Yes, the given sentence is a run-on sentence. It combines two independent clauses without proper punctuation or conjunction. To correct it, you can use a semicolon, period, or conjunction:
"The Pulitzer Prize is awarded each year; it honors excellence in journalism, letters, and music."
"The Pulitzer Prize is awarded each year. It honors excellence in journalism, letters, and music."
"The Pulitzer Prize is awarded each year, and it honors excellence in journalism, letters, and music."