Night Sky and the Pole Star

Face north and find Saptarishi (the Big Dipper). Join the two stars at the outer edge of its bowl, Merak and Dubhe, and extend the line about five times their distance apart. The fairly bright star you reach is Polaris, the Pole Star. It stays in the same place all night.

Saptarishi is the Indian name for the group of seven bright stars called the Big Dipper or Plough, part of the constellation Ursa Major. The stars are named after seven sages: Kratu, Pulaha, Pulastya, Atri, Angiras, Vasishtha and Marichi. It is best seen in the northern sky on evenings from February to June.

A constellation is a group of stars that seems to form a pattern or shape in the sky, such as Saptarishi, Orion or Cassiopeia. The stars in a constellation are usually at very different distances from us; they only look close together. Astronomers today divide the whole sky into 88 constellations.

Polaris lies almost exactly above Earth's North Pole, on the line of Earth's axis. As Earth spins, every other star seems to circle around that point, but a star on the axis itself stays nearly still. It is not exactly on the axis, so it traces a tiny circle about 1.5° across, three times the width of the full Moon.

Yes, but it is low in the south of India. Its height above the northern horizon equals your latitude: about 34° in Srinagar, 28° in Delhi, 19° in Mumbai and only 8° in Kanyakumari, where haze and buildings can hide it. It cannot be seen at all from south of the Equator.

As Earth goes round the Sun, the night side of Earth faces a different direction in space each month. So the stars overhead at, say, 9 pm slowly change through the year; each star rises about 4 minutes earlier every night.