FACTOID # 12: It's not the government they hate: Washington DC has the highest number of hate crimes per capita in the US.
 
 Home   Encyclopedia   Statistics   States A-Z   Flags   Maps   FAQ   About 
   
 
WHAT'S NEW
 

SEARCH ALL

FACTS & STATISTICS    Advanced view

Search encyclopedia, statistics and forums:

 

 

(* = Graphable)

 

 


Encyclopedia > Asteroid belt
The main asteroid belt (shown in white) between the orbits of Mars and Jupiter.
The main asteroid belt (shown in white) between the orbits of Mars and Jupiter.

The asteroid belt is the region of the Solar System located roughly between the orbits of the planets Mars and Jupiter where 98.5% of the known minor planets' orbits can be found.[1] Asteroids, or minor planets, are small celestial bodies composed of rock, ice, and some metal that orbit the Sun. This region is termed the main belt when contrasted with other concentrations of minor planets, since these may also be termed asteroid belts. Asteroid (plural form: Asteroids) may refer to: Asteroid, the astronomical object; this is the primary definition. ... Image File history File links Download high-resolution version (768x768, 188 KB)The inner Solar System, from the Sun to Jupiter. ... Image File history File links Download high-resolution version (768x768, 188 KB)The inner Solar System, from the Sun to Jupiter. ... Adjectives: Martian Atmosphere Surface pressure: 0. ... For other uses, see Jupiter (disambiguation). ... This article is about the Solar System. ... This article is about the astronomical term. ... Adjectives: Martian Atmosphere Surface pressure: 0. ... For other uses, see Jupiter (disambiguation). ... Minor planets, or asteroids or planetoids, are minor celestial bodies of the Solar system orbiting the Sun (mostly Small solar system bodies) that are smaller than major planets, but larger than meteoroids (commonly defined as being 10 meters across or less[1]), and that are not comets. ... Two bodies with a slight difference in mass orbiting around a common barycenter. ... 253 Mathilde, a C-type asteroid. ... Sol redirects here. ...


The asteroid belt formed from the primordial solar nebula as a group of planetesimals—the smaller precursors of the planets. However, gravitational perturbations by Jupiter impart too much orbital energy to the bodies in this region for them to accrete into a planet during collisions. Instead, the initial planetesimals have been broken up during the collisions, and the majority of the mass has been lost from this region since the formation of the Solar System. Some fragments from such collisions can eventually find their way into the inner Solar System, leading to meteorite impacts with the inner planets. Asteroid orbits continue to be appreciably perturbed whenever their period of revolution about the Sun forms an orbital resonance with Jupiter. At these orbital distances, a Kirkwood gap occurs as they are swept into different orbits. This article or section does not cite any references or sources. ... Planetesimals are solid objects thought to exist in protoplanetary disks and in debris disks. ... Gravity is a force of attraction that acts between bodies that have mass. ... In astrophysics, the term accretion is used for at least two distinct processes. ... Perturbation is a term used in astronomy to describe alterations to an objects orbit caused by gravitational interactions with other bodies. ... In celestial mechanics, an orbital resonance occurs when two orbiting bodies exert a regular, periodic gravitational influence on each other. ... Kirkwood gaps are gaps that appear in a graph if we classify the asteroids according to their periods, which is proportional to their mean radius from the Sun. ...


The majority of the mass within the main belt is contained in the largest asteroids. The three largest asteroids in the main belt (individually named 4 Vesta, 2 Pallas and 10 Hygiea) have mean diameters of more than 400 km, while the main belt's only dwarf planet, Ceres, is about 950 km in diameter. Together these four objects make up nearly half of the total mass in the belt.[2][3][4][5] The remainder form a distribution of smaller bodies that range down to the size of a particle of dust. The asteroid material is so thinly distributed however, that multiple unmanned spacecraft have traversed the belt without incident. Asteroids within the main belt are categorized by their spectra, and the majority can be grouped into three basic types: carbonaceous (C-type), silicate (S-type), and metal-rich (M-type). Collisions between large asteroids can form an asteroid family, whose members possess similar orbital characteristics and composition. Collisions also produce a fine dust that forms a major component of the zodiacal light. 4 Vesta (ves-ta) is the second most massive asteroid in the asteroid belt, with a mean diameter of about 530 km and an estimated mass 12% the mass of the entire asteroid belt. ... 2 Pallas (pal-us, Greek Παλλάς) was the first asteroid discovered after 1 Ceres. ... 10 Hygiea (hye-jee-a or hi-jee-a) is the fourth largest Main belt asteroid with a diameter of 407 km. ... Artists impression of Pluto (background) and Charon (foreground). ... Spectral type: G[8] Absolute magnitude: 3. ... In most modern usages of the word spectrum, there is a unifying theme of between extremes at either end. ... For other uses, see Carbon (disambiguation). ... C-type asteroids are carbonaceous asteroids. ... In chemistry, a silicate is a compound containing an anion in which one or more central silicon atoms are surrounded by electronegative ligands. ... S-type asteroids are of a silicaceous (stony) composition, hence the name. ... This article is about metallic materials. ... M-type asteroids are metallic asteroids; they are moderately bright (albedo . ... Minor planet is the official term for asteroids and trans-Neptunian objects. ... The zodiacal light in the eastern sky before the beginning of morning twilight. ...

Contents

History of observation

Giuseppe Piazzi, discoverer of the first asteroid, 1 Ceres.
Giuseppe Piazzi, discoverer of the first asteroid, 1 Ceres.

In 1766,[6] the astronomer Johann Daniel Titius von Wittenburg, drawing on the work of earlier writers, such as Christian Wolff and Charles Bonnet,[7] noted an apparent pattern in the layout of the planets. If one began a numerical sequence at 0, then 3, then 6, than 12, than 24, then 48, etc. doubling each time, and then added four to each number and divided by 10, this produced a remarkably close approximation to the orbits of the known planets as measured in astronomical units. This pattern, known as the Titius-Bode Law, predicted the semi-major axes of the six planets of the time (Mercury, Venus, Earth, Mars Jupiter and Saturn) provided one allowed for a "gap" between the orbits of Mars and Jupiter. In 1768, the astronomer Johann Elert Bode made note of Titius's relationship in his Anleitung zur Kenntniss des gestirnten Himmels (though he did not credit Titius, which led to many later referring to it as "Bode's law"), and declared, "Can one believe that the Founder of the universe had left this space empty? Certainly not."[7] When William Herschel discovered Uranus in 1781, the planet's position matched the law almost perfectly, leading astronomers to conclude that there had to be a planet between the orbits of Mars and Jupiter. Download high resolution version (696x885, 182 KB) This image has been released into the public domain by the copyright holder, its copyright has expired, or it is ineligible for copyright. ... Download high resolution version (696x885, 182 KB) This image has been released into the public domain by the copyright holder, its copyright has expired, or it is ineligible for copyright. ... 1 Ceres (IPA , Latin: ) is a dwarf planet in the asteroid belt. ... Johann Daniel Titius. ... Wittenburg is a city in the district Ludwigslust in Mecklenburg-Western Pomerania. ... Christian Wolff is the name of at least two notable individuals: an eighteenth-century philosopher and mathematician - see Christian Wolff (philosopher) a twentieth_century composer _ see Christian Wolff (composer) a German actor This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the... Bonnet Charles Bonnet (March 13, 1720 – May 20, 1793), Swiss naturalist and philosophical writer, was born at Geneva, of a French family driven into Switzerland by the religious persecution in the 16th century. ... The astronomical unit (AU or au or a. ... The Titius-Bode law (or Bodes law) is the observation that orbits of planets in the solar system closely follow a simple geometric rule. ... In geometry, the semi-major axis (also semimajor axis) a applies to ellipses and hyperbolas. ... Johann Elert Bode Johann Elert Bode (January 19, 1747 – November 23, 1826) was a German astronomer known for his contribution to the Titius-Bode law and his works to determine the orbit of Uranus, for which he also suggested the name. ... For other persons named William Herschel, see William Herschel (disambiguation). ... For other uses, see Uranus (disambiguation). ...


In 1800, astronomer Franz Xavier von Zach recruited a number of his fellows into an informal club he dubbed the "Lillienthal Society". Determined to bring the Solar System to order, the group came to be known as the "Himmelspolitzei", or Celestial Police, and eventually included such noted members as Herschel, British astronomer Royal Nevil Maskelyne, Charles Messier and Heinrich Olbers.[8] However, only a few months later, on January 1, 1801, Giuseppe Piazzi, Chair of Astronomy at the University of Palermo, Sicily, who was not a member of the Celestial Police, found, in the exact location predicted by the Titius-Bode Law, a tiny moving object he dubbed Ceres after the Roman goddess of the harvest and patron of Sicily. Piazzi initially believed it a comet, but its lack of a coma suggested it was a planet.[8] Nevil Maskelyne. ... Charles Messier Charles Messier (June 26, 1730 – April 12, 1817) was a French astronomer who in 1774 published a catalogue of 45 deep sky objects such as nebulae and star clusters. ... Categories: Astronomers stubs | 1758 births | 1840 deaths | German astronomers | German physicists | Lists of asteroids ... is the 1st day of the year in the Gregorian calendar. ... The Union Jack, flag of the newly formed United Kingdom of Great Britain and Ireland. ... Giuseppe Piazzi. ... The University of Palermo (Italian: Università degli Studi di Palermo) is a university located in Palermo, Italy, and founded in 1806. ... Sicily ( in Italian and Sicilian) is an autonomous region of Italy and the largest island in the Mediterranean Sea, with an area of 25,708 km² (9,926 sq. ... Spectral type: G[8] Absolute magnitude: 3. ... In Roman mythology, Ceres was the goddess of growing plants (particularly cereals) and of motherly love. ...


Fifteen months later, Olbers discovered a second object in the same region, Pallas, prompting him to suggest to William Herschel that these bodies were the remnants of a destroyed planet.[9] By 1807, further investigation revealed two new planets, 3 Juno and 4 Vesta.[10] Because of their star-like appearance, William Herschel suggested these objects be named asteroids, after the Greek root aster- meaning star.[11] However, for several decades it remained common practice to refer to these four objects as planets.[6] 2 Pallas (pal-us, Greek Παλλάς) was the first asteroid discovered after 1 Ceres. ... For other persons named William Herschel, see William Herschel (disambiguation). ... Juno (IPA: ), designated 3 Juno in the Minor Planet Center catalogue system, was the third asteroid to be discovered and is one of the largest main belt asteroids, being the second heaviest of the stony S-type. ... 4 Vesta (ves-ta) is the second most massive asteroid in the asteroid belt, with a mean diameter of about 530 km and an estimated mass 12% the mass of the entire asteroid belt. ... STAR is an acronym for: Organizations Society of Ticket Agents and Retailers], the self-regulatory body for the entertainment ticket industry in the UK. Society for Telescopy, Astronomy, and Radio, a non-profit New Jersey astronomy club. ...


The Napoleonic wars brought the first period of discovery in this region to a close,[10] and it would take until 1845 before another object (5 Astraea) was discovered. Shortly thereafter, however, new objects were found at an increasing rate, and counting them among the planets became increasingly cumbersome. Eventually, they were dropped from the planet list and William Herschel's name for them, asteroids, at last fell into common use.[6] The discovery of Neptune in 1846 led to the eventual discredit of the Titius-Bode Law in the eyes of scientists, as Neptune's orbit was nowhere near the predicted position. To date, no scientific explanation for the Law, and the consensus among astronomers is that it is a coincidence.[12] Combatants Austria[1] Portugal Prussia[1] Russia[2] Sicily  Spain[3]  Sweden United Kingdom[4] French Empire Holland Italy Naples [5] Duchy of Warsaw Bavaria[6] Saxony[7] Denmark-Norway [8] Commanders Archduke Charles Prince Schwarzenberg Karl Mack von Leiberich João Francisco de Saldanha Oliveira e Daun Gebhard von... 5 Astraea (as-tree-a; written Astræa in the early scientific litterature) is a large main belt asteroid. ... For other uses, see Neptune (disambiguation). ...


By mid-1868, 100 asteroids had been located, and the introduction of astrophotography in 1891 by Max Wolf accelerated the rate of discovery.[13] A total of 1,000 asteroids had been found by 1923, 10,000 by 1951, and 100,000 by 1982.[5] Modern asteroid survey systems now use automated means to locate new minor planets in ever-increasing quantities. Astrophotography is a specialised type of photography that entails making photographs of astronomical objects in the night sky such as planets, stars, and deep sky objects such as star clusters and galaxies. ... Maximilian Franz Joseph Cornelius Wolf (June 21, 1863 – October 3, 1932) was a German astronomer, a pioneer of astrophotography. ...


In 1866, Daniel Kirkwood announced the discovery of gaps in the distances of these bodies' orbits from the Sun. These gaps were located at positions where their period of revolution about the Sun was an integer fraction of Jupiter's orbital period. Kirkwood proposed that the gravitational perturbations of Jupiter led to the removal of asteroids from these orbits.[14] Daniel Kirkwood (September 27, 1814 - June 11, 1895) was an American astronomer. ... Sol redirects here. ... Perturbation is a term used in astronomy to describe alterations to an objects orbit caused by gravitational interactions with other bodies. ...


The Japanese astronomer Kiyotsugu Hirayama noticed in 1918 that the orbits of some of the asteroids had similar parameters, forming families or groups. In the 1970s, examination of asteroid colors led to a classification system. The three most common categories were designated C-type (carbonaceous), S-type (silicaceous) and M-type (metallic).[15] Kiyotsugu Hirayama (平山清次) (1874–1943) was a Japanese astronomer, best known for his discovery that many asteroid orbits were more similar to one another than chance would allow, leading to the concept of asteroid families, now called Hirayama families in his honour. ... C-type asteroids are carbonaceous asteroids. ... For other uses, see Carbon (disambiguation). ... S-type asteroids are of a silicaceous (stony) composition, hence the name. ... In chemistry, a silicate is a compound containing an anion in which one or more central silicon atoms are surrounded by electronegative ligands. ... M-type asteroids are metallic asteroids; they are moderately bright (albedo . ... This article is about metallic materials. ...


In 2006 it was announced that a population of comets had been discovered within the asteroid belt. It has been suggested that comets such as these may have provided a source of water for the formation of the Earth's oceans. According to some models, there was insufficient outgassing of water during the Earth's formulative period to form the oceans, requiring the introduction of an external source such as a cometary bombardment.[16] Comet Hale-Bopp Comet West For other uses, see Comet (disambiguation). ... Outgassing (sometimes called Offgassing, particularly when in reference to indoor air quality) is the slow release of a gas that was trapped, frozen, absorbed or adsorbed in some material. ...


Origin

The asteroid belt (showing inclinations), with the main belt in red and blue ("core" region in red)

Image File history File links Download high resolution version (1201x901, 44 KB) Summary Plot of inclination vs semi-major axis for numbered asteroids inward of about 6 AU. The main belt region is shown in red, and contains 93. ... Image File history File links Download high resolution version (1201x901, 44 KB) Summary Plot of inclination vs semi-major axis for numbered asteroids inward of about 6 AU. The main belt region is shown in red, and contains 93. ...

Formation

An early hypothesis of the asteroid belt's origins was that it was originally a planet that was somehow shattered. However, over time this hypothesis has fallen from favor, due to a number of key problems. One is the large amount of energy which would be required to achieve this kind of effect. Another is the low combined mass of the current asteroid belt, which has only a small fraction of the mass of the Earth's moon. Finally, the significant chemical differences between the asteroids is difficult to explain if they come from the same planet.[17] Today, most scientists accept the hypothesis that rather than fragmenting from an original planet, the asteroids never formed a planet at all. It has been suggested that this article or section be merged with Fifth planet (hypothetical). ... This article is about Earths moon. ...


Planetary formation is thought to have occurred via a process comparable to the long-standing nebular hypothesis, which states that a cloud of interstellar dust and gas collapsed under the influence of gravity to form a rotating disk of material that then further condensed to form the Sun and planets.[18] During the first few million years of the Solar System's history, an accretion process of sticky collisions caused clumping together of small particles, formation of larger clumps, and the gradual increase of the size of these bodies. Once the objects reached sufficient mass they could draw in other bodies through gravitational attraction, and become known as planetesimals. The gravitational accretion of these planetesimals led to the formation of the rocky planets and to the gas giants. Artists impression of a protoplanetary disc A protoplanetary disc (also protoplanetary disk, proplyd) is an accretion disc surrounding a T Tauri star. ... In astrophysics, the term accretion is used for at least two distinct processes. ... Planetesimals are solid objects thought to exist in protoplanetary disks and in debris disks. ... This article does not cite any references or sources. ...


In regions where the average velocity of the collisions was too high, the shattering of planetesimals tends to dominate over accretion,[19] preventing the formation of planet-sized bodies. When the orbital period of a planetismal forms an integer fraction of the orbital period of Jupiter, an orbital resonance occurs that can perturb the object into a different orbit. The region lying between the orbits of Mars and Jupiter contains many strong orbital resonances with Jupiter. As Jupiter migrated inward following its formation, these resonances would have swept across the asteroid belt, dynamically exciting the region's planetismal population in the process—increasing their velocities relative to each other.[20] Planetesimals in this region were (and continue to be) too strongly perturbed to form a planet. Instead the planetesimals orbit the Sun as before and occasionally collide.[21] The asteroid belt can be considered a relic of the primitive Solar System. In celestial mechanics, an orbital resonance occurs when two orbiting bodies exert a regular, periodic gravitational influence on each other. ... Perturbation is a term used in astronomy to describe alterations to an objects orbit caused by gravitational interactions with other bodies. ...


When the main belt was first being formed, the temperatures at a distance of 2.7 A.U. from the Sun formed a "snow line" where the temperatures fell below the condensation point of water. (1 A.U., or astronomical unit, equals the average distance between the Earth and the Sun.) Planetismals formed beyond this radius were able to accumulate ice.[22] Main-belt comets formed within the belt outside the snow line, and these are a leading candidate for the deposition of water to form the Earth's oceans.[23] Main-belt comets are bodies orbiting within the (main) asteroid belt which show cometary activity during a part of their orbit. ...


However, a recent hypothesis has partially revived the old "fifth planet" model for the asteroids' formation. A 2002 paper suggested that a large terrestrial planet formed among the inner planets, but the orbit was destabilized so that it began crossing the inner asteroid belt. As a result of this transition, a number of asteroids would have been ejected from the belt. Later this planet was either absorbed by the Sun or ejected from the system.[24] To meet Wikipedias quality standards, this article may require cleanup. ... For the Vanbrugh College dance party, see here. ... In the solar system the inner planets are the solid planets nearest the Sun: Mercury, Venus, Earth and Mars. ...


