Saturn's Auroras Filmed by Hubble
This unique Hubble image from early 2009 features Saturn with the rings edge-on and both poles in view, offering a stunning double view of its fluttering auroras. Saturn's auroras are analogous to the more familiar northern and southern light on Earth. At the time when Hubble snapped this picture, Saturn was approaching its equinox so both poles were equally illuminated by the Sun's rays. The northern auroral oval is slightly smaller and more intense than the southern one, implying that Saturn’s magnetic field is not equally distributed across the planet.
Credit: NASA, ESA and Jonathan Nichols (University of Leicester)

A new Hubble movie shows a rare view of Saturn with its many rings sitting edge-on, providing a dazzling glimpse of the planet's poles and the auroras that dance above them.

It takes Saturn almost thirty years to orbit the sun, with the opportunity to image both of its poles occurring only twice in that period, when the planet reaches its equinox (the point in a planet's orbit when the sun's rays fall perpendicular to the planet's equator).

Saturn hit this position last year, providing Hubble with the unique chance to keep a sustained view of the planet with both its poles in view. The movie they created from the data, collected over several days during January and March 2009, has aided astronomers studying both Saturn?s northern and southern auroras.

Given the rarity of such an event, this new footage will likely be the last and best equinox movie that Hubble captures of our planetary neighbor.

As Saturn was approaching its equinox, both poles were equally illuminated by the sun?s rays.

Charged particles blown out from the sun make their way through the solar system.? When they encounter a planet with a magnetic field, such as Saturn or the Earth, the field traps the particles, bouncing them back and forth between its two poles.

A natural consequence of the shape of the planet?s magnetic field, a series of invisible ?traffic lanes? exist between the two poles along which the electrically charged particles are confined as they oscillate between the poles.

The magnetic field is stronger at the poles and the particles tend to concentrate there, where they interact with atoms in the upper layers of the atmosphere, creating auroras, the familiar glow that the inhabitants of the Earth?s polar regions know as the northern and southern lights.

At first glance the light show of Saturn?s auroras appears symmetric at the two poles. However, analyzing the new data in greater detail, astronomers have discovered some subtle differences between the northern and southern auroras, which reveal important information about Saturn?s magnetic field.

The northern auroral oval is slightly smaller and more intense than the southern one, implying that Saturn?s magnetic field is not 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.

Video ? Hubble Spies Saturn?s Auroras

Images: Snapshots of Saturn

Images: Colorful Auroras