Dictionary:
as·ter·oid (ăs'tə-roid') 
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[From Greek asteroeidēs, starlike : astēr, star + -oeidēs, -oid.]
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Britannica Concise Encyclopedia:
asteroid |
For more information on asteroid, visit Britannica.com.
Sci-Tech Encyclopedia:
Asteroid |
One of the many thousands of small planets (minor planets) revolving around the Sun, mainly between the orbits of Mars and Jupiter. Newly discovered asteroids are assigned a catalog number and name (such as 433 Eros) only after they are observed often enough to compute an accurate orbit. There are over 73,000 cataloged asteroids. See also Planet.
The majority of asteroids have semi-major axes (mean distances to the Sun; symbolized a) between 2.2 and 3.2 astronomical units (1 AU = distance from Earth to the Sun = 1.496 × 108 km = 9.3 × 107 mi). However, numerous small asteroids orbit between Venus and Mars, and two large groups, the Trojan asteroids, orbit at Jupiter's distance from the Sun. See also Trojan asteroids.
In 1992, the first of the trans-Neptunian “asteroids” was discovered. Called Kuiper Belt objects (KBOs), about 900 had been found by mid-2004. They represent a population of bodies much more numerous than the main-belt or Trojan asteroids, but are more properly thought of as comets. There are also a modest number of minor planets orbiting the Sun in temporary orbits beyond Jupiter but well inside the Kuiper Belt; they are termed Centaurs. See also Comet; Kuiper Belt.
Most asteroid orbits are more elliptical and inclined to the plane of the ecliptic than the orbits of major planets. A number of small asteroids (Amor objects) cross, but do not intersect, the orbit of Mars, and a few even cross the Earth's orbit (Apollo objects) or orbit inside the Earth's orbit (Aten objects).
Improvements in radar technology make it possible to image small asteroids that pass close to the Earth almost as well as by spacecraft flybys. For more distant asteroids the chief technique used to measure asteroid diameters is radiometry, which compares the brightness of reflected visible sunlight from an asteroid with the brightness of the asteroid's emitted thermal radiation in the infrared. See also Albedo; Infrared astronomy; Occultation.
There are about 30 asteroids larger than 124 mi (200 km) in diameter; about 75% of them are soot black (geometric albedos of 3–5%). Asteroids are much more numerous at smaller sizes, generally following a size distribution characteristic of fragmentation processes, as would be expected if the asteroids were smashing into each other. Indeed, there are so many large asteroids confined in the volume of the asteroid belt that collisions sufficient to fragment all but the larger asteroids occur every few billion years, and much more often for smaller ones. Thus all asteroids have been extensively battered and many are collisional fragments.
Spectra of sunlight reflected from asteroids have shapes, including absorption bands, characteristic of different rock-forming minerals. Combined with the albedo data from radiometry, the spectral colors of surfaces of over 2000 asteroids show that more than three-quarters of them have very low albedos and are composed of carbon-rich material (often with hydrated, or water-rich, minerals). The black asteroids located in the middle and outer parts of the belt (called C type) resemble carbonaceous meteorites, which are believed to be among the most primitive materials in the solar system, little altered since the planets were forming. The black asteroids near the outer edge of the main belt have a reddish tinge and are not represented by known meteorites on the Earth; they are called P types, and may be even richer in organic components. Still farther out, many of the Trojans are even redder and more mysterious; they are termed D types. Closer to the inner edge of the belt, most asteroids are so-called S types, characterized by moderately high albedos and by absorption bands due to the common silicate minerals pyroxene and olivine. They also contain considerable metal, and probably are akin to either the stony-iron meteorites or the ordinary chondritic meteorites. The general progression of asteroid compositions is thought to reflect the variation with distance from the Sun in the composition of the original nebular dust from which the planets were formed. See also Cosmochemistry; Meteorite; Solar system.
