Dhruva Nakshatra, the Pole Star.

Astronomy Digital Picture – Photograph from a normal digital camera, and a short summary of the photo

23 Jan 2007

Dhruva Nakshatra (Polaris) is the brightest star in the constellation Ursa Minor. Its approximately aligned with the Earth’s axis of rotation, making it the current northern pole star. Picture above shows Usra Major (left) and polestar (right).

Polar Star directly indicates the latitude. Standing at the equator, the Polar Star is at the horizon in the north, being at the North Pole, the star is directly overhead.

Polaris will not always be the pole star. Over tens of thousands of years, perturbations to the Earth’s axis of rotation will cause it to point to other regions of the sky, tracing out a circle. Other stars along this circle were the pole star in the past and will be again in the future, including Thuban and Vega.

Polaris is 431 light years from Earth, according to astrometric measurements of the Hipparcos satellite

Hindu mythology – Dhruva was the prince blessed to eternal existence and glory as the Pole Star by Lord Vishnu. The story of Dhruva’s life is often told to children as an example for perseverance, devotion, steadfastness and fearlessness.

Tomorrow’s picture – Comet McNaught – An artistic view.