This isn’t a sound effect from a sci-fi movie. Instead, it’s the “voice” of the auroras on the planet Saturn – radio waves that have been shifted to wavelengths we can hear. They were recorded by the Cassini spacecraft as it closed in on Saturn two decades ago.
The radio waves are produced by the complex interplay between Saturn’s magnetic field and the solar wind – a steady flow of charged particles from the Sun.
Motions deep inside the planet generate the magnetic field, which is about as strong as Earth’s. But because Saturn is much bigger than Earth, its magnetic field is much bigger as well – it fills a huge volume of space.
The magnetic field forms a teardrop-shaped “bubble” around Saturn. That bubble deflects much of the solar wind. But some of the particles make it through. The lines of magnetic force guide some of them toward the magnetic poles. They spiral in, emitting radio waves as they do so. And when the particles hit the upper atmosphere, they create auroras – shimmering curtains powered by the Sun.
Saturn is putting in its best appearance of the year. It’s at opposition – it lines up opposite the Sun. It’s closest to Earth, so it shines brightest. And it’s in view all night. The giant planet looks like a bright golden star. It’s low in the east at nightfall, and climbs high across the south later on.
Script by Damond Benningfield