For astronomers, the beauty of Bok globules lies in their simplicity. Whereas the process of star formation in a giant molecular cloud is hidden in the confusion of complex turbulence and strong magnetic fields, the action inside a Bok globule is believed to be much simpler. The challenge for astronomers is to pull some information out of the darkness. Most of the remaining one percent is the very component that makes Bok globules opaque the interstellar dust. Ironically, the obscuring dust is also the means to understanding the cloud s structure.
Interstellar dust absorbs and reddens light in a way that astronomers understand very well.
By assessing the degree to which light is attenuated in different parts of the cloud, astronomers can deduce variations in the cloud s density. Using the Very Large Telescope and the New Technology Telescope, both in the Chilean Andes, Alves and his colleagues were able to measure the degree to which the dust extinguished light coming from stars behind the cloud. Infrared wavelengths, which are a little longer than visible light, merely wiggle through the dust in the cloud. What the Alves team found is that the density of matter in Barnard 68 increases steadily toward the center of the cloud. It conforms to one of the simplest models of stellar structure, a polytropic sphere, in which thermal pressure alone supports the globule against gravitational contraction something that the Dutch-American astronomer Bart Bok first predicted back in 1948.