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。

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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。

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