The Northern Lights, polar lights or Aurora Borealis is one of the most beautiful sights Nature has to offer. The Aurora Borealis name was coined by Galileo from the Roman Goddess of the dawn and the Greek name for the North wind. The Aurora can be viewed in a band called The Auroral Zone between 10 and 20 degrees from the geomagnetic poles of the Earth. Obviously a clear night and very dark skies are required to admire the full beauty of the aurora.
An aurora occurs when the solar wind and the magnetosphere interact. The magnetosphere is the region around a planet which governs charged particles around the magnetic field. The magnetic field and atmosphere is what protects us from deadly solar rays.
The sun blasting charged particles toward Earth are intercepted by the magnetosphere causing them to changes states. This changing of states requires energy which in turn emits light.
Depending on what molecules from the atmosphere interact with the charged particles, the Aurora can be different colours. If interacting with oxygen the Aurora will shine green. If they interact with nitrogen, blue or red is observed although these are harder to see due to a darker colour.
We all know of the northern lights, interestingly there are southern lights aswell. They are mostly viewed from South America and the Antarctic regions. Same causes and effects as the Northern lights although viewed from the magnetic South Pole as opposed to North.
So why are auroras so important? Planets with magnetic fields and atmospheres can tell observers what they are made of. We have green Aurora light so it tells the universe we have an oxygen rich atmosphere. If any of the exo planets we have found have a green aurora. We have found life!