Young stellar object

A star in an early stage of formation, often still accreting gas and dust from its surrounding cloud or disk. Its evolution is marked by changing luminosity, outflows, and circumstellar material.

Gravitational collapse: The contraction of matter under its own gravity, often initiating star formation in a dense molecular cloud. It begins the cloud-to-star transformation that produces young stellar objects.
Molecular cloud: A cold, dense interstellar cloud composed mainly of molecular hydrogen and containing the raw material for star formation. Young stellar objects form within collapsing dense regions of these clouds.
Infrared astronomy: The study of astronomical objects through infrared radiation, which can pass through dust more readily than visible light. Infrared observations expose young stars hidden inside dusty birth clouds.
Class 0 protostar: The youngest observational class of protostar, still deeply embedded in a massive envelope and strongly associated with outflows. It marks the earliest, most envelope-dominated phase in the usual infrared classification.
Episodic accretion: A pattern of irregular, intense bursts of mass transfer onto an object, separated by quieter intervals. Bursts may explain luminosities lower than steady-accretion models predict.
Protostar: A forming star still gaining mass from its surroundings before sustained hydrogen fusion begins in its core. This early phase is where a young stellar object is still assembling most of its mass.
Interstellar dust: Microscopic solid particles between stars that absorb and scatter light and radiate energy in the infrared. Dust around young stars obscures visible light and re-emits their energy at infrared wavelengths.
Submillimeter astronomy: Astronomy using radiation between the far-infrared and microwave bands, especially useful for cold dust and gas. Its wavelengths trace the cold envelopes and disks surrounding young stellar objects.
Class I protostar: An embedded young stellar object with a substantial infalling envelope and a growing circumstellar disk. It follows the earliest embedded phase as the envelope becomes less dominant.
Luminosity problem: The mismatch between observed protostellar luminosities and those predicted by simple models of steady mass accretion. It motivates models with variable accretion during early stellar growth.

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Rho Ophiuchi cloud complexNarrower topic: This category includes the developing stars distributed through the complex.