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Jeans instability

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description Jeans instability Overview

Jeans instability is the gravitational instability of a sufficiently large or dense region within a gas when self-gravity overwhelms the pressure effects that resist compression. The dividing scale is commonly expressed through the Jeans length or Jeans mass, which depends on quantities including density, temperature, and sound speed. Regions above the relevant threshold can contract and fragment, making the concept fundamental to models of molecular-cloud collapse, star formation, and cosmic structure formation.

help Jeans instability FAQ

What does Jeans instability describe in astrophysics?

It describes the process by which a homogeneous cloud of gas or dust undergoes gravitational collapse. This occurs when the cloud's internal gas pressure is no longer strong enough to resist its own self-gravity.

How does Jeans instability lead to star formation?

When the instability criteria are met, the gas and dust begin to clump together, increasing in density and attracting more material. This collapsing process eventually leads to the core temperatures needed to ignite nuclear fusion, forming a new star.

What is the Jeans length?

The Jeans length is a critical radius calculated by physicist James Jeans to determine whether a cloud will collapse. If a cloud's physical size is larger than this specific critical radius, it will succumb to Jeans instability.

What forces are in balance during the onset of Jeans instability?

The concept centers on the delicate balance between outward thermal pressure and inward gravitational forces. When thermal energy drops or the mass increases, gravity wins the battle, triggering the collapse.

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