What causes the collapse of a nebula?

Irregularities in the density of the gas causes a net gravitational force that pulls the gas molecules closer together. Some astronomers think that a gravitational or magnetic disturbance causes the nebula to collapse. As the gases collect, they lose potential energy, which results in an increase in temperature.

Explanation:

sodium i think the chemical element of atomic number 11, a soft silver-white reactive metal of the alkali metal group.

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