What are stars and constellations?

What is a star?

On a clear night we see many stars; some are bright and others are dim. Stars shine with their own light. The Sun is also a star, the one closest to us: an extremely hot ball of gases. Other stars look like tiny dots only because they are very far away, even though some are much bigger than the Sun.

Patterns among the stars

Look at the night sky for a while and some groups of stars seem to form shapes, like dots joined in a drawing. Long ago, watching the stars was a favourite pastime, and people linked these patterns with animals, things or characters from stories. Different cultures gave them different names. The imaginary shapes made the stars easier to recognise.

These patterns were useful too. Before modern technology, and even before the magnetic compass, recognising stars helped people, especially sailors and travellers, to find directions at sea or on land. Stars once guided the caravans that passed through Nubra in Ladakh, and star patterns are still a backup method in emergencies.

88 constellations

Groups of stars forming patterns were called constellations. Because cultures marked the sky in different ways, the International Astronomical Union (IAU) agreed on a single set of boundaries in the early twentieth century and listed 88 constellations, dividing the whole sky into 88 regions. Today, a constellation is one of these regions, but the word is still commonly used for the bright star patterns inside them.

Orion, Taurus and Canis Major

Orion is often pictured as a hunter. Three stars in a short straight line in the middle make his belt. Some people imagine Orion, followed by his dog (Canis Major), battling a bull (Taurus). In India, Orion is easiest to see from December to April, after sunset. To find Sirius, the brightest star in the night sky, find the belt first, then follow a line through its three stars towards the east.

Nakshatras

In Indian astronomy, a nakshatra is a certain star or a group of stars:

Nakshatra	What it is	Constellation
Ardra	the star Betelgeuse	Orion
Krittika	the star group Pleiades	Taurus
Rohini	the star Aldebaran	Taurus

The Big Dipper and the Pole Star

The Big Dipper, called Saptarishi in India, is a pattern of seven stars in the constellation Ursa Major; the Little Dipper is in Ursa Minor. The Pole Star (Dhruva tara), at the end of the Little Dipper, appears nearly stationary in the North, which helps locate North in the northern hemisphere. To find it, look north around 9 p.m. in summer and spot the Big Dipper. The two stars at the end of its cup are the pointers: follow a line through them for about five times the gap between them, and you reach a star that is not very bright. That is the Pole Star.

Stories in the stars

Many forest-dwelling communities and tribes of India have their own stories. Tribes in Central India see the four stars of the Big Dipper that make a rough rectangle as a “grandmother’s cot”, with the other three stars as thieves stealing it. Fishermen on the Konkan coast see the four stars as a boat, with the last three stars as its neck.

Seeing them yourself

Not every star or constellation is visible from every place on every night; the Pole Star, for example, cannot be seen from the southern hemisphere. Use images of the patterns and a sky-map app to know when and where to look, go with an adult to a dark, open place on a clear, moonless night, and wait about half an hour for your eyes to adjust. Next, read about the planets of the Solar System.