Asteroid - wikipedia Asteroid For other uses, see Asteroid ( disambiguation ). 253 Mathilde, a C - type asteroid measuring about 50 km ( 30 mi ) across, covered in craters half that size. Photograph taken in 1997 by the NEAR Shoemaker probe. 2014 JO25 imaged by radar during its 2017 Earth flyby Asteroids are minor planets, especially those of the inner Solar System. The larger ones have also been called planetoids. These terms have historically been applied to any astronomical object orbiting the Sun that did not show the disc of a planet and was not observed to have the characteristics of an active comet. As minor planets in the outer Solar System were discovered and found to have volatile - based surfaces that resemble those of comets, they were often distinguished from asteroids of the asteroid belt. In this article, the term `` asteroid '' refers to the minor planets of the inner Solar System including those co-orbital with Jupiter. There are millions of asteroids, many thought to be the shattered remnants of planetesimals, bodies within the young Sun 's solar nebula that never grew large enough to become planets. The large majority of known asteroids orbit in the asteroid belt between the orbits of Mars and Jupiter, or are co-orbital with Jupiter ( the Jupiter trojans ). However, other orbital families exist with significant populations, including the near - Earth objects. Individual asteroids are classified by their characteristic spectra, with the majority falling into three main groups : C - type, M - type, and S - type. These were named after and are generally identified with carbon - rich, metallic, and silicate ( stony ) compositions, respectively. The size of asteroids varies greatly, the largest is almost 1,000 km ( 625 mi ) across. Asteroids are differentiated from comets and meteoroids. In the case of comets, the difference is one of composition : while asteroids are mainly composed of mineral and rock, comets are composed of dust and ice. In addition, asteroids formed closer to the sun, preventing the development of the aforementioned cometary ice. The difference between asteroids and meteoroids is mainly one of size : meteoroids have a diameter of less than one meter, whereas asteroids have a diameter of greater than one meter. Finally, meteoroids can be composed of either cometary or asteroidal materials. Only one asteroid, 4 Vesta, which has a relatively reflective surface, is normally visible to the naked eye, and this only in very dark skies when it is favorably positioned. Rarely, small asteroids passing close to Earth may be visible to the naked eye for a short time. As of October 2017, the Minor Planet Center had data on almost 745,000 objects in the inner and outer Solar System, of which almost 504,000 had enough information to be given numbered designations. The United Nations declared June 30 as International Asteroid Day to educate the public about asteroids. The date of International Asteroid Day commemorates the anniversary of the Tunguska asteroid impact over Siberia, Russian Federation, on 30 June 1908. Contents 1 Discovery 1.1 Historical methods 1.2 Manual methods of the 1900s and modern reporting 1.3 Computerized methods 2 Terminology 3 Formation 4 Distribution within the Solar System 4.1 Asteroid belt 4.2 Trojans 4.3 Near - Earth asteroids 5 Characteristics 5.1 Size distribution 5.1. 1 Largest asteroids 5.2 Rotation 5.3 Composition 5.4 Surface features 5.5 Color 6 Classification 6.1 Orbital classification 6.1. 1 Quasi-satellites and horseshoe objects 6.2 Spectral classification 6.2. 1 Problems 7 Naming 7.1 Symbols 8 Exploration 8.1 Planned and future missions 9 Fiction 10 Gallery 11 See also 12 Notes 13 References 14 External links Discovery Sizes of the first ten asteroids to be discovered, compared to the Moon 243 Ida and its moon Dactyl. Dactyl is the first satellite of an asteroid to be discovered. The first asteroid to be discovered, Ceres, was originally considered to be a new planet. This was followed by the discovery of other similar bodies, which, with the equipment of the time, appeared to be points of light, like stars, showing little or no planetary disc, though readily distinguishable from stars due to their apparent motions. This prompted the astronomer Sir William Herschel to propose the term `` asteroid '', coined in Greek as ἀστεροειδής, or asteroeidēs, meaning ' star - like, star - shaped ', and derived from the Ancient Greek ἀστήρ astēr ' star, planet '. In the early second half of the nineteenth century, the terms `` asteroid '' and `` planet '' ( not always qualified as `` minor '' ) were still used interchangeably. Historical methods This section does not cite any sources. Please help improve this section by adding citations to reliable sources. Unsourced material may be challenged and removed. ( January 2018 ) Asteroid discovery methods have dramatically improved over the past two centuries. In the last years of the 18th century, Baron Franz Xaver von Zach organized a group of 24 astronomers to search the sky for the missing planet predicted at about 2.8 AU from the Sun by the Titius - Bode law, partly because of the discovery, by Sir William Herschel in 1781, of the planet Uranus at the distance predicted by the law. This task required that hand - drawn sky charts be prepared for all stars in the zodiacal band down to an agreed - upon limit of faintness. On subsequent nights, the sky would be charted again and any moving object would, hopefully, be spotted. The expected motion of the missing planet was about 30 seconds of arc per hour, readily discernible by observers. First asteroid image ( Ceres and Vesta ) from Mars -- viewed by Curiosity ( 20 April 2014 ). The first object, Ceres, was not discovered by a member of the group, but rather by accident in 1801 by Giuseppe Piazzi, director of the observatory of Palermo in Sicily. He discovered a new star - like object in Taurus and followed the displacement of this object during several nights. Later that year, Carl Friedrich Gauss used these observations to calculate the orbit of this unknown object, which was found to be between the planets Mars and Jupiter. Piazzi named it after Ceres, the Roman goddess of agriculture. Three other asteroids ( 2 Pallas, 3 Juno, and 4 Vesta ) were discovered over the next few years, with Vesta found in 1807. After eight more years of fruitless searches, most astronomers assumed that there were no more and abandoned any further searches. However, Karl Ludwig Hencke persisted, and began searching for more asteroids in 1830. Fifteen years later, he found 5 Astraea, the first new asteroid in 38 years. He also found 6 Hebe less than two years later. After this, other astronomers joined in the search and at least one new asteroid was discovered every year after that ( except the wartime year 1945 ). Notable asteroid hunters of this early era were J.R. Hind, Annibale de Gasparis, Robert Luther, H.M.S. Goldschmidt, Jean Chacornac, James Ferguson, Norman Robert Pogson, E.W. Tempel, J.C. Watson, C.H.F. Peters, A. Borrelly, J. Palisa, the Henry brothers and Auguste Charlois. In 1891, Max Wolf pioneered the use of astrophotography to detect asteroids, which appeared as short streaks on long - exposure photographic plates. This dramatically increased the rate of detection compared with earlier visual methods : Wolf alone discovered 248 asteroids, beginning with 323 Brucia, whereas only slightly more than 300 had been discovered up to that point. It was known that there were many more, but most astronomers did not bother with them, calling them `` vermin of the skies '', a phrase variously attributed to Eduard Suess and Edmund Weiss. Even a century later, only a few thousand asteroids were identified, numbered and named. Manual methods of the 1900s and modern reporting Until 1998, asteroids were discovered by a four - step process. First, a region of the sky was photographed by a wide - field telescope, or astrograph. Pairs of photographs were taken, typically one hour apart. Multiple pairs could be taken over a series of days. Second, the two films or plates of the same region were viewed under a stereoscope. Any body in orbit around the Sun would move slightly between the pair of films. Under the stereoscope, the image of the body would seem to float slightly above the background of stars. Third, once a moving body was identified, its location would be measured precisely using a digitizing microscope. The location would be measured relative to known star locations. These first three steps do not constitute asteroid discovery : the observer has only found an apparition, which gets a provisional