| 单词 | variable star |
| 释义 | variable star A star that varies in brightness (see luminosity). This variation, which can be regular or irregular, can be due either to changes in internal conditions (an example of this being a pulsating star in which the variation in brightness is due to the star expanding and contracting) or due to external reasons, such as a star being eclipsed by another star (or stars). Changes in brightness of a star occur both in its early stages and close to its death. Examples of variable stars are nova and supernova. Observations of variable stars provide important information concerning the mass, size, structure, temperature, and evolution of stars. There are more than 25 000 variable stars known, some of which can be seen with the naked eye. The time-scale from maximum to minimum brightness varies from less than a second to a few years |
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