A small, dense, round cloud of dust and gas that absorbs radiation and appears
as a black blob when seen against the background of a bright nebula or star
field; also known as Bok globule after Bart Bok
who first drew attention to them and suspected they might be protostars.
Their exact status, however, remains unclear. While it is generally assumed
they are the cores of fragments of molecular
clouds that are in the process of collapsing to form individual stars,
they could also be fragments that have become hung up by a combination of
internal magnetic and turbulent pressure and are failed star-forming cores.
| Dark globule Barnard 68 |
Globules are the smallest and most regular features of the interstellar
medium. Typically they have a mass of 20 to 100 solar masses and a diameter
of 1 to 2 light-years across. Having no internal heat source, globules are,
surprisingly, among the coldest known naturally-occurring phenomena with
a temperature only a few degrees above absolute zero.
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