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Protostar
A protostar is a large mass that forms by contraction of the gas of a giant molecular cloud in the interstellar medium. The protostellar phase is an early stage in the process of star formation. For a one solar-mass star it lasts about 10,000,000 years.〔(【引用サイトリンク】 url=http://www.swpc.noaa.gov/sites/default/files/images/u33/Chapter_1.pdf )〕 It starts with a core of increased density in a molecular cloud and ends with the formation of a pre-main-sequence star (either a T Tauri star if below two solar masses or a Herbig Ae/Be star if between two and eight solar masses〔Stars more massive than eight solar masses are not observed in the pre-main-sequence star phase, as by the time they blow away their surrounding dark nebula, they are already on the main sequence〕), which then develops into a main sequence star. This is heralded by the T Tauri wind, a type of super solar wind that marks the change from the star accreting mass into radiating energy.
==History==
The existence of 'protostars' was first proposed and postulated by Soviet-Armenian scientist, Viktor Ambartsumian.
Ambartsumian's research was in the so-called 'continuous emission', observed in the spectra of young stars of the T Tauri type and their associated neighbor stars. As opposed to the classical hypotheses suggesting that stars formed singly as a result of condensation of small masses of diffuse matter, the new hypothesis postulated the existence of massive star-forming bodies, "proto-stars". The process of disintegration of proto-stars is responsible for the formation of multiple members in star associations.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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