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Loading contentA vast spherical shell of icy bodies surrounding the Solar System, the source of the long-period comets.
A hypothesised spherical cloud of trillions of icy bodies at the outermost edge of the Sun's gravitational influence — the reservoir from which long-period and Halley-type comets are nudged inward.
9 modelled members.
The 'Great Comet of 1997', a long-period comet with an exceptionally large, active nucleus that remained visible to the naked eye for a record 18 months.
The most famous comet, visible from Earth every ~76 years, whose return in 1986 was met by an international fleet including ESA's Giotto — and the parent of two annual meteor showers.
The 'Great Comet of 1996', which passed very close to Earth and displayed one of the longest comet tails ever recorded.
The 'Great Comet of 2007', the brightest comet in decades, whose vast fanned dust tail was a spectacular sight from the Southern Hemisphere.
The brightest comet visible from the Northern Hemisphere since Hale–Bopp, a naked-eye spectacle in July 2020 discovered by the NEOWISE space telescope.
A long-period comet that made an exceptionally close pass of Mars in October 2014, observed up close by the fleet of Mars orbiters and rovers.
A large Halley-type comet on a 133-year orbit, the parent body of the reliable Perseid meteor shower each August.
The parent comet of the Leonid meteor shower, whose 33-year returns produce the periodic Leonid storms.
A long-period comet on a roughly 415-year orbit, the parent body of the Lyrid meteor shower seen each April.
Facts on this topic will be cited from these primary and reference sources.
Mission data, planetary science, space telescopes, and public-domain imagery.
Most NASA-produced imagery is in the public domain; individual items are checked for usage terms before publication.