Evolution

The current asteroid belt is believed to contain only a small fraction (by mass) of the primordial asteroid belt. Based on computer simulations, the original asteroid belt may have contained mass equivalent to the Earth. Primarily because of gravitational perturbations, most of this material was ejected from the belt within a period of about a million years of formation, leaving behind less than 0.1% of the original mass.[21]


Since their formation, the size distribution of the asteroid belt has remained relatively stable. That is, there has not been a significant increase or decrease in the typical dimensions of the main belt asteroids.[25] However, the asteroids have been affected by many subsequent processes, such as internal heating (in the first few tens of millions of years), surface melting from impacts, and space weathering from radiation and bombardment by micrometeorites. Hence, the asteroids themselves are not pristine samples of the early Solar System. By contrast, the objects in the outer Kuiper belt are believed to have experienced much less change since the Solar System's formation. Please wikify (format) this article as suggested in the Guide to layout and the Manual of Style. ... A Micrometeoroid (also micrometeorite, micrometeor) is a tiny meteoroid; a small particle of rock from space, usually weighing less than a gram, that poses a threat to space exploration. ... The Kuiper belt, derived from data from the Minor Planet Center. ...


The 4:1 orbital resonance with Jupiter, at a radius 2.06 AU, can be considered the inner boundary of the main belt. Perturbations by Jupiter send bodies straying there onto unstable orbits. Also, most bodies formed inside the radius of this gap were swept up by Mars (which has an aphelion out at 1.67 A.U.) or ejected by its gravitational perturbations in the early history of the Solar System.[26] An exception are the high inclination Hungaria asteroids which lie slightly closer to the Sun, and were protected from these disturbances by this high inclination. In celestial mechanics, an orbital resonance occurs when two orbiting bodies exert a regular, periodic gravitational influence on each other. ... The astronomical unit (AU or au or a. ... Adjectives: Martian Atmosphere Surface pressure: 0. ... This article is about several astronomical terms (apogee & perigee, aphelion & perihelion, generic equivalents based on apsis, and related but rarer terms. ... The Hungaria asteroids are a group of asteroids in the main belt that orbit the Sun between 1. ...


Characteristics

The asteroid 951 Gaspra, the first ever imaged by a spacecraft, taken by Galileo as it passed by it in 1991
The asteroid 951 Gaspra, the first ever imaged by a spacecraft, taken by Galileo as it passed by it in 1991

Despite popular imagery, the asteroid belt is mostly empty. The asteroids are spread over such a large volume that it would be highly improbable to reach an asteroid without aiming carefully. Nonetheless, hundreds of thousands of asteroids are currently known, and the total number ranges in the millions or more, depending on the lower size cutoff that is assumed. Over 200 asteroids are known to be larger than 100 km,[27] while a survey in the infrared wavelengths shows that the main belt has 700,000 to 1.7 million asteroids with a diameter of 1 km or more.[28] The absolute magnitudes of most of the known asteroids are 11–19, with the median at about 16.[29] Source : NASA File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Source : NASA File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... 951 Gaspra is an S-type asteroid that orbits very close to the inner edge of the asteroid belt. ... Galileo is prepared for mating with the IUS booster Galileo and Inertial Upper Stage being deployed after being launched by the Space Shuttle Atlantis on the STS-34 mission Galileo was an unmanned spacecraft sent by NASA to study the planet Jupiter and its moons. ... “km” redirects here. ... In astronomy, absolute magnitude is the apparent magnitude, m, an object would have if it were at a standard luminosity distance away from us, in the absence of interstellar extinction. ...


Mass

The total mass of the asteroid belt is estimated to be 3.0-3.6×1021 kilograms, which is just 4% of the Earth's Moon.[2][3] Although 98.5 percent of minor planets known to date have been found in the asteroid belt, new discoveries of previously unknown minor planet groups in the Solar System could soon eclipse it in number and mass. The Trojans, two swarms of asteroids located at Jupiter's L4 and L5 points, to date have revealed a collective mass roughly half that of the asteroid belt,[30] while the Kuiper belt, a second belt beyond the orbit of Neptune discovered in 1992, may possess a mass up to 200 times its mass.[31][32] The hypothetical Oort cloud, a great spherical swarm of trillions of cometary bodies estending to beyond 50,000 AU, may possess a total mass six thousand times that of the asteroid belt.[33] This article is about Earths moon. ... Image of the Trojan asteroids in front of and behind Jupiter along its orbital path. ... In celestial mechanics, the Lagrangian points, (also Lagrange point, L-point, or libration point) are the five stationary solutions of the circular restricted three-body problem. ... The Kuiper belt, derived from data from the Minor Planet Center. ... This image is an artists rendering of the Oort cloud and the Kuiper Belt. ...


Composition

During the early history of the Solar System, minor planets underwent some degree of melting, allowing elements to be partially or completely segregated by mass. Some of the progenitor bodies may even have undergone periods of explosive volcanism and formed magma oceans. However, because of the relatively small size of these bodies, this period of melting was necessarily brief (compared to the much larger planets), and had generally ended about 4.5 billion years ago, that is in the first few tens to a hundred million years.[34] This article is about volcanoes in geology. ... Magma is molten rock located beneath the surface of the Earth (or any other terrestrial planet), and which often collects in a magma chamber. ...

Allende is a carbonaceous chondrite meteorite that fell to Earth in Mexico, 1969.
Allende is a carbonaceous chondrite meteorite that fell to Earth in Mexico, 1969.

The current belt consists primarily of three categories of asteroids. In the outer portion of the belt, closer to Jupiter's orbit, carbon-rich asteroids predominate.[35] These C-type (carbonaceous) asteroids include over 75% of the visible asteroids. They are more red in hue than the other asteroid categories and have a very low albedo. Their surface composition is similar to carbonaceous chondrite meteorites. Chemically, their spectra indicate a match with the primordial composition of the early Solar System, with the lighter elements and volatiles (e.g. ices) removed. Image File history File links Size of this preview: 800 × 600 pixelsFull resolution (1024 × 768 pixel, file size: 132 KB, MIME type: image/jpeg) Description: A 520g individual of the Allende meteorite shower. ... Image File history File links Size of this preview: 800 × 600 pixelsFull resolution (1024 × 768 pixel, file size: 132 KB, MIME type: image/jpeg) Description: A 520g individual of the Allende meteorite shower. ... Meteorite falls are those meteorites that were witnessed by people or automated devices as they transitted the atmosphere or impacted the Earth, and were subsequently collected. ... C-type asteroids are carbonaceous asteroids. ... This article belongs in one or more categories. ... Albedo is the ratio of reflected to incident electromagnetic radiation. ... Some carbonaceous chondrites. ... Willamette Meteorite A meteorite is a natural object originating in outer space that survives an impact with the Earths surface without being destroyed. ...


Toward the inner portion of the belt, within 2.5 A.U. of the Sun, S-type (silicate) chondrite asteroids are more common.[35][36] The spectra of their surfaces reveal the presence of silicates as well as some metal, but no significant carbonaceous compounds. This indicates that they are made of materials that have been significantly modified from the primordial Solar System composition. The expected mechanism was melting early in their history, which caused mass differentiation. They have a relatively high albedo, and form about 17% of the total asteroid population. S-type asteroids are of a silicaceous (stony) composition, hence the name. ... In chemistry, a silicate is a compound containing an anion in which one or more central silicon atoms are surrounded by electronegative ligands. ...


A third category of asteroids, forming about 10% of the total population, is the M-type (metal-rich). These have a spectrum that resembles metallic iron-nickel, with a white or slightly red appearance and no absorption features in the spectrum. Some M-type asteroids are believed to be formed from the metallic cores of differentiated progenitor bodies that were disrupted through collision. However, there are also some silicate compounds that can produce a similar appearance. Thus, for example, the large M-type asteroid 22 Kalliope does not appear to be primarily composed of metal.[37] Within the main belt, the number distribution of M-type asteroids peaks at a semi-major axis of about 2.7 A.U.[38] Overall it is not yet clear whether all M-types are compositionally similar, or whether it is a label for several varieties which do not fit neatly into the main C and S classes.[39] M-type asteroids are metallic asteroids; they are moderately bright (albedo . ... This article is about metallic materials. ... 22 Kalliope (ka-lye-a-pee) is a very large main belt asteroid discovered by J. R. Hind on November 16, 1852. ...


One mystery of the asteroid belt is the relative rarity of V-type, or basaltic asteroids.[40] Theories of asteroid formation predict that objects the size of Vesta or larger should form crusts and mantles, which would be composed mainly of basaltic rock, resulting on more than half of all asteroids being composed either of basalt or olivine. Observations however suggest that 99 percent of the predicted basaltic material is missing.[41] Until 2001, most basaltic bodies discovered in the asteroid belt were believed to originate from the asteroid Vesta (hence their name V-type). However, the discovery of the asteroid (1459) Magnya revealed a slightly different chemical composition to the other basaltic asteroids discovered til then, suggesting a different origin.[41] The V-type asteroids or Vestoids are moderately bright, and very similar to the more common S-type, which are also made up of stony irons and ordinary chondrites. ... Basalt Basalt is an extrusive igneous rock, sometimes porphyritic, and is often both fine-grained and dense. ... The mineral olivine (also called chrysolite and, when gem-quality, peridot) is a magnesium iron silicate with the formula (Mg,Fe)2SiO4. ...


