|Right ascension||17h 30m|
|Type of object||Dark nebula|
|Distance from Earth||450 ly|
The Pipe nebula is a dark nebula in the constellation of Ophiuchus. The nebula is composed of four dust clouds catalogued by the astronomer E. E. Barnard (designated B59, B72, B77 and B78) and obscures a region of the centre of the Milky Way. Against this relatively bright background of stars, these clouds take the form of a large cloud with a long dark stem, resembling a pipe. The nebula is extremely large, with an apparent size of approximately 10º×10º. Since the nebula is thought to lie some 450 light years away, this means it is roughly 79 light years across.
The nebula is thought to contain some 10,000 solar masses of gas and dust. The nebula houses many dense, low mass cores of gas, estimated to be around 134 in number. Radio observations has been used to study the nebula and has revealed these cores to be cold and contain both carbon monoxide and ammonia among other chemical species. Observations made by the Herschel Space Observatory (an infrared telescope) suggest the temperature varies from 13-19 kelvin throughout the nebula, with the densest regions being the coldest. It was also found that the N2H+ molecule is the only one that traces the coldest and densest cores.