Stars and Stellar Evolution

Color is not a fundamental property used to classify stars. Instead, stars are classified based on their mass, temperature, and luminosity.

Stars generate energy through nuclear fusion reactions, where lighter elements are combined to form heavier elements, releasing vast amounts of energy.

Red dwarfs are the most common type of star, making up about 85% of all stars in the Milky Way galaxy.

Massive stars end their lives in a supernova explosion, which can be so powerful that it can outshine an entire galaxy.

If the core of a massive star is sufficiently massive, it collapses into a neutron star after a supernova explosion.

Low-mass stars like our Sun end their lives as white dwarfs, which are dense remnants that have exhausted their nuclear fuel.

The Hertzsprung-Russell diagram is a plot of stellar temperature versus luminosity, which helps astronomers understand the evolutionary stages of stars.

The main sequence on the Hertzsprung-Russell diagram represents stars that are fusing hydrogen in their cores, which is the longest and most stable phase of a star's life.

A red giant is a star that has exhausted its hydrogen fuel and is now fusing helium in its core, causing it to expand and become cooler.

A white dwarf is a dense remnant of a star that has exhausted its hydrogen and helium fuel and has collapsed under its own gravity.

A neutron star is a dense remnant of a star that has exhausted its hydrogen and helium fuel and has collapsed under its own gravity, resulting in a core composed primarily of neutrons.

A black hole is a region of spacetime where gravity is so strong that nothing, not even light, can escape.

The Chandrasekhar limit is the maximum mass a white dwarf can have before it collapses under its own gravity and becomes a neutron star.

The Tolman-Oppenheimer-Volkoff limit is the maximum mass a neutron star can have before it collapses under its own gravity and becomes a black hole.