The diversity of known basaltic meteorites mandated a diversity in their origins, and in 2007 two asteroids in the outer belt, (7472) Kumakiri and (10537) 1991 RY16, were found to possess a basaltic composition, though they could not have originated from Vesta. They are the only V-type asteroids discovered in the outer belt to date.[40]


The temperature of the asteroid belt varies with the distance from the Sun. For dust particles within the belt, typical temperatures range from 200 K (-73°C) at 2.2 A.U. down to 165 K (-108°C) at 3.2 A.U.[42] However, due to rotation, the surface temperature of an asteroid can vary considerably as the sides are alternately exposed to solar radiation and then to the stellar background.


Orbits and rotations

The asteroid belt (showing eccentricities), with the main belt in red and blue ("core" region in red)
The asteroid belt (showing eccentricities), with the main belt in red and blue ("core" region in red)

The large majority of the asteroids within the main belt have orbital eccentricities of less than 0.4, and an inclination of less than 30°. The orbital distribution of the asteroids peak at an eccentricity of around 0.07 and an inclination of less than 4°.[29] Thus while a typical asteroid has a relatively circular orbit and lies near the plane of the ecliptic, some asteroid orbits can be highly eccentric or travel well outside the ecliptic plane. Image File history File links Download high resolution version (1201x901, 49 KB) Summary Plot of eccentricity vs semi-major axis for numbered asteroids inward of about 6 AU. The main belt region is shown in red, and contains 93. ... Image File history File links Download high resolution version (1201x901, 49 KB) Summary Plot of eccentricity vs semi-major axis for numbered asteroids inward of about 6 AU. The main belt region is shown in red, and contains 93. ... Look up Eccentricity in Wiktionary, the free dictionary. ... The plane of the ecliptic is well seen in this picture from the 1994 lunar prospecting Clementine spacecraft. ...


Sometimes, the term main belt is used to refer only to the more compact "core" region where the greatest concentration of bodies is found. This lies between the strong 4:1 and 2:1 Kirkwood gaps at 2.06 and 3.27 A.U., and at orbital eccentricities less than roughly 0.33, along with orbital inclinations below about 20°. This "core" region contains approximately 93.4% of all numbered minor planets within the Solar System.[1] Kirkwood gaps are gaps that appear in a graph if we classify the asteroids according to their periods, which is proportional to their mean radius from the Sun. ... The astronomical unit (AU or au or a. ... In astrodynamics, under standard assumptions any orbit must be of conic section shape. ... For the science fiction novella by William Shunn, see Inclination (novella). ...


Measurements of the rotation periods of large asteroids in the main belt show that there is a lower limit. No asteroid with a diameter larger than 100 metres has a period of rotation of less than 2.2 hours. For asteroids rotating faster than approximately this rate, the centrifugal 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 the majority of asteroids with a diameter over 100 metres are actually rubble piles formed through accumulation of debris after collisions between asteroids.[43] Centrifugal force (from Latin centrum centre and fugere to flee) is a term which may refer to two different forces which are related to rotation. ... This article covers the physics of gravitation. ... In astronomy, rubble pile is the informal name for an asteroid that is not a monolith, consisting instead of numerous pieces of rock that have coalesced under the influence of gravity. ...


Kirkwood gaps

Main article: Kirkwood gap
Distribution of asteroid semi-major axes in the "core" of the main belt. Cyan arrows point to the Kirkwood gaps, where orbital resonances with Jupiter destabilize orbits.

The semi-major axis of an asteroid is used to describe the dimensions of its orbit around the Sun, and its value determines the minor planet's orbital period. When considering the semi-major axes of all asteroids, the main belt contains noticeable gaps, called Kirkwood gaps, in its distribution. They occur at the radii at which the mean orbital period of an asteroid is an integer fraction of the orbital period of Jupiter. This results in mean-motion resonance with the gas giant that is sufficient to perturb an asteroid to new orbital elements. In effect, asteroids that become located in such gap orbits (either primordially because of the migration of Jupiter's orbit,[44] or due to prior perturbations or collisions) are gradually nudged into different, random orbits with a larger or smaller semi-major axis. Kirkwood gaps are gaps that appear in a graph if we classify the asteroids according to their periods, which is proportional to their mean radius from the Sun. ... Image File history File links Kirkwood_Gaps. ... Image File history File links Kirkwood_Gaps. ... The semi-major axis of an ellipse In geometry, the term semi-major axis (also semimajor axis) is used to describe the dimensions of ellipses and hyperbolae. ... In celestial mechanics, an orbital resonance occurs when two orbiting bodies exert a regular, periodic gravitational influence on each other. ... For other uses, see Jupiter (disambiguation). ... The semi-major axis of an ellipse In geometry, the term semi-major axis (also semimajor axis) is used to describe the dimensions of ellipses and hyperbolae. ... The orbital period is the time it takes a planet (or another object) to make one full orbit. ... Kirkwood gaps are gaps that appear in a graph if we classify the asteroids according to their periods, which is proportional to their mean radius from the Sun. ... For the science fiction novel by John Barnes, see Orbital Resonance (novel). ... This article does not cite any references or sources. ... The elements of an orbit are the parameters needed to specify that orbit uniquely, given a model of two ideal masses obeying the Newtonian laws of motion and the inverse-square law of gravitational attraction. ...


However, the gaps are not seen in a simple snapshot of the locations of the asteroids at any one time. This is because asteroid orbits are elliptical, and many asteroids still cross through the radii corresponding to the gaps. The actual spatial density of asteroids in these gaps is not significantly different than in the neighboring regions.[45]


The main gaps occur at the 3:1, 5:2, 7:3 and 2:1 mean-motion resonances with Jupiter. Thus an asteroid in the 3:1 Kirkwood gap would orbit the Sun three times for each Jovian orbit. Weaker resonances occur at other values of semi-major axis, such that less asteroids are found with those values than with nearby ones. (For example, a 8:3 resonance for asteroids with a semi-major axis of 2.71 A.U.)[46]


The main or "core" population of the asteroid belt is sometimes divided into three zones, based on the most prominent Kirkwood gaps. Zone I lies between the 4:1 resonance (2.06 A.U.) and 3:1 resonance (2.5 A.U.) Kirkwood gaps. Zone II contines from the end of Zone I out to the 5:2 resonance gap (2.82 A.U.). Zone III runs from the outer edge of Zone II to the 2:1 resonance gap (3.28 A.U.).[47]


The main belt may also be divided into the inner and outer belts, with the inner belt formed by asteroids orbiting nearer to Mars than the 3:1 Kirkwood gap (2.5 A.U.), and the outer belt formed by those asteroids closer to Jupiter's orbit. (Some authors subdivide the inner and outer belts at the 2:1 resonance gap [3.3 A.U.], while others even define inner, middle and outer belts.)


Largest asteroids

See also: Largest asteroids The following is a collection of lists of notable asteroids in the Solar system, sometimes also including minor planets beyond the orbit of Jupiter. ...

The largest asteroid, Ceres.
The largest asteroid, Ceres.

The four largest asteroids are, in decreasing order of mass, 1 Ceres, 4 Vesta, 2 Pallas and 10 Hygiea. Together, they account for almost half of the belt's total mass, with one-third accounted for by Ceres alone.[4][5] Image File history File linksMetadata Ceres_optimized. ... Image File history File linksMetadata Ceres_optimized. ... 1 Ceres (IPA , Latin: ) is a dwarf planet in the asteroid belt. ... 4 Vesta (ves-ta) is the second most massive asteroid in the asteroid belt, with a mean diameter of about 530 km and an estimated mass 12% the mass of the entire asteroid belt. ... 2 Pallas (pal-us, Greek Παλλάς) was the first asteroid discovered after 1 Ceres. ... 10 Hygiea (hye-jee-a or hi-jee-a) is the fourth largest Main belt asteroid with a diameter of 407 km. ...


Ceres is the only asteroid large enough for its gravity to force it into a roughly round shape, and so, according to the IAU's 2006 resolution on the definition of planet, is now considered a dwarf planet.[48] Its orbital distance, 2.8 AU, is also the location of the asteroid belt's center of mass.[45] Ceres has a much higher absolute magnitude than the other asteroids, of around 3.32,[49] and may possess a surface layer of ice.[50] Like the planets, Ceres is diffrentiated; it has a crust, a mantle and a core.[50] Photograph of the planet Neptune and its moon Triton, taken by Voyager 2 as it entered the outer solar system. ... Artists impression of Pluto (background) and Charon (foreground). ... In physics, the center of mass of a system of particles is a specific point at which, for many purposes, the systems mass behaves as if it were concentrated. ...


Vesta, like Ceres, has a diffrentiated interior.[51] Vesta is almost but not quite spherical,[52] and the IAU has deferred its decision as to whether or not it qualifies as a dwarf planet.[53] Unlike Ceres however, Vesta formed inside the "frost line", and so is devoid of water.[54] Its composition is mainly of basaltic rock such as olivine.[41]


Pallas too lies on the boundary of hydrostatic equlibrium, and may still be listed as a dwarf planet by the IAU.[55] Pallas's composition is similar to that of Ceres; high in carbon and silicon.[56] Like Uranus, Pallas rotates on its side, with one pole facing the Sun and the other facing away.[57] For other uses, see Uranus (disambiguation). ...


