41. He discovered some comets, including periodic comet 22P / Kopff and the non-periodic C / 1906 E1. 42. He co-discovered periodic comet 153P / Ikeya-Zhang. 43. Periodic comets or short-period comets are generally defined as those having orbital periods of less than 200 years.44. It was their eleventh comet discovery overall including their discovery of two non-periodic comets , which use a different nomenclature. 45. His former mathematics professor published this note and Encke became famous as the discoverer of the short periodic comets . 46. In addition, Levy is the sole discoverer of two periodic comets : 255P / Levy and P / 1991 L3. 47. Other periodic comets that bear his name are 8P / Tuttle ( parent comet of the Ursid meteor shower; disc. 48. He also discovered the periodic comet P / 1997 B1 ( Kobayashi ), which he originally reported as an asteroid. 49. This is a periodic comet with an extremely short period of 3 years that stays entirely within the orbit of Jupiter. 50. Within the following time Encke was involved in the discovery and orbital parameter determination of other short periodic comets and asteroids.
