Stars

The star are self glowing heavenly bodies which generate the energy themselves by nuclear fusion reaction. The temperature of stars is very high. About 3000 stars can be seen in the skyinclearnight with naked eyes.The sun is the nearest star of earth. Alpha centauri is the nearest star of the sun.

Evolution of Stars:

1. Formation of star:

   Scientist believed that stars are formed by the nebula. The nebula will make the collection of inter seller objects into various places into smaller parts. By any means, any one of the mass will develop the gravitational force and stars to attract the other patches towards itself. As a result of which its mass increases and the pressure on the circle also increases. And when the temperature of center reaches 5 x 106 degree Celsius then it is called a protostar .In protostar gradually nuclear fusion reaction starts, due to excessive gravitational force, and it converts into stars.

2. Destruction of stars
   • Red giant:
     In stars, gravitation is pulling all matter to its core and that force is balanced by the repulsive force created by nuclear reaction in the core. When the stock of hydrogen starts to finish then gravitation starts to take over and compress the star. Due to high gravitational pressure helium starts to fuse to give carbon this release high amount of energy. Due to that energy stars expand their diameter. Red giants have the radius from 100 million to a billion kilometers. Since the surface area of the star increases the produced energy is distributed over large area. So the temperature of the star decreases. Our sun becomes red giant in about 5.5 billion years from now.
   • White dwarf:
     If the mass of red giant is smaller or equal to sun then gradually the outer part will start to escape into space, then the inner core which is still hot starts to seem white, which is called white dwarf.
   • Black dwarf:
     Gradually, the white dwarf continues to cool and finally it turns into black color which is called black dwarf. Finally, it starts to be invisible.
   • Supernova:
     If the red giant is extremely big, then in core, further fusion reaction will continue. Then the helium core turns into carbon, oxygen , neon, silicon and finally iron and finally core of star explodes and such exploding star is called the supernova.
   • Neutron star:
     Sometimes, after the supernova explosion, nothing of star is left, the central core of the star which is equal to the size of earth. In which the proton and electron fuse together to give neutral neutron is called neutron star.
   • Pulsar:
     A rapidly spinning neutron star surrounded by an extremely powerful magnetic field that can spin with it and is called pulsar.
   • Black hole:
     A black hole is a remnant of a star so condensed that it's gravitational pull is strong enough to prevent matter or even formed by identification contraction of heavy and large neutron stars under the action of their own gravity.