Saturn’s eerie polar light show

False-colour image of Saturn

This false-colour composite of 65 Cassini spacecraft images shows the glow of the aurora over Saturn's north polar region. The colours are: blue is sunlight reflecting from the rings and from one of Saturn's cloud levels; red shows where heat is coming from the interior of the planet; and green shows the aurora.

  • Mini-movie made of Saturn’s polar aurora
  • Uses data from NASA’s Cassini spacecraft
  • Aurora pulses in time with the Sun and Saturn’s spin

As if its rings weren’t spectacular enough, Saturn also puts on a light show for anyone who can see at the right wavelengths.

In this case, those eyes belong to NASA’s Cassini spacecraft, which has been orbiting the Ringed Planet since 2004.

Scientists using Cassini’s visual and infrared mapping spectrometer (VIMS) instrument have been studying Saturn’s aurora, the equivalent of Earth’s Northern and Southern Lights.

Aurorae occur when particles in the solar wind are directed along magnetic field lines towards a planet’s poles. Funnelling down into the atmosphere, they strike gas molecules and cause an eerie, but very pretty, glow.

“Cassini’s instruments have been imaging the aurora in magnificent detail, but to understand the overall nature of the auroral region we need to make a huge number of observations—which can be difficult because Cassini observation time is in high demand,” says Dr Tom Stallard of the University of Leicester in the UK.

Time-lapse video of Saturn's aurora

This time-lapse video covers 20 Earth hours—just under two whole Saturnian days. Parts of the aurora seem synchronised with the direction of the Sun (left-hand side), while other parts appear orchestrated with Saturn's magnetic field.

So Dr Stallard and his colleagues turned to other Cassini images that weren’t specifically targeted at the aurora—but which nevertheless happened to serendipitously capture it—to compile a short video that shows the aurora’s behaviour as Saturn rotates.

“Sometimes the aurora can be clearly seen, sometimes we have to add multiple images together to produce a signal,” Dr Stallard said.

The video shows the aurora changing considerably during the over the course of Saturn’s day, which is around 10 hours and 47 minutes in Earth time.

On the left-hand side of the video—the direction towards the Sun—the aurora brightens, indicating that it is being influenced by the Sun.

Other parts of the aurora seem more connected with the planet below; specifically, with the orientation of Saturn’s magnetic field as the planet spins.

“Saturn’s aurora are very complex and we are only just beginning to understand all the factors involved,” said Stallard.

Story by Jonathan Nally, editor

Images courtesy NASA / JPL / University of Leicester / University of Arizona.

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