Three measures of this property are calibrated relative to six different A0V (“A zero five”) stars in the Johnson–Morgan system. A layer of stellar atmosphere named for this property features prominent (15[1])H-alpha and Calcium II spectral lines (15[1])and lies (-5[1])between the photosphere and the transition (15[1])region. (15[2])Effective (15[1]-5[1])temperature (15[1])decreases along (15[1])diagonals (-5[1])of a diagram named for placing measures of this property on both axes. (15[2]-5[1])An (*) “index” of this property computed (10[1])as “B minus V” (10[5]-5[1])is sometimes (10[4])used (10[1]-5[1])as a substitute (10[1])for temperature on the (10[1])x-axis (-5[1])of a (-5[1])Hertzsprung–Russel (10[2]-5[3])diagram. (-5[2])Stars enter a tract (10[2])named for their (-5[1])size and this property (10[1]-5[2])near (-5[1])the end of (10[1]-5[1])the main sequence. (10[2]-5[2])Photometric (-5[1])scales measure this property (10[1]-5[3])that (-5[1])names (10[1])classes of (10[1])“dwarfs” and “giants.” (10[3]-5[1])For 10 points, name this property of stellar spectra that characterizes the chromosphere. ■END■ (10[18]0[3])