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About this tool
Interactive stellar evolution explorer charting stellar birth, main sequence hydrostatic equilibrium, nucleosynthesis, and stellar remnants.
The Star Life Cycle Explorer is an interactive stellar evolution model: set a star's initial mass anywhere from 0.1 to 40 solar masses and it follows the corresponding six-stage evolutionary track, with 8 solar masses as the branch point between the low-mass path and the high-mass path. Each stage shows surface temperature, radius, luminosity, the fusion process running at that point and how long it lasts, drawn live on a canvas so a red giant at 100 R☉ and a white dwarf at 0.01 R☉ are visibly different objects. It is written for students and teachers covering stellar evolution, hydrostatic equilibrium and nucleosynthesis.
Open Star Life Cycle Explorer on AltFTool — it loads instantly in your browser.
Drag the Initial Solar Mass slider between 0.1 and 40, and the Evolutionary Branch label flips at 8 solar masses.
Step through the Evolutionary Stage buttons, from Stellar Nebula and Protostar to White Dwarf or Neutron Star / Black Hole.
Read Surface Temp, Radius, Luminosity and Lifetime for that stage, plus the Core Fusion Stage caption on the canvas.
The slider does not just relabel a diagram — crossing 8 solar masses swaps in an entirely different sequence, ending in core collapse instead of a planetary nebula.
Temperature, radius, luminosity, lifetime and the specific fusion process are listed per stage, so you can see luminosity climb from 1 L☉ on the main sequence to 500,000 L☉ as a red supergiant.
Each stage is rendered on canvas — a diffuse nebula, a compact degenerate remnant, a supernova shock front — which makes the thousand-fold size changes concrete.
Roughly 8 solar masses, which is the threshold this explorer uses to switch between its two evolutionary tracks. Below it a star ends by shedding a planetary nebula and leaving a white dwarf; above it the core fuses successively heavier elements up to iron, at which point fusion stops releasing energy and the core collapses.
The main sequence is the long stable phase where a star fuses hydrogen into helium and outward radiation pressure exactly balances inward gravity — hydrostatic equilibrium. Stars spend about 90% of their lives in it: around 10 billion years for a one-solar-mass star like the Sun at 5,800 K, but only about 10 million years for a hot O-type star, because greater mass burns fuel disproportionately faster.
Because iron has the highest binding energy per nucleon, so fusing it consumes energy instead of releasing it. Once a massive star builds an iron core, there is nothing left to hold the core up against gravity, and the collapse and rebound is what drives a Type II supernova — elements heavier than iron are made in that explosion by rapid neutron capture.
All three are stellar remnants held up by different things, or by nothing. A white dwarf is an Earth-sized core about 0.01 R☉ supported by electron degeneracy pressure; a neutron star packs a stellar core into roughly 20 km supported by neutron degeneracy pressure; a black hole forms when even that fails and collapse continues past an event horizon.