designation, made up of the year of discovery, a letter representing the half - month of discovery, and finally a letter and a number indicating the discovery 's sequential number ( example : 1998 FJ ). The last step of discovery is to send the locations and time of observations to the Minor Planet Center, where computer programs determine whether an apparition ties together earlier apparitions into a single orbit. If so, the object receives a catalogue number and the observer of the first apparition with a calculated orbit is declared the discoverer, and granted the honor of naming the object subject to the approval of the International Astronomical Union. Computerized methods 2004 FH is the center dot being followed by the sequence ; the object that flashes by during the clip is an artificial satellite. There is increasing interest in identifying asteroids whose orbits cross Earth 's, and that could, given enough time, collide with Earth ( see Earth - crosser asteroids ). The three most important groups of near - Earth asteroids are the Apollos, Amors, and Atens. Various asteroid deflection strategies have been proposed, as early as the 1960s. The near - Earth asteroid 433 Eros had been discovered as long ago as 1898, and the 1930s brought a flurry of similar objects. In order of discovery, these were : 1221 Amor, 1862 Apollo, 2101 Adonis, and finally 69230 Hermes, which approached within 0.005 AU of Earth in 1937. Astronomers began to realize the possibilities of Earth impact. Two events in later decades increased the alarm : the increasing acceptance of the Alvarez hypothesis that an impact event resulted in the Cretaceous -- Paleogene extinction, and the 1994 observation of Comet Shoemaker - Levy 9 crashing into Jupiter. The U.S. military also declassified the information that its military satellites, built to detect nuclear explosions, had detected hundreds of upper - atmosphere impacts by objects ranging from one to ten meters across. All these considerations helped spur the launch of highly efficient surveys that consist of charge - coupled device ( CCD ) cameras and computers directly connected to telescopes. As of 2011, it was estimated that 89 % to 96 % of near - Earth asteroids one kilometer or larger in diameter had been discovered. A list of teams using such systems includes : Lincoln Near - Earth Asteroid Research ( LINEAR ) Near - Earth Asteroid Tracking ( NEAT ) Spacewatch Lowell Observatory Near - Earth - Object Search ( LONEOS ) Catalina Sky Survey ( CSS ) Campo Imperatore Near - Earth Object Survey ( CINEOS ) Japanese Spaceguard Association Asiago - DLR Asteroid Survey ( ADAS ) Pan-STARRS As of 20 September 2013, the LINEAR system alone has discovered 138,393 asteroids. Among all the surveys, 4711 near - Earth asteroids have been discovered including over 600 more than 1 km ( 0.6 mi ) in diameter. Terminology Euler diagram showing the types of bodies in the Solar System. ( see Small Solar System body ) A composite image, to scale, of the asteroids that have been imaged at high resolution except Ceres. As of 2011, they are, from largest to smallest : 4 Vesta, 21 Lutetia, 253 Mathilde, 243 Ida and its moon Dactyl, 433 Eros, 951 Gaspra, 2867 Šteins, 25143 Itokawa. The largest asteroid in the previous image, Vesta ( left ), with Ceres ( center ) and the Moon ( right ) shown to scale. Traditionally, small bodies orbiting the Sun were classified as comets, asteroids, or meteoroids, with anything smaller than ten meters across being called a meteoroid. Beech and Steel 's 1995 paper proposed a meteoroid definition including size limits. The term `` asteroid '', from the Greek word for `` star - like '', never had a formal definition, with the broader term minor planet being preferred by the International Astronomical Union. However, following the discovery of asteroids below ten meters in size, Rubin and Grossman 's 2010 paper revised the previous definition of meteoroid to objects between 10 μm and 1 meter in size in order to maintain the distinction between asteroids and meteoroids. The smallest asteroids discovered ( based on absolute magnitude H ) are 2008 TS with H = 33.2 and 2011 CQ 1 with H = 32.1 both with an estimated size of about 1 meter. In 2006, the term `` small Solar System body '' was also introduced to cover both most minor planets and comets. Other languages prefer `` planetoid '' ( Greek for `` planet - like '' ), and this term is occasionally used in English especially for larger minor planets such as the dwarf planets as well as an alternative for asteroids since they are not star - like. The word `` planetesimal '' has a similar meaning, but refers specifically to the small building blocks of the planets that existed when the Solar System was forming. The term `` planetule '' was coined by the geologist William Daniel Conybeare to describe minor planets, but is not in common use. The three largest objects in the asteroid belt, Ceres, Pallas, and Vesta, grew to the stage of protoplanets. Ceres is a dwarf planet, the only one in the inner Solar System. When found, asteroids were seen as a class of objects distinct from comets, and there was no unified term for the two until `` small Solar System body '' was coined in 2006. The main difference between an asteroid and a comet is that a comet shows a coma due to sublimation of near surface ices by solar radiation. A few objects have ended up being dual - listed because they were first classified as minor planets but later showed evidence of cometary activity. Conversely, some ( perhaps all ) comets are eventually depleted of their surface volatile ices and become asteroid - like. A further distinction is that comets typically have more eccentric orbits than most asteroids ; most `` asteroids '' with notably eccentric orbits are probably dormant or extinct comets. For almost two centuries, from the discovery of Ceres in 1801 until the discovery of the first centaur, Chiron in 1977, all known asteroids spent most of their time at or within the orbit of Jupiter, though a few such as Hidalgo ventured far beyond Jupiter for part of their orbit. When astronomers started finding more small bodies that permanently resided further out than Jupiter, now called centaurs, they numbered them among the traditional asteroids, though there was debate over whether they should be considered asteroids or as a new type of object. Then, when the first trans - Neptunian object ( other than Pluto ), Albion, was discovered in 1992, and especially when large numbers of similar objects started turning up, new terms were invented to sidestep the issue : Kuiper - belt object, trans - Neptunian object, scattered - disc object, and so on. These inhabit the cold outer reaches of the Solar System where ices remain solid and comet - like bodies are not expected to exhibit much cometary activity ; if centaurs or trans - Neptunian objects were to venture close to the Sun, their volatile ices would sublimate, and traditional approaches would classify them as comets and not asteroids. The innermost of these are the Kuiper - belt objects, called `` objects '' partly to avoid the need to classify them as asteroids or comets. They are thought to be predominantly comet - like in composition, though some may be more akin to asteroids. Furthermore, most do not have the highly eccentric orbits associated with comets, and the ones so far discovered are larger than traditional comet nuclei. ( The much more distant Oort cloud is hypothesized to be the main reservoir of dormant comets. ) Other recent observations, such as the analysis of the cometary dust collected by the Stardust probe, are increasingly blurring the distinction between comets and asteroids, suggesting `` a continuum between asteroids and comets '' rather than a sharp dividing line. The minor planets beyond Jupiter 's orbit are sometimes also called `` asteroids '', especially in popular presentations. However, it is becoming increasingly common for the term `` asteroid '' to be restricted to minor planets of the inner Solar System. Therefore, this article will restrict itself for the most part to the classical asteroids : objects of the asteroid belt, Jupiter trojans, and near - Earth objects. When the IAU introduced the class small Solar System bodies in 2006 to include most objects previously classified as minor planets and comets, they created the class of dwarf planets for the largest minor planets -- those that have enough mass to have become ellipsoidal under their own gravity. According to the IAU, `` the term ' minor planet ' may still be used, but generally the term ' Small Solar System Body ' will be