- Gamma Cephei Ab (abbreviated γ Cephei Ab, γ Cep Ab), formally named Tadmor /ˈtædmɔːr/, is an exoplanet approximately 45 light-years away in the constellation of Cepheus (the King). The planet was confirmed to be in orbit around Gamma Cephei A in 2003, but was first suspected to exist around 1988 (making this planet arguably the first true exoplanet discovered).