A star is a huge, more or less spherical mass of glowing gas emitting large amount of radiant energy. Billions of stars form a galaxy. There are three types of stars. They are
(i) double and multiple stars
(ii) intrinsically variable stars and
(iii) Novae and super novae.
In a galaxy, there are only a few single stars like the Sun. Majority of the stars are either double stars (binaries) or multiple stars The binary stars are pairs of stars moving round their common centre of gravity in stable equilibrium. An intrinsically variable star shows variation in its apparent brightness. Some stars suddenly attain extremely large brightness, that they may be seen even during daytime and then they slowly fade away. Such stars are called novae. Supernovae is a large novae.
The night stars in the sky have been given names such as Sirius (Vyadha), Canopas (Agasti), Spica (Chitra), Arcturus (Swathi), Polaris (Dhruva) … etc. After the Sun, the star Alpha Centauri is nearest to Earth.