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 for this quantity. High values of this quantity inhibit the reduction of outward pressure during pair production, thereby preventing pair-instability supernovae. Population (*) II stars located at the halos of spiral galaxies are low in this quantity, while Population III stars have values of this quantity near zero. 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 (10[1])which measures the proportion of elements heavier than helium (10[1])in a star. ■END■ (0[2])