Apollo, Amor, and Aten asteroids are of special interest, particularly because they stand a chance of striking the Earth. Indeed, Meteor Crater (Arizona), and other craters on the Earth and the Moon, testify to the potential for collisions with near-Earth asteroids. Many scientists believe that just such a collision 6.5 × 107 years ago rendered most species of life, including the dinosaurs, extinct. A huge, eroded crater of that age on the Yucatán peninsula in Mexico must have been caused by the impact of an asteroid or comet about 10 mi (16 km) in diameter. In 1908, a small asteroid, perhaps 160 ft (50 m) across, exploded over the Tunguska region of Siberia with energy equivalent to 15 megatons of TNT. Only about one-third of the potentially threatening objects have been discovered so far.
After some tens of millions of years, most of the current crop of near-Earth asteroids will have struck the Earth, the Moon, the Sun, or one of the other inner planets, or will have been ejected from the solar system. Most are probably fragments of main-belt asteroids, traveling in chaotic orbits, just like their smaller cousins, the meteorites.
Current cosmogonical models for the origin of planets involve accretion from myriads of asteroidlike planetesimals. It is likely that asteroids are a remnant of the planetesimals that failed to accrete into a planet between Mars and Jupiter. Perhaps bombardment of the asteroid zone by large planetesimals scattered from massive, nearby Jupiter increased the relative velocities of asteroids to the present value of 3 mi/s (5 km/s) so that asteroids fragment rather than accrete when they meet each other. Instead of forming a planet, the asteroids have been smashing each other to bits.
Evidently some asteroids of primitive, nonvolatile solar composition were heated within the first few hundred million years after the origin of the solar system, perhaps by the solar wind or extinct radionuclides, and they melted. While the unmelted, weak, C-type asteroids may have been depleted by a large factor by collisions, most of the strong stony-iron cores of the melted proto-asteroids have survived; perhaps they are among the M- and S-type asteroids observed today. The asteroids still collide and fragment, occasionally spraying the inner solar system with chips that produce craters or fall as meteorites.
Columbia Encyclopedia:
asteroid |
The orbits of most asteroids lie partially between the orbits of Mars and Jupiter. These so-called main-belt, or cisjovian, asteroids are divided into subgroups named for the main asteroid in the grouping: Hungarias, Floras, Phocaea, Koronis, Eos, Themis, Cybeles, and Hildas. The near-earth asteroids, which closely approach the earth, are classed as Atens (with orbits between the earth and the sun), Apollos (with orbits similar to that of the earth), and Amors (with orbits between the earth and Mars). Two groups of asteroids share Jupiter's orbit; they are known as Trojan asteroids. In 1990, a similar asteroid was found in the orbit of Mars. Centaurs are asteroids with orbits in the outer solar system.
Asteroids are also classified by composition and albedo, most being one of three types. The majority (C-type) are similar to carbon-chrondite meteorites with approximately the same composition as the sun (excluding hydrogen) and are relatively dark. Those with a composition of nickel iron mixed with silicates of iron and magnesium (S-type) are relatively bright. The M-type are composed of nickel iron and are bright. Some of the Trojan asteroids appear to be captured comets, composed of ice and dirt, rather than rocky asteroids.
Toward the end of the 18th cent. astronomers were searching for a planet whose orbit should, according to Bode's law, have an average distance from the sun of 2.8 AU On Jan. 1, 1801, G. Piazzi discovered Ceres while studying the sky in the constellation Taurus; Ceres was later found to have an orbit very near that predicted by Bode's law. Ceres and the asteroids Juno, Pallas, and Vesta, which were discovered soon (1802-7) after Ceres, were initially regarded as planets by many astronomers, a view that was not overturned until additional asteroids were identified in the 1840s and 50s. By 1890 more than 300 asteroids had been discovered by visual means. In 1891, Max Wolf introduced the method of identifying an asteroid by the record of its path on an exposed photographic plate; it appears as a short line in a time exposure, rather than as the sharp point of a star. Brucia was the first asteroid discovered by this method. A more modern approach uses two photographs taken less than an hour apart and examined through a stereomicroscope that allows the asteroid to appear suspended above the background of stars. Still more modern techniques were employed in the discoveries of Ixion, found in 2001 using virtual telescope techniques, and of Quaoar, found in 2002 using photographs taken with the Hubble Space Telescope.
