127-511: A Mars-crossing asteroid ( MCA , also Mars-crosser , MC ) is an asteroid whose orbit crosses that of Mars . Some Mars-crossers numbered below 100000 are listed here. They include the two numbered Mars trojans 5261 Eureka and (101429) 1998 VF 31 . Many databases, for instance the JPL Small-Body Database (JPL SBDB), only list asteroids with a perihelion greater than 1.3 AU as Mars-crossers. An asteroid with
254-518: A dwarf planet under International Astronomical Union (IAU) Resolution XXVI 5 . A 2012 analysis of Vesta's shape and gravity field using data gathered by the Dawn spacecraft has shown that Vesta is currently not in hydrostatic equilibrium . Temperatures on the surface have been estimated to lie between about −20 °C (253 K) with the Sun overhead, dropping to about −190 °C (83.1 K) at
381-470: A comet, not an asteroid, if it shows a coma (tail) when warmed by solar radiation, although recent observations suggest a continuum between these types of bodies. Of the roughly one million known asteroids, the greatest number are located between the orbits of Mars and Jupiter , approximately 2 to 4 AU from the Sun, in a region known as the main asteroid belt . The total mass of all the asteroids combined
508-579: A coordinate system, correcting the pole but rotating the Claudian longitude by 150° to coincide with Olbers Regio. It was accepted by the IAU, although it disrupts the maps prepared by the Dawn team, which had been positioned so they would not bisect any major surface features. Vesta is the second most massive body in the asteroid belt , although it is only 28% as massive as Ceres, the most massive body. Vesta
635-478: A crust, a mantle and a core. No meteorites from Ceres have been found on Earth. Vesta, too, has a differentiated interior, though it formed inside the Solar System's frost line , and so is devoid of water; its composition is mainly of basaltic rock with minerals such as olivine. Aside from the large crater at its southern pole, Rheasilvia , Vesta also has an ellipsoidal shape. Vesta is the parent body of
762-644: A diameter of one kilometer or larger. A small number of NEAs are extinct comets that have lost their volatile surface materials, although having a faint or intermittent comet-like tail does not necessarily result in a classification as a near-Earth comet, making the boundaries somewhat fuzzy. The rest of the near-Earth asteroids are driven out of the asteroid belt by gravitational interactions with Jupiter . Many asteroids have natural satellites ( minor-planet moons ). As of October 2021 , there were 85 NEAs known to have at least one moon, including three known to have two moons. The asteroid 3122 Florence , one of
889-436: A differentiated interior. Vesta is only slightly larger ( 525.4 ± 0.2 km ) than 2 Pallas ( 512 ± 3 km ) in mean diameter, but is about 25% more massive. Vesta's shape is close to a gravitationally relaxed oblate spheroid , but the large concavity and protrusion at the southern pole (see ' Surface features ' below) combined with a mass less than 5 × 10 kg precluded Vesta from automatically being considered
1016-407: A few other asteroids discovered over the next few years. 20 Massalia was the first asteroid that was not assigned an iconic symbol, and no iconic symbols were created after the 1855 discovery of 37 Fides . Many asteroids are the shattered remnants of planetesimals , bodies within the young Sun's solar nebula that never grew large enough to become planets . It is thought that planetesimals in
1143-487: A group headed by Franz Xaver von Zach , editor of the German astronomical journal Monatliche Correspondenz (Monthly Correspondence), sent requests to 24 experienced astronomers (whom he dubbed the " celestial police "), asking that they combine their efforts and begin a methodical search for the expected planet. Although they did not discover Ceres, they later found the asteroids 2 Pallas , 3 Juno and 4 Vesta . One of
1270-425: A larger body. Because the asteroid Juno had been discovered in 1804, this made Vesta the fourth object to be identified in the region that is now known as the asteroid belt . The discovery was announced in a letter addressed to German astronomer Johann H. Schröter dated 31 March. Because Olbers already had credit for discovering a planet (Pallas; at the time, the asteroids were considered to be planets), he gave
1397-514: A letter with his proposal to the British astronomer William Herschel , suggesting that a search near the locations where the orbits of Ceres and Pallas intersected might reveal more fragments. These orbital intersections were located in the constellations of Cetus and Virgo . Olbers commenced his search in 1802, and on 29 March 1807 he discovered Vesta in the constellation Virgo—a coincidence, because Ceres, Pallas, and Vesta are not fragments of
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#17327985784531524-443: A magnitude of from +6.5 to +7.3. Even when in conjunction with the Sun, Vesta will have a magnitude around +8.5; thus from a pollution-free sky it can be observed with binoculars even at elongations much smaller than near opposition. In 2010, Vesta reached opposition in the constellation of Leo on the night of 17–18 February, at about magnitude 6.1, a brightness that makes it visible in binocular range but generally not for
1651-521: A number of meteorites suspected to be Vestan fragments. It is estimated that 1 out of 16 meteorites originated from Vesta. The other identified Solar System samples are from Earth itself, meteorites from Mars , meteorites from the Moon , and samples returned from the Moon , the comet Wild 2 , and the asteroids 25143 Itokawa , 162173 Ryugu , and 101955 Bennu . In 1981, a proposal for an asteroid mission
1778-465: A numerical procession known as the Titius–Bode law (now discredited). Except for an unexplained gap between Mars and Jupiter, Bode's formula seemed to predict the orbits of the known planets. He wrote the following explanation for the existence of a "missing planet": This latter point seems in particular to follow from the astonishing relation which the known six planets observe in their distances from
1905-413: A one-year exploration and left the orbit of Vesta on 5 September 2012 en route to its final destination, Ceres. Researchers continue to examine data collected by Dawn for additional insights into the formation and history of Vesta. Heinrich Olbers discovered Pallas in 1802, the year after the discovery of Ceres . He proposed that the two objects were the remnants of a destroyed planet . He sent
2032-604: A perihelion less than this is classed as a near-Earth object even though it is crossing the orbit of Mars as well as crossing (or coming near to) that of Earth. Nevertheless, these objects are listed on this page. A grazer is an object with a perihelion below the aphelion of Mars (1.67 AU) but above the Martian perihelion (1.38 AU). The JPL SBDB lists 13,500 Mars-crossing asteroids. Only 18 MCAs are brighter than absolute magnitude (H) 12.5, which typically makes these asteroids with H<12.5 more than 13 km in diameter depending on