Hygiea was also listed on the IAU's initial candidate planet list, and may yet become a dwarf planet.[55] Hygiea is a carbonaceous asteroid,[58] and, unlike the other largest asteroids, lies relatively close to the ecliptic plane.[59] The plane of the Ecliptic is well seen in this picture from the 1994 lunar prospecting Clementine spacecraft. ...


Collisions

The zodiacal light, created in part by dust from collisions in the asteroid belt.

The high population of the main belt makes for a very active environment, where collisions between asteroids occur frequently (on astronomical time scales). Collisions between main belt bodies with a mean radius of 10-km are expected to occur about once every 10 million years.[60] A collision may fragment an asteroid into numerous smaller pieces (leading to the formation of a new asteroid family). Conversely, collisions that occur at low relative speeds may also join two asteroids together. After more than 4 billion years of such processes, the members of the asteroid belt now bear little resemblance to the original population. Image File history File links Metadata No higher resolution available. ... Image File history File links Metadata No higher resolution available. ... The zodiacal light in the eastern sky before the beginning of morning twilight. ... Minor planet is the official term for asteroids and trans-Neptunian objects. ...


In addition to the asteroid bodies, the main belt also contains bands of dust with particle radii of up to a few hundred micrometres. This fine material is produced, at least in part, from collisions between asteroids, and by the impact of micrometeorites upon the asteroids. Due to Poynting-Robertson drag, the pressure of solar radiation causes this dust to slowly spiral inward toward the Sun.[61] A micrometre (American spelling: micrometer, symbol µm) is an SI unit of length equal to one millionth of a metre, or about a tenth of the diameter of a droplet of mist or fog. ... The Poynting-Robertson effect, also known as Poynting-Robertson drag, named after John Henry Poynting and Howard Percy Robertson, is a process by which solar radiation causes dust particles in a solar system to slowly spiral inward. ... Solar irradiance spectrum at top of atmosphere. ... Sol redirects here. ...


The combination of this fine asteroid dust, as well as ejected cometary material, produces the zodiacal light. This faint auroral glow can be viewed at night extending from the direction of the Sun along the plane of the ecliptic. Particles that produce the visible zodiacal light average about 40 μm in radius. The typical lifetimes of such particles is on the order of 700,000 years. Thus, in order to maintain the bands of dust, new particles must be steadily produced within the asteroid belt.[61] The zodiacal light in the eastern sky before the beginning of morning twilight. ... Sol redirects here. ... The plane of the ecliptic is well seen in this picture from the 1994 lunar prospecting Clementine spacecraft. ...


Meteorites

Some of the debris from collisions can form meteoroids that enter the Earth's atmosphere.[62] More than 99.8 percent of the 30,000 meteorites found on Earth to date are believed to have originated in the asteroid belt.[63] A September 2007 study by a joint US-Czech team has suggested that a large-body collision undergone by the asteroid 298 Baptistina sent a number of fragments into the inner solar system. The impacts of these fragments are believed to have created both the Tycho crater on the Moon and the Chicxulub crater in Mexico, the remnant of the massive impact which triggered the extinction of the dinosaurs 65 million years ago.[64] “Meteor” redirects here. ... Worlds second largest Meteorite in Culiacan, Mexico A meteorite is a relatively small extra-terrestrial body that reaches the Earths surface. ... September 2007 is the ninth month of that year. ... 298 Baptistina is a typical Main belt asteroid. ... An inner planet is any one of the Solar systems rocky planets that lie inside the asteroid belt: Mercury (planet), Venus (planet), Earth (planet) and Mars (planet). ... Tycho is a prominent lunar impact crater located in the southern lunar highlands. ... Wikipedia does not yet have an article with this exact name. ... Badlands near Drumheller, Alberta where erosion has exposed the KT boundary. ...


Families and groups

Main article: Asteroid family
This plot of orbital inclination (ip) versus eccentricity (ep) for the numbered main belt asteroids clearly shows several clumps of asteroid families.
This plot of orbital inclination (ip) versus eccentricity (ep) for the numbered main belt asteroids clearly shows several clumps of asteroid families.

Approximately one third of the asteroids in the main belt are members of an asteroid family. These are asteroids that share similar orbital elements, such as semimajor axis, eccentricity, and orbital inclination as well as similar spectral features, all of which indicate a common origin in the breakup of a larger body. Graphical displays of these elements, for members of the main belt, show concentrations indicating the presence of an asteroid family. There are about 20–30 associations that are almost certainly asteroid families, and likely have a common origin. Additional groupings have been found but these are less certain. Asteroid families can be confirmed when the members display common spectral features.[65] Smaller associations of asteroids are called groups or clusters. Minor planet is the official term for asteroids and trans-Neptunian objects. ... Image File history File links Size of this preview: 799 × 599 pixelsFull resolution (1201 × 901 pixel, file size: 114 KB, MIME type: image/png) A diagram showing proper orbital elements (inclination ip vs. ... Image File history File links Size of this preview: 799 × 599 pixelsFull resolution (1201 × 901 pixel, file size: 114 KB, MIME type: image/png) A diagram showing proper orbital elements (inclination ip vs. ... The elements of an orbit are the parameters needed to specify that orbit uniquely, given a model of two ideal masses obeying the Newtonian laws of motion and the inverse-square law of gravitational attraction. ... In geometry, the semi-major axis (also semimajor axis) a applies to ellipses and hyperbolas. ... (This page refers to eccitricity in astrodynamics. ... For the science fiction novella by William Shunn, see Inclination (novella). ...


Some of the most prominent families in the main belt (in order of increasing semi-major axis) consist of the Flora, Eunoma, Koronis, Eos and Themis families.[38] For example, the Flora family, one of the largest, with more than 800 known members, may have formed from a collision less than a billion years ago.[66] The largest asteroid to be a true member of a family (as opposed to an interloper in the case of Ceres with the Gefion family) is 4 Vesta. The Vesta family is believed to have formed as the result of a crater-forming impact on Vesta. Likewise the HED meteorites may also have originated from Vesta as a result of this collision.[67] The Flora family of asteroids is a large grouping of S-type asteroids in the inner main belt, whose origin and properties are relatively poorly understood at present. ... The Eunomia family is a group of several hundred asteroids that share similar orbital and spectral properties. ... The Koronis family is a family of asteroids in the Main Belt between Mars and Jupiter. ... Eos family is a prominent family of asteroids that are believed to have formed as a result from an ancient catastrophic collision between asteroids. ... The Themis Asteroid Family The Themis Asteroid Family is a Hirayama family of asteroids found in the outer portion of the main asteroid belt, between the orbits of Mars and Jupiter. ... The Gefion family of asteroids is a grouping of S-type asteroids in the intermediate main belt. ... 4 Vesta (ves-ta) is the second most massive asteroid in the asteroid belt, with a mean diameter of about 530 km and an estimated mass 12% the mass of the entire asteroid belt. ... Vesta family is a family of asteroids that are believed to have originated from asteroid 4 Vesta. ... The Johnstown Diogenite. ...


Three prominent bands of dust have been found within the main belt. These have similar orbital inclinations as the Eos, Koronis and Themis asteroid families, and so are possibly associated with those groupings.[68]


Periphery

Skirting the inner edge of the belt (ranging between 1.78 and 2.0 A.U. with a mean semi-major axis of 1.9 A.U.) is the Hungaria family of minor planets. They are named after the main member of this family—434 Hungaria, and the group contains at least 52 named asteroids. The Hungaria group are separated from the main body by the 4:1 Kirkwood gap and their orbits have a high inclination. Some members of this group belong to the Mars-crossing category of asteroids, and gravitational perturbations by Mars is a likely factor in reducing the total population of this group.[69] The Hungaria asteroids are a group of asteroids in the main belt that orbit the sun between 1. ... 434 Hungaria is a relatively small Main belt asteroid. ...


Another high-inclination group in the inner part of the main belt is the Phocaea family. These are composed primarily of S-type asteroids, where as the neighboring Hungaria family includes some E-types.[70] The Phocaea family orbit between 2.25 and 2.5 A.U. from the Sun. The Phocaea asteroids are a group of asteroids that orbit the sun between 2. ... E-type asteroids are inner-belt asteroids that contain enstatite. ...


Skirting the outer edge of the main belt is the Cybele group, orbiting between 3.3 and 3.5 A.U. These have a 7:4 orbital resonance with Jupiter. The Hilda family orbit between 3.5 and 4.2 A.U., and have relatively circular orbits and a stable 3:2 orbital resonance with Jupiter. There are relatively few asteroids beyond 4.2 A.U., until reaching Jupiter's orbit. Here the two large groups of Trojan asteroids can be found, although they are not usually considered part of the main asteroid belt. 65 Cybele is one of the largest asteroids in the main belt. ... Hilda asteroids are asteroids with a semi-major axis between 3. ... Image of the Trojan asteroids in front of and behind Jupiter along its orbital path. ...


New families

Some asteroid families have formed recently, in astronomical terms. The Karin Cluster apparently formed about 5.7 million years ago from a collision with a 16-km radius progenitor asteroid.[71] The Veritas family formed about 8.3 million years ago, and evidence for this event has been found in the form of interplanetary dust recovered from ocean sediment.[72] The Karin Cluster is a group of at least 90 asteroids in the Koronis family in the main belt. ... 490 Veritas 490 Veritas is a minor planet orbiting Sun. ... Animated map exhibiting the worlds oceanic waters. ...


