This Halcyon Classics ebook is Donald A. Wollheim's sci-fi thriller THE SECRET OF THE NINTH PLANET.
On the day that the theft of the solar system's light begins, Burl Denning is with an archaeological expedition in the Andes, only a few miles from the source of the "disturbance." Within hours the United States Air Force has ordered the expedition to investigate the strange phenomenon that is causing a dimness and a drop in temperature throughout the world.
This is the start of a fantastic adventure that eventually takes Burl, a high-school senior, on the first circumnavigation of the solar system. On planet after planet, he and the crew of the Magellan, a gleaming, powerful, and virtually untested spaceship, discover the weird trappings of a brilliantly-designed Sun-tap station. Each planetfall brings unexpected hazards, as the ship draws closer and closer to solving the mystery of the theft.