2159-450: A process that can happen only in a body that, like Vesta, is differentiated. Vesta's differentiation is one of the reasons why scientists consider it a protoplanet. Alternatively, it is proposed that the troughs may be radial sculptures created by secondary cratering from Rheasilvia. Compositional information from the visible and infrared spectrometer (VIR), gamma-ray and neutron detector (GRaND), and framing camera (FC), all indicate that
2286-432: A protoplanet. However, the presence of iron meteorites and achondritic meteorite classes without identified parent bodies indicates that there once were other differentiated planetesimals with igneous histories, which have since been shattered by impacts. On the basis of the sizes of V-type asteroids (thought to be pieces of Vesta's crust ejected during large impacts), and the depth of Rheasilvia crater (see below),
2413-573: A relatively reflective surface , is normally visible to the naked eye in dark skies when it is favorably positioned. Rarely, small asteroids passing close to Earth may be briefly visible to the naked eye. As of April 2022 , the Minor Planet Center had data on 1,199,224 minor planets in the inner and outer Solar System, of which about 614,690 had enough information to be given numbered designations. In 1772, German astronomer Johann Elert Bode , citing Johann Daniel Titius , published
2540-440: A rich source of information about Vesta. Vesta is the brightest asteroid visible from Earth. It is regularly as bright as magnitude 5.1, at which times it is faintly visible to the naked eye. Its maximum distance from the Sun is slightly greater than the minimum distance of Ceres from the Sun, although its orbit lies entirely within that of Ceres. NASA's Dawn spacecraft entered orbit around Vesta on 16 July 2011 for
2667-401: A sample in 2020 which was delivered back to Earth in 2023. NASA's Lucy , launched in 2021, is tasked with studying ten different asteroids, two from the main belt and eight Jupiter trojans . Psyche , launched October 2023, aims to study the metallic asteroid Psyche . Near-Earth asteroids have the potential for catastrophic consequences if they strike Earth, with a notable example being
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#17327985784532794-532: A series of days. Second, the two films or plates of the same region were viewed under a stereoscope . A body in orbit around the Sun would move slightly between the pair of films. Under the stereoscope, the image of the body would seem to float slightly above the background of stars. Third, once a moving body was identified, its location would be measured precisely using a digitizing microscope. The location would be measured relative to known star locations. These first three steps do not constitute asteroid discovery:
2921-565: A single orbit. If so, the object receives a catalogue number and the observer of the first apparition with a calculated orbit is declared the discoverer, and granted the honor of naming the object subject to the approval of the International Astronomical Union . By 1851, the Royal Astronomical Society decided that asteroids were being discovered at such a rapid rate that a different system
3048-407: A survey orbit, two high-altitude orbits (60–70 m/pixel) and a low-altitude mapping orbit (20 m/pixel), including digital terrain models, videos and atlases. Scientists also used Dawn to calculate Vesta's precise mass and gravity field. The subsequent determination of the J 2 component yielded a core diameter estimate of about 220 km assuming a crustal density similar to that of
3175-417: A traditional symbol for a star, as the generic symbol for an asteroid. The circle was then numbered in order of discovery to indicate a specific asteroid. The numbered-circle convention was quickly adopted by astronomers, and the next asteroid to be discovered ( 16 Psyche , in 1852) was the first to be designated in that way at the time of its discovery. However, Psyche was given an iconic symbol as well, as were
3302-461: Is 270 km (168 mi) across. More-recent, sharper craters range up to 158 km (98 mi) Varronilla and 196 km (122 mi) Postumia. Dust fills up some craters, creating so-called dust ponds . They are a phenomenon where pockets of Dust are seen in Celestial bodies without a significant atmosphere. These are smooth deposits of dust accumulated in depressions on the surface of
3429-401: Is able to capture other asteroids into temporary 1:1 resonant orbital relationships (for periods up to 2 million years or more) and about forty such objects have been identified. Decameter-sized objects detected in the vicinity of Vesta by Dawn may be such quasi-satellites rather than proper satellites. Vesta's rotation is relatively fast for an asteroid (5.342 h) and prograde , with
3556-410: Is also known. Numerical orbital dynamics stability simulations indicate that Saturn and Uranus probably do not have any primordial trojans. Near-Earth asteroids, or NEAs, are asteroids that have orbits that pass close to that of Earth. Asteroids that actually cross Earth's orbital path are known as Earth-crossers . As of April 2022 , a total of 28,772 near-Earth asteroids were known; 878 have
3683-418: Is because space weathering acts differently. Vesta's surface shows no significant trace of nanophase iron because the impact speeds on Vesta are too low to make rock melting and vaporization an appreciable process. Instead, regolith evolution is dominated by brecciation and subsequent mixing of bright and dark components. The dark component is probably due to the infall of carbonaceous material, whereas
3810-427: Is by far the largest asteroid, with a diameter of 940 km (580 mi). The next largest are 4 Vesta and 2 Pallas , both with diameters of just over 500 km (300 mi). Vesta is the brightest of the four main-belt asteroids that can, on occasion, be visible to the naked eye. On some rare occasions, a near-Earth asteroid may briefly become visible without technical aid; see 99942 Apophis . The mass of all
3937-489: Is called the 'hearth-god(dess) star', 灶神星 Zàoshénxīng , naming the asteroid for Vesta's role, similar to the Chinese names of Uranus , Neptune , and Pluto . Upon its discovery, Vesta was, like Ceres, Pallas, and Juno before it, classified as a planet and given a planetary symbol . The symbol represented the altar of Vesta with its sacred fire and was designed by Gauss. In Gauss's conception, now obsolete, this
List of Mars-crossing minor planets - Misplaced Pages Continue
4064-433: Is close to the modern value for the mean diameter, but the subsequent estimates ranged from a low of 390 km (242 mi) up to a high of 602 km (374 mi) during the next century. The measured estimates were based on photometry . In 1989, speckle interferometry was used to measure a dimension that varied between 498 and 548 km (309 and 341 mi) during the rotational period. In 1991, an occultation of
