How Black Holes Form
Most black holes are born from dying stars — but not just any stars. Only the most massive ones.
Stellar Black Holes: From Star Death
When a star burns fuel, nuclear fusion pushes outward against gravity. This balance keeps stars stable for millions or billions of years.
When fuel runs out:
Small stars (like our Sun) → White dwarf (Earth-sized cinder)
Medium stars (8-20 solar masses) → Supernova → Neutron star (city-sized, incredibly dense)
Massive stars (20+ solar masses) → Supernova → Black hole
The Collapse Process
- Fuel exhausted: Fusion stops in the core
- Gravity wins: Without outward pressure, the core collapses
- Implosion: Outer layers fall inward at 25% light speed
- Supernova: Rebounding shockwave blasts outer layers away
- Black hole forms: If remaining core exceeds ~3 solar masses, nothing stops collapse
The core shrinks to a point — the singularity.
Supermassive Black Holes
These giants (millions to billions of solar masses) are harder to explain:
- Direct collapse of massive gas clouds
- Merging of smaller black holes
- Rapid growth in the early universe
Supermassive black holes exist at most galaxy centers. How they grew so large so fast remains a puzzle.
Primordial Black Holes (Theoretical)
The Big Bang's density fluctuations might have created black holes directly — no star required. These "primordial" black holes could be tiny (smaller than atoms) or massive.
Black Hole Mergers
When two black holes orbit each other, they spiral inward and merge. This releases enormous energy as gravitational waves — ripples in spacetime detected by LIGO in 2015.
Related Reading
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