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, (15[1])thereby preventing pair-instability supernovae. (15[1])Population (*) II stars (10[1])located at the halos of spiral galaxies are low in this quantity, (10[1])while Population III stars have values of this quantity near zero. (10[1])This quantity is denoted Z in the equation “X plus Y plus Z equals 1,” (10[1])where X and Y represent the abundances of the two lightest (10[1])elements. For 10 points, name this quantity which measures the proportion of elements heavier than helium in a star. ■END■ (0[2])