Assertion: supernova | /r/HasProperty | unique
Facets:
Source sentences:
text: The supernova originated in the collapse and subsequent explosion of a supergiant star, and it is unique in that its progenitor star had been observed and cataloged prior to the event.
text: This supernova is also unique in that it took place away from the type of environment where supernovas usually occur; most observed supernovas happen in dense star clusters, but this one happened in a relatively isolated spot in space, some 54,000 light years from the center of its host dwarf galaxy.