself any evening this for the next month by facing south at nightfall.