The Lost Planets: Peter van de Kamp and the Vanishing Exoplanets around Barnard's Star

There are innumerable planets revolving around innumerable stars across our galaxy. Between 2009 and 2018, NASA's Kepler space telescope discovered thousands of them. But exoplanets—planets outside the solar system—appeared in science fiction before they appeared in telescopes. Astronomers in the early decades of the twentieth century spent entire careers searchi...