Stellar isochrone

In stellar evolution, an isochrone is a curve on the Hertzsprung-Russell diagram, representing a population of stars of the same age but with different mass.

Newborn stars of low or intermediate mass are born cold but extremely luminous.

They then evolve quickly towards their stellar endpoints: white dwarfs, neutron stars, or black holes.

[3] If the initial mass function of the open cluster is known, isochrones can be calculated at any age by taking every star in the initial population, using numerical simulations to evolve it forwards to the desired age, and plotting the star's luminosity and magnitude on the HR diagram.

[4] The resulting curve is an isochrone, which can be compared against the observational color-magnitude diagram to determine how well they match.