Question

Which of the following statements about the rate of stellar evolution is true? The more massive the original star, the slower the evolution, because there is more material for thermonuclear burning. The chemical makeup of the original nebula is the major factor in deciding the rate of evolution. Star mass has no bearing upon stellar evolution, because all stars evolve at the same rate, controlled by nuclear fusion and core temperature. The more massive the original star, the faster the evolution.

Answer 1

Answer:

The more massive the original star, the faster the evolution.

Explanation:

The evolution of a star is determined exclusively by its mass. For example, a star with more than 8 solar masses will end up its life as a neutron star or a black hole. On the other hand, a star with less of 8 solar masses will end up its life as a planetary nebula or a white dwarf.

In stars there is an equilibrium between two forces, the force of gravity in the inward direction due to its own mass and the radiation pressure in the upward direction as a consequence of the nuclear reaction in its core, which is known as hydrostatic equilibrium.

The radiation pressure gets from the nuclear reactions at the core (when lighter elements fuse in heavier elements), but if the nuclear reactions stop, hence, the radiation pressure will also do it and the force of gravity will overcome and break the equilibrium.

Once that happens, the star can end up its life or evolve if it has the necessary mass to do it. For example, when the Sun exhausts its hydrogen it is going to evolve in a red giant.

In the case of a massive star, it will evolve to different phases in a faster way, that is due to the fact that it is burning its fuel at a higher rate because it has different mechanism of nuclear reaction (PP-chain, CNO, Alpha triplet) since it has higher temperatures and pressures due to the impact of an intense gravitational field caused by its mass.

Summary:

- Stars evolve according to its mass

- The gravitational field is greater in massive stars

- Massive stars can have other types of nuclear reactions

- Less massive stars (main sequence star), like the Sun, burn their fuel through the PP-chain reaction.