Question

main sequence stars change quickly when they grow into a red giant. be sure to discuss the role of the force of gravity and/or fusion force in your explanation for why a main sequence star eventually grows in size to become a red giant. dont forget to include evidence to support your claim. depending on a stars initial mass, the last stage of a stars life cycle is either a white dwarf, neutron star, or black hole. these are some of the most dense objects in the universe. be sure to discuss the role of the force of gravity and/or fusion force in your explanation for why stars become much smaller and incredibly dense (compact) at the end of their life cycles.

Explanation:

1. Main - sequence star to red - giant transition: During the main - sequence phase, a star is in hydrostatic equilibrium, with the inward force of gravity balanced by the outward pressure from nuclear fusion (usually hydrogen fusing into helium in the core). As the hydrogen in the core is depleted, the core contracts due to gravity. This contraction heats up the outer layers of the star, causing them to expand. The star grows in size and becomes a red giant. Evidence for this comes from observing the change in luminosity and size of stars over time in star clusters.
2. End - stage of star life - cycle and density: At the end of a star's life cycle, depending on its mass, it can become a white dwarf, neutron star, or black hole. In a white dwarf, the core is mainly composed of carbon and oxygen, and it is supported against further gravitational collapse by electron degeneracy pressure. Neutron stars are formed from the collapse of more massive stars. The core collapses under gravity, and protons and electrons combine to form neutrons. Neutron degeneracy pressure supports the neutron star against further collapse. Black holes form when the mass of the collapsing core is so large that no known force can stop the gravitational collapse, creating a region of infinite density (a singularity) surrounded by an event horizon.

Answer:

1. Main - sequence stars become red giants when hydrogen in the core is depleted. Gravity causes the core to contract, heating the outer layers and making them expand. Evidence: Observations of star clusters showing different stages of stellar evolution.
2. Stars become small and dense at the end of their life - cycles due to gravitational collapse and the support mechanisms against it. White dwarfs are supported by electron degeneracy pressure, neutron stars by neutron degeneracy pressure, and black holes result from extreme gravitational collapse with no known opposing force.