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The Formation of a Star, Stellar Evolution based on Mass, The star's…
The Formation of a Star
Nebula: Stars are born in clouds of gas and dust- mostly hydrogen and helium. The dust and gases in a nebula are very spread out, but gravity can slowly begin to pull together clumps of dust and gas. As these clumps get bigger and bigger, their gravity gets stronger and stronger.
Turbulence deep within these clouds gives rise to knots with sufficient mass that the gas and dust can begin to collapse under its own gravitational attraction.
A protostar is formed as gravity begins to pull the gases together into a ball. This process is known as accretion. As gravity pulls the gases closer to the center of the ball, gravitational energy begins to heat them, causing the gasses to emit radiation.
Main sequence stars fuse hydrogen atoms to form helium atoms in their cores. About 90 percent of the stars in the universe, including the sun, are main-sequence stars. These stars can range from about a tenth of the mass of the sun to up to 200 times as massive. Hy
Type I
Neutron Star
Neutron stars are the remnants of giant stars that died in a fiery explosion known as a supernova. After such an outburst, the cores of these former stars compact into an ultradense object with the mass of the sun packed into a ball the size of a city.
Type II
Red Super Giant
The biggest stars in the Universe are the red supergiants. They form when a star runs out of hydrogen fuel in their core, begins collapsing, and then outer shells of hydrogen around the core get hot enough to begin fusion. While a red giant might form when a star with the mass of our Sun runs out of fuel, a red supergiant occurs when a star with more than 10 solar masses begins this phase.
Red Giant
A red giant forms after a star has run out of hydrogen fuel for nuclear fusion, and has begun the process of dying. It is smaller than a Red Super Giant
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The star's core, however is very hot which creates pressure within the gas. This pressure counteracts the force of gravity, putting the star into what is called hydrostatic equilibrium.
But the dense core continues to collapse, generating pressures so high that protons and electrons are squeezed together into neutrons, as well as lightweight particles called neutrinos that escape into the distant universe. The end result is a star whose mass is 90% neutrons, which can't be squeezed any tighter, and therefore the neutron star can't break down any further.