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Bok Globules

The birth of a baby is one of the most amazing miracles to behold in the natural world. From conception to birth, the change that a baby endures beginning as a single cell and ending up as a full grown and functioning human being in the short span of forty weeks is unrivaled in nature. Stellar birth, however, is also an extremely amazing event. Although the birth of a star takes an eternity in comparison to the human gestational cycle, it is one of the most amazing processes that occur within the celestial realms. One place where the birth of stars occurs is within dark molecular clouds called Bok Globules.

A pair of Bok Globules

Bok globules are dark, dense clouds of dust and gas found within H II regions, which are low density clouds of gas and plasma that can be as big as several hundred light-years in diameter. These Bok globules typically have a mass that ranges between 0.1 and 2000 solar masses, a unit of astronomical mass measurement that is equal to the mass of the Sun.  They are contained with an area of about a light year or so in diameter. Molecular hydrogen, carbon dioxide, helium, and a small percentage of silicate dust are found within these clouds.

These astronomical phenomena where first observed by astronomer Bart Bok in the 1940s. Bok and his researcher partner E.F. Reilly published a paper in 1947 that stated these clouds were similar to the cocoons of insects. They hypothesized that these clouds were undergoing gravitational collapse to form protostars from which star clusters and star systems were formed. This hypothesis was difficult to verify due to the fact that the clouds obscure all visible light being emitted from within the cloud. However, infrared analysis observations published in 1990 confirmed that stars were being formed within the Bok globules.

Bok globules are the smallest manifestations of dark nebulae, which are interstellar clouds that contain a very high concentration of dust that allows them to scatter and absorb visible light. Bok globules support both the inflow and outflow of material, a process common in the development of protostars. These clouds are known to have a temperature of around 10 Kelvin.

Bok globules are still being intensely researched and their inmost properties are still being analyzed. While there is still much information to be garnered from Bok globules, what is known is that they actually serve as a cocoon protecting infant protostars from being stripped by radioactive stellar winds from other nearby stars and the block all visible light. Bok globules are an amazing phenomena and the understanding of these clouds will give us an even greater insight into the birth of stars.

References

http://astronomy.swin.edu.au/cms/astro/cosmos/B/Bok+Globule

http://www.universetoday.com/2009/02/02/journey-inside-a-bok-globule/

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