More than 200 asteroids have been identified that regularly intersect the orbit of the earth, and over geologic time asteroids in similar orbits have struck the earth. Hermes, discovered in 1937 and subsequently lost until 2003 when it was identified as a pair of asteroids, comes within 378,000 mi (608,000 km), and Eros comes within 14 million mi (22 million km). More recently, a small asteroid provisionally designated 2002 MN, 150-360 ft (45-110 m) in diameter, passed within 75,000 mi (121,000 km) of the earth-about a third of the distance to the moon-in 2002. Astronomers have observed about several hundred small asteroids, most measuring less than 55 yd (50 m) across, in near-earth orbits that are spread thinly between the earth and Mars. Many of these small asteroids have orbits that intersect the earth's.
Asteroids have been implicated in several mass extinctions of large numbers of animal and plant species in the past. From evidence found in sediments, Luis Walter Alvarez and others hypothesized that the great mass extinction of the dinosaurs and other species 65 million years ago, at the end of the Cretaceous period, was caused by the atmospheric and climatic effects of an asteroid impact; a possible crater exists in the Yucatán region of Mexico. In 1992, scientists reported that the appearance of patterns of shattered quartz crystals imbedded in Triassic shale and other fossil evidence suggest that another major mass extinction, about 200 million years ago, was caused by three closely spaced asteroid impacts.
The origin of asteroids is unclear; one theory claims that they were formed from material that could not condense into a single planet because of perturbation effects involving Jupiter. Some asteroids are actually nuclei of comets that are no longer active.
The space probe Galileo, which passed near and photographed Gaspra (1991) and Ida (1993), provided the first close images of an asteroid. The pictures revealed that Ida has a natural satellite, Dactyl. Ida, in the main asteroid belt between Mars and Jupiter, is about 35 mi (56 km) long and 15 mi (24 km) in diameter. Its tiny moon is about a mile (1.6 km) in diameter and orbits about 60 mi (97 km) above Ida. Since then several other asteroids have been found to have companions, leading astronomers to believe that it may not be uncommon. The probe NEAR-Shoemaker examined Mathilde (1997) on its way to rendezvous (1999) and orbit (2000) Eros. After providing the most information ever obtained about an asteroid (measurements of size, shape, mass, and gravitational field; elemental and mineral composition of the surface; topographic mapping; and measurement of the magnetic field and its interaction with the solar wind), NEAR-Shoemaker made an originally unplanned landing on Eros in 2001, returning close-up images as it descended and data about surface composition. In 1999 the probe Deep Space 1 accomplished the then closest-ever flyby of an asteroid, coming within 16 mi (26 km) of the surface of Braille; spectroscopic data suggests that Braille broke off from Vesta millions of years ago.
Bibliography
See T. Gehrels and M. S. Matthews, ed., Hazards Due to Comets and Asteroids (1995); J. S. Lewis, Rain of Iron and Ice: The Very Real Threat of Comet and Asteroid Bombardment (1997); C. T. Russell, ed., The Near Earth Asteroid Rendezvous Mission (1998); N. F. Michelson, The Asteroid Ephemeris 1900-2050 (1999).
Cosmic Lexicon:
Asteroid |
A small, mostly rocky body orbiting the Sun. Asteroids range in size from 1000 kilometers in diameter to tiny objects you could hold in your hand. Most asteroids orbit the Sun between Mars and Jupiter, and are the source of most meteorites.
Science Dictionary:
asteroid |
A small planet that revolves around the sun. The largest asteroid is only about six hundred miles in diameter. (See asteroid belt.)
