| 单词 | magnitude |
| 释义 | magnitude A measure of the relative brightness of a star or other celestial object. The apparent magnitude depends on the star's luminosity, its distance, and the absorption of light between the object and the earth. In 1856 the astronomer N. R. Pogson devised a scale in which a difference of five magnitudes corresponds to a brightness ratio of 100 to 1. Two stars that differ by one magnitude therefore have a brightness ratio of (100)0.2:1 = 2.512, known as the Pogson ratio . This scale is now universally adopted. Apparent magnitudes are not a measure of luminosity, which is defined in terms of the absolute magnitude . This is the apparent magnitude of a body if it was situated at a standard distance of 10 parsecs |
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