protosters

Protoster is a term occasionally used in astronomy to denote a very young stellar object in the early stages of formation. It is not widely adopted in scientific literature, where protostar is the standard term. When used, protoster typically refers to the same physical object—an infant star still gathering mass from its natal cloud.

Formation and evolution of protosters follow the general picture of star formation in molecular clouds. A cold, dense core collapses under gravity, creating a central condensation that accretes material from an infalling envelope and is surrounded by a circumstellar disk. The central object heats up and becomes a protostar, while jets and bipolar outflows help remove excess angular momentum and gas. The evolution is commonly described using the Class 0 to Class III scheme, based on the spectral energy distribution and envelope properties.

Observationally, protostars are often deeply embedded in dust, making infrared and submillimeter observations essential. Signatures include infrared excess from the disk and envelope, outgoing jets, and characteristic spectral slopes that change as the object evolves. Measuring luminosity, accretion rate, and mass helps place protostars within an evolutionary sequence and informs models of disk formation and planet-building processes.

Significance of studying protostars lies in constraining the timeline of star formation, the development of circumstellar disks, and the early environments in which planetary systems form. The protostellar phase sets initial conditions for pre-main-sequence evolution and planet formation.

Related topics include protostar, star formation, and young stellar objects.