Many asteroids have been placed in groups and families based on their orbital characteristics. Apart from the broadest divisions, it is customary to name a group of asteroids after the first member of that group to be discovered. Groups are relatively loose dynamical associations, whereas families are tighter and result from the catastrophic break-up of a large parent asteroid sometime in the past. Families are more common and easier to identify within the main asteroid belt, but several small families have been reported among the Jupiter trojans. Main belt families were first recognized by Kiyotsugu Hirayama in 1918 and are often called Hirayama families in his honor.
Orbital classification
Asteroid
Asteroid | Orbital classification
Orbital classification; Quasi-satellites and horseshoe objects ; Spectral classification They are grouped into families Some of the most prominent families in the asteroid belt (in order of increasing semi-major axes) are the Flora, Eunoma, Koronis, Eos, and Themis families. These are commonly categorized according to two criteria: the characteristics of their orbits, and features of their reflectance spectrum. Individual asteroids within the asteroid belt are categorized by their spectra, with most falling into three basic groups: carbonaceous (C-type), silicate (S-type), and metal-rich (M-type).
large objects ( 10 m) in space originating from a region between jupiter and mars
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Asteroid belt
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can you explain its structure?
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Asteroids become darker and redder with age due to space weathering. Composition is calculated from three primary sources: albedo, surface spectrum, and density.
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how is it classified into groups?
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Many asteroids have been placed in groups and families based on their orbital characteristics. Apart from the broadest divisions, it is customary to name a group of asteroids after the first member of that group to be discovered. Groups are relatively loose dynamical associations, whereas families are tighter and result from the catastrophic break-up of a large parent asteroid sometime in the past. Families are more common and easier to identify within the main asteroid belt, but several small families have been reported among the Jupiter trojans. Main belt families were first recognized by Kiyotsugu Hirayama in 1918 and are often called Hirayama families in his honor.
Asteroid | Orbital classification
In 1975, astronomers Clark R. Chapman, David Morrison, and Ben Zellner developed a simple taxonomic system for asteroids based on color, albedo, and spectral shape. The three categories were labelled "C" for dark carbonaceous objects, "S" for stony (silicaceous) objects, and "U" for those that did not fit into either C or S. This basic division of asteroid spectra has since been expanded and clarified. A number of classification schemes are currently in existence, and while they strive to retain some mutual consistency, quite a few asteroids are sorted into different classes depending on the particular scheme. This is due to the use of different criteria for each approach.
Asteroid spectral types | Taxonomic systems
In the Tholen classification the X-group consists of the following types: Since in this scheme the albedo is crucial in discriminating between the above types, some objects for which albedo information was not available were assigned an X-type. An example of this is 50 Virginia.
X-type asteroid | Tholen classification
Asteroids are commonly categorized according to two criteria: the characteristics of their orbits, and features of their reflectance spectrum.
Asteroid | Classification
In 1975, an asteroid taxonomic system based on color, albedo, and spectral shape was developed by Chapman, Morrison, and Zellner. These properties are thought to correspond to the composition of the asteroid's surface material. The original classification system had three categories: C-types for dark carbonaceous objects (75% of known asteroids), S-types for stony (silicaceous) objects (17% of known asteroids) and U for those that did not fit into either C or S. This classification has since been expanded to include many other asteroid types. The number of types continues to grow as more asteroids are studied. The two most widely used taxonomies now used are the Tholen classification and SMASS classification.
Asteroid | Spectral classification
" is a non-family asteroid from the main belt's background population when applying the hierarchical clustering method to its proper orbital elements. Based on osculating Keplerian orbital elements, the asteroid has also been classified as a member of the Flora family (), a giant asteroid family and the largest family of stony asteroids in the main-belt. It orbits the Sun in the inner asteroid belt at a distance of 1.7–2.6 AU once every 3 years and 2 months (1,164 days; semi-major axis of 2.17 AU). Its orbit has an eccentricity of 0.19 and an inclination of 4° with respect to the ecliptic.
(6265) 1985 TW3 | Orbit and classification
Near-Earth asteroids are divided into groups based on their semi-major axis (a), perihelion distance (q), and aphelion distance (Q): Atiras and Amors do not cross the Earth's orbit and are not immediate impact threats, but their orbits may change to become Earth-crossing orbits in the future. , 36 Atiras, 1,510 Atens, 10,199 Apollos and 8,583 Amors have been discovered and cataloged.