4191-467: Is estimated that the impact responsible excavated about 1% of the volume of Vesta, and it is likely that the Vesta family and V-type asteroids are the products of this collision. If this is the case, then the fact that 10 km (6.2 mi) fragments have survived bombardment until the present indicates that the crater is at most only about 1 billion years old. It would also be the site of origin of
4318-529: Is however the most massive body that formed in the asteroid belt, as Ceres is believed to have formed between Jupiter and Saturn. Vesta's density is lower than those of the four terrestrial planets but is higher than those of most asteroids, as well as all of the moons in the Solar System except Io . Vesta's surface area is about the same as the land area of Pakistan , Venezuela , Tanzania , or Nigeria ; slightly under 900,000 square kilometres (350,000 sq mi; 90,000,000 ha; 220,000,000 acres). It has
4445-417: Is named after Vesta , the virgin goddess of home and hearth from Roman mythology . Vesta is thought to be the second-largest asteroid , both by mass and by volume, after the dwarf planet Ceres . Measurements give it a nominal volume only slightly larger than that of Pallas (about 5% greater), but it is 25% to 30% more massive. It constitutes an estimated 9% of the mass of the asteroid belt . Vesta
4572-506: Is occasionally visible to the naked eye from dark skies (without light pollution ). In May and June 2007, Vesta reached a peak magnitude of +5.4, the brightest since 1989. At that time, opposition and perihelion were only a few weeks apart. It was brighter still at its 22 June 2018 opposition, reaching a magnitude of +5.3. Less favorable oppositions during late autumn 2008 in the Northern Hemisphere still had Vesta at
4699-853: Is only 3% that of Earth's Moon . The majority of main belt asteroids follow slightly elliptical, stable orbits, revolving in the same direction as the Earth and taking from three to six years to complete a full circuit of the Sun. Asteroids have historically been observed from Earth. The first close-up observation of an asteroid was made by the Galileo spacecraft . Several dedicated missions to asteroids were subsequently launched by NASA and JAXA , with plans for other missions in progress. NASA's NEAR Shoemaker studied Eros , and Dawn observed Vesta and Ceres . JAXA's missions Hayabusa and Hayabusa2 studied and returned samples of Itokawa and Ryugu , respectively. OSIRIS-REx studied Bennu , collecting
4826-576: Is proposed to be degassing of impact-heated volatile-bearing material. Along with the pitted terrain, curvilinear gullies are found in Marcia and Cornelia craters. The curvilinear gullies end in lobate deposits, which are sometimes covered by pitted terrain, and are proposed to form by the transient flow of liquid water after buried deposits of ice were melted by the heat of the impacts. Hydrated materials have also been detected, many of which are associated with areas of dark material. Consequently, dark material
4953-544: Is so slow and rather uniform, it has occurred to me several times that it might be something better than a comet". In April, Piazzi sent his complete observations to Oriani, Bode, and French astronomer Jérôme Lalande . The information was published in the September 1801 issue of the Monatliche Correspondenz . By this time, the apparent position of Ceres had changed (mostly due to Earth's motion around
5080-484: Is that both moons may be captured main-belt asteroids . Both moons have very circular orbits which lie almost exactly in Mars's equatorial plane , and hence a capture origin requires a mechanism for circularizing the initially highly eccentric orbit, and adjusting its inclination into the equatorial plane, most probably by a combination of atmospheric drag and tidal forces , although it is not clear whether sufficient time
5207-439: Is that comets typically have more eccentric orbits than most asteroids; highly eccentric asteroids are probably dormant or extinct comets. The minor planets beyond Jupiter's orbit are sometimes also called "asteroids", especially in popular presentations. However, it is becoming increasingly common for the term asteroid to be restricted to minor planets of the inner Solar System. Therefore, this article will restrict itself for
List of Mars-crossing minor planets - Misplaced Pages Continue
5334-413: Is the only known remaining rocky protoplanet (with a differentiated interior ) of the kind that formed the terrestrial planets . Numerous fragments of Vesta were ejected by collisions one and two billion years ago that left two enormous craters occupying much of Vesta's southern hemisphere. Debris from these events has fallen to Earth as howardite–eucrite–diogenite (HED) meteorites , which have been
5461-487: Is the youngest and cross-cuts Calpurnia. Minucia is the oldest. The majority of the equatorial region of Vesta is sculpted by a series of parallel troughs designated Divalia Fossae ; its longest trough is 10–20 kilometres (6.2–12.4 mi) wide and 465 kilometres (289 mi) long. Despite the fact that Vesta is a one-seventh the size of the Moon, Divalia Fossae dwarfs the Grand Canyon . A second series, inclined to
5588-599: Is thought to be largely composed of carbonaceous chondrite, which was deposited on the surface by impacts. Carbonaceous chondrites are comparatively rich in mineralogically bound OH. A large collection of potential samples from Vesta is accessible to scientists, in the form of over 1200 HED meteorites (Vestan achondrites ), giving insight into Vesta's geologic history and structure. NASA Infrared Telescope Facility (NASA IRTF) studies of asteroid (237442) 1999 TA 10 suggest that it originated from deeper within Vesta than
5715-658: The Chicxulub impact , widely thought to have induced the Cretaceous–Paleogene mass extinction . As an experiment to meet this danger, in September 2022 the Double Asteroid Redirection Test spacecraft successfully altered the orbit of the non-threatening asteroid Dimorphos by crashing into it. In 2006, the International Astronomical Union (IAU) introduced the currently preferred broad term small Solar System body , defined as an object in
5842-505: The Discovery Program , which was intended to be a series of low-cost scientific missions. In 1996, the program's study team recommended a mission to explore the asteroid belt using a spacecraft with an ion engine as a high priority. Funding for this program remained problematic for several years, but by 2004 the Dawn vehicle had passed its critical design review and construction proceeded. It launched on 27 September 2007 as
5969-575: The HED meteorites . All the known V-type asteroids taken together account for only about 6% of the ejected volume, with the rest presumably either in small fragments, ejected by approaching the 3:1 Kirkwood gap , or perturbed away by the Yarkovsky effect or radiation pressure . Spectroscopic analyses of the Hubble images have shown that this crater has penetrated deep through several distinct layers of
6096-587: The Keck Observatory ). The arrival of Dawn in July 2011 revealed the complex surface of Vesta in detail. The most prominent of these surface features are two enormous impact basins, the 500-kilometre (311 mi)-wide Rheasilvia, centered near the south pole; and the 400 km (249 mi) wide Veneneia. The Rheasilvia impact basin is younger and overlies the Veneneia. The Dawn science team named
