Assertion: nebula's star | /r/CapableOf | blow off layers of material
Facets:
value: periodically
type: TEMPORAL
Source sentences:
text: In this case, the image shows a planetary nebula in the act of forming, with the dying central star periodically blowing off layers of material that expand for a while before the next layer is blown off, thus creating the bubble-within-a-bubble appearance of the nebula.