In physics, the Jeans instability causes the collapse of interstellar gas clouds and subsequent star formation. It occurs when the internal gas pressure is not strong enough to prevent gravitational collapse of a region filled with matter. For stability, the cloud must be in hydrostatic equilibrium, which in case of a spherical cloud translates to:
- ,
where is the enclosed mass, is the pressure, is the density of the gas at, is the gravitational constant and is the radius. The equilibrium is stable if small perturbations are damped and unstable if they are amplified. In general, the cloud is unstable if it is either very massive at a given temperature or very cool at a given mass for gravity to overcome the gas pressure.
Read more about Jeans Instability: Jeans Mass, Jeans Length, Jeans' Length As Oscillation Wavelength, Fragmentation
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