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 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. Plot Helping his father on an archeological expedition in the Peruvian Andes, Burl Denning looks forward to studying engineering when he enters college in the fall. The expedition's study of Inca ruins is interrupted by the arrival of a small guided missile from California. Inside the missile they find a message informing them that over the past several days the Sun's light has dimmed all over the world, threatening the onset of a new ice age, and that the source of the dimming has been traced to a point seven miles from their camp. Burl and his father hike to the location they were given and come to a dome surrounded by a wall. Inside the dome they find alien machinery that will not respond to their manipulations of the controls. Burl tries to pick up a small sphere and it blasts him with what feels like an electric shock. He then discovers that the controls will respond to him, so he shuts down the installation and sees immediately that the sunlight outside the dome has returned to normal. Picked up by the military and taken to California, the Dennings are told that astronomers have detected a dimming of sunlight on Mercury and Mars and suspect it's occurring on the other planets as well. Worse, calculations show that if the Sun-stealers’ program continues, the Sun will blow up as a nova in two to three years. Fortunately the means to solve the problem stands readily at hand for those who dare to use it – a giant