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What is the life cycle of a star?


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Answered 2015-11-20 19:12:48

The life cycle of a star can follow a few different paths depending on the mass it starts out with. Really massive stars may live for only a few million years before going supernova, while low mass stars such as the Sun may take billions of years to use up their fuel and then die relatively quietly.

In star life cycles, a highmass star means a star with at least about 8 times the mass of our Sun

Birth
  • All stars are formed when a giant cloud of gas and dust, called a molecular cloud or nebula, begins to collapse under the influence of its own gravity
  • This may be triggered by a collision with another molecular cloud, the shockwave from a nearby supernova, or even the collision of galaxies
  • As the cloud contracts, it breaks apart. An individual fragment will condense into a hot, dense sphere known as a protostar
  • A new star is born when the protostar becomes hot enough to begin fusing hydrogen into helium. Now, the star will enter the main sequence, or adult, phase
  • If a star is too low in mass to initiate nuclear fusion it will become a brown dwarf
Main sequence
  • A star will remain in this state for most of its lifetime, fusing hydrogen to make helium and releasing energy in the process
  • A star may fall on different points on the main sequence depending on its mass. In general, the more massive the star the shorter its lifespan on the main sequence
  • Red dwarfs are small, dim stars that fuse hydrogen at a slow rate, and may remain on the main sequence for hundreds of billions of years.
  • Low massstars such as our Sun will be on the main sequence for several billion years
  • High massstars may only stay on the main sequence for a few million years
Maturity
  • Eventually a star will run out of its hydrogen fuel, and begin fusing helium and other elements instead. At that point it will leave the main sequence phase
  • Red dwarf stars will use up all their hydrogen and collapse directly into white dwarfs
  • Low mass stars like our Sun will expand and become red giants.
  • This happens when a star runs out of hydrogen at its core. The core will collapse and begin fusing helium while hydrogen fusion is transferred to the outer layers
  • This causes the star to swell to many times its original size and become cooler as the heat is distributed over a larger area
  • More massive stars will grow into supergiants, which are among the largest stars in the Universe
  • In this stage a star will maintain hydrostatic equilibrium by fusing heavier and heavier elements as the lighter ones run out. The largest stars can produce elements up to iron
Death and stellar remnants
  • Low mass stars like our Sun will eventually die by shedding their outer layers as a planetary nebula
  • The core will collapse into a white dwarf,which will eventually cool into a black dwarf
  • More massive stars will die in a tremendous explosion called a supernova
  • This happens when a massive stars begins to fuse iron. This absorbs energy and caused the core to violently collapse while the outer layers are ejected
  • The extreme heat produced by supernovae is responsible for the nucleosynthesis of elements heavier than iron, up to uranium
  • After a supernova, the core may compress into a neutron star or a black hole.
  • Neutron stars are much denser than white dwarfs, to the point where protons and electrons combine to form neutrons (hence the name)
  • Black holes are denser still, so much so that they produce an extremely strong gravitational force that even light cannot escape.

For more information see "Sources and related links", below.
The life of a star varies from one star to another depending on the mass of the star ranging from a few million years to trillions of years.
The explanation varies depending on the type of star we're discussing.

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The "star life cycle" refers to stars. Earth is not a star.


The life cycle of a star is similar to the life cycle of a human because both humans and stars are born and die.


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The Hertzsprung-Russel diagram shows the life cycle of all stars.


It will "burn" a lot hotter, have a shorter lifespan and will have a violent death. See related question.


A star starts its life cycle as a Gaseous object giving of light, it then starts to build up and also gives off helium.


The "protostar". That's not classed as a true star, but I think that's the answer.


It is approx half-way through its 10 billion year life cycle.




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The life cycle of a star is determined primarily by its mass. The hotter a star the bluer its color. The difference between apparent brightness and luminosity is that luminosity is a good indicator of the energy output of a star.




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Astro means star its study of the life cycle of stars


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