China tourism for However, there are nuclei that are giant size. The asteroidal comet and centaur P/Chiron has a nucleus ? km in diameter. Some long-period comets are extraordinarily large, km in diameter or greater. The sire of the sungrazer comet family is thought to have been ? km in diameter. Sarabat’s Comet of is believed to have been at least km some say km. Bailey et al. estimate that comets larger than km cross Earth’s orbit approximately once every years and come within Jupiter’s orbit once every years or so. China tourism 2016.