AST 309 Lecture Notes - Lecture 7: Bok Globule, Gravitational Energy, Protostar
Document Summary
All about protostars and how they are observed. On the other end of the size scale from gmc"s, are very small globules of molecular material, called bok globules. These clouds are small in size ~ 1 light year across or smaller with masses ranging from 2-50 solar masses. Bok globules can be very compact and very dense, and very cold. They will contain dust which will extinct much of the visible light, making them dark. But infrared surveys of bok globules show that most of these objects likely contain young stars at their centers, so they are also sites of active star formation. Protostars are actually at any given moment in hydrostatic equilibrium. Gravity pulls material toward the center, and is balanced by the outward push of pressure. As more material rains in, and as the heat from its interior is radiated away, the protostar becomes more compact, and pressure increases.
