STARS AND PLANETS Star A star is a luminous and biggest object in the universe that emit light naturally. Sun is also a star. The study of birth , life and death of a stars is called stellar evolution. First stage in the birth of star is called protostar and the death of star is called supernova . FORMATION OF A STAR BY CLOUD OF DUST How stars are formed ? Stars are made by cloud of gases and dust that scattered throughout the galaxies. The cloud of dust is called the orion nebula . As gravitational force of attraction applied on cloud they collapses and when cloud collapse the material at the center get heat up so that all stars and planet have high temperature at core. A star build by continuous process of gravitational pull cloud collapse to make its size bigger. The size of star (or mass of a star) reaches from 15 to 130 solar masses . At center the temperature gets extremely high, it tigger the fusion reaction. All the material that has fallen in then evolves into a hot and br