Question

what occurs inside a main sequence star? *
1 point
fusion stops
energy from fusion exceeds gravity
a supernova
it reaches a state of stellar equilibrium
what forms when the core of a giant star can no longer support fusion? *
1 point
giant
neutron
red dwarf
white dwarf

Explanation:

First Question:

To determine what occurs inside a main sequence star, we analyze each option:

• "Fusion stops" is incorrect because main sequence stars rely on nuclear fusion (e.g., hydrogen to helium in the core) to generate energy, and fusion continues during this stage.
• "Energy from fusion exceeds gravity" is incorrect. In a main sequence star, the outward pressure from fusion (thermal pressure) balances the inward pull of gravity (hydrostatic equilibrium), not that fusion energy exceeds gravity.
• "A supernova" is incorrect. A supernova is a later stage in a massive star's life cycle, occurring after the main sequence and red giant phases when the star undergoes a catastrophic explosion.
• "It reaches a state of stellar equilibrium" is correct. Main sequence stars are in hydrostatic (stellar) equilibrium, where the inward gravitational force is balanced by the outward pressure from nuclear fusion in the core. This balance allows the star to maintain a stable size and energy output during the main sequence phase.

To determine what forms when the core of a giant star can no longer support fusion, we analyze each option:

• "giant" is incorrect. A giant star (e.g., red giant) is a phase before the core can no longer support fusion. When fusion in the core stops, the star evolves beyond the giant phase.
• "neutron" is incorrect. A neutron star forms from the core of a massive star (after a supernova explosion) when the core collapses under gravity, and protons and electrons are crushed into neutrons. However, this is specific to very massive stars, and the question here is about a giant star (which could be a lower-mass giant, like a red giant that will become a white dwarf).
• "red dwarf" is incorrect. Red dwarfs are small, cool main sequence stars that fuse hydrogen for a very long time and do not become giants in the same way as more massive stars. They are not formed from the core of a giant star.
• "white dwarf" is correct. For a low- to medium-mass giant star (e.g., a red giant that was once a main sequence star like our Sun), when the core can no longer support fusion (after exhausting its nuclear fuel), the outer layers are expelled, and the core collapses under gravity to form a white dwarf. A white dwarf is a dense remnant supported by electron degeneracy pressure.

Answer:

It reaches a state of stellar equilibrium

Second Question: