Star Lifecycle: Mass-Driven Evolution & HR Diagram (2D)

A single number — the mass a star is born with — decides almost everything about its life: how hot and bright it burns, how long it survives, and what it leaves behind. This 2D companion turns the mass slider into a full evolutionary track computed from the mass–luminosity relation, an approximate mass–radius relation and the Stefan–Boltzmann law, then plays it out stage by stage — protostar, main sequence, giant, and a genuinely different ending depending on where the 8 M☉ and 25 M☉ thresholds fall: white dwarf for a Sun-like star, neutron star or black hole for a massive one — while a live Hertzsprung–Russell diagram traces the exact temperature/luminosity path in real time. It is the flat, physically-grounded sibling of the site's interactive 3D star lifecycle.