Gravity and Stellar Evolution
Outside the protostar, the remains of the cloud forms into a rotating disc. By collisions and the action of gravity the dust and gas slowly forms into ever-larger clumps. Eventually planets, moons, asteroids and comets are created.
The ultimate fate of a star depends on its mass. A star about he same mass as the Sun will first become a red giant before ejecting its outer atmosphere, enriched with elements it has made, into the space between the stars. There the matter will be ready to form a new generation of stars, while the Sun becomes a white dwarf and slowly fades away.
A star more than about eight times the mass of the Sun will finally destroy itself in a supernova explosion, which can be as bright as the light of an entire galaxy of stars. The force of gravity causes the central regions of the star to collapse, releasing vast amounts of gravitational potential energy. During the first few minutes of the supernova, heavy elements are created by nuclear fusion and dispersed into space in the explosion/
In a supernova explosion, the central regions of the star collapse to form either a black hole or a rapidly rotating neutron star. Often neutron stars emit intense beams of radio energy. If the orientation of the neutron star is right then as the radio beam sweeps past the Earth, typically many times a second, the remnant is observed as a radio pulsar.
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