Wikipedia:
Asteroid |
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Asteroids, sometimes called minor planets or planetoids, are small Solar System bodies in orbit around the Sun, especially in the inner Solar System; they are smaller than planets but larger than meteoroids. The term "asteroid" has historically been applied primarily to minor planets of the inner Solar System, as the outer Solar System was poorly known when it came into common usage. The distinction between asteroids and comets is made on visual appearance: Comets show a perceptible coma while asteroids do not.
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In 1975, an asteroid taxonomic system based on colour, albedo, and spectral shape was developed by Clark R. Chapman, David Morrison, and Ben Zellner.[1] These properties are thought to correspond to the composition of the asteroid's surface material. The original classification system had three categories: C-types for dark carbonaceous objects (75% of known asteroids), S-types for stony (silicaceous) objects (17% of known asteroids) and U for those that did not fit into either C or S. This classification has since been expanded to include a number of other asteroid types. The number of types continues to grow as more asteroids are studied.
The two most widely used taxonomies currently used are the Tholen classification and SMASS classification. The former was proposed in 1984 by David J. Tholen, and was based on data collected from an eight-color asteroid survey performed in the 1980s. This resulted in 14 asteroid categories.[2] In 2002, the Small Main-Belt Asteroid Spectroscopic Survey resulted in a modified version of the Tholen taxonomy with 24 different types. Both systems have three broad categories of C, S, and X asteroids, where X consists of mostly metallic asteroids, such as the M-type. There are also a number of smaller classes.[3]
Note that the proportion of known asteroids falling into the various spectral types does not necessarily reflect the proportion of all asteroids that are of that type; some types are easier to detect than others, biasing the totals.
Originally, spectral designations were based on inferences of an asteroid's composition.[4] However, the correspondence between spectral class and composition is not always very good, and there are a variety of classifications in use. This has led to significant confusion. While asteroids of different spectral classifications are likely to be composed of different materials, there are no assurances that asteroids within the same taxonomic class are composed of similar materials.
At present, the spectral classification based on several coarse resolution spectroscopic surveys in the 1990s is still the standard. Scientists have been unable to agree on a better taxonomic system,[citation needed] largely due to the difficulty of obtaining detailed measurements consistently for a large sample of asteroids (e.g. finer resolution spectra, or non-spectral data such as densities would be very useful).
The first named minor planet, Ceres, was discovered in 1801 by Giuseppe Piazzi, and was originally considered a new planet.[note 1] This was followed by the discovery of other similar bodies, which with the equipment of the time appeared to be points of light, like stars, showing little or no planetary disc (though readily distinguishable from stars due to their apparent motions). This prompted the astronomer Sir William Herschel to propose the term "asteroid", from Greek αστεροειδής, asteroeidēs = star-like, star-shaped, from ancient Greek Aστήρ, astēr = star. In the early second half of the nineteenth century, the terms "asteroid" and "planet" (not always qualified as "minor") were still used interchangeably; for example, the Annual of Scientific Discovery for 1871, page 316, reads "Professor J. Watson has been awarded by the Paris Academy of Sciences, the astronomical prize, Lalande foundation, for the discovery of 8 new asteroids in one year. The planet Lydia (No. 110), discovered by M. Borelly at the Marseilles Observatory [...] M. Borelly had previously discovered 2 planets bearing the numbers 91 and 99 in the system of asteroids revolving between the orbits of Mars and Jupiter" (emphasis added).
Asteroid discovery methods have dramatically improved over the past two centuries.
In the last years of the 18th century, Baron Franz Xaver von Zach organized a group of 24 astronomers to search the sky for the missing planet predicted at about 2.8 AU from the Sun by the Titius-Bode law, partly as a consequence of the discovery, by Sir William Herschel in 1781, of the planet Uranus at the distance predicted by the law. This task required that hand-drawn sky charts be prepared for all stars in the zodiacal band down to an agreed-upon limit of faintness. On subsequent nights, the sky would be charted again and any moving object would, hopefully, be spotted. The expected motion of the missing planet was about 30 seconds of arc per hour, readily discernible by observers.
