Charles Messier was a French astronomer who lived in the 1700's.  He was a comet hunter.  As he hunted for comets, he saw the same cloud-like objects many times.  He decided to compile a list of these objects to avoid confusion with comets.  Each of these 110 objects were given a number starting with the letter M to identify it.  This is their Messier number.  

     Today, in April, a Messier marathon is held.  If you're fast and experienced, you can see all of these objects in one night.