The Cassini-Huygens spacecraft is an unmaned vehicle gathering data about Saturn and its various moons. A few years ago, it sent back the following transmission:
What's going on there??? The answer is the Northen Lights, except the north of Saturn, rather than Earth.
The Sun spits out a huge number of electrically-charged, radioactive particles in all directions with a significant amount of force. It's called solar wind and you can picture it like a river of energy flowing from the surface of the Sun.
When electrically charged particles (like those in the solar wind) interact with magnetic fields they get deflected. On Earth, most of these particles are specifically directed to the north and south poles, where the magnetic field points. When these particles start flying into the Earth, they get mixed up in the ionosphere, Earth's very own electrically-charged bubble. The resulting mixture of electric and magnetic interactions causes the Northern Lights (Aurora Borealis) or the Southern Lights (Aurora Australis). But Earth is not unique.
Jupiter and Saturn have their own magnetic fields, and their own ionospheres (Uranus and Neptune probably have them too) which means solar wind does the same thing to them, creating the same beautiful light displays. But not all of light is visible. Some of it falls in the very low-energy part of the light spectrum: invisible radio-waves. These radio waves aren't picked up by our eyes, but to a probe like Cassini, they're a beautiful symphony.
What's happening in that video is that Cassini is picking up on radio waves from the North (or possibly South) pole of Saturn. Those radio waves can then be converted into audio sounds for the human ear. In other words, Saturn is acting like a radio station, pumping out its own surreal music. The resulting radio-to-audio waves are what you're hearing in the youtube clip!