Prestellar core

A dense, cold concentration of interstellar gas and dust with no protostar, often gravitationally bound and capable of collapsing into one.

Jeans instability: The onset of gravitational collapse when a cloud’s self-gravity overcomes pressure support. It describes when a prestellar core can no longer resist collapse.
Molecular cloud: A cold, dense interstellar cloud composed primarily of molecular hydrogen. Prestellar cores form as compact condensations within molecular clouds.
Early molecular cloud surveys: Observational programs that mapped molecular gas in star-forming regions using radio telescopes. They established the cloud structures in which dense cores were identified.
L1544: A dense core in the Taurus molecular cloud complex, widely studied as a starless object near gravitational collapse. Its inward motions and chemical structure make it a benchmark prestellar core.
Virial equilibrium: A balance between kinetic, thermal, magnetic, and gravitational energies in a physical system. Virial analysis helps determine whether a core is gravitationally bound.
Bok globule: A small, dark, dense cloud of gas and dust found against a bright background. Some globules contain individual prestellar cores or very young stars.
Submillimeter astronomy: Astronomy that observes radiation at wavelengths between far-infrared and microwave bands. Its instruments made cold dust condensations detectable across star-forming clouds.
L1498: A starless core in the Taurus molecular cloud complex with a well-measured density structure. It provides a comparatively quiescent case for testing core models.
Magnetic support: The resistance to gravitational collapse supplied by magnetic fields in conducting gas. Magnetic fields can delay collapse even in a dense core.
Dust continuum emission: Thermal radiation emitted by interstellar dust grains across a continuous range of wavelengths. Astronomers map cold core material through its faint millimeter and submillimeter emission.

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Pre-main-sequence starBroader topic: It precedes the stellar object itself, marking the boundary between cloud collapse and stellar evolution.