6223-520: The Moon . L 4 ( leading cloud ): L 5 ( trailing cloud ): Candidates These objects are not catalogued as Mars-crossers in databases such as the Jet Propulsion Laboratory 's online Small-body Database Browser . Instead, they are categorized as Near Earth Objects (NEOs). Asteroid An asteroid is a minor planet —an object that is neither a true planet nor an identified comet — that orbits within
6350-462: The Solar System that is neither a planet , a dwarf planet , nor a natural satellite ; this includes asteroids, comets, and more recently discovered classes. According to IAU, "the term 'minor planet' may still be used, but generally, 'Small Solar System Body' will be preferred." Historically, the first discovered asteroid, Ceres , was at first considered a new planet. It was followed by
6477-473: The Vestian family and other V-type asteroids , and is the source of the HED meteorites , which constitute 5% of all meteorites on Earth. 4 Vesta Vesta ( minor-planet designation : 4 Vesta ) is one of the largest objects in the asteroid belt , with a mean diameter of 525 kilometres (326 mi). It was discovered by the German astronomer Heinrich Wilhelm Matthias Olbers on 29 March 1807 and
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#17327985784536604-424: The albedo . The smallest known MCAs have an absolute magnitude (H) of around 24 and are typically less than 100 meters in diameter. There are over 21,600 known Mars-crossers of which only 5751 have received a MPC number. Earth having more gravity and surface area than Mars attracts more impactors than Mars. Earth is impacted about 20 times more than the Moon, and Mars only gets impacted about 3 to 5 times more than
6731-403: The inner Solar System . They are rocky, metallic, or icy bodies with no atmosphere, classified as C-type ( carbonaceous ), M-type ( metallic ), or S-type ( silicaceous ). The size and shape of asteroids vary significantly, ranging from small rubble piles under a kilometer across and larger than meteoroids , to Ceres , a dwarf planet almost 1000 km in diameter. A body is classified as
6858-454: The naked eye . Under perfect dark sky conditions where all light pollution is absent it might be visible to an experienced observer without the use of a telescope or binoculars. Vesta came to opposition again on 5 August 2011, in the constellation of Capricornus at about magnitude 5.6. Vesta was at opposition again on 9 December 2012. According to Sky and Telescope magazine, this year Vesta came within about 6 degrees of 1 Ceres during
6985-467: The protoplanetary disk , and in this region the accretion of planetesimals into planets during the formative period of the Solar System was prevented by large gravitational perturbations by Jupiter . Contrary to popular imagery, the asteroid belt is mostly empty. The asteroids are spread over such a large volume that reaching an asteroid without aiming carefully would be improbable. Nonetheless, hundreds of thousands of asteroids are currently known, and
7112-421: The thermal infrared suggest a composition containing mainly phyllosilicates , which are well known from the surface of Mars. The spectra are distinct from those of all classes of chondrite meteorites, again pointing away from an asteroidal origin. Both sets of findings support an origin of Phobos from material ejected by an impact on Mars that reaccreted in Martian orbit, similar to the prevailing theory for
7239-527: The 1980s by France, Germany, Italy and the United States, but none were approved. Exploration of Vesta by fly-by and impacting penetrator was the second main target of the first plan of the multi-aimed Soviet Vesta mission , developed in cooperation with European countries for realisation in 1991–1994 but canceled due to the dissolution of the Soviet Union . In the early 1990s, NASA initiated
7366-559: The Ancient Greek ἀστήρ astēr 'star, planet'. In the early second half of the 19th century, the terms asteroid and planet (not always qualified as "minor") were still used interchangeably. Traditionally, small bodies orbiting the Sun were classified as comets , asteroids, or meteoroids , with anything smaller than one meter across being called a meteoroid. The term asteroid, never officially defined, can be informally used to mean "an irregularly shaped rocky body orbiting
7493-555: The HED meteorites. Vesta is thought to consist of a metallic iron–nickel core 214–226 km in diameter, an overlying rocky olivine mantle , with a surface crust . From the first appearance of calcium–aluminium-rich inclusions (the first solid matter in the Solar System , forming about 4.567 billion years ago), a likely time line is as follows: Vesta is the only known intact asteroid that has been resurfaced in this manner. Because of this, some scientists refer to Vesta as
7620-531: The HED. Dawn data can be accessed by the public at the UCLA website. Vesta comes into view as the Dawn spacecraft approaches and enters orbit: Detailed images retrieved during the high-altitude (60–70 m/pixel) and low-altitude (~20 m/pixel) mapping orbits are available on the Dawn Mission website of JPL/NASA. Its size and unusually bright surface make Vesta the brightest asteroid, and it
7747-652: The Jovian disruption. Ceres and Vesta grew large enough to melt and differentiate , with heavy metallic elements sinking to the core, leaving rocky minerals in the crust. In the Nice model , many Kuiper-belt objects are captured in the outer asteroid belt, at distances greater than 2.6 AU. Most were later ejected by Jupiter, but those that remained may be the D-type asteroids , and possibly include Ceres. Various dynamical groups of asteroids have been discovered orbiting in
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#17327985784537874-448: The Solar System was thought to have eleven planets. However, in 1845, new asteroids started being discovered at a rapid pace, and by 1851 there were fifteen, each with its own symbol, in addition to the eight major planets ( Neptune had been discovered in 1846). It soon became clear that it would be impractical to continue inventing new planetary symbols indefinitely, and some of the existing ones proved difficult to draw quickly. That year,
8001-486: The Sun that does not qualify as a planet or a dwarf planet under the IAU definitions". The main difference between an asteroid and a comet is that a comet shows a coma (tail) due to sublimation of its near-surface ices by solar radiation. A few objects were first classified as minor planets but later showed evidence of cometary activity. Conversely, some (perhaps all) comets are eventually depleted of their surface volatile ices and become asteroid-like. A further distinction
8128-455: The Sun), and was too close to the Sun's glare for other astronomers to confirm Piazzi's observations. Toward the end of the year, Ceres should have been visible again, but after such a long time it was difficult to predict its exact position. To recover Ceres, mathematician Carl Friedrich Gauss , then 24 years old, developed an efficient method of orbit determination . In a few weeks, he predicted
