Hubble captures Saturn's northern and southern lights
The Hubble space telescope has for the first time snapped the flickering aurorae that light up both of Saturn's poles.
The opportunity to image both of Saturn's poles occurs only twice in its 30-year orbit - so it wasn't until 2009 that Hubble got the chance to image Saturn with the rings edge-on and both poles in view. At the same time Saturn was approaching its equinox, so both poles were equally lit by the Sun.
When the charged particles of the solar wind get close to a planet's magnetic field they get trapped, bouncing back and forth between its two poles.
The magnetic field is stronger at the poles, and the particles tend to concentrate there. They interact with atoms in the upper layers of the atmosphere, creating aurorae - the northern and southern lights.
At first glance the light show of Saturn's aurorae appears pretty symmetrical. However, looking closer, astronomers have discovered some subtle differences.
The northern auroral oval is slightly smaller and more intense than the southern one, implying that Saturn's magnetic field isn't equally distributed across the planet; it is slightly uneven and stronger in the north than the south.
As a result, the electrically charged particles in the north are accelerated to higher energies as they are fired toward the atmosphere than those in the south. This confirms a previous result obtained by the space probe Cassini, in orbit around the ringed planet since 2004.
There's a video, here.