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The revised Hipparcos parallax gives a distance to Polaris of about 433 light-years (133 parsecs), while calculations by other methods derive distances around 30% closer.
Polaris is a triple star system, composed of the primary star, Polaris Aa (a yellow supergiant), in orbit with a smaller companion (Polaris Ab); the pair in orbit with Polaris B (discovered in August 1779 by William Herschel).
The celestial pole will move away from α UMi after the 21st century, passing close by Gamma Cephei by about the 41st century, moving towards Deneb by about the 91st century.
The celestial pole was close to Thuban around 2750 BC, It was about the same angular distance from β UMi as to α UMi by the end of late antiquity. 320 BC described the celestial pole as devoid of stars.
included a table of the first two batches of names approved by the WGSN; which included Polaris for the star α Ursae Minoris Aa.
In antiquity, Polaris was not yet the closest naked-eye star to the celestial pole, and the entire constellation of Ursa Minor was used for navigation rather than any single star.
Therefore, it makes an excellent fixed point from which to draw measurements for celestial navigation and for astrometry.
The moving of Polaris towards and, in the future, away from the celestial pole, is due to the precession of the equinoxes.
It is very close to the north celestial pole, making it the current northern pole star.
The variability of Polaris had been suspected since 1852; this variation was confirmed by Ejnar Hertzsprung in 1911. Prior to 1963, the amplitude was over 0.1 magnitude and was very gradually decreasing.
After 1966 it very rapidly decreased until it was less than 0.05 magnitude; since then, it has erratically varied near that range.
It has steadily increased by around 4.5 seconds per year except for a hiatus in 1963–1965.
This was originally thought to be due to secular redward evolution across the Cepheid instability strip, but it may be due to interference between the primary and the first-overtone pulsation modes.