This is Barnard 68, a dark absorption nebula found near the constellation Ophiucus. This molecular cloud absorbs practically all the visible light emitted by the stars near it, thus, the darkness.
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It is not known exactly how molecular clouds like Barnard 68 form, but it is known that these clouds are themselves likely places for new stars to form. In fact, Barnard 68 itself has been found likely to collapse and form a new star system. It is possible to look right through the cloud in infrared light.
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(Image Credit: FORS Team, 8.2-meter VLT Antu, ESO)
Source: neatorama