The secret of the ninth planet

The Secret of the Ninth Planet is a science-fiction novel written by Donald A. Wollheim and first published in the United States in 1959 by the John C. Winston Co. Wollheim takes his heroes on a grand tour of the Solar System as that team struggles to prevent an alien force from Pluto from blowing up the Sun. This is the last of three juvenile novels that Wollheim wrote for Winston, the other two being The Secret of Saturn's Rings and The Secret of the Martian Moons. This is one of the thirty-five juvenile novels that comprise the Winston Science Fiction set, which novels were published in the 1950s for a readership of teen-aged boys. The typical protagonist in these books was a boy in his late teens who was proficient in the art of electronics, a hobby that was easily available to the readers.