R.G. Harrington and Fritz Zwicky discovered this object in 1953. George Abell (1955) cataloged it as globular cluster, while Zwicky (1957) classified it as a nearby dwarf galaxy, named the Capricornus Dwarf and suspected to be a Local Group member because of its resolution into stars. Later observations have confirmed it as a globular cluster within the halo of our Milky Way galaxy.
Palomar 12 lies out at about 62,000 light years from us and 52,000 light years from the Galactic Center. It is receding from us at about 28 km/s.
Irwin (1999) has brought up the hypothesis that Palomar 12 may once have been a member of SagDEG, the Sagittarius Dwarf Elliptical Galaxy discovered 1994 and currently in a close and potentially final encounter with our Milky Way Galaxy. Palomar 12 is thought to have escaped somewhen in the past and since been integrated in the Galactic Globular Cluster system and thus the Milky Way's Halo.