Why three numbers (0.08, 8, 25 M☉)?

~0.08 M☉ separates brown dwarfs from hydrogen-burning stars. ~8 M☉ is a rough lower bound for iron-core collapse supernovae in many textbooks. ~25 M☉ is a cartoon split between neutron star and black hole remnants; real models depend on winds, rotation, and binary interaction.

Where is the asymptotic giant branch?

Merged into “red giant” for clarity; intermediate-mass stars have an AGB phase before the planetary nebula.

Stellar Life Cycle

This page shows a qualitative branching diagram for single-star evolution as a function of initial mass: collapse from a molecular cloud, protostar phase, main-sequence core hydrogen burning, then post-main-sequence evolution. Below the hydrogen-burning minimum mass (~0.08 M☉), objects become brown dwarfs. Stars up to roughly 8 M☉ typically eject envelopes and leave white dwarfs. More massive stars may explode as core-collapse supernovae, leaving neutron stars or black holes depending on core mass, mass loss, and metallicity — thresholds here are pedagogical, not precise models.

Who it's for: Introductory astrophysics; complements the HR diagram and nuclear binding pages.

Key terms

main sequence
planetary nebula
white dwarf
supernova
neutron star
black hole

How it works

**Stellar evolution** depends primarily on **initial mass**. A **molecular cloud** collapses into a **protostar**, then settles on the **main sequence** while fusing hydrogen in the core. After central hydrogen is exhausted, low- and intermediate-mass stars expand along the **giant** branch, shed envelopes as **planetary nebulae**, and leave **white dwarfs**. Above roughly **8 M☉**, a star can end in a **core-collapse supernova**; the compact remnant may be a **neutron star** or, for the most massive cores, a **black hole**. Thresholds are **schematic** — metallicity, rotation, and binary interaction change the story. Low- and intermediate-mass stars (≲8 M☉) shed their envelopes and leave a white dwarf — the Chandrasekhar mass (~1.4 M☉) caps the core.

Key equations

M_min(H burning) ~ 0.08 M☉ (brown dwarf below)

SN core-collapse: typical lower bound ~ 8 M☉ (uncertain)

Frequently asked questions

Why three numbers (0.08, 8, 25 M☉)?: ~0.08 M☉ separates brown dwarfs from hydrogen-burning stars. ~8 M☉ is a rough lower bound for iron-core collapse supernovae in many textbooks. ~25 M☉ is a cartoon split between neutron star and black hole remnants; real models depend on winds, rotation, and binary interaction.
Where is the asymptotic giant branch?: Merged into “red giant” for clarity; intermediate-mass stars have an AGB phase before the planetary nebula.