People used to think comets were warnings of disasters. Today we know that they are icy visitors from the most distant regions of the Solar System. Other stars have exoplanets and they seem to have exocomets too.
It visits every 75 years or so, appearing like a celestial ghost in our skies. In the past it has been a bad omen and scary object, but last time it came it was a big event around the world. What is it? Halley's Comet, the most famous comet of all.
Where do comets come from? The Oort Cloud is home to a trillion comets at the edge of the Solar System, nearly half way to the next star. Sometimes they get kicked out and sometimes they come to visit the inner Solar System.