The Hayashi track is a concept in astrophysics, particularly in the study of stellar evolution and the evolution of young stars. It refers to a path on the Hertzsprung-Russell (H-R) diagram, which plots stars according to their luminosity and temperature (or color). The Hayashi track describes the evolutionary phase of pre-main-sequence stars, specifically those that are still in the process of contracting and heating up before they initiate hydrogen fusion in their cores.
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