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北极星[North Star] [2005-8-13]
iamet 发表在 ¤〖天文〗
| The North Star is a star located close to the North Pole of the celestial sphere, i.e., the projection of the North Pole onto the sky. The North Star is current Polaris (right ascension [img]http://scienceworld.wolfram.com/astronomy/nimg21.gif[img], declination  ) since it is closest to the north celestial pole. However, due to precession of the equinoxes, the pole rotates through the sky with a period of about 26,000 years. Consequently, Vega ( , ) will become the North Star in ten to twelve thousand years. |
学好数理化，走遍天下都不怕！ | |
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