Remains of a Supernova - The Crab Nebula
Image taken from http://chandra.harvard.edu/photo/0052/
This picture shows the Crab Nebula - a cloud of gas and dust that's left over from a supernova that was seen on Earth in 1054 AD. Supernovae are so powerful that the single exploding star can become as bright as a whole galaxy. That's why supernovae are often used to look at the large-scale properties of the universe - they can be seen at great distances.