Sentence:  "Presolar grains were isolated in primitive meteorites only 15 years ago. These grains of <WSD>stardust</WSD> formed in the atmospheres of evolved stars and in nova and supernova ejecta." 
Meaning of the word marked with <WSD> tags:  A type of cosmic dust that condensed from cooling ejected gases from individual presolar stars and incorporated into the cloud from which the Solar System condensed.