The Birth of a Star

Buried deep within the dark, almost black expanses of interstellar clouds are hundreds to thousands of local regions, called globules, that are contracting under their own gravity. Such contractions are the beginning of the formation of new generations of stars.

What causes globules of gas and dust to contract?


The Forces Acting on Globules

To answer "What causes globules to contract?" let's first recognize that competing forces act on the gas and dust. The two principal forces are gravity and pressure. Gravity is an attractive force that attempts to contract the gas and dust. Pressure has the opposite effect. It tries to disperse the matter.

When gravity and pressure are roughly in balance, the gas and dust are stable. There is little contraction or expansion.