In 2014, Kapteyn's Star was announced to host two planets, Kapteyn b and Kapteyn c. Kapteyn b is the oldest-known potentially habitable planet, estimated to be 11 billion years old. However, Robertson et al. (2015) noted that the orbital period of Kapteyn b is an integer fraction (1/3) of their estimated stellar rotation period and thus the planetary signal is most likely an artifact of stellar activity. The authors do not rule out the existence of Kapteyn c, calling for further observation. Guinan et al. (2016) (as well as earlier authors) found a lower value for the stellar rotation, which lends support to the original planetary finding. Additional data will be needed to confirm the rotation period and resolve the dispute.