Images of auroras over Saturn’s north pole in ultraviolet light with the Hubble Space Telescope capture moments when Saturn’s magnetic field is affected by bursts of particles streaming from the Sun. Click to enlarge. Credit: NASA, ESA, Jonathan Nichols (University of Leicester)
Saturn shines brightly in the late May evening sky. You can see it now at nightfall by following an arc starting with fiery Mars and passing through Spica. Continue and you’ll end up at Antares, the alpha luminary in Scorpius. Did you know that it also shimmers with auroras too just like the Earth?
Recent Hubble Space Telescope photos taken in ultraviolet light, where the aurora shines brightly, show bursts of light shooting around Saturn’s polar regions traveling at more than three times faster than the speed of the gas giant’s roughly 10-hour rotation period.
Saturn’s auroras shine brightly in UV but would appear deep red at the bottom and violet at top with the naked eye. That’s because hydrogen gas dominates the planet’s atmosphere and emits light in different colors when bombarded by the energetic electrons in the solar wind. On Earth, excited oxygen and nitrogen molecules produce the more familiar greens, reds and blues of northern lights.
A magnetosphere is that area of space around a planet that’s controlled by the planet’s magnetic field. The shape of the Earth’s magnetosphere is the direct result of being blasted by solar wind, compressed on its sunward side and elongated on the night side forming a magnetotail. Saturn’s is similar. Credit: NASA
University of Leicester researchers recently discovered an amazing connection between Saturn’s and Earth’s auroras. Both planets are surrounded by teardrop-shaped magnetic domains called magnetospheres generated by the churning of materials within their cores. In each case, the side facing the sun is compressed and flattened, while the other side is drawn out into a long tail called a magnetotail.
“Our observations show a burst of auroras that are moving very, very quickly across the polar region of the planet. We can see that the magnetotail is undergoing huge turmoil and reconfiguration, caused by buffering from solar wind,” said Jonathan Nichols, of the University of Leicester’s Department of Physics and Astronomy, who led the Hubble observations.
NASA’s THEMIS Spacecraft See magnetic reconnection / collapse in Earth’s magnetotail
What’s happening – and you can see it clearly in the video above – is that the incoming solar wind connects to and ‘peels back’ a portion of the magnetic field on the dayside of both Earth and Saturn. When the lines pinch together and reconnect on the back or magnetotail-side, a torrent of solar electrons is funneled into the upper atmospheres of both planets. Voila – aurora borealis! Here’s another video showing it from a slightly different perspective.
Dance of Saturn’s auroras
“The particular pattern of auroras that we saw relates to the collapsing of the magnetotail,” Nichols added. “We have always suspected this was what also happens on Saturn. This evidence really strengthens the argument.”
Cool beyond cool. Earth and Saturn are auroral buddies.
Follow the arc from fiery Mars in the south through Spica to find Saturn. Keep going all the way to Antares. All four are magnitude 1 or brighter. The map shows the sky around 10:30 p.m. local time facing south. Stellarium