Answer: bopp

AnswerCrossword Clue
BOPPHalf a comet's name
BOPPHale's comet co-finder
BOPPComet Hale-..
BOPPHale-.. comet
BOPP1995 comet spotter Thomas
BOPPComet Hale-...
BOPPHale- ... comet
BOPPHale-... comet
BOPPHale-... (comet seen in 1997)
BOPPComet Hale- --