Also containing HII regions and molecular clouds, for 10 points, name this region of space that consists mostly of hydrogen, the gas and dust that floats between stars.
This object's extinction curve features a bump at 220nm due to the presence of graphite, and one type of matter here is distributed according to the MRN power law, which was later extended by Drane. McKee and Ostriker proposed a three-phase model of it, adding a dynamic phase to the equilibrum two-phase FGH model, which divided it into cold-dense and intercloud regions. Evidence for the existence of this region came from the dip in a broad oscillating Ca II absorption line of delta-Ori and other so-called forbidden transitions, and this regions primary heating mechanisms are photoelectric grain heating and low-energy cosmic rays. This region also contains superbubbles created by stellar winds, and is responsible for the ubiquitous 21-cm H line. Also containing HII regions and molecular clouds, for 10 points, name this region of space that consists mostly of hydrogen, the gas and dust that floats between stars.
This object's extinction curve features a bump at 220nm due to the presence of graphite, and one type of matter here is distributed according to the MRN power law, which was later extended by Drane.
{Interstellar Medium} or {ISM} (Do not accept “Intergalactic Medium”)