8255-401: The Sun, their volatile ices would sublimate , and traditional approaches would classify them as comets. The Kuiper-belt bodies are called "objects" partly to avoid the need to classify them as asteroids or comets. They are thought to be predominantly comet-like in composition, though some may be more akin to asteroids. Most do not have the highly eccentric orbits associated with comets, and
8382-489: The Sun. Let the distance from the Sun to Saturn be taken as 100, then Mercury is separated by 4 such parts from the Sun. Venus is 4 + 3 = 7. The Earth 4 + 6 = 10. Mars 4 + 12 = 16. Now comes a gap in this so orderly progression. After Mars there follows a space of 4 + 24 = 28 parts, in which no planet has yet been seen. Can one believe that the Founder of the universe had left this space empty? Certainly not. From here we come to
8509-544: The accretion epoch), whereas most smaller asteroids are products of fragmentation of primordial asteroids. The primordial population of the main belt was probably 200 times what it is today. Three largest objects in the asteroid belt, Ceres , Vesta , and Pallas , are intact protoplanets that share many characteristics common to planets, and are atypical compared to the majority of irregularly shaped asteroids. The fourth-largest asteroid, Hygiea , appears nearly spherical although it may have an undifferentiated interior, like
8636-502: The asteroid belt evolved much like the rest of objects in the solar nebula until Jupiter neared its current mass, at which point excitation from orbital resonances with Jupiter ejected over 99% of planetesimals in the belt. Simulations and a discontinuity in spin rate and spectral properties suggest that asteroids larger than approximately 120 km (75 mi) in diameter accreted during that early era, whereas smaller bodies are fragments from collisions between asteroids during or after
8763-510: The asteroid belt is estimated to be 2.39 × 10 kg, which is just 3% of the mass of the Moon; the mass of the Kuiper Belt and Scattered Disk is over 100 times as large. The four largest objects, Ceres, Vesta, Pallas, and Hygiea, account for maybe 62% of the belt's total mass, with 39% accounted for by Ceres alone. Trojans are populations that share an orbit with a larger planet or moon, but do not collide with it because they orbit in one of
8890-501: The asteroid later named 5 Astraea . It was the first new asteroid discovery in 38 years. Carl Friedrich Gauss was given the honor of naming the asteroid. After this, other astronomers joined; 15 asteroids were found by the end of 1851. In 1868, when James Craig Watson discovered the 100th asteroid, the French Academy of Sciences engraved the faces of Karl Theodor Robert Luther , John Russell Hind , and Hermann Goldschmidt ,
9017-610: The astronomers selected for the search was Giuseppe Piazzi , a Catholic priest at the Academy of Palermo, Sicily. Before receiving his invitation to join the group, Piazzi discovered Ceres on 1 January 1801. He was searching for "the 87th [star] of the Catalogue of the Zodiacal stars of Mr la Caille ", but found that "it was preceded by another". Instead of a star, Piazzi had found a moving star-like object, which he first thought
9144-572: The body (like craters), contrasting from the Rocky terrain around them. On the surface of Vesta, we have identified both type 1 (formed from impact melt) and type 2 (electrostatically made) dust ponds within 0˚–30°N/S, that is, Equatorial region. 10 craters have been identified with such formations. The "snowman craters" are a group of three adjacent craters in Vesta's northern hemisphere. Their official names, from largest to smallest (west to east), are Marcia, Calpurnia, and Minucia. Marcia
9271-496: The bright component is the original Vesta basaltic soil. Some small Solar System bodies are suspected to be fragments of Vesta caused by impacts. The Vestian asteroids and HED meteorites are examples. The V-type asteroid 1929 Kollaa has been determined to have a composition akin to cumulate eucrite meteorites, indicating its origin deep within Vesta's crust. Vesta is currently one of only eight identified Solar System bodies of which we have physical samples, coming from
9398-435: The center of Olbers Regio , a dark feature 200 km across. When Dawn arrived at Vesta, mission scientists found that the location of the pole assumed by the IAU was off by 10°, so that the IAU coordinate system drifted across the surface of Vesta at 0.06° per year, and also that Olbers Regio was not discernible from up close, and so was not adequate to define the prime meridian with the precision they needed. They corrected
9525-543: The circle had been simplified to parentheses, (4) Vesta , which were easier to typeset. Other punctuation, such as 4) Vesta and 4, Vesta , was also briefly used, but had more or less completely died out by 1949. Photometric observations of Vesta were made at the Harvard College Observatory in 1880–1882 and at the Observatoire de Toulouse in 1909. These and other observations allowed
9652-539: The core, role of water in asteroid evolution and what meteorites found on Earth come from these bodies, with the ultimate goal of understanding the conditions and processes present at the solar system's earliest epoch and the role of water content and size in planetary evolution. Vesta became the first asteroid to have its mass determined. Every 18 years, the asteroid 197 Arete approaches within 0.04 AU of Vesta. In 1966, based upon observations of Vesta's gravitational perturbations of Arete, Hans G. Hertz estimated
9779-415: The crust is thought to be roughly 10 kilometres (6 mi) thick. Findings from the Dawn spacecraft have found evidence that the troughs that wrap around Vesta could be graben formed by impact-induced faulting (see Troughs section above), meaning that Vesta has more complex geology than other asteroids. Vesta's differentiated interior implies that it was in hydrostatic equilibrium and thus a dwarf planet in
9906-439: The crust, and possibly into the mantle , as indicated by spectral signatures of olivine . The large peak at the center of Rheasilvia is 20 to 25 km (12–16 mi) high and 180 km (112 mi) wide, and is possibly a result of a planetary-scale impact. Several old, degraded craters approach Rheasilvia and Veneneia in size, although none are quite so large. They include Feralia Planitia , shown at right, which
10033-466: The discovery of other similar bodies, which with the equipment of the time appeared to be points of light like stars, showing little or no planetary disc, though readily distinguishable from stars due to their apparent motions. This prompted the astronomer Sir William Herschel to propose the term asteroid , coined in Greek as ἀστεροειδής, or asteroeidēs , meaning 'star-like, star-shaped', and derived from