The first asteroid, 1 Ceres, was not discovered by a member of the group, but rather by accident in 1801 by Giuseppe Piazzi, director of the observatory of Palermo in Sicily. He discovered a new star-like object in Taurus and followed the displacement of this object during several nights. His colleague, Carl Friedrich Gauss, used these observations to determine the exact distance from this unknown object to the Earth. Gauss' calculations placed the object between the planets Mars and Jupiter. Piazzi named it after Ceres, the Roman goddess of agriculture.
Three other asteroids (2 Pallas, 3 Juno, and 4 Vesta) were discovered over the next few years, with Vesta found in 1807. After eight more years of fruitless searches, most astronomers assumed that there were no more and abandoned any further searches.
However, Karl Ludwig Hencke persisted, and began searching for more asteroids in 1830. Fifteen years later, he found 5 Astraea, the first new asteroid in 38 years. He also found 6 Hebe less than two years later. After this, other astronomers joined in the search and at least one new asteroid was discovered every year after that (except the wartime year 1945). Notable asteroid hunters of this early era were J. R. Hind, Annibale de Gasparis, Robert Luther, H. M. S. Goldschmidt, Jean Chacornac, James Ferguson, Norman Robert Pogson, E. W. Tempel, J. C. Watson, C. H. F. Peters, A. Borrelly, J. Palisa, the Henry brothers and Auguste Charlois.
In 1891, however, 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 previous visual methods: Wolf alone discovered 248 asteroids, beginning with 323 Brucia, whereas only slightly more than 300 had been discovered up to that point. Still, a century later, only a few thousand asteroids were identified, numbered and named. It was known that there were many more, but most astronomers did not bother with them, calling them "vermin of the skies".
Until 1998, asteroids were discovered by a four-step process. First, a region of the sky was photographed by a wide-field telescope, or Astrograph. Pairs of photographs were taken, typically one hour apart. Multiple pairs could be taken over a series of days. Second, the two films of the same region were viewed under a stereoscope. Any body in orbit around the Sun would move slightly between the pair of films. Under the stereoscope, the image of the body would appear 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.[5]
These first three steps do not constitute asteroid discovery: the observer has only found an apparition, which gets a provisional designation, made up of the year of discovery, a letter representing the half-month of discovery, and finally a letter and a number indicating the discovery's sequential number (example: 1998 FJ74).
The final step of discovery is to send the locations and time of observations to the Minor Planet Center, where computer programs determine whether an apparition ties together previous apparitions into a single orbit. If so, the object receives a catalogue number and the observer of the first apparition with a calculated orbit is declared the discoverer, and granted the honor of naming the object subject to the approval of the International Astronomical Union.
There is increasing interest in identifying asteroids whose orbits cross Earth's, and that could, given enough time, collide with Earth (see Earth-crosser asteroids). The three most important groups of near-Earth asteroids are the Apollos, Amors, and Atens. Various asteroid deflection strategies have been proposed, as early as the 1960s.
The near-Earth asteroid 433 Eros had been discovered as long ago as 1898, and the 1930s brought a flurry of similar objects. In order of discovery, these were: 1221 Amor, 1862 Apollo, 2101 Adonis, and finally 69230 Hermes, which approached within 0.005 AU of the Earth in 1937. Astronomers began to realize the possibilities of Earth impact.
Two events in later decades increased the level of alarm: the increasing acceptance of Walter Alvarez' hypothesis that an impact event resulted in the Cretaceous-Tertiary extinction, and the 1994 observation of Comet Shoemaker-Levy 9 crashing into Jupiter. The U.S. military also declassified the information that its military satellites, built to detect nuclear explosions, had detected hundreds of upper-atmosphere impacts by objects ranging from one to 10 metres across.
