"The Secret of the Ninth Planet" by Donald A. Wollheim is a science-fiction novel published in 1959. When the Sun's light mysteriously begins to dim across Earth, threatening a new ice age, young Burl Denning discovers alien machinery in the Peruvian Andes. As calculations reveal the Sun may explode within years, Burl joins a desperate expedition aboard an experimental antigravity spaceship to hunt down similar installations throughout the solar system and confront an alien force from Pluto. (This is an automatically generated summary.)