Hertzsprung Russell Diagram
Channel: Dominik Hezel
Date: 2023-04-12

The Hertzsprung-Russell Diagram (mostly only called ›HRD‹) describes the evolution of stars from their birth to death. It is one of the most fundamental diagrams in astronomy. And in fact, the HRD is not one diagram, but comes in various flavours depending on what is plotted on the x- and y-axis. This versatility underlines the fundamental character of the HRD. The Sun plots in the middle of the main sequence, is a G2V star and in the middle of its life cycle. Stars typically start their journey in the lower right (small & cold), travel through the main sequence to the somewhat upper left (hot & larger), then kink to the upper right and become a red giant, super-giant, AGB-star, … (cold & big) – depending on their initial mass. They finally end in the lower left as dwarf, neutron star or black hole, … (hot & small) – again depending on their initial mass.