In the more distant past, the Datura cluster apparently formed about 450 million years ago from a collision with a main belt asteroid. The age estimate is based on the probability of the members having their current orbits, rather than from any physical evidence. However this cluster may have been a source for some zodiacal dust material.[73] Other recent cluster formations, such as the Iannini cluster (circa 1–5 million years ago), may have provided additional sources of this asteroid dust.[74]


Exploration

Artist's concept of the Dawn Mission spacecraft with Vesta (left) & Ceres (right). NASA image.
Artist's concept of the Dawn Mission spacecraft with Vesta (left) & Ceres (right). NASA image.

The first spacecraft to traverse the asteroid belt was Pioneer 10, after entering the belt region on July 16, 1972. At the time there was some concern that the debris in the belt would pose a hazard to the spacecraft. Since that time though the belt has been safely traversed by 9 Earth-based craft without incident. These craft include Pioneer 11, Voyagers 1 and 2, Galileo (which imaged the asteroid 951 Gaspra in 1991 and 243 Ida in 1993}, Cassini (which imaged 2685 Masursky in 2000), NEAR (which imaged 253 Mathilde in 1997), Stardust (which imaged 5535 Annefrank in 2002), New Horizons (which imaged 132524 APL in 2006) and Ulysses. Due to the low density of materials within the belt, the odds of a probe running into an asteroid are now estimated at less than one in a billion.[75] Image File history File links Download high-resolution version (1500x1147, 950 KB) Dawn spacecraft (final configuration) Source: http://dawn. ... Image File history File links Download high-resolution version (1500x1147, 950 KB) Dawn spacecraft (final configuration) Source: http://dawn. ... This article is about the American space agency. ... Pioneer 10 was the first spacecraft to travel through the asteroid belt, and was the first spacecraft to make direct observations of Jupiter. ... is the 197th day of the year (198th in leap years) in the Gregorian calendar. ... Year 1972 (MCMLXXII) was a leap year starting on Saturday (link will display full calendar) of the Gregorian calendar. ... Position of Pioneer 10 and 11 Pioneer 11 was the second mission to investigate Jupiter and the outer solar system and the first to explore the planet Saturn and its main rings. ... Voyager Project redirects here. ... Galileo is prepared for mating with the IUS booster Galileo and Inertial Upper Stage being deployed after being launched by the Space Shuttle Atlantis on the STS-34 mission Galileo was an unmanned spacecraft sent by NASA to study the planet Jupiter and its moons. ... 951 Gaspra is an S-type asteroid that orbits very close to the inner edge of the asteroid belt. ... NASA image of 243 Ida. ... Cassini–Huygens is a joint NASA/ESA/ASI unmanned space mission intended to study Saturn and its moons. ... The asteroid 2685 Masursky is a main belt asteroid. ... Artists conception of the NEAR Shoemaker spacecraft Near Earth Asteroid Eros as seen from the NEAR spacecraft. ... 253 Mathilde is a Main belt asteroid that was visited by the NEAR Shoemaker spacecraft on its way to asteroid 433 Eros. ... An artists rendering of Stardust (NASA image) The Stardust capsule with cometary and interstellar samples landed at the U.S. Air Force Utah Test and Training Range at 10:10 UTC (15 January 2006) in the Bonneville Salt Flats. ... Image of 5535 Annefrank taken by the Stardust space probe 5535 Annefrank is an inner main belt asteroid, and member of the Augusta family. ... New Horizons on the launchpad New Horizons is a robotic spacecraft mission conducted by NASA. It is expected to be the first spacecraft to fly by and study the dwarf planet Pluto and its moons, Charon, Nix and Hydra. ... The two spots in this image are two images of asteroid taken on June 11 (bottom, at a distance of 3. ... Ulysses spacecraft Ulysses is an unmanned probe designed to study the Sun at all latitudes. ...


All spacecraft images of belt asteroids to date have come from brief flyby opportunities by probes headed for other targets. Only the NEAR and Hayabusa missions have studied asteroids for a protracted period in orbit and at the surface, and these were used to study near-Earth asteroids. However, the Dawn Mission has been being dispatched to explore Vesta and Ceres in the main belt. If the probe is still operational after examining these two large bodies, an extended mission is possible that could allow additional exploration.[76] In orbital mechanics and aerospace engineering, a gravitational slingshot or gravity assist is the use of the gravity of a planet or other celestial body to alter the path and speed of a spacecraft. ... For other uses, see Hayabusa (disambiguation). ... The Apollo Asteroid 6489 golevka Near-Earth asteroids (NEAs) are asteroids whose orbits are close to Earths orbit. ... The Dawn Mission is a NASA mission that will send the Dawn spacecraft, a robotic space probe, to the asteroid belt. ... 4 Vesta (ves-ta) is the second most massive asteroid in the asteroid belt, with a mean diameter of about 530 km and an estimated mass 12% the mass of the entire asteroid belt. ... Spectral type: G[8] Absolute magnitude: 3. ...


See also

Asteroids have become a common theme in science fiction. ... The centaurs are a class of icy planetoids that orbit the Sun between Jupiter and Neptune, named after the mythical race of centaurs. ... It has been suggested that Colonization of Ceres be merged into this article or section. ... Debris disk around star AU Microscopii. ... Image of the Trojan asteroids in front of and behind Jupiter along its orbital path. ...