preferred. '' Currently only the largest object in the asteroid belt, Ceres, at about 975 km ( 606 mi ) across, has been placed in the dwarf planet category. Formation Artist 's impression shows how an asteroid is torn apart by the strong gravity of a white dwarf. It is thought that planetesimals in the asteroid belt evolved much like the rest of the solar nebula until Jupiter neared its current mass, at which point excitation from orbital resonances with Jupiter ejected over 99 % of planetesimals in the belt. Simulations and a discontinuity in spin rate and spectral properties suggest that asteroids larger than approximately 120 km ( 75 mi ) in diameter accreted during that early era, whereas smaller bodies are fragments from collisions between asteroids during or after the Jovian disruption. Ceres and Vesta grew large enough to melt and differentiate, with heavy metallic elements sinking to the core, leaving rocky minerals in the crust. In the Nice model, many Kuiper - belt objects are captured in the outer asteroid belt, at distances greater than 2.6 AU. Most were later ejected by Jupiter, but those that remained may be the D - type asteroids, and possibly include Ceres. Distribution within the Solar System See also : List of minor - planet groups, List of notable asteroids, and List of minor planets The asteroid belt ( white ) and Jupiter 's trojan asteroids ( green ) Various dynamical groups of asteroids have been discovered orbiting in the inner Solar System. Their orbits are perturbed by the gravity of other bodies in the Solar System and by the Yarkovsky effect. Significant populations include : Asteroid belt Main article : Asteroid belt The majority of known asteroids orbit within the asteroid belt between the orbits of Mars and Jupiter, generally in relatively low - eccentricity ( i.e. not very elongated ) orbits. This belt is now estimated to contain between 1.1 and 1.9 million asteroids larger than 1 km ( 0.6 mi ) in diameter, and millions of smaller ones. These asteroids may be remnants of the protoplanetary disk, and in this region the accretion of planetesimals into planets during the formative period of the Solar System was prevented by large gravitational perturbations by Jupiter. Trojans Main article : Trojan ( astronomy ) Trojans are populations that share an orbit with a larger planet or moon, but do not collide with it because they orbit in one of the two Lagrangian points of stability, L4 and L5, which lie 60 ° ahead of and behind the larger body. The most significant population of trojans are the Jupiter trojans. Although fewer Jupiter trojans have been discovered ( As of 2010 ), it is thought that they are as numerous as the asteroids in the asteroid belt. Trojans have been found in the orbits of other planets, including Venus, Earth, Mars, Uranus, and Neptune. Near - Earth asteroids Main article : Near - Earth asteroids Near - Earth asteroids, or NEAs, are asteroids that have orbits that pass close to that of Earth. Asteroids that actually cross Earth 's orbital path are known as Earth - crossers. As of June 2016, 14,464 near - Earth asteroids are known and the number over one kilometer in diameter is estimated to be 900 -- 1,000. Frequency of bolides, small asteroids roughly 1 to 20 meters in diameter impacting Earth 's atmosphere. Characteristics Size distribution The asteroids of the Solar System, categorized by size and number Asteroids vary greatly in size, from almost 7006100000000000000 ♠ 1000 km for the largest down to rocks just 1 meter across. The three largest are very much like miniature planets : they are roughly spherical, have at least partly differentiated interiors, and are thought to be surviving protoplanets. The vast majority, however, are much smaller and are irregularly shaped ; they are thought to be either surviving planetesimals or fragments of larger bodies. The dwarf planet Ceres is by far the largest asteroid, with a diameter of 975 km ( 606 mi ). The next largest are 4 Vesta and 2 Pallas, both with diameters of just over 500 km ( 300 mi ). Vesta is the only main - belt asteroid that can, on occasion, be visible to the naked eye. On some rare occasions, a near - Earth asteroid may briefly become visible without technical aid ; see 99942 Apophis. The mass of all the objects of the asteroid belt, lying between the orbits of Mars and Jupiter, is estimated to be about 2.8 -- 7021320000000000000 ♠ 3.2 × 10 kg, or about 4 % of the mass of the Moon. Of this, Ceres comprises 7020950000000000000 ♠ 0.95 × 10 kg, a third of the total. Adding in the next three most massive objects, Vesta ( 9 % ), Pallas ( 7 % ), and Hygiea ( 3 % ), brings this figure up to 51 % ; whereas the three after that, 511 Davida ( 1.2 % ), 704 Interamnia ( 1.0 % ), and 52 Europa ( 0.9 % ), only add another 3 % to the total mass. The number of asteroids then increases rapidly as their individual masses decrease. The number of asteroids decreases markedly with size. Although this generally follows a power law, there are ' bumps ' at 7003500000000000000 ♠ 5 km and 7005100000000000000 ♠ 100 km, where more asteroids than expected from a logarithmic distribution are found. Approximate number of asteroids ( N ) larger than a certain diameter ( D ) 0.1 km 0.3 km 0.5 km 1 km 3 km 5 km 10 km 30 km 50 km 100 km 200 km 300 km 500 km 900 km 7007250000000000000 ♠ 25 000 000 7006400000000000000 ♠ 4000000 7006200000000000000 ♠ 2000000 7005750000000000000 ♠ 750 000 7005200000000000000 ♠ 200 000 7004900000000000000 ♠ 90 000 7004100000000000000 ♠ 10 000 7003110000000000000 ♠ 1100 600 200 30 5 Largest asteroids See also : Largest asteroids The relative masses of the twelve largest asteroids known, compared to the remaining mass of the asteroid belt. 1 Ceres 4 Vesta 2 Pallas 10 Hygiea 31 Euphrosyne 704 Interamnia 511 Davida 532 Herculina 15 Eunomia 3 Juno 16 Psyche 52 Europa all others Although their location in the asteroid belt excludes them from planet status, the three largest objects, Ceres, Vesta, and Pallas, are intact protoplanets that share many characteristics common to planets, and are atypical compared to the majority of `` potato '' - shaped asteroids. The fourth largest asteroid, Hygiea, has an undifferentiated interior, like the majority of asteroids. Between them, the four largest asteroids constitute half the mass of the asteroid belt. Ceres is the only asteroid with a fully ellipsoidal shape and hence the only one that is a dwarf planet. It has a much higher absolute magnitude than the other asteroids, of around 3.32, and may possess a surface layer of ice. Like the planets, Ceres is differentiated : it has a crust, a mantle and a core. No meteorites from Ceres have been found on Earth. Vesta, too, has a differentiated interior, though it formed inside the Solar System 's frost line, and so is devoid of water ; its composition is mainly of basaltic rock such as olivine. Aside from the large crater at its southern pole, Rheasilvia, Vesta also has an ellipsoidal shape. Vesta is the parent body of the Vestian family and other V - type asteroids, and is the source of the HED meteorites, which constitute 5 % of all meteorites on Earth. Pallas is unusual in that, like Uranus, it rotates on its side, with its axis of rotation tilted at high angles to its orbital plane. Its composition is similar to that of Ceres : high in carbon and silicon, and perhaps partially differentiated. Pallas is the parent body of the Palladian family of asteroids. Hygiea is the largest carbonaceous asteroid and, unlike the other largest asteroids, lies relatively close to the plane of the ecliptic. It is the largest member and presumed parent body of the Hygiean family of asteroids. Attributes of largest asteroids Name Orbital radius ( AU ) Orbital period ( years ) Inclination to ecliptic Orbital eccentricity Diameter ( km ) Diameter ( % of Moon ) Mass ( × 10 kg ) Mass ( % of Ceres ) Density ( g / cm ) Rotation period ( hr ) Axial tilt Surface temperature Vesta 2.36 3.63 7.1 ° 0.089 573 × 557 × 446 ( mean 525 ) 15 % 260 28 % 3.44 ± 0.12 5.34 29 ° 85 -- 270 K Ceres 2.77 4.60 10.6 ° 0.079 975 × 975 × 909 ( mean 953 ) 28 % 940 100 % 2.12 ± 0.04 9.07 ≈ 3 ° 167 K Pallas 2.77 4.62 34.8 ° 0.231 580 × 555 × 500 ( mean 545 ) 16 % 210 22 % 2.71 ± 0.11 7.81 ≈ 80 ° 164 K Hygiea 3.14 5.56 3.8 ° 0.117 530 × 407 × 370 ( mean 435 ) 12 % 87 9 % 2.76 ± 1.2 27.6 ≈ 60 ° 164 K Rotation Measurements of the rotation rates of large asteroids in the asteroid belt show that there is an upper limit. No asteroid with a diameter larger than 100 meters has a rotation period smaller than 2.2 hours. For asteroids rotating faster than approximately this rate, the inertial force at the surface is greater than the gravitational force, so any loose surface material would be flung out. However, a solid object should be able to rotate much more rapidly. This suggests that most asteroids with a diameter over 100 meters are rubble piles formed through accumulation of debris after collisions between asteroids. Composition Cratered terrain on 4 Vesta The physical composition of asteroids is varied and in most cases poorly understood. Ceres appears to be composed of a rocky core covered by an icy mantle, where Vesta is thought to have a nickel - iron core, olivine mantle, and basaltic crust. 