Assertion: nebula's structure | /r/HasProperty | thousands of years
Facets:
Source sentences:
text: This means that the outer structure may be just thousands of years old, but the inner hourglass must be a more recent outflow event.
text: This means that the outer structure may be just thousands of years old, but the inner hourglass must be a more recent outflow event.
text: This means that the outer structure may be just thousands of years old, but the inner hourglass must be a more recent outflow event.