Wikipedia definition
1. Extinct cometExtinct comets are comets that have expelled most of their volatile ice and have little left to form a tail or coma. The volatile material contained in the comet nucleus evaporates away, and all that remains is inert rock or rubble that can resemble an asteroid. Comets may go through a transition phase as they come close to extinction. A comet may be dormant rather than extinct, if its volatile component is sealed beneath an inactive surface layer.
Read “Extinct comet” on English Wikipedia
Read “彗星・小惑星遷移天体” on Japanese Wikipedia
Read “Extinct comet” on DBpedia


to talk about this word.