10160-406: The distance of Jupiter by 4 + 48 = 52 parts, and finally to that of Saturn by 4 + 96 = 100 parts. Bode's formula predicted another planet would be found with an orbital radius near 2.8 astronomical units (AU), or 420 million km, from the Sun. The Titius–Bode law got a boost with William Herschel 's discovery of Uranus near the predicted distance for a planet beyond Saturn . In 1800,
10287-503: The equator, is found further north. This northern trough system is named Saturnalia Fossae , with its largest trough being roughly 40 km wide and over 370 km long. These troughs are thought to be large-scale graben resulting from the impacts that created Rheasilvia and Veneneia craters, respectively. They are some of the longest chasms in the Solar System , nearly as long as Ithaca Chasma on Tethys . The troughs may be graben that formed after another asteroid collided with Vesta,
10414-421: The first space mission to Vesta. On 3 May 2011, Dawn acquired its first targeting image 1.2 million kilometers from Vesta. On 16 July 2011, NASA confirmed that it received telemetry from Dawn indicating that the spacecraft successfully entered Vesta's orbit. It was scheduled to orbit Vesta for one year, until July 2012. Dawn 's arrival coincided with late summer in the southern hemisphere of Vesta, with
10541-472: The fourth, when I had the satisfaction to see it had moved at the same rate as on the preceding days. Piazzi observed Ceres a total of 24 times, the final time on 11 February 1801, when illness interrupted his work. He announced his discovery on 24 January 1801 in letters to only two fellow astronomers, his compatriot Barnaba Oriani of Milan and Bode in Berlin. He reported it as a comet but "since its movement
10668-466: The honor of naming his new discovery to German mathematician Carl Friedrich Gauss , whose orbital calculations had enabled astronomers to confirm the existence of Ceres, the first asteroid, and who had computed the orbit of the new planet in the remarkably short time of 10 hours. Gauss decided on the Roman virgin goddess of home and hearth, Vesta . Vesta was the fourth asteroid to be discovered, hence
10795-543: The inner Solar System. Their orbits are perturbed by the gravity of other bodies in the Solar System and by the Yarkovsky effect . Significant populations include: The majority of known asteroids orbit within the asteroid belt between the orbits of Mars and Jupiter , generally in relatively low- eccentricity (i.e. not very elongated) orbits. This belt is estimated to contain between 1.1 and 1.9 million asteroids larger than 1 km (0.6 mi) in diameter, and millions of smaller ones. These asteroids may be remnants of
10922-492: The inner asteroid belt, interior to the Kirkwood gap at 2.50 AU. Its orbit is moderately inclined ( i = 7.1°, compared to 7° for Mercury and 17° for Pluto ) and moderately eccentric ( e = 0.09, about the same as for Mars). True orbital resonances between asteroids are considered unlikely. Because of their small masses relative to their large separations, such relationships should be very rare. Nevertheless, Vesta
11049-421: The large crater at Vesta's south pole ( Rheasilvia ) in sunlight. Because a season on Vesta lasts eleven months, the northern hemisphere, including anticipated compression fractures opposite the crater, would become visible to Dawn 's cameras before it left orbit. Dawn left orbit around Vesta on 4 September 2012 11:26 p.m. PDT to travel to Ceres . NASA/DLR released imagery and summary information from
11176-404: The largest minor planets—those massive enough to have become ellipsoidal under their own gravity. Only the largest object in the asteroid belt has been placed in this category: Ceres , at about 975 km (606 mi) across. Despite their large numbers, asteroids are a relatively recent discovery, with the first one—Ceres—only being identified in 1801. Only one asteroid, 4 Vesta , which has
11303-720: The largest potentially hazardous asteroids with a diameter of 4.5 km (2.8 mi), has two moons measuring 100–300 m (330–980 ft) across, which were discovered by radar imaging during the asteroid's 2017 approach to Earth. Near-Earth asteroids are divided into groups based on their semi-major axis (a), perihelion distance (q), and aphelion distance (Q): It is unclear whether Martian moons Phobos and Deimos are captured asteroids or were formed due to impact event on Mars. Phobos and Deimos both have much in common with carbonaceous C-type asteroids , with spectra , albedo , and density very similar to those of C- or D-type asteroids. Based on their similarity, one hypothesis
11430-512: The law was a coincidence. Piazzi named the newly discovered object Ceres Ferdinandea, "in honor of the patron goddess of Sicily and of King Ferdinand of Bourbon ". Three other asteroids ( 2 Pallas , 3 Juno , and 4 Vesta ) were discovered by von Zach's group over the next few years, with Vesta found in 1807. No new asteroids were discovered until 1845. Amateur astronomer Karl Ludwig Hencke started his searches of new asteroids in 1830, and fifteen years later, while looking for Vesta, he found
11557-416: The majority of asteroids. The four largest asteroids constitute half the mass of the asteroid belt. Ceres is the only asteroid that appears to have a plastic shape under its own gravity and hence the only one that is a dwarf planet . It has a much higher absolute magnitude than the other asteroids, of around 3.32, and may possess a surface layer of ice. Like the planets, Ceres is differentiated: it has
11684-584: The majority of the surface composition of Vesta is consistent with the composition of the howardite, eucrite, and diogenite meteorites. The Rheasilvia region is richest in diogenite, consistent with the Rheasilvia-forming impact excavating material from deeper within Vesta. The presence of olivine within the Rheasilvia region would also be consistent with excavation of mantle material. However, olivine has only been detected in localized regions of
11811-417: The mass of Vesta at (1.20 ± 0.08) × 10 M ☉ ( solar masses ). More refined estimates followed, and in 2001 the perturbations of 17 Thetis were used to calculate the mass of Vesta to be (1.31 ± 0.02) × 10 M ☉ . Dawn determined it to be 1.3029 × 10 M ☉ . Vesta orbits the Sun between Mars and Jupiter, within the asteroid belt , with a period of 3.6 Earth years, specifically in
11938-514: The most part to the classical asteroids: objects of the asteroid belt , Jupiter trojans , and near-Earth objects . For almost two centuries after the discovery of Ceres in 1801, all known asteroids spent most of their time at or within the orbit of Jupiter, though a few, such as 944 Hidalgo , ventured farther for part of their orbit. Starting in 1977 with 2060 Chiron , astronomers discovered small bodies that permanently resided further out than Jupiter, now called centaurs . In 1992, 15760 Albion
12065-426: The north pole pointing in the direction of right ascension 20 h 32 min, declination +48° (in the constellation Cygnus ) with an uncertainty of about 10°. This gives an axial tilt of 29°. Two longitudinal coordinate systems are used for Vesta, with prime meridians separated by 150°. The IAU established a coordinate system in 1997 based on Hubble photos, with the prime meridian running through
