Why is Sagittarius A* called so? At the center of the Milky Way, we have a supermassive black hole. It's name is "Sagittarius A*". I was wondering that why is it called so? I mean, why "A*" why not just "A". Is there a naming system for super massive black holes?

Thanks!
Check this wiki link out. "The name Sgr A* was coined by Brown in a 1982 paper because the radio source was "exciting", and excited states of atoms are denoted with asterisks."

There is no unified naming system for black holes. They are usually named after their host galaxy. Others are identified by the name of the survey in which they were observed. A few black holes are catalogued by their constellation and the order in which they were discovered

EDIT: The 1982 paper by Brown and Lo can be found here.