Barnard’s Star hosts four hostile small planets whose unusual chemistry and orbital rhythm reveal how compact planetary systems can form and survive. Just under six light-years from Earth, Barnard’s Star hosts four small worlds unlike any planet in our own Solar System. A rare mineral may limit waterResearchers at the University of Cambridge examined the chemical composition of Barnard’s Star to infer what its planets may be made of. Barnard’s Star may avoid that fate through orbital resonance, in which the planets’ orbital periods follow a repeating numerical pattern. Similar orbital relationships help stabilize Jupiter’s moons and may protect the Barnard’s Star planets from gravitational disruption.