It may have once been part of the globular cluster Omega Centauri, itself the likely core of a dwarf galaxy swallowed up by the Milky Way in the distant past.

The discovery of two planets—Kapteyn b and Kapteyn c—was announced in 2014,[9] but had a mixed history of rejections and confirmations, until a 2021 study refuted both planets.

[10] Under the name CPD-44 612 it was included in the Cape photographic Durchmusterung for the equinox 1875 (−38 to −52) by David Gill and Jacobus Cornelius Kapteyn in 1897.

It became clear that the star had a very high proper motion of more than 8 arcseconds per year and had moved significantly.

[19] Based upon their element abundances, these stars may once have been members of Omega Centauri, a globular cluster that is thought to be the remnant of a dwarf galaxy that merged with the Milky Way.

[16][20][21] Kapteyn's Star is between one quarter and one third the size and mass of the Sun and has a much cooler effective temperature at about 3500 K, with some disagreement in the exact measurements between different observers.

[16] The stellar classification is sdM1,[3] which indicates that it is a subdwarf with a luminosity lower than that of a main-sequence star at the same spectral type of M1.

[2] The announcement of the planetary system was accompanied by a science-fiction short-story, "Sad Kapteyn", written by writer Alastair Reynolds.

[33] Guinan et al. (2016) (as well as earlier authors) found a lower value for the stellar rotation, which lended support to the original planetary finding.