How come cobalt 60 decays into nickel?

According to Cobalt-60 (Wikipedia), Co-60 decays via beta- decay to Ni-60. In Beta decay, a proton becomes a neutron or vice versa. In this case (β- decay), a neutron becomes a proton, and an electron is produced. read more

Cobalt-60 therapy can be used anywhere on the body. It is particularly useful in brain tumor patients because it is so precise. Because of its effectiveness and simple design, doctors have used cobalt-60 therapy to treat cancer for almost 60 years. Source : Gamma Knife - Cobalt-60 Therapy. Cobalt-60 is also used in a process called industrial radiography, to inspect metal parts and welds for defects. read more

60 Co decays by beta decay to the stable isotope nickel-60 (60 Ni). The activated nickel nucleus emits two gamma rays with energies of 1.17 and 1.33 MeV, hence the overall nuclear equation of the reaction is 59 27 Co + n → 60 27 Co → 60 28 Ni + e − + ν e + gamma rays. read more