At a given mass and age, a metal-poor star will be slightly warmer. Population II stars ' metallicities are roughly ⁠ 1 / 1000 ⁠ to ⁠ 1 / 10 ⁠ of the Sun's ( [ F e H ] = − − 3.0 . . . − − 1.0 ) , but the group appears cooler than population I overall, as heavy population II stars have long since died. Above 40 solar masses, metallicity influences how a star will die: Outside the pair-instability window, lower metallicity stars will collapse directly to a black hole, while higher metallicity stars undergo a type Ib/c supernova and may leave a neutron star.