The Secret of the Ninth Planet is a science-fiction novel written by Donald A. Wollheim and first published in 1959. Wollheim takes his heroes on a grand tour of the solar system as that team struggles to prevent an alien force from blowing up the sun.
Donald Allen Wollheim (October 1, 1914 – November 2, 1990) was an American science fiction editor, publisher, writer, and fan. As an author, he published under his own name as well as under pseudonyms, including David Grinnell. A founding member of the Futurians, he was a leading influence on science fiction development and fandom in the 20th-century United States.