Assertion: nebula | /r/HasProperty | h ii region
Facets:
value: with standing for hydrogen
type: OTHER
Source sentences:
text: The boundary between an emission nebula (H II region) and the surrounding gas (H I, or neutral hydrogen, region) is sharp: the thickness of the transition layer is about 0.05 parsec.
text: These nebulae are also called HII regions, with the "H" standing for hydrogen and the "II" indicating that the gas is ionized.