A pole star is a visible star, preferably a prominent one, that is approximately aligned with the Earth's axis of rotation; that is, a star whose apparent position is close to one of the celestial poles, and which lies approximately directly overhead when viewed from the Earth's North Pole or South Pole. A similar concept also applies to other planets than the Earth. In practice, the term Pole Star usually refers to Polaris, which is the current northern pole star, also known as the North Star.
The south celestial pole currently lacks a bright star like Polaris to mark its position. At present, the naked-eye star nearest to this imaginary point is the faint Sigma Octantis, which is sometimes known as the South Star.
While other stars' apparent positions in the sky change throughout the night, as they appear to rotate around the celestial poles, pole stars' apparent positions remain virtually fixed. This makes them especially useful in celestial navigation: they are a dependable indicator of the direction toward the respective geographic pole although not exact; they are virtually fixed, and their angle of elevation can also be used to determine latitude.
The identity of the pole stars gradually changes over time because the celestial poles exhibit a slow continuous drift through the star field. The primary reason for this is the precession of the Earth's rotational axis, which causes its orientation to change over time. If the stars were fixed in space, precession would cause the celestial poles to trace out imaginary circles on the celestial sphere approximately once every 26,000 years, passing close to different stars at different times. However, the stars themselves exhibit motion relative to each other, and this so-called proper motion is another cause of the apparent drift of pole stars.
Other articles related to "pole star, stars, star, pole":
42 Draconis is presently the northern pole star of Venus. ...
... have been designed in accord with the pattern of stars composing the constellation Draco ... The star pattern of the constellation Draco fits with fair precision to the Serpent Mound, with the ancient Pole Star, Thuban (α Draconis), at its geographical center within the first of seven coils from the head ... through the backward motion of precessionary circle of the ecliptic when Thuban was the Pole Star ...
... of the sighting tube to fix the position of the pole star, Shen Kuo wrote Before Han times it was believed that the pole star was in the center of the sky, so it was ... a little more than 1 degree away from the summit star ... I then tried to find the true pole by means of the tube ...
... the book reconstructs a myth of a heavenly mill which rotates around the pole star, and grinds out the world's salt and soil, and is associated with the maelstrom ... The millstone falling off its frame represents the passing of one age's pole star (symbolized by a ruler or king of some sort), and its restoration and the overthrow of the old king of authority and the empowering of ...
... In Japan, the Pole Star was represented by Myouken Bosatsu, ja妙見菩薩 ... In the Greek Magical Papyri the Pole star was identified with Set-Typhon, and given authority over the Gods ...
Famous quotes containing the words star and/or pole:
“What is this flesh I purchased with my pains,
This fallen star my milk sustains,
This love that makes my hearts blood stop
Or strikes a sudden chill into my bones
And bids my hair stand up?”
—William Butler Yeats (18651939)
“The discovery of the North Pole is one of those realities which could not be avoided. It is the wages which human perseverance pays itself when it thinks that something is taking too long. The world needed a discoverer of the North Pole, and in all areas of social activity, merit was less important here than opportunity.”
—Karl Kraus (18741936)