發信人: EPS.bbs@crux.chem.nsysu.edu.tw (觀測如作戰), 看板: astronomy
標  題: Re: 請問北極星
發信站: 中山南十字BBS站 (Sat Apr 12 08:10:37 2003)
轉信站: Lion!news.nsysu!crux
Origin: crux.chem.nsysu.edu.tw

【 在 supernova.bbs@bbs.ntu.edu.tw (∫思念dt=愛戀+C) 的大作中提到: 】
:  Well, anyway, I have a question about this tile.
:  Although we know that the Sirius, now is not the "pole star".
:  (the nearest star to the north celestial pole)
:  is there any probability that in the future, the sirius will become
:  the "pole star" ?
:  Because you know that due to the precession of the earth, the Vega,
:  will become the "pole star" in several tens thousand years later.
:  So, EPS, do you know that is it possible that Sirius could become the pole
:  star in the future ? I don't know actually. If it is not possible,
:  could you give me a reason ? thank you very much. (due to the large
:  inclination angle of the Canis Major ? )

這問題有意思,N年後織女星會變成北極星,那麼,位於天球南半球的
天狼星在M年後會不會變成南極星? (當然現在它不是)

那就要看它在不在天球南極的進動軌道上了.

猜一下的話,織女星赤緯約40度,可以最後逛到天北極去,天狼星赤緯只有
20度不到,要逛到天南極去....應該不可能. 地軸在天球上的進動軌道是
半徑23.5度的圓,所以只有赤緯大於90-23.5*2=43度的有機會成為極星而已.


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※ 來源:•南十字 crux.chem.nsysu.edu.tw•[FROM: 128.171.163.167]