10 Hygiea, however, which appears to have a uniformly primitive composition of carbonaceous chondrite, is thought to be the largest undifferentiated asteroid. Most of the smaller asteroids are thought to be piles of rubble held together loosely by gravity, though the largest are probably solid. Some asteroids have moons or are co-orbiting binaries : Rubble piles, moons, binaries, and scattered asteroid families are thought to be the results of collisions that disrupted a parent asteroid, or, possibly, a planet. Asteroids contain traces of amino acids and other organic compounds, and some speculate that asteroid impacts may have seeded the early Earth with the chemicals necessary to initiate life, or may have even brought life itself to Earth ( also see panspermia ). In August 2011, a report, based on NASA studies with meteorites found on Earth, was published suggesting DNA and RNA components ( adenine, guanine and related organic molecules ) may have been formed on asteroids and comets in outer space. Asteroid collision -- building planets ( artist concept ). Composition is calculated from three primary sources : albedo, surface spectrum, and density. The last can only be determined accurately by observing the orbits of moons the asteroid might have. So far, every asteroid with moons has turned out to be a rubble pile, a loose conglomeration of rock and metal that may be half empty space by volume. The investigated asteroids are as large as 280 km in diameter, and include 121 Hermione ( 268 × 186 × 183 km ), and 87 Sylvia ( 384 × 262 × 232 km ). Only half a dozen asteroids are larger than 87 Sylvia, though none of them have moons ; however, some smaller asteroids are thought to be more massive, suggesting they may not have been disrupted, and indeed 511 Davida, the same size as Sylvia to within measurement error, is estimated to be two and a half times as massive, though this is highly uncertain. The fact that such large asteroids as Sylvia can be rubble piles, presumably due to disruptive impacts, has important consequences for the formation of the Solar System : Computer simulations of collisions involving solid bodies show them destroying each other as often as merging, but colliding rubble piles are more likely to merge. This means that the cores of the planets could have formed relatively quickly. On 7 October 2009, the presence of water ice was confirmed on the surface of 24 Themis using NASA 's Infrared Telescope Facility. The surface of the asteroid appears completely covered in ice. As this ice layer is sublimated, it may be getting replenished by a reservoir of ice under the surface. Organic compounds were also detected on the surface. Scientists hypothesize that some of the first water brought to Earth was delivered by asteroid impacts after the collision that produced the Moon. The presence of ice on 24 Themis supports this theory. In October 2013, water was detected on an extrasolar body for the first time, on an asteroid orbiting the white dwarf GD 61. On 22 January 2014, European Space Agency ( ESA ) scientists reported the detection, for the first definitive time, of water vapor on Ceres, the largest object in the asteroid belt. The detection was made by using the far - infrared abilities of the Herschel Space Observatory. The finding is unexpected because comets, not asteroids, are typically considered to `` sprout jets and plumes ''. According to one of the scientists, `` The lines are becoming more and more blurred between comets and asteroids. '' In May 2016, significant asteroid data arising from the Wide - field Infrared Survey Explorer and NEOWISE missions have been questioned, but the criticism has yet to undergo peer review. Surface features Most asteroids outside the `` big four '' ( Ceres, Pallas, Vesta, and Hygiea ) are likely to be broadly similar in appearance, if irregular in shape. 50 - km ( 31 - mi ) 253 Mathilde is a rubble pile saturated with craters with diameters the size of the asteroid 's radius, and Earth - based observations of 300 - km ( 186 - mi ) 511 Davida, one of the largest asteroids after the big four, reveal a similarly angular profile, suggesting it is also saturated with radius - size craters. Medium - sized asteroids such as Mathilde and 243 Ida that have been observed up close also reveal a deep regolith covering the surface. Of the big four, Pallas and Hygiea are practically unknown. Vesta has compression fractures encircling a radius - size crater at its south pole but is otherwise a spheroid. Ceres seems quite different in the glimpses Hubble has provided, with surface features that are unlikely to be due to simple craters and impact basins, but details will be expanded with the Dawn spacecraft, which entered Ceres orbit on 6 March 2015. Color Asteroids become darker and redder with age due to space weathering. However evidence suggests most of the color change occurs rapidly, in the first hundred thousands years, limiting the usefulness of spectral measurement for determining the age of asteroids. Classification Asteroids are commonly classified according to two criteria : the characteristics of their orbits, and features of their reflectance spectrum. Orbital classification Main articles : Asteroid group and Asteroid family Many asteroids have been placed in groups and families based on their orbital characteristics. Apart from the broadest divisions, it is customary to name a group of asteroids after the first member of that group to be discovered. Groups are relatively loose dynamical associations, whereas families are tighter and result from the catastrophic break - up of a large parent asteroid sometime in the past. Families are more common and easier to identify within the main asteroid belt, but several small families have been reported among the Jupiter trojans. Main belt families were first recognized by Kiyotsugu Hirayama in 1918 and are often called Hirayama families in his honor. About 30 -- 35 % of the bodies in the asteroid belt belong to dynamical families each thought to have a common origin in a past collision between asteroids. A family has also been associated with the plutoid dwarf planet Haumea. Quasi-satellites and horseshoe objects Some asteroids have unusual horseshoe orbits that are co-orbital with Earth or some other planet. Examples are 3753 Cruithne and 2002 AA 29. The first instance of this type of orbital arrangement was discovered between Saturn 's moons Epimetheus and Janus. Sometimes these horseshoe objects temporarily become quasi-satellites for a few decades or a few hundred years, before returning to their earlier status. Both Earth and Venus are known to have quasi-satellites. Such objects, if associated with Earth or Venus or even hypothetically Mercury, are a special class of Aten asteroids. However, such objects could be associated with outer planets as well. Spectral classification Main article : Asteroid spectral types This picture of 433 Eros shows the view looking from one end of the asteroid across the gouge on its underside and toward the opposite end. Features as small as 35 m ( 115 ft ) across can be seen. In 1975, an asteroid taxonomic system based on color, albedo, and spectral shape was developed by Clark R. Chapman, David Morrison, and Ben Zellner. These properties are thought to correspond to the composition of the asteroid 's surface material. The original classification system had three categories : C - types for dark carbonaceous objects ( 75 % of known asteroids ), S - types for stony ( silicaceous ) objects ( 17 % of known asteroids ) and U for those that did not fit into either C or S. This classification has since been expanded to include many other asteroid types. The number of types continues to grow as more asteroids are studied. The two most widely used taxonomies now used are the Tholen classification and SMASS classification. The former was proposed in 1984 by David J. Tholen, and was based on data collected from an eight - color asteroid survey performed in the 1980s. This resulted in 