USS Achernar (NCC-1732) was a Constitution-class heavy cruiser on active duty in Starfleet during at least the 23rd century. It was the lead ship and prototype for the Achernar-subclass of heavy cruisers. (Star Fleet Technical Manual, Ships of the Star Fleet, vol. 1) Achernar was flagship of the Starfleet Fourth Fleet, under the command of Admiral T'Pam, in the 2280s. (Starfleet International: USS Achernar)