Indian astronomers has made the important discovery that the stars visible at night are similar to the Sun visible during day time.
There is an old Sanskrit shloka (couplet) which states "Sarva Dishanaam, Suryaha, Suryaha, Suryaha" which means that there are suns in all directions. This couplet which describes the night sky as full of suns. In other words, it was recognized that the sun is also a star, though the nearest one. This understanding is demonstrated in another Sloka which says that when one sun sinks below the horizon, a thousand suns take its place.