Dark Matter Halo
An extended, nearly spherical region of dark matter enveloping a galaxy or galaxy cluster that extends far beyond the visible stellar disk.
Governing formula
NFW Density Profile: ρ(r) = ρ₀ / ((r/r_s) (1 + r/r_s)²)
SI unit
kpc (Halo Radius) & M_☉ (Halo Mass)
In depth
Dark matter halos contain ~80–90% of total galaxy mass. Their gravitational potential wells govern galactic rotation curves, preventing stars in outer spiral arms from flying apart.
Examples in the real world
The Milky Way dark matter halo extending out to ~300 kiloparsecs, stabilizing galactic disk rotation.