All of these considerations helped spur the launch of highly efficient automated systems that consist of Charge-Coupled Device (CCD) cameras and computers directly connected to telescopes. Since 1998, a large majority of the asteroids have been discovered by such automated systems. A list of teams using such automated systems includes:[6]
The LINEAR system alone has discovered 97,470 asteroids, as of September 18, 2008.[7] Between all of the automated systems, 4711 near-Earth asteroids have been discovered[8] including over 600 more than 1 km (1 mi) in diameter. The rate of discovery peaked in 2000, when 38,679 minor planets were numbered, and has been going down steadily since then (719 minor planets were numbered in 2007).[9]
A newly discovered asteroid is given a provisional designation (such as 2002 AT4) consisting of the year of discovery and an alphanumeric code indicating the half-month of discovery and the sequence within that half-month. Once an asteroid's orbit has been confirmed, it is given a number, and later may also be given a name (e.g. 433 Eros). The formal naming convention uses parentheses around the number (e.g. (433) Eros), but dropping the parentheses is quite common. Informally, it is common to drop the number altogether, or to drop it after the first mention when a name is repeated in running text.
The first few asteroids discovered were assigned symbols like the ones traditionally used to designate Earth, the Moon, the Sun and planets. The symbols quickly became ungainly, hard to draw and recognize. By the end of 1851 there were 15 known asteroids, each (except one) with its own symbol(s).[10]
| Asteroid | Symbol |
|---|---|
| Ceres |    |
| 2 Pallas |   |
| 3 Juno |  .png){kind=small}  |
| 4 Vesta | .svg){kind=small}    |
| 5 Astraea |  |
| 6 Hebe |  |
| 7 Iris |  |
| 8 Flora |  |
| 9 Metis |  |
| 10 Hygiea |  |
| 11 Parthenope |  |
| 12 Victoria |  |
| 13 Egeria | Never assigned. |
| 14 Irene | "A dove carrying an olive-branch, with a star on its head," never drawn.[11] |
| 15 Eunomia |  |
| 28 Bellona |  |
| 35 Leukothea |  |
| 37 Fides |  |
| 2060 Chiron |  |
Johann Franz Encke made a major change in the Berliner Astronomisches Jahrbuch (BAJ, Berlin Astronomical Yearbook) for 1854. He introduced encircled numbers instead of symbols, although his numbering began with Astraea, the first four asteroids continuing to be denoted by their traditional symbols. This symbolic innovation was adopted very quickly by the astronomical community. The following year (1855), Astraea's number was bumped up to 5, but Ceres through Vesta would be listed by their numbers only in the 1867 edition. A few more asteroids (28 Bellona,[12] 35 Leukothea,[13] and 37 Fides[14]) would be given symbols as well as using the numbering scheme. The circle would become a pair of parentheses, and the parentheses sometimes omitted altogether over the next few decades.[11]
Until the age of space travel, objects in the asteroid belt were merely pinpricks of light in even the largest telescopes and their shapes and terrain remained a mystery. The best modern ground-based telescopes, as well as the Earth-orbiting Hubble Space Telescope, can resolve a small amount of detail on the surfaces of the very largest asteroids, but even these mostly remain little more than fuzzy blobs. Limited information about the shapes and compositions of asteroids can be inferred from their light curves (their variation in brightness as they rotate) and their spectral properties, and asteroid sizes can be estimated by timing the lengths of star occulations (when an asteroid passes directly in front of a star). Radar imaging can yield good information about asteroid shapes and orbital and rotational parameters, especially for near-Earth asteroids.
The first close-up photographs of asteroid-like objects were taken in 1971 when the Mariner 9 probe imaged Phobos and Deimos, the two small moons of Mars, which are probably captured asteroids. These images revealed the irregular, potato-like shapes of most asteroids, as did subsequent images from the Voyager probes of the small moons of the gas giants.
The first true asteroid to be photographed in close-up was 951 Gaspra in 1991, followed in 1993 by 243 Ida and its moon Dactyl, all of which were imaged by the Galileo probe en route to Jupiter.
The first dedicated asteroid probe was NEAR Shoemaker, which photographed 253 Mathilde in 1997, before entering into orbit around 433 Eros, finally landing on its surface in 2001.
