We should know soon whether a hypothetical distant planet is orbiting at the edge of our solar system. Planet Nine (also called Planet X), if it’s really there, is five to 10 times the mass of Earth and has been distorting the paths of smaller objects. Volcanologist and science writer Robin George Andrews tracks the evidence and the growing enthusiasm among some astronomers that we’ll soon have a ninth planet to replace poor Pluto. (One of these astronomers is the person who knocked Pluto out of the planetary pantheon and is hoping for atonement.)