Assertion: nebula's material | /r/CapableOf | collapse under its own weight
Facets:
Source sentences:
text: As the material collapses under its own weight, massive stars may form in the center, and their ultraviolet radiation ionizes the surrounding gas, making it visible at optical wavelengths.
text: According to the English wikipedia article on nebulae, under the section Formation, «as the material collapses under its own weight, massive stars may form in the center, and their ultraviolet radiation ionizes the surrounding gas, making it visible at optical wavelengths.