12192-501: The northern hemisphere, not within Rheasilvia. The origin of this olivine is currently unclear. Though olivine was expected by astronomers to have originated from Vesta's mantle prior to the arrival of the Dawn orbiter, the lack of olivine within the Rheasilvia and Veneneia impact basins complicates this view. Both impact basins excavated Vestian material down to 60–100 km, far deeper than the expected thickness of ~30–40 km for Vesta's crust. Vesta's crust may be far thicker than expected or
12319-526: The number 4 in its formal designation. The name Vesta , or national variants thereof, is in international use with two exceptions: Greece and China. In Greek , the name adopted was the Hellenic equivalent of Vesta, Hestia ( 4 Εστία ); in English, that name is used for 46 Hestia (Greeks use the name "Hestia" for both, with the minor-planet numbers used for disambiguation). In Chinese , Vesta
12446-516: The number—e.g. (433) Eros—but dropping the parentheses is quite common. Informally, it is also common to drop the number altogether, or to drop it after the first mention when a name is repeated in running text. In addition, names can be proposed by the asteroid's discoverer, within guidelines established by the International Astronomical Union. The first asteroids to be discovered were assigned iconic symbols like
12573-436: The objects of the asteroid belt , lying between the orbits of Mars and Jupiter , is estimated to be (2394 ± 6) × 10 kg , ≈ 3.25% of the mass of the Moon. Of this, Ceres comprises 938 × 10 kg , about 40% of the total. Adding in the next three most massive objects, Vesta (11%), Pallas (8.5%), and Hygiea (3–4%), brings this figure up to a bit over 60%, whereas the next seven most-massive asteroids bring
12700-463: The observer has only found an apparition, which gets a provisional designation , made up of the year of discovery, a letter representing the half-month of discovery, and finally a letter and a number indicating the discovery's sequential number (example: 1998 FJ 74 ). The last step is sending the locations and time of observations to the Minor Planet Center , where computer programs determine whether an apparition ties together earlier apparitions into
12827-453: The ones so far discovered are larger than traditional comet nuclei . Other recent observations, such as the analysis of the cometary dust collected by the Stardust probe, are increasingly blurring the distinction between comets and asteroids, suggesting "a continuum between asteroids and comets" rather than a sharp dividing line. In 2006, the IAU created the class of dwarf planets for
12954-560: The ones traditionally used to designate the planets. By 1852 there were two dozen asteroid symbols, which often occurred in multiple variants. In 1851, after the fifteenth asteroid, Eunomia , had been discovered, Johann Franz Encke made a major change in the upcoming 1854 edition of the Berliner Astronomisches Jahrbuch (BAJ, Berlin Astronomical Yearbook ). He introduced a disk (circle),
13081-566: The origin of Earth's moon. Asteroids vary greatly in size, from almost 1000 km for the largest down to rocks just 1 meter across, below which an object is classified as a meteoroid . The three largest are very much like miniature planets: they are roughly spherical, have at least partly differentiated interiors, and are thought to be surviving protoplanets . The vast majority, however, are much smaller and are irregularly shaped; they are thought to be either battered planetesimals or fragments of larger bodies. The dwarf planet Ceres
13208-405: The past, but it is not today. The impacts that created the Rheasilvia and Veneneia craters occurred when Vesta was no longer warm and plastic enough to return to an equilibrium shape, distorting its once rounded shape and prohibiting it from being classified as a dwarf planet today. Vesta's surface is covered by regolith distinct from that found on the Moon or asteroids such as Itokawa . This
13335-455: The path of Ceres and sent his results to von Zach. On 31 December 1801, von Zach and fellow celestial policeman Heinrich W. M. Olbers found Ceres near the predicted position and thus recovered it. At 2.8 AU from the Sun, Ceres appeared to fit the Titius–Bode law almost perfectly; however, Neptune, once discovered in 1846, was 8 AU closer than predicted, leading most astronomers to conclude that
13462-404: The pole, but also established a new prime meridian 4° from the center of Claudia , a sharply defined crater 700 meters across, which they say results in a more logical set of mapping quadrangles. All NASA publications, including images and maps of Vesta, use the Claudian meridian, which is unacceptable to the IAU. The IAU Working Group on Cartographic Coordinates and Rotational Elements recommended
13589-472: The problem was addressed by Benjamin Apthorp Gould , who suggested numbering asteroids in their order of discovery, and placing this number in a disk (circle) as the generic symbol of an asteroid. Thus, the fourth asteroid, Vesta, acquired the generic symbol ④ . This was soon coupled with the name into an official number–name designation, ④ Vesta , as the number of minor planets increased. By 1858,
13716-472: The proposal was refused by the ESA. A joint NASA –ESA asteroid mission was then drawn up for a Multiple Asteroid Orbiter with Solar Electric Propulsion (MAOSEP), with one of the mission profiles including an orbit of Vesta. NASA indicated they were not interested in an asteroid mission. Instead, the ESA set up a technological study of a spacecraft with an ion drive. Other missions to the asteroid belt were proposed in
13843-446: The rotation rate of Vesta to be determined by the 1950s. However, the early estimates of the rotation rate came into question because the light curve included variations in both shape and albedo . Early estimates of the diameter of Vesta ranged from 383 kilometres (238 mi) in 1825, to 444 km (276 mi). E.C. Pickering produced an estimated diameter of 513 ± 17 km (319 ± 11 mi) in 1879, which
13970-427: The same birth cloud as Mars. Another hypothesis is that Mars was once surrounded by many Phobos- and Deimos-sized bodies, perhaps ejected into orbit around it by a collision with a large planetesimal . The high porosity of the interior of Phobos (based on the density of 1.88 g/cm , voids are estimated to comprise 25 to 35 percent of Phobos's volume) is inconsistent with an asteroidal origin. Observations of Phobos in
14097-402: The star SAO 93228 by Vesta was observed from multiple locations in the eastern United States and Canada. Based on observations from 14 different sites, the best fit to the data was an elliptical profile with dimensions of about 550 km × 462 km (342 mi × 287 mi). Dawn confirmed this measurement. These measurements will help determine the thermal history, size of
