Sailing in the Solar Wind
Have you ever seen the lights of the Auroras? If you’re close enough to the North or South Pole, you can see elegant trails of green light dancing across the night sky. People who've witnessed them often say it was one of the most overwhelming experiences they ever had! This beautiful phenomenon is caused by particles flying at Earth from the Sun, called the 'solar wind'. The particles collide with Earth's magnetic field, which carries them to the poles. There they sneak through the magnetic field and interact with Earth's atmosphere, causing it to glow with colourful light. The boundary where the solar wind meets the magnetic field is called a 'bow shock'. You could compare it to what happens when the bow of a ship sails through the water. On the left of this picture, you see the bow shock of Saturn in blue. Just like Earth, Saturn has a magnetic field, leading to the same phenomenon: Auroras at the poles. The Cassini spacecraft, which is currently orbiting around Saturn, has crossed the bow shock over a hundred times taking readings of its strength. So far, it has always returned similar results. However, this time, Cassini sent back a measurement that made astronomers stare at their computer screens in disbelief. The bow shock appeared to be ten times stronger than usual! This caused incoming particles from the Sun to bounce back into space, instead of creating an Aurora. You could say Saturn acted as a trampoline!
The Auroras are not always green, they can be all colours of the rainbow! The colour depends on how high in the atmosphere the light is shining.