Nebula Formation Dynamics (2D): Jeans Instability & Gravitational Collapse

Cloud Conditions

Temperature (thermal support) 80 K

Self-gravity strength (G) 1.20×

Gas parcels (cloud density) 160

Turbulent support 0.40

Run

Live readout

Elapsed

0.0 s

Cloud mass M

160

Density ρ

—

Jeans mass M_J

—

M / M_J

—

Virial α = 2K/|U|

—

Protostars formed

Largest clump

1.0

How this works

Every gas parcel pulls on every other one by real (softened) Newtonian gravity, integrated every frame. Random thermal and turbulent kicks act as pressure, resisting collapse. When two parcels touch they merge — mass and momentum conserved — and grow into a protostar.

The instability threshold follows the real Jeans-mass scaling:

M_J ∝ T^1.5 / √(G·ρ)

Higher temperature → higher M_J → harder to collapse.
Higher density or gravity → lower M_J → easier to collapse.

When the current cloud mass M exceeds M_J (ratio > 1), the cloud is gravitationally unstable and clumps form. The virial parameter α = 2·(kinetic energy)/|potential energy| is computed directly from the simulated particles — α < 1 means the cloud is bound and collapsing, α > 1 means it is unbound and dispersing, matching the same criterion astronomers use on real molecular clouds.

Gas parcel Growing clump Protostar