14224-496: The three most successful asteroid-hunters at that time, on a commemorative medallion marking the event. In 1891, Max Wolf pioneered the use of astrophotography to detect asteroids, which appeared as short streaks on long-exposure photographic plates. This dramatically increased the rate of detection compared with earlier visual methods: Wolf alone discovered 248 asteroids, beginning with 323 Brucia , whereas only slightly more than 300 had been discovered up to that point. It
14351-439: The total number ranges in the millions or more, depending on the lower size cutoff. Over 200 asteroids are known to be larger than 100 km, and a survey in the infrared wavelengths has shown that the asteroid belt has between 700,000 and 1.7 million asteroids with a diameter of 1 km or more. The absolute magnitudes of most of the known asteroids are between 11 and 19, with the median at about 16. The total mass of
14478-449: The total up to 70%. The number of asteroids increases rapidly as their individual masses decrease. The number of asteroids decreases markedly with increasing size. Although the size distribution generally follows a power law , there are 'bumps' at about 5 km and 100 km , where more asteroids than expected from such a curve are found. Most asteroids larger than approximately 120 km in diameter are primordial (surviving from
14605-714: The two Lagrangian points of stability, L 4 and L 5 , which lie 60° ahead of and behind the larger body. In the Solar System, most known trojans share the orbit of Jupiter . They are divided into the Greek camp at L 4 (ahead of Jupiter) and the Trojan camp at L 5 (trailing Jupiter). More than a million Jupiter trojans larger than one kilometer are thought to exist, of which more than 7,000 are currently catalogued. In other planetary orbits only nine Mars trojans , 28 Neptune trojans , two Uranus trojans , and two Earth trojans , have been found to date. A temporary Venus trojan
14732-416: The violent impact events that created Rheasilvia and Veneneia may have mixed material enough to obscure olivine from observations. Alternatively, Dawn observations of olivine could instead be due to delivery by olivine-rich impactors, unrelated to Vesta's internal structure. Pitted terrain has been observed in four craters on Vesta: Marcia, Cornelia, Numisia and Licinia. The formation of the pitted terrain
14859-492: The winter pole. Typical daytime and nighttime temperatures are −60 °C (213 K) and −130 °C (143 K), respectively. This estimate is for 6 May 1996, very close to perihelion , although details vary somewhat with the seasons. Before the arrival of the Dawn spacecraft , some Vestan surface features had already been resolved using the Hubble Space Telescope and ground-based telescopes (e.g.,
14986-425: The younger, more prominent crater Rheasilvia , after the mother of Romulus and Remus and a mythical vestal virgin . Its width is 95% of the mean diameter of Vesta. The crater is about 19 km (12 mi) deep. A central peak rises 23 km (14 mi) above the lowest measured part of the crater floor and the highest measured part of the crater rim is 31 km (19 mi) above the crater floor low point. It
15113-407: Was a comet: The light was a little faint, and of the colour of Jupiter , but similar to many others which generally are reckoned of the eighth magnitude . Therefore I had no doubt of its being any other than a fixed star. [...] The evening of the third, my suspicion was converted into certainty, being assured it was not a fixed star. Nevertheless before I made it known, I waited till the evening of
15240-489: Was available for this to occur for Deimos. Capture also requires dissipation of energy. The current Martian atmosphere is too thin to capture a Phobos-sized object by atmospheric braking. Geoffrey A. Landis has pointed out that the capture could have occurred if the original body was a binary asteroid that separated under tidal forces. Phobos could be a second-generation Solar System object that coalesced in orbit after Mars formed, rather than forming concurrently out of
15367-438: Was calculated and registered within that specific year. For example, the first two asteroids discovered in 1892 were labeled 1892A and 1892B. However, there were not enough letters in the alphabet for all of the asteroids discovered in 1893, so 1893Z was followed by 1893AA. A number of variations of these methods were tried, including designations that included year plus a Greek letter in 1914. A simple chronological numbering system
15494-534: Was discovered, the first object beyond the orbit of Neptune (other than Pluto ); soon large numbers of similar objects were observed, now called trans-Neptunian object . Further out are Kuiper-belt objects , scattered-disc objects , and the much more distant Oort cloud , hypothesized to be the main reservoir of dormant comets. They inhabit the cold outer reaches of the Solar System where ices remain solid and comet-like bodies exhibit little cometary activity; if centaurs or trans-Neptunian objects were to venture close to
15621-471: Was drawn [REDACTED] . His form is in the pipeline for Unicode 17.0 as U+1F777 . The asteroid symbols were gradually retired from astronomical use after 1852, but the symbols for the first four asteroids were resurrected for astrology in the 1970s. The abbreviated modern astrological variant of the Vesta symbol is [REDACTED] (U+26B6 ⚶ ) . After the discovery of Vesta, no further objects were discovered for 38 years, and during this time
15748-450: Was established in 1925. Currently all newly discovered asteroids receive a provisional designation (such as 2002 AT 4 ) consisting of the year of discovery and an alphanumeric code indicating the half-month of discovery and the sequence within that half-month. Once an asteroid's orbit has been confirmed, it is given a number, and later may also be given a name (e.g. 433 Eros ). The formal naming convention uses parentheses around
15875-534: Was known that there were many more, but most astronomers did not bother with them, some calling them "vermin of the skies", a phrase variously attributed to Eduard Suess and Edmund Weiss . Even a century later, only a few thousand asteroids were identified, numbered and named. In the past, asteroids were discovered by a four-step process. First, a region of the sky was photographed by a wide-field telescope or astrograph . Pairs of photographs were taken, typically one hour apart. Multiple pairs could be taken over
16002-451: Was needed to categorize or name asteroids. In 1852, when de Gasparis discovered the twentieth asteroid, Benjamin Valz gave it a name and a number designating its rank among asteroid discoveries, 20 Massalia . Sometimes asteroids were discovered and not seen again. So, starting in 1892, new asteroids were listed by the year and a capital letter indicating the order in which the asteroid's orbit
16129-556: Was submitted to the European Space Agency (ESA). Named the Asteroidal Gravity Optical and Radar Analysis (AGORA), this spacecraft was to launch some time in 1990–1994 and perform two flybys of large asteroids. The preferred target for this mission was Vesta. AGORA would reach the asteroid belt either by a gravitational slingshot trajectory past Mars or by means of a small ion engine . However,
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