14 asteroid categories. In 2002, the Small Main - Belt Asteroid Spectroscopic Survey resulted in a modified version of the Tholen taxonomy with 24 different types. Both systems have three broad categories of C, S, and X asteroids, where X consists of mostly metallic asteroids, such as the M - type. There are also several smaller classes. The proportion of known asteroids falling into the various spectral types does not necessarily reflect the proportion of all asteroids that are of that type ; some types are easier to detect than others, biasing the totals. Problems Originally, spectral designations were based on inferences of an asteroid 's composition. However, the correspondence between spectral class and composition is not always very good, and a variety of classifications are in use. This has led to significant confusion. Although asteroids of different spectral classifications are likely to be composed of different materials, there are no assurances that asteroids within the same taxonomic class are composed of similar materials. Naming Main article : Minor planet § Naming 2013 EC, shown here in radar images, has a provisional designation A newly discovered asteroid is given a provisional designation ( such as 2002 AT 4 ) consisting of the year of discovery and an alphanumeric code indicating the half - month of discovery and the sequence within that half - month. Once an asteroid 's orbit has been confirmed, it is given a number, and later may also be given a name ( e.g. 433 Eros ). The formal naming convention uses parentheses around the number ( e.g. ( 433 ) Eros ), but dropping the parentheses is quite common. Informally, it is common to drop the number altogether, or to drop it after the first mention when a name is repeated in running text. In addition, names can be proposed by the asteroid 's discoverer, within guidelines established by the International Astronomical Union. Symbols Main article : Astronomical symbols The first asteroids to be discovered were assigned iconic symbols like the ones traditionally used to designate the planets. By 1855 there were two dozen asteroid symbols, which often occurred in multiple variants. Asteroid Symbol Year 1 Ceres ⚳ Ceres ' scythe, reversed to double as the letter C 1801 2 Pallas ⚴ Athena 's ( Pallas ' ) spear 1801 3 Juno ⚵ A star mounted on a scepter, for Juno, the Queen of Heaven 1804 4 Vesta ⚶ The altar and sacred fire of Vesta 1807 5 Astraea A scale, or an inverted anchor, symbols of justice 1845 6 Hebe Hebe 's cup 1847 7 Iris A rainbow ( iris ) and a star 1847 8 Flora A flower ( flora ), specifically the Rose of England 1847 9 Metis The eye of wisdom and a star 1848 10 Hygiea Hygiea 's serpent and a star, or the Rod of Asclepius 1849 11 Parthenope A harp, or a fish and a star ; symbols of the sirens 1850 12 Victoria The laurels of victory and a star 1850 13 Egeria A shield, symbol of Egeria 's protection, and a star 1850 14 Irene A dove carrying an olive branch ( symbol of irene ' peace ' ) with a star on its head, or an olive branch, a flag of truce, and a star 1851 15 Eunomia A heart, symbol of good order ( eunomia ), and a star 1851 16 Psyche A butterfly 's wing, symbol of the soul ( psyche ), and a star 1852 17 Thetis A dolphin, symbol of Thetis, and a star 1852 18 Melpomene The dagger of Melpomene, and a star 1852 19 Fortuna The wheel of fortune and a star 1852 26 Proserpina Proserpina 's pomegranate 1853 28 Bellona Bellona 's whip and lance 1854 29 Amphitrite The shell of Amphitrite and a star 1854 35 Leukothea A lighthouse beacon, symbol of Leucothea 1855 37 Fides The cross of faith ( fides ) 1855 In 1851, after the fifteenth asteroid ( Eunomia ) had been discovered, Johann Franz Encke made a major change in the upcoming 1854 edition of the Berliner Astronomisches Jahrbuch ( BAJ, Berlin Astronomical Yearbook ). He introduced a disk ( circle ), a traditional symbol for a star, as the generic symbol for an asteroid. The circle was then numbered in order of discovery to indicate a specific asteroid ( although he assigned 1 to the fifth, Astraea, while continuing to designate the first four only with their existing iconic symbols ). The numbered - circle convention was quickly adopted by astronomers, and the next asteroid to be discovered ( 16 Psyche, in 1852 ) was the first to be designated in that way at the time of its discovery. However, Psyche was given an iconic symbol as well, as were a few other asteroids discovered over the next few years ( see chart above ). 20 Massalia was the first asteroid that was not assigned an iconic symbol, and no iconic symbols were created after the 1855 discovery of 37 Fides. That year Astraea 's number was increased to 5, but the first four asteroids, Ceres to Vesta, were not listed by their numbers until the 1867 edition. The circle was soon abbreviated to a pair of parentheses, which were easier to typeset and sometimes omitted altogether over the next few decades, leading to the modern convention. Exploration See also : Sample return mission, Asteroid mining, and Colonization of the asteroids Until the age of space travel, objects in the asteroid belt were merely pinpricks of light in even the largest telescopes and their shapes and terrain remained a mystery. The best modern ground - based telescopes and the Earth - orbiting Hubble Space Telescope can resolve a small amount of detail on the surfaces of the largest asteroids, but even these mostly remain little more than fuzzy blobs. Limited information about the shapes and compositions of asteroids can be inferred from their light curves ( their variation in brightness as they rotate ) and their spectral properties, and asteroid sizes can be estimated by timing the lengths of star occulations ( when an asteroid passes directly in front of a star ). Radar imaging can yield good information about asteroid shapes and orbital and rotational parameters, especially for near - Earth asteroids. In terms of delta - v and propellant requirements, NEOs are more easily accessible than the Moon. The first close - up photographs of asteroid - like objects were taken in 1971, when the Mariner 9 probe imaged Phobos and Deimos, the two small moons of Mars, which are probably captured asteroids. These images revealed the irregular, potato - like shapes of most asteroids, as did later images from the Voyager probes of the small moons of the gas giants. The first true asteroid to be photographed in close - up was 951 Gaspra in 1991, followed in 1993 by 243 Ida and its moon Dactyl, all of which were imaged by the Galileo probe en route to Jupiter. The first dedicated asteroid probe was NEAR Shoemaker, which photographed 253 Mathilde in 1997, before entering into orbit around 433 Eros, finally landing on its surface in 2001. Other asteroids briefly visited by spacecraft en route to other destinations include 9969 Braille ( by Deep Space 1 in 1999 ), and 5535 Annefrank ( by Stardust in 2002 ). In September 2005, the Japanese Hayabusa probe started studying 25143 Itokawa in detail and was plagued with difficulties, but returned samples of its surface to Earth on 13 June 2010. The European Rosetta probe ( launched in 2004 ) flew by 2867 Šteins in 2008 and 21 Lutetia, the third - largest asteroid visited to date, in 2010. In September 2007, NASA launched the Dawn spacecraft, which orbited 4 Vesta from July 2011 to September 2012, and has been orbiting the dwarf planet 1 Ceres since 2015. 