Kapteyn's Star was a star in the Milky Way Galaxy. It was a class M1 red dwarf located in the galactic halo. In the mirror universe the Terran Empire had a top-secret research facility on an asteroid orbiting Kapteyn's Star. In 2410 they were developing a biological weapon for use against nonhumans in this facility, but the Klingon-Cardassian Alliance discovered the project and allied with the prime universe Federation to attack the facility and destroy it. (Bait and Switch: "Dreaming of Your Face")