List of comets: classification, naming, and notable examples

Classification and naming

Comets are commonly divided into periodic and non-periodic types. Periodic comets return to the inner solar system on timescales short enough to observe multiple apparitions; they usually receive a P prefix in catalogues and sometimes a number indicating the order of confirmed returns (for example, 1P/Halley). Non-periodic comets are usually given a C prefix and may appear only once in recorded history because their orbital period is extremely long or because they are on hyperbolic paths that eject them from the solar system. For summary lists and catalogs see comet lists and specialized pages on periodic comets and non-periodic comets.

History and notable discoveries

Observers have recorded comets for millennia; once regarded as omens, comets became objects of scientific interest after the development of telescopic astronomy. Certain comets are famous because of their visibility or scientific importance: Halley's Comet (1P) returns roughly every 76 years and helped establish the periodic nature of some comets. Bright visitors such as Hale–Bopp and NEOWISE captured public attention in recent decades. Others, like Shoemaker–Levy 9, taught astronomers about planetary impacts when its fragments struck Jupiter, and spacecraft missions such as Rosetta to 67P/Churyumov–Gerasimenko provided in situ study of cometary structure and composition.

Why comets matter

Comets are valuable scientific targets because they preserve materials from the solar system's formation. Studying their chemistry informs models of planet formation and the distribution of water and organic molecules. Comets are also associated with meteor showers when Earth crosses debris trails, and they remain relevant to planetary defense because of potential impact risks from larger bodies on similar orbits.

Reading a comet list

A typical comet list entry gives the designation, discovery credit, orbital period (if known), and sometimes the date of the last or next perihelion passage. The prefix conventions (P for periodic, C for non-periodic) and numbering help track repeated returns. Some catalogs also record the comet's orbital class (short-period versus long-period), absolute brightness, and associated meteor showers or spacecraft visits.

Selected examples

• 1P/Halley — Prototypical periodic comet with a ~76-year period and many historical observations.
• C/1995 O1 (Hale–Bopp) — Exceptionally bright long-period comet visible to the naked eye for months.
• 67P/Churyumov–Gerasimenko — Target of ESA's Rosetta mission; studied at close range.
• C/2020 F3 (NEOWISE) — Recent bright visitor widely observed in 2020.
• Shoemaker–Levy 9 — Fragmented comet that impacted Jupiter, demonstrating collision processes.

For extended catalogs, periodic-comet tables and discovery histories consult specialized databases and lists linked above. A well-constructed list helps both amateur observers and researchers by concisely summarizing the designations, orbital behavior, and notable attributes of each comet.