Results for pole star
On this page:
 
Medical Dictionary:

daughter star


n.

One of the figures forming the diaster of a dividing cell. Also called polar star.

 
 
Wikipedia: pole star
Long exposure of stars appearing to circle the North Celestial pole. The daily rotation of Earth creates the appearance of rings around the pole.
Enlarge
Long exposure of stars appearing to circle the North Celestial pole. The daily rotation of Earth creates the appearance of rings around the pole.

A pole star is a visible star that is approximately aligned with the Earth's axis of rotation; that is, a star that lies in the direction pointed to by one of Earth's poles. There are potentially both north and south pole stars, but whether there is either depends on the current stellar configuration. The term the pole star usually refers to the star Polaris (colloquially referred to as the "north star") which is the current northern pole star.

Pole stars change over time because stars exhibit a slow but distinct drift with respect to the Earth's axis. The primary reason for this is the precession of the Earth's rotational axis that causes its orientation to change over time. If the stars were fixed in space, precession would cause the position of a pole star to trace out an imaginary circle on the celestial sphere approximately once every 26,000 years. However, the stars themselves exhibit motion relative to each other (including the sun), and this so-called proper motion is another cause of the apparent drift of a pole star.

Pole stars are often used in celestial navigation. While other stars' positions change throughout the night, the pole stars' position in the sky does not. Therefore, they are a dependable indicator of the direction toward its respective pole.

North pole


Further information: North Star

At the present time, Polaris is the pole star in the northern direction. Its mean position (taking account of precession and proper motion) will reach a maximum declination of +89°32'23", so 1657" or 0.4603° from the celestial north pole, in February 2102. (Its current declination is +89°15'50.8".) Its maximum apparent declination (taking account of nutation and aberration) will be +89°32'50.62", so 1629" or 0.4526° from the celestial north pole, on 24 March 2100. (ref: Jean Meeus, Mathematical Astronomy Morsels Ch.50; Willmann-Bell 1997)

South pole


Further information: South Star

Sigma Octantis is the closest star to the south celestial pole, but it is too faint to serve as a useful pole star. The Southern Cross constellation functions as an approximate southern pole constellation, by pointing to where a southern pole star would be. At the equator it is possible to see both Polaris and the Southern Cross.

Other planets

Other resources


See also


External links


 
 

Join the WikiAnswers Q&A community. Post a question or answer questions about "pole star" at WikiAnswers.

 

Copyrights:

Medical Dictionary. The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company Read more
Wikipedia. This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Pole star" Read more

Search for answers directly from your browser with the FREE Answers.com Toolbar!  
Click here to download now. 

Get Answers your way! Check out all our free tools and products.

On this page:   E-mail   print Print  Link  

 

Keep Reading

Mentioned In: