Stars in the Limelight:
Among Galilee's my discoveries with the telescope was his observation that the white nebulous band In the sky known as the Milky Way (Akash cranga) was in fact made up of very many stars. Ti this time, the model of the universe had consisted merely of the then known Solar System, with stars being nothing more than point sources of light. With'the availability of bigger and better telescopes in the post-Galilean era, the remaining planets of the Solar System, Uranus, Neptune and Pluto were discovered and the stars came to be examined in greater detail. The first ever study of the stars was made by the English astronomer William Herschel (1738-1822), who had earlier discovered the planet Uranus. Herschel showed in 1785 that the stars were not the backdrop to 'the Solar System but were individual objects that extended to infin~ty.. He prepared the first ever map of the Milky Way Galaxy and showed that it was, in fact, a part of a flat disc of countless stars.
In his model, the Solar System was situated within the Alky Way Galaxy which constituted the whole Universe. At that time, the telescopes were not very powerful. One could see in the sky,point-like objects, the stars. One could also see white fuzzy clouds called nebulae. When we entered the twentieth century, the model of the universe was still heliocentric.Our Sun was at the centre of the Milky Way Galaxy which with its stars and nebulae was the whole of the universe. However, it did not take long for the heliocentric model to be abandoned. We will now describe, in brief, the observations that led to the rejection of heliocentric model.