Life's cosmic prerequisites unfold in stages: a molecular cloud gravitationally collapses into a protostar, the young star ignites and clears a planetary disc, and on any planet sitting in the habitable zone — where liquid water can persist — prebiotic chemistry can start assembling simple molecules into more complex ones:
L(t) ∝ collapse_progress³ // star brightens as it contracts (Kelvin–Helmholtz-like)
HZ = [HZ_r − 1.5, HZ_r + 1.5] AU // liquid-water habitable band
bond_rate = chem_rate · exp(−|r − HZ_r| / 2) // bonding favoured inside the HZ
- Cloud collapse rate — how fast the nebula contracts into a star; scales infall speed of cloud particles.
- Planet count — number of planets that condense out of the protoplanetary disc.
- Habitable-zone radius — orbital distance (AU) where a planet's surface temperature allows liquid water.
- Prebiotic chemistry rate — how fast simple molecules bond into amino-acid-like chains on a habitable-zone planet.
This mirrors the real astrobiology pipeline scientists use to rank exoplanets as habitability candidates: stellar age and luminosity, orbital distance versus the habitable zone, and (much harder to observe) prebiotic chemical complexity.