Polaris

Polaris the Pole Star. - The images were captured by Pip Stakkert using the astro-modded Canon 200d DSLR with  a Samyang F2 135mm lens on a fixed tripod. 20x8sec lights at F2 and ISO800 stacked and developed using Affinity Photo software (uncropped).

Polaris, the Pole Star or alpha Ursa Minor is  the nearest Cepheid variable star to the Solar System. Cepheid variable stars are useful 'standard candles' as the rate of change in  luminosity, their pulse' is related to their absolute luminosity. By knowing absolute luminosity and apparent luminosity of a star it is possible to compute distances to remote stars and galaxies.

Polaris, although seen by the naked eye as a single point of light, is in fact a triple star system some 330 light years distant from the Earth.. The brightest component Polaris Aa is a F71b evolved yellow supergiant star with a mass 5.4 times that of the Sun.

  

Polaris lies almost directly over the Earth's axis of rotation and as a consequence it appears fixed in the sky whilst all the other stars  seem to rotate around it. The elevation of Polaris above the horizon gives the approximate latitude of the observer. - Kurt Thrust current Director of the Jodrell Plank Observatory

Demonstration of the apparent rotation of stars around the fixed Pole Star