References

  1. ^ a b This value was obtained by a simple count up of all bodies in that region using data for 120437 numbered minor planets from the Minor Planet Center orbit database, dated February 8, 2006.
  2. ^ a b Krasinsky, G. A.; Pitjeva, E. V.; Vasilyev, M. V.; Yagudina, E. I. (July 2002). "Hidden Mass in the Asteroid Belt". Icarus 158 (1): 98-105. DOI:10.1006/icar.2002.6837. 
  3. ^ a b Pitjeva, E. V. (2005). "High-Precision Ephemerides of Planets—EPM and Determination of Some Astronomical Constants" (PDF). Solar System Research 39 (3): 176. DOI:10.1007/s11208-005-0033-2. 
  4. ^ a b For recent estimates of the masses of Ceres, 4 Vesta, 2 Pallas and 10 Hygiea, see the references in the infoboxes of their respective articles.
  5. ^ a b c Yeomans, Donald K. (July 13, 2006). JPL Small-Body Database Browser. NASA JPL. Retrieved on 2007-04-25. — Asteroids are numbered by order of discovery.
  6. ^ a b c J. Hilton (2001). When Did the Asteroids Become Minor Planets?. US Naval Observatory. Retrieved on 2007-10-01.
  7. ^ a b Michael Hoskin. BODE'S LAW AND THE DISCOVERY OF CERES. Churchill College, Cambridge. Retrieved on 2007-10-01.
  8. ^ a b "Call the police! The story behind the discovery of the asteroids". Astronomy Now (Jume 2007): 60-61. 
  9. ^ A Brief History of Asteroid Spotting. Open2.net. Retrieved on 2007-05-15.
  10. ^ a b Staff (2002). Astronomical Serendipity. NASA JPL. Retrieved on 2007-04-20.
  11. ^ DeForest, Jessica (2000). Greek and Latin Roots. Michigan State University. Retrieved on 2007-07-25.
  12. ^ Is it a coincidence that most of the planets fall within the Titius-Bode law's boundaries?. astronomy.com. Retrieved on 2007-10-16.
  13. ^ Hughes, David W. (2007). A Brief History of Asteroid Spotting. BBC. Retrieved on 2007-04-20.
  14. ^ Fernie, J. Donald (1999). "The American Kepler". The Americal Scientist 87 (5): 398. Retrieved on 2007-02-04. 
  15. ^ Hughes, David W. (2007). Finding Asteroids In Space. BBC. Retrieved on 2007-04-20.
  16. ^ Lakdawalla, Emily (April 28, 2006). Discovery of a Whole New Type of Comet. The Planetary Society. Retrieved on 2007-04-20.
  17. ^ Masetti, M.; Mukai, K. (December 1, 2005). Origin of the Asteroid Belt. NASA Goddard Spaceflight Center. Retrieved on 2007-04-25.
  18. ^ Watanabe, Susan (July 20, 2001). Mysteries of the Solar Nebula. NASA. Retrieved on 2007-04-02.
  19. ^ Edgar, R.; Artymowicz, P. (2004). "Pumping of a Planetesimal Disc by a Rapidly Migrating Planet" (PDF). Monthly Notices of the Royal Astronomical Society 354 (3): 769-772. Retrieved on 2007-04-16. 
  20. ^ Scott, E. R. D. (March 13-17, 2006). "Constraints on Jupiter's Age and Formation Mechanism and the Nebula Lifetime from Chondrites and Asteroids". Proceedings 37th Annual Lunar and Planetary Science Conference, League City, Texas: Lunar and Planetary Society. Retrieved on 2007-04-16. 
  21. ^ a b Petit, J.-M.; Morbidelli, A.; Chambers, J. (2001). "The Primordial Excitation and Clearing of the Asteroid Belt" (PDF). Icarus 153: 338-347. Retrieved on 2007-03-22. 
  22. ^ Lecar, M.; Podolak, M.; Sasselov, D.; Chiang, E. (2006). "Infrared cirrus - New components of the extended infrared emission". The Astrophysical Journal 640: 1115–1118. Retrieved on 2007-04-11. 
  23. ^ Berardelli, Phil. "Main-Belt Comets May Have Been Source Of Earths Water", Space Daily, March 23, 2006. Retrieved on 2007-04-11. 
  24. ^ David, Leonard (March 18, 2002). Long-Destroyed Fifth Planet May Have Caused Lunar Cataclysm. Space.com. Retrieved on 2007-04-25.
  25. ^ Stiles, Lori. "Asteroids Caused the Early Inner Solar System Cataclysm", University of Arizona News, September 15, 2005. Retrieved on 2007-04-18. 
  26. ^ Alfvén, H.; Arrhenius, G. (1976). The Small Bodies. SP-345 Evolution of the Solar System. NASA. Retrieved on 2007-04-12.
  27. ^ Yeomans, Donald K. (April 26, 2007). JPL Small-Body Database Search Engine. NASA JPL. Retrieved on 2007-04-26. — search for asteroids in the main belt regions with a diameter >100.
  28. ^ Tedesco, E. F.; Desert, F.-X. (2002). "The Infrared Space Observatory Deep Asteroid Search". The Astronomical Journal 123: 2070–2082. Retrieved on 2007-04-10. 
  29. ^ a b Williams, Gareth (April 3, 2007). Distribution of the Minor Planets. Minor Planets Center. Retrieved on 2007-04-15.
  30. ^ DAVID C. JEWITT AND CHADWICK A. TRUJILLO (2007). POPULATION AND SIZE DISTRIBUTION OF SMALL JOVIAN TROJAN ASTEROIDS. Retrieved on 2007-10-18.
  31. ^ Audrey Delsanti and David Jewitt. The Solar System Beyond The Planets. Institute for Astronomy, University of Hawaii. Retrieved on 2007-03-09.
  32. ^ David Jewitt. Kuiper Belt Page. Retrieved on 2007-10-15.
  33. ^ PR Weissman (1981). The mass of the Oort cloud. California Institute of Technology. Retrieved on 2007-05-26.
  34. ^ Taylor, G. J.; Keil, K.; McCoy, T.; Haack, H.; Scott, E. R. D. (1993). "Asteroid differentiation - Pyroclastic volcanism to magma oceans". Meteoritics 28 (1): 34-52. Retrieved on 2007-04-19. 
  35. ^ a b Wiegert, P.; Balam, D.; Moss, A.; Veillet, C.; Connors, M.; Shelton, I. (2007). "Evidence for a Color Dependence in the Size Distribution of Main-Belt Asteroids". The Astronomical Journal 133: 1609–1614. Retrieved on 2007-03-27. 
  36. ^ Clark, B. E. (1996). "New News and the Competing Views of Asteroid Belt Geology". Lunar and Planetary Science 27: 225-226. Retrieved on 2007-03-27. 
  37. ^ Margot, J. L.; Brown, M. E. (2003). "A Low-Density M-type Asteroid in the Main Belt". Science 300 (5627): 1939-1942. Retrieved on 2007-04-10. 
  38. ^ a b Lang, Kenneth R. (2003). Asteroids and meteorites. NASA's Cosmos. Retrieved on 2007-04-02.
  39. ^ Mueller, M.; Harris, A. W.; Delbo, M.; MIRSI Team (2005). "21 Lutetia and other M-types: Their sizes, albedos, and thermal properties from new IRTF measurements". Bulletin of the American Astronomical Society 37: 627. Retrieved on 2007-07-23. 
  40. ^ a b Duffard, R.; Roig, F. (2007). Two new basaltic asteroids in the Outer Main Belt. Retrieved on 2007-10-14.
  41. ^ a b c Ker Than (2007). Strange Asteroids Baffle Scientists. space.com. Retrieved on 2007-10-14.
  42. ^ Low, F. J. et al (1984). "Infrared cirrus - New components of the extended infrared emission". Astrophysical Journal, Part 2 - Letters to the Editor 278: L19-L22. Retrieved on 2007-04-11. 
  43. ^ Rossi, Alessandro (May 20, 2004). The mysteries of the asteroid rotation day. The Spaceguard Foundation. Retrieved on 2007-04-09.
  44. ^ Liou, Jer-Chyi; Malhotra, Renu (1997). "Depletion of the Outer Asteroid Belt". Science 275 (5298): 375-377. Retrieved on 2007-08-01. 
  45. ^ a b McBride, N.; Hughes, D. W. (1990). "The spatial density of asteroids and its variation with asteroidal mass". Monthly Notices of the Royal Astronomical Society 244: 513-520. Retrieved on 2007-04-19. 
  46. ^ Ferraz-Mello, S. (June 14-18, 1993). "Kirkwood Gaps and Resonant Groups". proceedings of the 160th International Astronomical Union: 175-188, Belgirate, Italy: Kluwer Academic Publishers. Retrieved on 2007-03-28. 
  47. ^ Klacka, Jozef (1992). "Mass distribution in the asteroid belt". Earth, Moon, and Planets 56 (1): 47-52. Retrieved on 2007-04-12. 
  48. ^ The Final IAU Resolution on the Definition of "Planet" Ready for Voting. IAU (August 24, 2006). Retrieved on 2007-03-02.
  49. ^ Parker, J. W.; Stern, S. A.; Thomas, P. C.; Festou, M. C.; Merline, W. J.; Young, E. F.; Binzel, R. P.; Lebofsky, L. A. (2002). "Analysis of the First Disk-resolved Images of Ceres from Ultraviolet Observations with the Hubble Space Telescope". The Astronomical Journal 123: 549–557. Retrieved on 2007-04-15. 
  50. ^ a b Asteroid 1 Ceres. The Planetary Society. Retrieved on 2007-10-20.
  51. ^ Key Stages in the Evolution of the Asteroid Vesta. Hubble Space Telescope news release (1995). Retrieved on 2007-10-20.
  52. ^ P. C. Thomas et al Vesta: Spin Pole, Size, and Shape from HST Images, Icarus, Vol. 128, p. 88 (1997)
  53. ^ IAU draft resolution (2006). Retrieved on 2007-10-20.
  54. ^ CT Russel et al. (2007). Dawn mission and operations. NASA/JPL. Retrieved on 2007-10-20.
  55. ^ a b IAU 2006 General Assembly: Result of the IAU Resolution votes. Retrieved on 2007-03-29.
  56. ^ Larson, H. P.; Feierberg, M. A.; Lebofsky, L. A. (1983). The composition of asteroid 2 Pallas and its relation to primitive meteorites. Retrieved on 2007-10-20.
  57. ^ J. Torppa et al (1996). "Shapes and rotational properties of thirty asteroids from photometric data". Icarus 164 (2): 346-383. Retrieved on 2007-03-15. 
  58. ^ M. A. Barucci et al. (2002). 10 Hygiea: ISO Infrared Observations. Retrieved on 2007-10-21.
  59. ^ Ceres the Planet. Retrieved on 2007-19-20.
  60. ^ Backman, D. E. (March 06, 1998). Fluctuations in the General Zodiacal Cloud Density. Backman Report. NASA Ames Research Center. Retrieved on 2007-04-04.
  61. ^ a b Reach, William T. (1992). "Zodiacal emission. III - Dust near the asteroid belt". Astrophysical Journal 392 (1): 289-299. Retrieved on 2007-04-04. 
  62. ^ Kingsley, Danny (May 1, 2003). Mysterious meteorite dust mismatch solved. ABC Science. Retrieved on 2007-04-04.
  63. ^ Meteors and Meteorites. NASA. Retrieved on 2007-10-17.
  64. ^ Breakup event in the main asteroid belt likely caused dinosaur extinction 65 million years ago. Southwest Reasearch Institute (2007). Retrieved on 2007-10-14.
  65. ^ Lemaitre, Anne (August 31-September 4, 2004). "Asteroid family classification from very large catalogues". Procedings Dynamics of Populations of Planetary Systems: 135-144, Belgrade, Serbia and Montenegro: Cambridge University Press. Retrieved on 2007-04-15. 
  66. ^ Martel, Linda M. V. (March 9, 2004). Tiny Traces of a Big Asteroid Breakup. Planetary Science Research Discoveries. Retrieved on 2007-04-02.
  67. ^ Drake, Michael J. (2001). "The eucrite/Vesta story". Meteoritics & Planetary Science 36 (4): 501-513. Retrieved on 2007-02-04. 
  68. ^ Love, S. G.; Brownlee, D. E. (1992). "The IRAS dust band contribution to the interplanetary dust complex - Evidence seen at 60 and 100 microns". Astronomical Journal 104 (6): 2236-2242. Retrieved on 2007-04-11. 
  69. ^ Spratt, Christopher E. (1990). "The Hungaria group of minor planets". Journal of the Royal Astronomical Society of Canada 84 (2): 123-131. Retrieved on 2007-02-04. 
  70. ^ Carvano, J. M.; Lazzaro, D.; Mothé-Diniz, T.; Angeli, C. A.; Florczak, M. (2001). "Spectroscopic Survey of the Hungaria and Phocaea Dynamical Groups". Icarus 149 (1): 173-189. Retrieved on 2007-02-04. 
  71. ^ "SwRI researchers identify asteroid breakup event in the main asteroid belt", SpaceRef.com, June 12, 2002. Retrieved on 2007-04-15. 
  72. ^ McKee, Maggie. "Eon of dust storms traced to asteroid smash", New Scientist Space, January 18, 2006. Retrieved on 2007-04-15. 
  73. ^ Nesvorný, D.; Vokrouhlick, D.; Bottke, W. F. (2006). "The Breakup of a Main-Belt Asteroid 450 Thousand Years Ago". Science 312 (5779): 1490. Retrieved on 2007-04-15. 
  74. ^ Nesvorný, D.; Bottke, W. F.; Levison, H. F.; Dones, L. (2003). "Recent Origin of the Solar System Dust Bands". The Astrophysical Journal 591: 486–497. Retrieved on 2007-04-15. 
  75. ^ Stern, Alan. "New Horizons Crosses The Asteroid Belt", Space Daily, June 2, 2006. Retrieved on 2007-04-14. 
  76. ^ Staff (April 10, 2007). Dawn Mission Home Page. NASA JPL. Retrieved on 2007-04-14.

