Planet the Drake equation, which estimates the number of intelligent, communicating civilizations that exist in the Milky Way. There are exoplanets that are much closer to their parent star than any planet in the Solar System is to the Sun, and there are also exoplanets that are much farther from their star. Mercury, the closest planet to the Sun at 0.4 AU, takes 88 days for an orbit, but the shortest known orbits for exoplanets take only a few hours, e.g. Kepler-70b. The Kepler-11 system has five of its planets in shorter orbits than Mercury's, all of them much more massive
Return to the Lost Planet on the development of this genre in Israel. The plot follows on precisely from "The Lost Planet". A previous expedition to Hesikos, the wandering 'lost planet' which is now within a few days flight of Earth, has crash-landed, and Dr Lachlan McKinnon (its organiser), Professor Hermanoff and American engineer Spike Stranahan are marooned. McKinnon's colleagues must build and launch a spaceship from their Scottish base to travel to Hesikos, but to construct the ship they must obtain the expert assistance of Dr Andrieff, a scientist and engineer, who risks exile from his Eastern European country by so doing. The crew,