1. Black hole: a region of space resulting from the collapse of a star; extremely high gravitational field 2. Toni Morrison won the Nobel Prize for literature in 1993. 3. Emily Dickinson published only a handful of poems during her life.

Common knowledge is general information that your readers may know or could easily locate in any number of reference sources. If you knew a piece of info BEFORE you started reading about your research topic, it is common knowledge. If a piece of information that was new to you when you began your research is referred to again and again in all your sources--cite the first article you read it in.