The fact that this property cannot be close to zero in the current universe is the reason that no stars (**) over 110 solar masses have been discovered.
In objects in which this property is very low, pair production in the core can reduce thermal pressure, thereby causing gravitational collapse and an explosion that does not leave a black hole in its wake. That process leads to a pair-instability supernova, which can only happen when this property is very low. The fact that this property cannot be close to zero in the current universe is the reason that no stars (**) over 110 solar masses have been discovered. A decrease in this property, and an increase in mass, characterizes the transition between (*) Population I, Population II, and Population III stars. For 10 points, name this property that is very low in the oldest stars of the universe, a term that refers to the non-hydrogen and -helium content of a star.
In objects in which this property is very low, pair production in the core can reduce thermal pressure, thereby causing gravitational collapse and an explosion that does not leave a black hole in its wake.
metallicity [or metal content; or equivalents including metal]