These terms have historically been applied to any astronomical object orbiting the Sun that did not show the disk of a planet and was not observed to have the characteristics of an active comet, but as small objects in the outer Solar System were discovered, their volatile-based surfaces were found to more closely resemble comets, and so were often distinguished from traditional asteroids.

SOHO's 2000th comet was discovered by Polish amateur astronomer Michał Kusiak on 26 December 2010, and the numbers are expected to continue rising steadily for the foreseeable future.

It was especially noted that the birth and death of some notable persons coincided with separate appearances of the comet, such as with writers Mark Twain ( who correctly speculated that he'd " go out with the comet " in 1910 ) and Eudora Welty, to whose life Mary Chapin Carpenter dedicated the song Halley Came to Jackson.

Comet Shoemaker – Levy 9 ( formally designated D / 1993 F2 ) was a comet that broke apart and collided with Jupiter in July 1994, providing the first direct observation of an extraterrestrial collision of Solar System objects.

This generated a large amount of coverage in the popular media, and the comet was closely observed by astronomers worldwide.

The comet was discovered by astronomers Carolyn and Eugene M. Shoemaker and David Levy.

It was the first comet observed to be orbiting a planet, and had probably been captured by the planet around 20 – 30 years earlier.

The comet was later observed as a series of fragments ranging up to in diameter.

The comet was thus a serendipitous discovery, but one that quickly overshadowed the results from their main observing program.

Comet Shoemaker – Levy 9 was the ninth periodic comet ( a comet whose orbital period is 200 years or less ) discovered by the Shoemakers and Levy, hence its name.

It was their eleventh comet discovery overall including their discovery of two non-periodic comets, which use a different nomenclature.

The discovery image gave the first hint that comet Shoemaker – Levy 9 was an unusual comet, as it appeared to show multiple nuclei in an elongated region about 50 arcseconds long and 10 arcseconds wide.

Brian Marsden of the Central Bureau for Astronomical Telegrams noted that the comet lay only about 4 degrees from Jupiter as seen from Earth, and that while this could of course be a line of sight effect, its apparent motion in the sky suggested that it was physically close to the giant planet.

Orbital studies of the new comet soon revealed that it was orbiting Jupiter rather than the Sun, unlike all other comets known at the time.

Before the comet was captured by Jupiter, it was probably a short-period comet with an aphelion just inside Jupiter's orbit, and a perihelion interior to the asteroid belt.

Each fragment of the comet was denoted by a letter of the alphabet, from " fragment A " through to " fragment W ", a practice already established from previously observed broken-up comets.

More exciting for planetary astronomers was that the best orbital solutions suggested that the comet would pass within of the center of Jupiter, a distance smaller than the planet's radius, meaning that there was an extremely high probability that SL9 would collide with Jupiter in July 1994.

The discovery that the comet was likely to collide with Jupiter caused great excitement within the astronomical community and beyond, as astronomers had never before seen two significant Solar System bodies collide.

A monster will also become angry if either player collects a skull ( the only negative item in the game ), and the monster is hit by the resulting comet crossing the screen.

Such a spectrometer will also be used by the Philae lander of the Rosetta spacecraft to probe the surface of the 67P / Churyumov-Gerasimenko comet.

Tombaugh discovered nearly 800 asteroids during his search for Pluto and years of follow-up searches looking for another candidate for the postulated Planet X. Tombaugh is also credited with the discovery of comet C / 1931 AN, though its orbit is currently unknown.

Dyson has also proposed the creation of a Dyson tree, a genetically-engineered plant capable of growing on a comet.

There are two main classes of comet, short-period comets ( also called ecliptic comets ) and long-period comets ( also called nearly isotropic comets ).

However, the discovery of the object 1996 PW, an asteroid in an orbit more typical of a long-period comet, suggests that the cloud may also contain rocky objects.

Gibbs also applied his vector methods to the determination of planetary and comet orbits, and he developed the concept of mutually reciprocal triads of vectors which later proved to be of importance in crystallography.

Mg-rich olivine has also been discovered in meteorites, the Moon, Mars, in the dust of comet Wild 2, within the core of comet Tempel 1, falling into infant stars, as well as on asteroid 25143 Itokawa.

Chinese chroniclers also mention a comet in that year.

This appearance of the comet is also noted in the Anglo-Saxon Chronicle.

The comet was also observed from space by the International Cometary Explorer.

Thus a probable candidate for the impactor is a carbonaceous asteroid but also a comet is possible because comets are assumed to consist of material similar to carbonaceous chondrites.

Several disaster films have also been made: released during the turbulence of World War I, the Danish feature film The End of the World revolves around the near-miss of a comet which causes fire showers and social unrest in Europe.

The Vega probes to Venus and comet Halley launched in 1985 also used this basic Venera design, including landers but also atmospheric balloons which relayed data for about two days.

This is somewhat supported by the results of the analysis of the organics from the comet samples returned by the Stardust mission but the minerals also indicated a surprising contribution from high-temperature chemistry in the solar nebula.

On 3 January, 3: 56: 20 Moscow Time, at a distance of 119, 500 km from Earth, a large ( 1 kg ) cloud of sodium gas was released by the spacecraft, thus making this probe also the first artificial comet.

Comet Hale – Bopp was already being discussed as a possible " great comet "; the astronomical community eventually realised that Hyakutake might also become spectacular because of its close approach.

Besides approaching close to the Earth, the comet would also be visible throughout the night to northern hemisphere observers at its closest approach because of its path, passing very close to the pole star.

The meteoroids spread out along the entire orbit of the comet to form a meteoroid stream, also known as a " dust trail " ( as opposed to a comet's " dust tail " caused by the very small particles that are quickly blown away by solar radiation pressure ).

The second, denser belt, most likely also populated by asteroids, lies between the first belt and the outer comet disk.

60558 Echeclus was discovered without a coma but recently became active, and so it is now accordingly also classified as both a comet and an asteroid.

On March 6, 1815, Olbers also discovered a periodic comet, now named after him ( formally designated 13P / Olbers ).

This implied that the spacecraft had crossed the ' wake ' of an object, most likely a comet ; the object responsible was not immediately identified.

Later this comet was identified as the origin of the Taurids meteor showers.

The parent body of the Quadrantids was recently tentatively identified ( in a paper by Peter Jenniskens ) as the minor planet 2003 EH < sub > 1 </ sub >, which in turn may be the same object as the comet C / 1490 Y1 2003 EH < sub > 1 </ sub > Is the Quadrantid Shower Parent Comet that was observed by Chinese, Japanese and Korean astronomers some 500 years ago.

Comet Encke has sometimes been identified as the comet in question.

Biela's Comet or Comet Biela ( official designation: 3D / Biela ) was a periodic Jupiter-family comet first recorded in 1772 by Montaigne and Messier and finally identified as periodic in 1826 by Wilhelm von Biela.

Donati pioneered spectroscopy of comets to determine their physical composition, in particular with the comet 1864b, which spectrum he found containing three emitting lines which would four years later be identified by William Huggins to be carbon.

* 1744 ( Enkyō 1 ): Great comet was visible in sky for many months ; this comet is likely to have been what is today identified as C / 1743 X1 ( De Cheseaux ).... Click link for online Harvard-Smithsonian / NASA Astrophysics Data System

He experienced a sort of conversion to Western learning when he learned that the comet of 1910 had been identified as a reappearance of Halley's comet.