What's up to four times as big as Jupiter, is so distant that astronomers haven't been able to find it in more than 80 years, and is the stuff of legends and conspiracy theories? "Planet X." A mystery object that most astronomers would rather not discuss. Whenever a discussion of the possibility that the massive planet exists does flare up, most astrophysicists and professional astronomers treat the subject with the same respect they give to UFOs. But now some scientists think they have actually found the elusive Planet X. And if they have, many that have been debunking it for years are like to experience conniption fits.