Other important stars

Apart from the Sun, the two other main stars are Alpha Centauri A and Alpha Centauri B. The third star, Proxima Centauri, is the closest star of the Earth, other than the Sun. It is about 4.22 light-years away from Earth. A light-year is a unit of distance, which is commonly adopted for measuring vast distances in the infinite space. It is the distance travelled by a ray of light in one year. Light moves at a velocity of about 3000.000 kilometers each second. That means, in a year a beam of light travels approximately equal to 95 million km. This distance is a ‘light year’.  

‘Sirius’, also known as the ‘Dog Star’, is the brightest star in the Canis Major or the Big Dog constellation. It is very luminous, as it is actually a binary star system, consisting of a white main-sequence star named Sirius A, and a faint white dwarf companion named Sirius B.

‘Polaris’ is another better known star, which is the 45^th brightest star in the clear night sky. It is also known as, the Pole Star, Lodestar, and sometimes Guiding Star. It is very close to the north celestial pole, and that is why it has been used as a navigational tool in the northern hemisphere for centuries. Actually, this particular star is known as Alpha Ursae Minoris because it is the alpha star in the constellation Ursa Minor, popularly known as the Little Bear. In fact, being a single supergiant, Polaris is actually a trinary star system, comprised of a main star and two smaller companions.

The stars appear to rise in the east and sets in the west. But, there is an exception. At the North Pole, nobody will see a rising or setting star. There the stars seem to move around the sky in circles to the horizon and the Polaris stays right overhead in the direction of the North Pole.