How does the Hertzsprung-Russell diagram illustrate stellar evolution?

The Hertzsprung-Russell diagram shows the relationship between a star's luminosity and temperature, revealing stages of stellar evolution.

The Hertzsprung-Russell (H-R) diagram is a plot of a star's luminosity against its surface temperature. The diagram reveals a pattern of stars that fall into different regions, indicating different stages of stellar evolution. Stars in the main sequence, for example, are fusing hydrogen into helium in their cores and are in a stable state. As they exhaust their hydrogen fuel, they move off the main sequence and expand into red giants. Red giants are much larger than main-sequence stars, but they are cooler and less luminous.

The H-R diagram also shows the relationship between a star's mass and its position on the diagram. More massive stars are hotter and more luminous than less massive stars. The most massive stars are located in the upper left corner of the diagram, while the least massive stars are in the lower right corner.

The H-R diagram also reveals the final stages of stellar evolution. As a star exhausts its nuclear fuel, it will eventually shed its outer layers and form a planetary nebula. The remaining core of the star, known as a white dwarf, will be located in the lower left corner of the diagram, with low luminosity and high temperature.

In conclusion, the Hertzsprung-Russell diagram is a powerful tool for understanding the different stages of stellar evolution. By plotting a star's luminosity and temperature, we can determine its mass, stage of evolution, and eventual fate.