Identification of stars

On a clear night sky about 6000 stars are visible to the naked eye. Some stars appear to form groups and ancient astronomers construct figures of animals and mythological heroes from them.And this groups are called constellations. At present,the whole sky is divide into 88 constellations with boundaries defined by the International astronomical union. Twelve of them lie in the path of the sun and moon when we seen from the earth. They are called the signs of the zodiac(Rasis). In the Indian astronomy there are 27 group of stars or 'Nakshatras' on or near the path of the sun and the moon. The moon occupies the position of one (star) nakshatra on each day and the day is named by the name of the nakshatra in which the moon is bound at sun rise.

Some bright stars are easily distinguishable and are given specific names such as 'Sirius', 'Polestar', 'Canopus', 'Altair' etc. Besides star groups were listed by Greek letters alpha, beta, gamma, etc by Bayer in 1603. In modern times, almost all visible stars through telescopes are identified by numbers and entered in catalogs. The important catalogs are,

1. BCVS catalog

2. Fundamental catalog

3. New general catalog

4. Index catalog etc.

These catalogs contain the position and names of stars, star clusters, gaseous nebula, Planetary nebula, external galaxies, Quasars (may be star), Pulsars etc. All this are identified by their position in the celestial sphere.

Astronomy And Astrophysics

                                  A study about the celestial objects and the various phenomena connected with them can be said as Astronomy. Astrophysics is only its extension where the nature of stars and other cosmic objects are studied using physical laws. Observations using telescope show that stars are self luminous spherical objects like the sun.some of them are much larger and brighter and others are smaller and dim. Some stars have larger size than sun but appears as dim because they are far away from us. Astronomy is an observational science where the experiments occur naturally in the stars, galaxies or interstellar medium,uncontrolled by the observer. Since repetition of an event is impossible, a statistical study of a large number of similar events are conducted before arriving at conclusions.