Assertion: lagoon nebula | /r/IsA | emission
Facets:
Source sentences:
text: It is classified as an emission nebula, which are localized regions of ionized gas which emits light in different colors at wavelengths not always visible to the human eye.
text: The Lagoon Nebula, or Messier 8 (M8), is a large interstellar cloud classified as an emission nebula and an H II region.