4 Vesta is the second - largest asteroid visited to date. On 13 December 2012, China 's lunar orbiter Chang'e 2 flew within 3.2 km ( 2 mi ) of the asteroid 4179 Toutatis on an extended mission. Planned and future missions The Japan Aerospace Exploration Agency ( JAXA ) launched the Hayabusa 2 probe in December 2014, and plans to return samples from 162173 Ryugu in December 2020. In May 2011, NASA selected the OSIRIS - REx sample return mission to asteroid 101955 Bennu ; it launched on September 8, 2016. In early 2013, NASA announced the planning stages of a mission to capture a near - Earth asteroid and move it into lunar orbit where it could possibly be visited by astronauts and later impacted into the Moon. On 19 June 2014, NASA reported that asteroid 2011 MD was a prime candidate for capture by a robotic mission, perhaps in the early 2020s. It has been suggested that asteroids might be used as a source of materials that may be rare or exhausted on Earth ( asteroid mining ), or materials for constructing space habitats ( see Colonization of the asteroids ). Materials that are heavy and expensive to launch from Earth may someday be mined from asteroids and used for space manufacturing and construction. In the U.S. Discovery program the Psyche spacecraft proposal to 16 Psyche and Lucy spacecraft to Jupiter trojans made it to the semifinalist stage of mission selection. Fiction Main article : Asteroids in fiction Asteroids and the asteroid belt are a staple of science fiction stories. Asteroids play several potential roles in science fiction : as places human beings might colonize, resources for extracting minerals, hazards encountered by spacecraft traveling between two other points, and as a threat to life on Earth or other inhabited planets, dwarf planets and natural satellites by potential impact. Gallery 951 Gaspra is the first asteroid to be imaged in close - up, imaged by Galileo on 29 October 1991 ( enhanced color ) Several views of 433 Eros in natural color, imaged by NEAR on 12 February 2000 Vesta imaged by Dawn on 9 July 2011 Ceres imaged by Dawn on 4 February 2015 See also Amor asteroid Apollo asteroid Asteroid Day Asteroid impact avoidance Aten asteroid Atira asteroid BOOTES ( Burst Observer and Optical Transient Exploring System ) Category : Asteroids Category : Asteroid groups and families Category : Binary asteroids Centaur ( minor planet ) Chang'e 2 lunar orbiter Constellation program Dawn spacecraft Dwarf planet Impact event List of asteroid close approaches to Earth List of minor planets named after people List of minor planets named after places List of minor planets List of notable asteroids List of impact craters on Earth List of unconfirmed impact craters on Earth Lost asteroid Marco Polo ( spacecraft ) Meanings of minor planet names Mesoplanet Minor planet Near - Earth object NEOShield NEOSSat ( Near Earth Object Surveillance Satellite ) Canada 's new satellite Pioneer 10 spacecraft Rosetta spacecraft Space portal Astronomy portal Notes Jump up ^ Ceres is the largest asteroid and is now classified as a dwarf planet. All other asteroids are now classified as small Solar System bodies along with comets, centaurs, and the smaller trans - Neptunian objects. Jump up ^ In an oral presentation, Clifford Cunningham presented his finding that the word was coined by Charles Burney, Jr., the son of a friend of Herschel, Jump up ^ For example, the Annual of Scientific Discovery for 1871, page 316, reads `` Professor J. Watson has been awarded by the Paris Academy of Sciences, the astronomical prize, Lalande foundation, for the discovery of eight new asteroids in one year. The planet Lydia ( No. 110 ), discovered by M. Borelly at the Marseilles Observatory (... ) M. Borelly had previously discovered two planets bearing the numbers 91 and 99 in the system of asteroids revolving between Mars and Jupiter ''. Jump up ^ The definition of `` small Solar System bodies '' says that they `` include most of the Solar System asteroids, most trans - Neptunian objects, comets, and other small bodies ''. Jump up ^ For instance, a joint NASA -- JPL public - outreach website states : `` We include Trojans ( bodies captured in Jupiter 's 4th and 5th Lagrange points ), Centaurs ( bodies in orbit between Jupiter and Neptune ), and trans - Neptunian objects ( orbiting beyond Neptune ) in our definition of `` asteroid '' as used on this site, even though they may more correctly be called `` minor planets '' instead of asteroids. '' Jump up ^ Below 1 meter, these are considered to be meteoroids. The definition in the 1995 paper ( Beech and Steel ) has been updated by a 2010 paper ( Rubin and Grossman ) and the discovery of 1 - meter asteroids. Jump up ^ The values of Juno and Herculina may be off by as much as 16 %, and Euphrosyne by a third. The order of the lower eight may change as better data is acquired, but the values do not overlap with any known asteroid outside these twelve. 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External links Find more aboutAsteroidat Wikipedia 's sister projects Definitions from Wiktionary Media from Wikimedia Commons News from Wikinews Texts from Wikisource Textbooks from Wikibooks Alphabetical list of minor planet names ( ASCII ) ( Minor Planet Center ) Asteroid articles in Planetary Science Research Discoveries ESA Space Situational Awareness : Near - Earth Object Segment IAU Committee on Small Body Nomenclature JPL Asteroid Watch Site NASA Asteroid and Comet Watch Site Near Earth Asteroid Tracking ( NEAT ) Near Earth Objects Dynamic Site NEO MAP ( Armagh Observatory ) Spaceguard Centre TECA Table of next close approaches to the Earth When Did the Asteroids Become Minor Planets ? Asteroids Main Notable asteroids Physical characteristics dynamic method Impact avoidance Tracking Capture Gravitational keyhole Earth - crosser Close approaches Binary moon contact P -- L Distribution Interior to Earth vulcanoids Mercury - crossers Venus - crossers Main - belt Kirkwood gap comets Trojans Venus trojan Earth Mars Jupiter Uranus trojan Neptune trojan Near - Earth Aten Amor Apollo Apohele Earth - crossers Between Earth and the main belt Mars crossers Mars trojans Outer Solar System, does not include distant minor planets Jupiter - crossers Jupiter trojan Classification Orbital Group Family ( list ) Spectral Tholen C - group B - type F - type G - type C - type S - type X-group M - type E-type P - type small classes A-type D - type J - type T - type Q - type R - type V - type SMASS C - group B - type C - type Cg Ch Cgh Cb S - group A-type Q - type R - type K - type L - type S - type Sa Sq Sr Sk Sl X-group X-type Xe Xc Xk small types T - type D - type Ld - type O - type V - type Exploration Asteroid Redirect Mission Asteroids visited by spacecraft Human mission Mining Ceres Colonization Lists Near - Earth Minor planets Lost Discovering observatories Space missions See also : Asteroids in fiction Asteroids in astrology occultation Comet Ceres Geography General Geology of Ceres Craters Achita Annona Asari Coniraya Dantu Darzamat Ezinu Fejokoo Hamori Haulani Kerwan Mondamin Nawish Occator Urvara Yalode Zadeni Montes Ahuna Mons Other features Bright spots Astronomy Classification Asteroid Definition of planet Dwarf planet Planet 2006 definition of planet Discovery Barnaba Oriani Carl Friedrich Gauss Francis Wollaston Franz Xaver von Zach Giuseppe Piazzi Heinrich Olbers Jérôme Lalande Johann Elert Bode Tobias Mayer Possible trojans ( 185105 ) 2006 SV 23 1372 Haremari Exploration Dawn mission Ceres Polar Lander ( proposed ) Related Ceres in fiction Colonization In astrology Solar System bodies formerly considered to be planets Comets Features Nucleus Coma Tails Antitail Comet dust Meteor shower Types Periodic Numbered Lost Halley - type Jupiter - family Encke - type Main - belt Non-periodic Hyperbolic Unknown - orbit Great Comet Sungrazing ( Kreutz ) Extinct Rock Exocomet Interstellar Related Naming of comets Centaur Comet discoverers LINEAR Extraterrestrial atmosphere Oort cloud Small Solar System body Asteroid Space missions Planned and proposed DESTINY CAESAR Comet Hopper CONDOR CORSAIR CRAF Hayabusa Mk2 Marco Polo Vesta Past and current CONTOUR Deep Impact / EPOXI Deep Space 1 Giotto ICE Rosetta Philae Timeline Sakigake Stardust / NeXT Suisei Ulysses Vega program Vega 1 Vega 2 Latest C / 2016 U1 ( NEOWISE ) C / 2015 G2 ( MASTER ) C / 2015 F5 ( SWAN - XingMing ) C / 2015 F3 C / 2014 Q2 ( Lovejoy ) C / 2014 E2 ( Jacques ) C / 2013 US10 ( Catalina ) C / 2013 A1 ( Siding Spring ) C / 2012 S4 ( PANSTARRS ) C / 2012 K1 ( PANSTARRS ) Culture and speculation Antimatter comet Comets in fiction Fictional comets Comet vintages Lists of comets ( more ) Periodic comets Until 1985 ( all ) 1P / Halley 2P / Encke 3D / Biela 4P / Faye 5D / Brorsen 6P / d'Arrest 7P / Pons -- Winnecke 8P / Tuttle 9P / Tempel 10P / Tempel 11P / Tempel -- Swift -- LINEAR 12P / Pons -- Brooks 13P / Olbers 14P / Wolf 15P / Finlay 16P / Brooks 17P / Holmes 18D / Perrine -- Mrkos 19P / Borrelly 20D / Westphal 21P / Giacobini -- Zinner 22P / Kopff 23P / Brorsen -- Metcalf 24P / Schaumasse 25D / Neujmin 26P / Grigg -- Skjellerup 27P / Crommelin 28P / Neujmin 29P / Schwassmann -- Wachmann 30P / Reinmuth 31P / Schwassmann -- Wachmann 32P / Comas Solà 33P / Daniel 34D / Gale 35P / Herschel -- Rigollet 36P / Whipple 37P / Forbes 38P / Stephan -- Oterma 39P / Oterma 40P / Väisälä 41P / Tuttle -- Giacobini -- Kresák 42P / Neujmin 43P / Wolf -- Harrington 44P / Reinmuth 45P / Honda -- Mrkos -- Pajdušáková 46P / Wirtanen 47P / Ashbrook -- Jackson 48P / Johnson 49P / Arend -- Rigaux 50P / Arend 51P / Harrington 52P / Harrington -- Abell 53P / Van Biesbroeck 54P / de Vico -- Swift -- NEAT 55P / Tempel -- Tuttle 56P / Slaughter -- Burnham 57P / du Toit -- Neujmin -- Delporte 58P / Jackson -- Neujmin 59P / Kearns -- Kwee 60P / Tsuchinshan 61P / Shajn -- Schaldach 62P / Tsuchinshan 63P / Wild 64P / Swift -- Gehrels 65P / Gunn 66P / du Toit 67P / Churyumov -- Gerasimenko 68P / Klemola 69P / Taylor 70P / Kojima 71P / Clark 72P / Denning -- Fujikawa 73P / Schwassmann -- Wachmann 74P / Smirnova -- Chernykh 75D / Kohoutek 76P / West -- Kohoutek -- Ikemura 77P / Longmore 78P / Gehrels 79P / du Toit -- Hartley 80P / Peters -- Hartley 81P / Wild 82P / Gehrels 83D / Russell 84P / Giclas 85P / Boethin 86P / Wild 87P / Bus 88P / Howell 89P / Russell 90P / Gehrels 91P / Russell 92P / Sanguin 93P / Lovas 94P / Russell 95P / Chiron 96P / Machholz 97P / Metcalf -- Brewington 98P / Takamizawa 99P / Kowal 100P / Hartley 101P / Chernykh 102P / Shoemaker After 1985 ( notable ) 103P / Hartley 105P / Singer Brewster 107P / Wilson -- Harrington 109P / Swift -- Tuttle 111P / Helin -- Roman -- Crockett 114P / Wiseman -- Skiff 128P / Shoemaker -- Holt 139P / Väisälä -- Oterma 144P / Kushida 147P / Kushida -- Muramatsu 153P / Ikeya -- Zhang 163P / NEAT 168P / Hergenrother 169P / NEAT 177P / Barnard 178P / Hug -- Bell 205P / Giacobini 209P / LINEAR 238P / Read 246P / NEAT 252P / LINEAR 255P / Levy 273P / Pons -- Gambart 276P / Vorobjov 289P / Blanpain 311P / PANSTARRS 322P / SOHO 332P / Ikeya - Murakami 354P / LINEAR P / 1997 B1 ( Kobayashi ) P / 2010 B2 ( WISE ) P / 2011 NO1 ( Elenin ) Comet - like asteroids 596 Scheila 2060 Chiron ( 95P ) 4015 Wilson -- Harrington ( 107P ) 7968 Elst -- Pizarro ( 133P ) 165P / LINEAR 166P / NEAT 167P / CINEOS 60558 Echeclus ( 174P ) 118401 LINEAR ( 176P ) 238P / Read 259P / Garradd 311P / PANSTARRS 324P / La Sagra P / 2010 A2 ( LINEAR ) P / 2012 F5 ( Gibbs ) P / 2012 T1 ( PANSTARRS ) P / 2013 R3 ( Catalina - PANSTARRS ) ( 300163 ) 2006 VW139 Lost Recovered 11P / Tempel -- Swift -- LINEAR 15P / Finlay 17P / Holmes 27P / Crommelin 54P / de Vico -- Swift -- NEAT 55P / Tempel -- Tuttle 57P / du Toit -- Neujmin -- Delporte 69P / Taylor 72P / Denning -- Fujikawa 80P / Peters -- Hartley 97P / Metcalf -- Brewington 107P / Wilson -- Harrington 109P / Swift -- Tuttle 113P / Spitaler 122P / de Vico 157P / Tritton 177P / Barnard 205P / Giacobini 206P / Barnard -- Boattini 271P / van Houten -- Lemmon 273P / Pons -- Gambart 289P / Blanpain Destroyed 3D / Biela 73P / Schwassmann -- Wachmann D / 1993 F2 ( Shoemaker -- Levy 9 ) Not found D / 1770 L1 ( Lexell ) 5D / Brorsen 18D / Perrine -- Mrkos 20D / Westphal 25D / Neujmin 34D / Gale 75D / Kohoutek 83D / Russell Visited by spacecraft 21P / Giacobini -- Zinner ( 1985 ) 1P / Halley ( 1986 ) 26P / Grigg -- Skjellerup ( 1992 ) 19P / Borrelly ( 2001 ) 81P / Wild ( 2004 ) 9P / Tempel ( 2005, 2011 ) C / 2006 P1 ( 2007 ) 103P / Hartley ( 2010 ) 67P / Churyumov -- Gerasimenko ( 2014 ) Non-Periodic comets ( notable ) Until 1910 C / - 43 K1 ( Caesar 's Comet ) X / 1106 C1 ( Great Comet of 1106 ) C / 1577 V1 ( Great Comet of 1577 ) C / 1652 Y1 C / 1680 V1 ( Great Comet of 1680, Kirsch 's Comet, Newton 's Comet ) ) C / 1702 H1 ( Comet of 1702 ) C / 1729 P1 ( Comet of 1729, Comet Sarabat ) C / 1743 X1 ( Great Comet of 1744, Comet Klinkenberg - Chéseaux ) C / 1760 A1 ( Great Comet of 1760 ) C / 1769 P1 ( Great Comet of 1769 ) C / 1807 R1 ( Great Comet of 1807 ) C / 1811 F1 ( Great Comet of 1811 ) C / 1819 N1 ( Great Comet of 1819 ) C / 1823 Y1 ( Great Comet of 1823 ) C / 1843 D1 ( Great March Comet of 1843 ) C / 1847 T1 ( Miss Mitchell 's Comet ) C / 1858 L1 ( Comet Donati ) C / 1861 G1 ( Comet Thatcher ) C / 1861 J1 ( Great Comet of 1861 ) C / 1865 B1 ( Great Southern Comet of 1865 ) X / 1872 X1 ( Pogson 's Comet ) C / 1874 H1 ( Comet Coggia ) C / 1881 K1 ( Comet Tebbutt ) C / 1882 R1 ( Great Comet of 1882 ) C / 1887 B1 ( Great Southern Comet of 1887 ) C / 1890 V1 ( Comet Zona ) C / 1901 G1 ( Great Comet of 1901 ) C / 1910 A1 ( Great January Comet of 1910 ) After 1910 C / 1911 O1 ( Brooks ) C / 1911 S3 ( Beljawsky ) C / 1927 X1 ( Skjellerup -- Maristany ) C / 1931 P1 ( Ryves ) C / 1941 B2 ( de Kock - Paraskevopoulos ) ( de ) C / 1947 X1 ( Southern Comet ) ( de ) C / 1948 V1 ( Eclipse ) C / 1956 R1 ( Arend -- Roland ) C / 1957 P1 ( Mrkos ) ( de ) C / 1961 O1 ( Wilson - Hubbard ) ( de ) C / 1961 R1 ( Humason ) C / 1962 C1 ( Seki - Lines ) ( de ) C / 1963 R1 ( Pereyra ) C / 1965 S1 ( Ikeya - Seki ) C / 1969 Y1 ( Bennett ) C / 1970 K1 ( White -- Ortiz -- Bolelli ) C / 1973 E1 ( Kohoutek ) C / 1975 V1 ( West ) C / 1980 E1 ( Bowell ) C / 1983 H1 ( IRAS -- Araki -- Alcock ) C / 1989 X1 ( Austin ) C / 1989 Y1 ( Skorichenko -- George ) C / 1992 J1 ( Spacewatch -- Rabinowitz ) C / 1993 Y1 ( McNaught -- Russell ) C / 1995 O1 ( Hale -- Bopp ) C / 1996 B2 ( Hyakutake ) C / 1997 L1 ( Zhu -- Balam ) C / 1998 H1 ( Stonehouse ) C / 1998 J1 ( SOHO ) C / 1999 F1 ( Catalina ) C / 1999 S4 ( LINEAR ) C / 2000 U5 ( LINEAR ) C / 2000 W1 ( Utsunomiya - Jones ) C / 2001 OG108 ( LONEOS ) C / 2001 Q4 ( NEAT ) C / 2002 T7 ( LINEAR ) C / 2004 F4 ( Bradfield ) ( de ) C / 2004 Q2 ( Machholz ) C / 2006 A1 ( Pojmański ) C / 2006 M4 ( SWAN ) C / 2006 P1 ( McNaught ) C / 2007 E2 ( Lovejoy ) C / 2007 F1 ( LONEOS ) C / 2007 K5 ( Lovejoy ) C / 2007 N3 ( Lulin ) C / 2007 Q3 ( Siding Spring ) C / 2007 W1 ( Boattini ) C / 2008 Q1 ( Matičič ) C / 2009 F6 ( Yi -- SWAN ) C / 2009 R1 ( McNaught ) C / 2010 X1 ( Elenin ) C / 2011 L4 ( PANSTARRS ) C / 2011 W3 ( Lovejoy ) C / 2012 E2 ( SWAN ) C / 2012 F6 ( Lemmon ) C / 2012 K1 ( PANSTARRS ) C / 2012 S1 ( ISON ) C / 2012 S4 ( PANSTARRS ) C / 2013 A1 ( Siding Spring ) C / 2013 R1 ( Lovejoy ) C / 2013 US10 ( Catalina ) C / 2013 V5 ( Oukaimeden ) C / 2014 E2 ( Jacques ) C / 2014 Q2 ( Lovejoy ) C / 2015 V2 ( Johnson ) After 1910 ( by name ) Arend -- Roland Austin Beljawsky Bennett Boattini Bowell Bradfield ( de ) Brooks Catalina C / 1999 F1 C / 2013 US10 de Kock -- Paraskevopoulos ( de ) Eclipse Elenin Hale - Bopp Humason Hyakutake Ikeya - Seki IRAS -- Araki -- Alcock ISON Jacques Johnson Kohoutek Lemmon LINEAR C / 1999 S4 C / 2000 U5 C / 2002 T7 LONEOS C / 2001 OG108 C / 2007 F1 Lovejoy C / 2007 E2 C / 2007 K5 C / 2011 W3 C / 2013 R1 C / 2014 Q2 Lulin Machholz Matičič McNaught C / 2006 P1 C / 2009 R1 McNaught -- Russell Mrkos ( de ) NEAT Oukaimeden Pan-STARRS C / 2011 L4 C / 2012 K1 C / 2012 S4 311P Pereyra Pojmański Ryves Seki -- Lines ( de ) Siding Spring C / 2007 Q3 C / 2013 A1 Skjellerup -- Maristany Skorichenko -- George SOHO Southern ( de ) Spacewatch -- Rabinowitz Stonehouse SWAN C / 2006 M4 C / 2012 E2 Utsunomiya -- Jones West White -- Ortiz -- Bolelli Wilson -- Hubbard ( de ) Yi -- SWAN Zhu -- Balam Commons Wikinews The Solar System The Sun Mercury Venus Earth Mars Ceres Jupiter Saturn Uranus Neptune Pluto Haumea Makemake Eris Planets Terrestrial planets Mercury Venus Earth Mars Giant planets Jupiter Saturn Uranus Neptune Dwarf planets Ceres Pluto Haumea Makemake Eris Rings Jovian Saturnian ( Rhean ) Charikloan Chironean Uranian Neptunian Haumean Moons Terrestrial Moon other near - Earth objects Martian Phobos Deimos Jovian Ganymede Callisto Io Europa all 69 Saturnian Titan Rhea Iapetus Dione Tethys Enceladus Mimas Hyperion Phoebe all 62 Uranian Titania Oberon Umbriel Ariel Miranda all 27 Neptunian Triton Proteus Nereid all 14 Plutonian Charon Nix Hydra Kerberos Styx Haumean Hiʻiaka Namaka Makemakean S / 2015 ( 136472 ) 1 Eridian Dysnomia Lists Solar System objects By size By discovery date Minor planets Gravitationally rounded objects Possible dwarf planets Natural satellites Comets Small Solar System bodies Meteoroids Minor planets moons Comets Damocloids Mercury - crossers Venus - crossers Venus trojans Near - Earth objects Earth - crossers Earth trojans Mars - crossers Mars trojans Asteroid belt Asteroids first discovered : Ceres Pallas Juno Vesta Families Notable asteroids Kirkwood gap Main - belt comets Jupiter trojans Jupiter - crossers Centaurs Saturn - crossers Uranus trojans Uranus - crossers Neptune trojans Cis - Neptunian objects Trans - Neptunian objects Neptune - crossers Plutoids Kuiper belt Plutinos Cubewanos Scattered disc Detached objects Sednoids Hills cloud Oort cloud Hypothetical objects Vulcan Vulcanoids Phaeton Planet V Theia Fifth giant Planets beyond Neptune Tyche Nemesis Planet Nine Exploration ( outline ) Discovery Astronomy Timeline Spaceflight Robotic spacecraft Human spaceflight List of crewed spacecraft Colonization List of probes Timeline Mercury Venus Moon Mars Ceres Asteroids Mining Comets Jupiter Saturn Uranus Neptune Pluto Deep space Outline of the Solar System Portals Solar System Astronomy Earth sciences Mars Jupiter Uranus Cosmology Solar System → Local Interstellar Cloud → Local Bubble → Gould Belt → Orion Arm → Milky Way → Milky Way subgroup → Local Group → Virgo Supercluster → Laniakea Supercluster → Observable universe → Universe Each arrow ( → ) may be read as `` within '' or `` part of ''. Minor planets navigator 1 Ceres 2 Pallas Small Solar System bodies Minor planets Designation Groups List Moon Meanings of names Asteroid Aten asteroid Asteroid belt Family Jupiter trojan Near - Earth Spectral types Distant minor planet Centaur Damocloid Neptune trojan Trans - Neptunian object Detached Kuiper belt Oort cloud Scattered disc Comets Extinct Great Halley - type Hyperbolic Long - period Lost Main - belt Near - parabolic Periodic Sungrazing Other Meteoroids Spacecraft missions to minor planets including dwarf planets and asteroids Orbiters NEAR Shoemaker Hayabusa Dawn Hayabusa2 ( en route ) OSIRIS - REx ( en route ) Landers NEAR Shoemaker Hayabusa MASCOT ( en route ) MINERVA - II 1A, 1B, 2 ( en route ) Flybys Galileo NEAR Shoemaker Cassini -- Huygens Deep Space 1 Stardust / NExT Rosetta / Philae New Horizons Chang'e 2 Failed Clementine MINERVA Deep Impact PROCYON Planned NEA Scout ( probe, 2019 ) Lucy ( multiple flybys, 2021 ) DESTINY+ ( multiple flybys, 2022 ) Psyche ( orbiter, 2022 ) Proposed DART HAMMER OKEANOS Cancelled AGORA AIDA ( AIM ) Asteroid Redirect Mission Clementine 2 CRAF Don Quijote Hayabusa Mk2 MAOSEP Marco Polo MarcoPolo - R New Horizons 2 Vesta Related Asteroid belt Asteroid capture Asteroid mining Human mission to an asteroid Colonization of asteroids Ceres Colonization Pluto Exploration Vesta Small Solar System bodies Near - Earth object Trans - Neptunian object Colonization Trojan Spacecraft missions to comets List of artificial objects on extra-terrestrial surfaces Italics indicate active current missions. Modern impact events On Earth Pre-2000 1490 Ch'ing - yang 1783 Great Meteor 1860 Great Meteor 1908 Tunguska 1913 Great Meteor Procession 1930 Curuçá River 1938 Chicora meteor 1947 Sikhote - Alin meteorite 1969 Murchison meteorite 1972 Great Daylight Fireball 1990 Earth - grazing meteoroid Post-2000 2002 Eastern Mediterranean 2002 Vitim 2007 Carancas 2008 TC3 impact 2009 Sulawesi superbolide 2012 Sutter 's Mill meteorite 2012 UK meteoroid 2012 Novato meteorite 2013 Chelyabinsk meteor Chelyabinsk meteorite 2014 AA impact 2014 Ontario fireball 2015 Kerala meteorite 2015 Thailand bolide WT1190F impact 2017 China bolide On Jupiter 1994 Comet Shoemaker -- Levy 9 2009 Jupiter impact 2010 Jupiter impact Lists Asteroid close approaches to Earth Comets Bolides Meteor air bursts Meteorite falls Minor planets crossing Earth 's orbit See also Asteroid impact avoidance Bolide Earth - grazing fireball Meteor procession Meteor shower Meteorite Meteoroid Near - Earth object Potentially hazardous object Planetary defense Main topics Asteroid Bolide Earth - grazing fireball Impact event List of meteor air bursts Meteor procession Meteor shower Meteorite Meteoroid Near - Earth object Potentially hazardous object Defense Asteroid impact avoidance Asteroid close approaches Earth - crossing minor planets Gravity tractor Ion Beam Shepherd Damage scales Palermo scale Torino scale Space probes Dawn Deep Impact DART Halley Armada Hayabusa Hayabusa2 MASCOT NEAR Shoemaker NEA Scout New Horizons OSIRIS - REx PROCYON Rosetta Philae Stardust NEO tracking ATLAS Catalina Sky Survey LINEAR LONEOS NEAT NEOSSat NEOCam NEODyS OGS Telescope Orbit@home Pan-STARRS SCAP Sentinel Space Telescope Sentry Spacewatch WISE Organizations B612 Foundation Japan Spaceguard Association Meteoritical Society NEOShield Spaceguard The Spaceguard Foundation Space Situational Awareness Programme Planetary Defense Coordination Office Potential threats 1950 DA 1994 WR 101955 Bennu 2002 MN ( 410777 ) 2009 FD 2010 RF 99942 Apophis Films / video The End of the World ( 1916 ) When Worlds Collide ( 1951 ) Gorath ( 1962 ) The Green Slime ( 1968 ) The Paradise Syndrome ( 1968 ) A Fire in the Sky ( 1978 ) Meteor ( 1979 ) NOVA : Doomsday Asteroid ( 1995 ) Asteroid ( 1997 ) Deep Impact ( 1998 ) Armageddon ( 1998 ) Avengers : Age of Ultron ( 2015 ) Judgment Day ( 1999 ) Post Impact ( 2004 ) Deadly Skies ( 2006 ) Super Comet : After the Impact ( 2007 ) Impact ( 2009 ) NOVA : Last Extinction ( 2009 ) Meteor Storm ( 2010 ) HORIZON : Asteroids -- The Good, the Bad and the Ugly ( 2010 ) Melancholia ( 2011 ) NOVA : Meteor Strike ( 2013 ) NOVA : Asteroid : Doomsday or Payday ? ( 2013 ) Impact Earth ( 2015 ) Global catastrophic risks Future of the Earth Ultimate fate of the universe Technological Grey goo Kinetic bombardment Mutual assured destruction Dead Hand Doomsday device Synthetic intelligence / Artificial intelligence Existential risk from artificial intelligence See Template AI takeover Technological singularity Transhumanism Sociological Malthusian catastrophe New World Order ( conspiracy theory ) Nuclear holocaust winter famine cobalt Societal collapse World War III Ecological Climate change Extinction risk from global warming Runaway climate change Global terrestrial stilling Ice age Ecocide Human impact on the environment See Template Ozone depletion Cascade effect Earth Overshoot Day Overexploitation Overpopulation Human overpopulation Biological Extinction Extinction event Human extinction Genetic erosion Genetic pollution Dysgenics Pandemic Biological agent Transhumanism Physical Big Crunch Big Rip Coronal mass ejection Gamma - ray burst Hypercane Impact event Asteroid Comet Potentially hazardous object Rogue planet Solar flare Supervolcano winter Mythological Eschatology Buddhist Christian Hindu Islamic Jewish Norse Zoroastrian 2011 end times prediction 2012 phenomenon Apocalypse Armageddon Blood moon prophecy Book of Revelation Doomsday Clock End time Last Judgment List of dates predicted for apocalyptic events Nibiru cataclysm Rapture Revelation 12 sign prophecy Third Temple Year 2000 problem Fiction Alien invasion Apocalyptic and post-apocalyptic fiction List of apocalyptic and post-apocalyptic fiction Disaster films List of disaster films List of fictional doomsday devices Zombie apocalypse Categories Apocalypticism Future problems Hazards Risk analysis Doomsday scenarios GND : 4174799 - 9 BNF : cb11976093k ( data ) NDL : 00572326 Retrieved from `` https://en.wikipedia.org/w/index.php?title=Asteroid&oldid=835561079 '' Categories : Asteroids Minor planets Hidden categories : CS1 maint : Uses authors parameter Use dmy dates from June 2013 Articles containing potentially dated statements from October 2017 All articles containing potentially dated statements Articles containing Ancient Greek - language text Articles needing additional references from January 2018 All articles needing additional references All articles with unsourced statements Articles with unsourced statements from October 2017 Articles containing potentially dated statements from 2011 Articles containing potentially dated statements from September 2013 Wikipedia indefinitely move - protected pages Articles containing potentially dated statements from 2010 Articles containing potentially dated statements from June 2016 Interlanguage link template link number Wikipedia articles with GND identifiers Wikipedia articles with BNF identifiers Talk Contents About Wikipedia Wikiversity Afrikaans Alemannisch Aragonés অসমীয়া Asturianu Avañe'ẽ Azərbaycanca বাংলা Bahasa Banjar Bân - lâm - gú Башҡортса Беларуская Беларуская ( тарашкевіца ) ‎ भोजपुरी Български Boarisch Bosanski Brezhoneg Català Чӑвашла Čeština Cymraeg Dansk Deutsch Eesti Ελληνικά Emiliàn e rumagnòl Español Esperanto Euskara فارسی Fiji Hindi Français Frysk Gaeilge Gaelg Galego 한국어 Հայերեն हिन्दी Hornjoserbsce Hrvatski Ido Ilokano Bahasa Indonesia Interlingua Ирон Íslenska Italiano עברית Basa Jawa ಕನ್ನಡ Kapampangan Къарачай - малкъар ქართული Қазақша Kiswahili Kreyòl ayisyen Kurdî Кыргызча Лезги ລາວ Latina Latviešu Lëtzebuergesch Lietuvių Limburgs Lumbaart Magyar Македонски മലയാളം Malti मराठी მარგალური Bahasa Melayu Baso Minangkabau Mirandés မြန်မာဘာသာ Nederlands 日本 語 Napulitano Нохчийн Norsk Norsk nynorsk Occitan Oʻzbekcha / ўзбекча ਪੰਜਾਬੀ پنجابی Patois Piemontèis Plattdüütsch Polski Português Qaraqalpaqsha Ripoarisch Română Runa Simi Русиньскый Русский Саха тыла Scots Seeltersk Shqip Sicilianu සිංහල Simple English Slovenčina Slovenščina کوردی Српски / srpski Srpskohrvatski / српскохрватски Basa Sunda Suomi Svenska Tagalog தமிழ் Taqbaylit Татарча / tatarça తెలుగు ไทย Тоҷикӣ ᏣᎳᎩ Türkçe Türkmençe Тыва дыл Українська اردو Vèneto Tiếng Việt 文言 West - Vlams Winaray 吴语 ייִדיש 粵語 Žemaitėška 中文 129 more Edit links This page was last edited on 9 April 2018, at 13 : 00. 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Question: relatively small bodies which generally orbit the sun between mars and jupiter are called
Answer: asteroids