Lost comet Comet Shoemaker–Levy 9, which collided with Jupiter in 1994. Lost comet A comet is "lost" when it has been missed at its most recent perihelion passage. This generally happens when data is insufficient to reliably calculate the comet's orbit and predict its location. The "D/" designation is used for a periodic comet that no longer exists or is deemed to have disappeared. Lost comets can be compared to lost minor planets, although calculation of comet orbits differs because of nongravitational forces, such as emission of jets of gas from the nucleus. Some astronomers have specialized in this area, such as
Great Comet of 1744 "dust striae" seen in the tails of some comets, such as Comet West and C/2006 P1 (McNaught). Chéseaux, on March 9, was the last known observer in the northern hemisphere to see the comet, but it remained visible for observers in the southern hemisphere, some of whom reported a tail length of approximately 90 degrees on March 18. The comet was not seen after April 22, 1744. The comet also was noted in Japanese astronomical records in the "Nihon Odai Ichiran" of the Kanpō era. Researchers have found in Chinese astronomical records that some Chinese observations describe audible sounds associated