Stars are formed from giant cloud of dust and gas. Due to gravity the cloud collapses in a rotating disc. As the disc rotates more and more gases are pulled towards the centre and thus creating a hot and dense centre called protostar. If enough mass collapses into protostar a bipolar flow occurs. Two massive gas jets erupts from protostar and blasting away remaining gas and dust from its surface. At this point the young star stabilizes. The energy in the Star is created through a process called Nuclear fusion.The Star will die once it runs out of gases to burn. The star will first expand into a red super giant. The core contracts and outer layer expands. Then comes the stage called Supernova. The core collapses in an instant. The repulsive electrical forces overcomes the gravitational force, causing a massive, short lived explosion blowing away the star’s outer layer. After super nova the star may turn into either a black hole or a neutron star. After Supernova the mass of the core becomes 3 to 4 times that of the Sun. The core collapses due to gravitation forming a Black hole. The gravitational force in a black hole is so strong that even light cannot escape from it. Neutron star is the ultra dense core of a star after super nova. It is formed when the star is not so massive to form a black hole. A pulsar is a rotating Neutron Star radiating electromagnetic radiations at a rate of upto 1000 pulses per second.