Lucky Starr and the Big Sun of Mercury is the fourth novel in the Lucky Starr series, six juvenile science fiction novels by Isaac Asimov that originally appeared under the pseudonym Paul French. The novel was first published by Doubleday & Company in March 1956. Since 1972, reprints have included a foreword by Asimov explaining that advancing knowledge of conditions on Mercury has rendered some of the novel's descriptions of that world inaccurate. Setting Lucky Starr and the Big Sun of Mercury was written in 1955, when it was believed that Mercury was tidally locked to the Sun. A character notes that there are places on Mercury's sunside where it is hot enough to melt lead and boil sulfur, while the nightside is the only planetary surface in the Solar System that never sees the Sun. Most of the novel's action takes place in and around an astronomical observatory located at the planet's north pole, where libration results in a half-mile movement of the terminator. The observatory was built fifty years before on the site of a mining complex, which has since been abandoned. Plot summary It has been a year since the events in Lucky Starr and the Oceans of Venus, and in that time a government-funded research project, Project Light, is built at the astronomical observatory on Mercury's north pole to conduct research into the newly discovered sub-etheric optics in hope of transmitting solar energy through hyperspace. The head of Project Light is the leading scientist in sub-etheric optics, Scott Mindes. A series of accidents has plagued Project Light, which David "Lucky" Starr and John Bigman Jones have come to investigate. Shortly after meeting Starr and Bigman, Mindes takes them onto the surface of Mercury and explains his worries; but works himself into a frenzy and fires a blaster at Starr, whereupon Bigman tackles him and he is brought unconscious into the observatory. Starr and Bigman meet Mindes' friend Dr. Karl Gardoma, the observatory's physician; Jonathan Urteil, who works for a political opponent of the Council of Science named Senator Swenson; Dr. Lance Peverale, the head of the observatory; and Dr. Hanley Cook, Pevarale's chief assistant, who wants to succeed Peverale. The next day, at a banquet in Starr's honor, Peverale states his belief that the Sirians are behind the troubles plaguing Project Light; whereupon Starr replies that the Sirians' most likely locations are the abandoned mines located