is the 39th day of the year in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... Georgij A. Krasinsky is a Russian astronomer active at the Institute of Applied Astronomy, Russian Academy of Science, St Petersburg. ... Elena Vladimirovna Pitjeva is a Russian theoretical physicist at the Institute of Applied Astronomy, Russian Academy of Sciences, St. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... Elena Vladimirovna Pitjeva is a Russian theoretical physicist at the Institute of Applied Astronomy, Russian Academy of Sciences, St. ... PDF is an abbreviation with several meanings: Portable Document Format Post-doctoral fellowship Probability density function There also is an electronic design automation company named PDF Solutions. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... Spectral type: G[8] Absolute magnitude: 3. ... 4 Vesta (ves-ta) is the second most massive asteroid in the asteroid belt, with a mean diameter of about 530 km and an estimated mass 12% the mass of the entire asteroid belt. ... 2 Pallas (pal-us, Greek Παλλάς) was the first asteroid discovered after 1 Ceres. ... 10 Hygiea (hye-jee-a or hi-jee-a) is the fourth largest Main belt asteroid with a diameter of 407 km. ... is the 194th day of the year (195th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 115th day of the year (116th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 274th day of the year (275th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 274th day of the year (275th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 135th day of the year (136th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 110th day of the year (111th in leap years) in the Gregorian calendar. ... Year 2000 (MM) was a leap year starting on Saturday (link will display full 2000 Gregorian calendar). ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 206th day of the year (207th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 289th day of the year (290th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 110th day of the year (111th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 35th day of the year in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 110th day of the year (111th in leap years) in the Gregorian calendar. ... is the 118th day of the year (119th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 110th day of the year (111th in leap years) in the Gregorian calendar. ... is the 335th day of the year (336th in leap years) in the Gregorian calendar. ... Year 2005 (MMV) was a common year starting on Saturday (link displays full calendar) of the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 115th day of the year (116th in leap years) in the Gregorian calendar. ... is the 201st day of the year (202nd in leap years) in the Gregorian calendar. ... Year 2001 (MMI) was a common year starting on Monday (link displays the 2001 Gregorian calendar). ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 92nd day of the year (93rd in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 106th day of the year (107th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 106th day of the year (107th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 81st day of the year (82nd in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 101st day of the year (102nd in leap years) in the Gregorian calendar. ... is the 82nd day of the year (83rd in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 101st day of the year (102nd in leap years) in the Gregorian calendar. ... is the 77th day of the year (78th in leap years) in the Gregorian calendar. ... Also see: 2002 (number). ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 115th day of the year (116th in leap years) in the Gregorian calendar. ... is the 258th day of the year (259th in leap years) in the Gregorian calendar. ... Year 2005 (MMV) was a common year starting on Saturday (link displays full calendar) of the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 108th day of the year (109th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 102nd day of the year (103rd in leap years) in the Gregorian calendar. ... is the 116th day of the year (117th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 116th day of the year (117th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 100th day of the year (101st in leap years) in the Gregorian calendar. ... is the 93rd day of the year (94th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 105th day of the year (106th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 291st day of the year (292nd in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 68th day of the year (69th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 288th day of the year (289th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 146th day of the year (147th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 109th day of the year (110th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 86th day of the year (87th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 86th day of the year (87th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 100th day of the year (101st in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 92nd day of the year (93rd in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 204th day of the year (205th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 287th day of the year (288th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 287th day of the year (288th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 101st day of the year (102nd in leap years) in the Gregorian calendar. ... is the 140th day of the year (141st in leap years) in the Gregorian calendar. ... Year 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 99th day of the year (100th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 213th day of the year (214th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 109th day of the year (110th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 87th day of the year (88th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 102nd day of the year (103rd in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 61st day of the year (62nd in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 105th day of the year (106th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 293rd day of the year (294th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 293rd day of the year (294th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 293rd day of the year (294th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 293rd day of the year (294th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 88th day of the year (89th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 293rd day of the year (294th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 74th day of the year (75th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 294th day of the year (295th in leap years) in the Gregorian calendar. ... March 6 is the 65th day of the year in the Gregorian Calendar (66th in Leap years). ... Year 1998 (MCMXCVIII) was a common year starting on Thursday (link will display full 1998 Gregorian calendar). ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 94th day of the year (95th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 94th day of the year (95th in leap years) in the Gregorian calendar. ... is the 121st day of the year (122nd in leap years) in the Gregorian calendar. ... Year 2003 (MMIII) was a common year starting on Wednesday of the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 94th day of the year (95th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 290th day of the year (291st in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 287th day of the year (288th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 105th day of the year (106th in leap years) in the Gregorian calendar. ... is the 68th day of the year (69th in leap years) in the Gregorian calendar. ... Year 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 92nd day of the year (93rd in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 35th day of the year in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 101st day of the year (102nd in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 35th day of the year in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 35th day of the year in the Gregorian calendar. ... is the 163rd day of the year (164th in leap years) in the Gregorian calendar. ... Also see: 2002 (number). ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 105th day of the year (106th in leap years) in the Gregorian calendar. ... is the 18th day of the year in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 105th day of the year (106th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 105th day of the year (106th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 105th day of the year (106th in leap years) in the Gregorian calendar. ... is the 153rd day of the year (154th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... April 14 is the 104th day of the year (105th in leap years) in the Gregorian calendar, with 261 days remaining. ... is the 100th day of the year (101st in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... April 14 is the 104th day of the year (105th in leap years) in the Gregorian calendar, with 261 days remaining. ...

Further reading

  • Elkins-Tanton, Linda T. (2006). Asteroids, Meteorites, and Comets, First edition, New York: Chelsea House. ISBN 0-8160-5195-X. 

External links

  • Staff (October 31, 2006). Asteroids. NASA. Retrieved on 2007-04-20.
  • Asteroids Page at NASA's Solar System Exploration
  • Munsell, Kirk (September 16, 2005). Asteroids Page Asteroids: Overview. NASA's Solar System Exploration. Retrieved on 2007-05-26.
  • Arnett, William A. (February 26, 2006). Asteroids. The Nine Planets. Retrieved on 2007-04-20.
  • Main Asteroid Belt. Sol Company. Retrieved on 2007-04-20.
  • Hsieh, Henry H. (March 1, 2006). Main-Belt Comets. University of Hawaii. Retrieved on 2007-04-20.
  • Staff (2007). Space Topics: Asteroids and Comets. The Planetary Society. Retrieved on 2007-04-20.
  • Plots of eccentricity vs. semi-major axis and inclination vs. semi-major axis at Asteroid Dynamic Site
 v  d  e The Solar System
The Sun Mercury Venus The Moon Earth Phobos and Deimos Mars Ceres The asteroid belt Jupiter Moons of Jupiter Saturn Moons of Saturn Uranus Moons of Uranus Moons of Neptune Neptune Moons of Pluto Pluto The Kuiper Belt Dysnomia Eris The Scattered Disc The Oort Cloud
The Sun · Mercury · Venus · Earth · Mars · Ceres · Jupiter · Saturn · Uranus · Neptune · Pluto · Eris
Planets · Dwarf planets · Moons: Terrestrial · Martian · Jovian · Saturnian · Uranian · Neptunian · Plutonian · Eridian
Small bodies:   Meteoroids · Asteroids/Asteroid moons (Asteroid belt) · Centaurs · TNOs (Kuiper belt/Scattered disc) · Comets (Oort cloud)
See also astronomical objects, the solar system's list of objects, sorted by radius or mass, and the Solar System Portal

  Results from FactBites:
 
Main Asteroid Belt (1425 words)
While most asteroids may be only the size of pebbles, 16 asteroids have a diameter of 240 km (150 miles) and Ceres, the largest, has a diameter of about about 914 km (568 miles).
Indeed, if all asteroids down to the size of meter- or yard-sized boulders or less were combined together, the resulting object would measure less than 1,300 to 1,500 km (810 to 930 miles) across, which is less than one third to one half the diameter of the Earth's Moon.
Asteroids located closer to Mars and Earth that exhibit the same spectra are composed of rocky minerals ("stone") mixed with iron.
  More results at FactBites »

 
 

COMMENTARY     


Share your thoughts, questions and commentary here
Your name
Your comments

Want to know more?
Search encyclopedia, statistics and forums:

 


Press Releases |  Feeds | Contact
The Wikipedia article included on this page is licensed under the GFDL.
Images may be subject to relevant owners' copyright.
All other elements are (c) copyright NationMaster.com 2003-5. All Rights Reserved.
Usage implies agreement with terms, 1022, m