According to a 2005 paper by Fischer et al, this quantity for the host star is a strong predictor of whether gas giants are likely to be detectable using Doppler spectroscopy. In 2022, astronomers discovered that objects in the C-19 stellar stream had an unusually low value (-5[1])for this quantity. High values of this quantity inhibit the reduction of outward pressure during pair production, thereby preventing pair-instability supernovae. Population (*) III stars have values (10[1])of this quantity (-5[1])near zero, (10[1])whereas Population II stars located at the halos of spiral galaxies are low in this quantity. This quantity is denoted Z in the equation “X plus Y plus Z equals 1,” where X and Y represent the abundances of the two lightest elements. (10[1])For 10 points, name this quantity which measures the proportion of elements heavier than helium in a star. ■END■ (10[1])