The Evolution of the star of the mass similar to that of the mass of the Sun wil

Question

The Evolution of the star of the mass similar to that of the mass of the Sun will most likely take following steps: 1_______ the stage before the ignition of the nuclear reactions converting _______ into _______. 2 _______ Star -- star is in equilbrium during this stage: the force of _______ is equal to the force of _______ pressure stabilizing the star's radius. The conversion of the _______ into _______ via nuclear _______ is providing the radiation in the stellar _______. This stage typically last up to _______ billion years. 3 _______ -- as result of depletion of the _______ in the stellar _______, and increased density of _______ the star can now convert _______ into the _______. This set of reactions provide the net energy that is much _______ than the one fuelling the previous stage. As result the force of _______is higher than the force of _______ acting on he star which leads to the _______ of star's radius. The star of Sun's mass will last in this stage for up to 10 _______ years.

Explanation / Answer

Stellar evolution is the process by which a star undergoes a sequence of radical changes during its lifetime. Depending on the mass of the star, this lifetime ranges from only a few million years for the most massive to trillions of years for the least massive, which is considerably longer than the age of the universe. All stars are born from collapsing clouds of gas and dust, often called nebulae or molecular clouds. Over the course of millions of years, these protostars settle down into a state of equilibrium, becoming what is known as a main sequence star. Nuclear fusion powers a star for most of its life. Initially the energy is generated by the fusion of hydrogen atoms at the core of the main sequence star. Later, as the preponderance of atoms at the core becomes helium, stars like the Sun begin to fuse hydrogen along a spherical shell surrounding the core. This process causes the star to gradually grow in size, passing through the subgiant stage until it reaches the red giant phase. Stars with at least half the mass of the Sun can also begin to generate energy through the fusion of helium at their core, while more massive stars can fuse heavier elements along a series of concentric shells. Once a star like the Sun has exhausted its nuclear fuel, its core collapses into a dense white dwarf and the outer layers are expelled as a planetary nebula. Stars with around ten or more times the mass of the Sun can explode in a supernova as their inert iron cores collapse into an extremely dense neutron star or black hole. While the universe is not old enough for any of the smallest red dwarf stars to have reached the end of their lives, stellar models suggest they will slowly become brighter and hotter before running out of hydrogen fuel and becoming low mass white dwarfs.[1] Stellar evolution is not studied by observing the life of a single star, as most stellar changes occur too slowly to be detected, even over many centuries. Instead, astrophysicists come to understand how stars evolve by observing numerous stars at various points in their lifetime, and by simulating stellar structure using computer models.

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