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In astronomy, Bok globules are isolated and relatively small containing dense cosmic dust and gas from which star formation may take place. Bok globules are found within H II regions, and typically have a mass of about two to 50 contained within a region about a light year or so across (about ). They contain molecular hydrogen (H2), carbon oxides and helium, and around 1% (by mass) silicate dust. Bok globules most commonly result in the formation of Binary star- or multiple-star systems.
An analysis of near-infrared observations published in 1990 confirmed that stars were being born inside Bok globules. Further observations have revealed that some Bok globules contain embedded warm sources, some contain Herbig–Haro objects, and some show Bipolar outflow of Molecular cloud. Millimeter-wave emission line studies have provided evidence for the infall of material onto an accreting protostar. It is now thought that a typical Bok globule contains about 10 of material in a region about a light-year or so across, and that Bok globules most commonly result in the formation of double- or multiple-star systems.
Bok globules are still a subject of intense research. Known to be some of the coldest objects in the natural universe, their structure and density remains somewhat a mystery. Methods applied so far have relied on column density derived from near-infrared extinction and even star counting in a bid to probe these objects further.
Bok globules that are irradiated by ultraviolet light from hot nearby stars exhibit stripping of materials to produce a tail. These types are called " cometary globules" ( CG). Cometary globules. 1 Formation, evolution and morphology, B. Lefloch and B. Lazareff, 1994.
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