Assertion: supernova's progenitor | /r/HasProperty | observed
Facets:
value: just yet
type: DEGREE
Source sentences:
text: WO stars are extremely rare and visually relatively faint, so it is difficult to say whether such progenitors are missing or just yet to be observed.
text: Again it should be observable wherever it occurs, but it is less likely that the progenitor will ever have been observed.