Supernovae

How Stars Explode

Four Explosion Pathways

Each panel cycles continuously: progenitor → flash → expanding shockwave → remnant. Cycles are offset so the four types stay out of phase. Real supernovae brighten over weeks and fade over years.

Two Mechanisms, Many Flavours

Despite the spectral variety, all supernovae fall into two physical mechanisms. Thermonuclear (Type Ia) — a white dwarf accreting mass past the Chandrasekhar limit detonates carbon in a runaway fusion chain. Core-collapse (Types Ib/Ic, II, hypernovae) — a massive star's iron core implodes in under a second.

The spectral type (presence or absence of H, He) reflects the progenitor's envelope, not the underlying physics — a Type Ic is a Type II that lost its outer layers to a strong stellar wind or a companion.

Energetics

Total energy — ~10⁴⁴ J — equals the Sun's entire 10 Gyr output

Light — ~1% of total energy — outshines the host galaxy

Kinetic — ~99% — ejecta moves at 10,000 km/s

Neutrinos — Core-collapse: ~99% of energy escapes as neutrinos

Element factory — Forges all stable nuclei heavier than iron via r-process

ED: Supernova Remnants

The galaxy is littered with the aftermath. Every neutron star you fly past in Elite Dangerous was once the iron core of a massive star — left behind when its envelope was blasted off in a Type II event.

Black holes from stellar collapse trace back to the most massive O-type progenitors. Smaller-mass stars give neutron stars; heaviest progenitors collapse all the way to a singularity.

Type Ia supernovae leave no remnant. The white dwarf is completely vaporised — only an expanding shell of iron-peak elements drifting through space.

Supernova Classification

Type	Trigger	Spectrum	Outcome	Energy	Note
Ia	WD exceeds Chandrasekhar limit	No H, strong Si II	No remnant — total disruption	10⁴⁴ J	Standard candle for cosmology
Ib	Core-collapse, H envelope lost	No H, strong He	Neutron star	10⁴⁴ J	Stripped progenitor (Wolf-Rayet)
Ic	Core-collapse, H + He lost	No H, no He	Neutron star or black hole	10⁴⁴ J	Sometimes paired with long GRBs
II-P	Red supergiant core-collapse	Strong H, plateau in light	Neutron star	10⁴⁴ J	Most common — ~50% of all SN
II-L	Stripped supergiant collapse	H, linear decay	Neutron star	10⁴⁴ J	Light curve declines linearly
IIn	Collapse into dense CSM	Narrow H emission lines	Variable	10⁴⁴⁻⁴⁵ J	Pre-explosion mass loss interaction
Hyper.	Extreme-mass collapse (≥40 M☉)	Broad, energetic	Black hole	10⁴⁵⁻⁴⁶ J	Often associated with long GRBs
Pair-i.	Pair-instability (130–250 M☉)	Hydrogen-rich, no remnant	No remnant	10⁴⁵⁻⁴⁶ J	Theoretical extreme — Pop III stars