Other asteroids briefly visited by spacecraft en route to other destinations include 9969 Braille (by Deep Space 1 in 1999), and 5535 Annefrank (by Stardust in 2002).
In September 2005, the Japanese Hayabusa probe started studying 25143 Itokawa in detail and may return samples of its surface to earth. The Hayabusa mission has been plagued with difficulties, including the failure of two of its three control wheels, rendering it difficult to maintain its orientation to the sun to collect solar energy. Following that, the next asteroid encounters will involve the European Rosetta probe (launched in 2004), which flew by 2867 Šteins in 2008 and will buzz 21 Lutetia in 2010.
In September 2007, NASA launched the Dawn Mission, which will orbit the dwarf planet Ceres and the asteroid 4 Vesta in 2011-2015, with its mission possibly then extended to 2 Pallas.
It has been suggested that asteroids might be used in the future as a source of materials which may be rare or exhausted on earth (asteroid mining), or materials for constructing space habitats (see Colonization of the asteroids). Materials that are heavy and expensive to launch from earth may someday be mined from asteroids and used for space manufacturing and construction.
Asteroids and asteroid belts are a staple of science fiction stories. Asteroids play several potential roles in science fiction: as places which human beings might colonize; as resources for extracting minerals; as a hazard encountered by spaceships travelling between two other points; and as a threat to life on Earth due to potential impacts.
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Misspellings:
asteroid |
Common misspelling(s) of asteroid
Translations:
asteroid |
Dansk (Danish)
n. - asteroide, småplanet
adj. - stjerneformet
Nederlands (Dutch)
asteroïde, zeeaster, klein planeet
Français (French)
n. - astéroïde
adj. - de forme astéroïde
Deutsch (German)
n. - Asteroid, Planetoid
adj. - sternartig, (Bot.) asterblutig, seesternähnlich
Ελληνική (Greek)
n. - (αστρον.) αστεροειδής
Português (Portuguese)
n. - asteróide (m)
Español (Spanish)
n. - asteroide, planetoide
adj. - relativo a asteroides o planetoides
Svenska (Swedish)
n. - asteroid
中文（简体）(Chinese (Simplified))
小行星, 小游星, 海星, 星状的
中文（繁體）(Chinese (Traditional))
n. - 小行星, 小遊星, 海星
adj. - 星狀的
한국어 (Korean)
n. - 불가사리, 소행성
adj. - 별 모양의
العربيه (Arabic)
(الاسم) السيير : الكويكب أحد الكواكب السياره الصغيره الواقعه بين المريخ والمشتري, نجم البحر, على شكل نجمه, شبيه بنجمه البحر
עברית (Hebrew)
n. - גוף סלעי קטן הסובב את השמש בד"כ בין מסלולי מאדים וצדק, דג-הכוכב, בן-כוכב, אסטרואיד
adj. - דמוי כוכב
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asteroid |
Some good "asteroid" pages on the web:
 How? science.howstuffworks.com |
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| How many asteroids are in the asteroid belt? Read answer... |
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 | Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved. Read more |
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| Britannica Concise Encyclopedia. Britannica Concise Encyclopedia. © 1994-2009 Encyclopædia Britannica, Inc. All rights reserved. Read more |
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| Sci-Tech Encyclopedia. McGraw-Hill Encyclopedia of Science and Technology. Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved. Read more |
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| Columbia Encyclopedia. The Columbia Electronic Encyclopedia, Sixth Edition Copyright © 2003, Columbia University Press. Licensed from Columbia University Press. All rights reserved. www.cc.columbia.edu/cu/cup/. Read more |
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| Cosmic Lexicon. Copyright 1996 Planetary Science Research Discoveries. Read more |
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| Science Dictionary. The New Dictionary of Cultural Literacy, Third Edition Edited by E.D. Hirsch, Jr., Joseph F. Kett, and James Trefil. Copyright © 2002 by Houghton Mifflin Company. Published by Houghton Mifflin. All rights reserved. Read more |
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