1·However, the amount of helium in the universe, as measured by spectroscopy, suggests that there are far more baryons in the universe than estimates based on galactic luminosity indicate.
然而，通过光谱学测量，宇宙中氦的数量表明，宇宙中重子的数量要比基于星系光度所估计的要多得多。
2·A complete MK designation includes both spectral type and luminosity class -for instance, the sun is a G2V.
一个完整的MK系统代号包含光谱类型和光度型两部分——例如，太阳属于G 2 V类恒星。
3·In principle, one can trace that history back in cosmic time by observing a so-called standard candle, a class of astronomical object whose intrinsic luminosity is uniform.
原理上，我们可以通过观测所谓的标准烛光(一种天体，它的绝对光度是相同的)来追溯宇宙内的历史。
4·Specifically, luminosity is proportional to radius squared.
具体来说，光度与半径的平方呈正比。
5·Stars are also classified by their luminosity under the Morgan-Keenan system.
恒星在MK系统下，也经常根据光度分类。