Near-Earth object | Orbital classification
The SMASS classification does not use albedo, but several spectral types are distinguished on the basis of spectral features which were too subtle to be visible in the broad-band ECAS survey used for the Tholen scheme. The X-group contains the types: Apart from the Xe-type, there is no significant correlation between the split into these SMASS types and the Tholen E, M, and P-types. All the types in the X-group contain a mixture of asteroids classified as either type E, M, or P.
X-type asteroid | SMASS classification
When the orbital elements of main belt asteroids are plotted (typically inclination vs. eccentricity, or vs. semi-major axis), a number of distinct concentrations are seen against the rather uniform distribution of non-family background asteroids. These concentrations are the asteroid families "(see above)". Interlopers are asteroids classified as family members based on their so-called proper orbital elements but having spectroscopic properties distinct from the bulk of the family, suggesting that they, contrary to the true family members, did not originate from the same parent body that once fragmented upon a collisional impact.
Asteroid family | Identification of members, interlopers and background asteroids
Millions of asteroids exist, many are shattered remnants of planetesimals, bodies within the young Sun's solar nebula that never grew large enough to become planets. The vast majority of known asteroids orbit within the main asteroid belt located between the orbits of Mars and Jupiter, or are co-orbital with Jupiter (the Jupiter trojans). However, other orbital families exist with significant populations, including the near-Earth objects. Individual asteroids are classified by their characteristic spectra, with the majority falling into three main groups: C-type, M-type, and S-type. These were named after and are generally identified with carbon-rich, metallic, and silicate (stony) compositions, respectively.
Asteroid | Overview
When applying the Hierarchical Clustering Method to its proper orbital elements, "Barbaradoore" is a member of the Phocaea family (), a large family of stony S-type asteroids with nearly two thousand known members. It orbits the Sun in the inner main-belt at a distance of 1.7–3.0 AU once every 3 years and 7 months (1,303 days). Its orbit has an eccentricity of 0.29 and an inclination of 22° with respect to the ecliptic.
19982 Barbaradoore | Orbit and classification
Additional groupings have been found that are less certain. Asteroid families can be confirmed when the members display common spectral features. Smaller associations of asteroids are called groups or clusters. Some of the most prominent families in the asteroid belt (in order of increasing semi-major axes) are the Flora, Eunoma, Koronis, Eos, and Themis families. The Flora family, one of the largest with more than 800 known members, may have formed from a collision less than 1 billion years ago. 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.
Asteroid belt | Families and groups
In the SMASS classification, several generally "stony" types of asteroids are brought together into a wider S-group which contains the following types:
S-type asteroid | SMASS classification
About 30–35% of the bodies in the asteroid belt belong to dynamical families each thought to have a common origin in a past collision between asteroids. A family has also been associated with the plutoid dwarf planet .
Asteroid | Orbital classification
In the Tholen classification, the C-type is grouped along with three less numerous types into a wider C-group of carbonaceous asteroids which contains:
C-type asteroid | C-group (Tholen)
An asteroid spectral type is assigned to asteroids based on their emission spectrum, color, and sometimes albedo. These types are thought to correspond to an asteroid's surface composition. For small bodies that are not internally differentiated, the surface and internal compositions are presumably similar, while large bodies such as Ceres and Vesta are known to have internal structure. Over the years, there has been a number of surveys that resulted in a set of different taxonomic systems such as the Tholen, SMASS and Bus–DeMeo classification.
Asteroid spectral types | Introduction
Identified members of this morphology class include:
Active asteroid | Members
In the SMASS classification, the wider C-group contains the types:
C-type asteroid | C-group (SMASS)
"Albitskij" is a member of the Adeona family (), a large family of carbonaceous asteroids, when applying the Hierarchical Clustering Method to its proper orbital elements. It has also been dynamically classified as a member of the Eunomia family (as many other members of the Adeona family), which can be ruled out, due to the fact, that this family consist of stony rather than carbonaceous asteroid. The asteroid orbits the Sun in the central main belt at a distance of 2.3–3.0 AU once every 4 years and 4 months (1,587 days). Its orbit has an eccentricity of 0.13 and an inclination of 12° with respect to the ecliptic.
1783 Albitskij | Orbit and classification
The Collaborative Asteroid Lightcurve Link assumes an albedo of 0.30 – a compromise value between 0.4 and 0.2, corresponding to the Hungaria asteroids both as family and orbital group – and calculates a diameter of 3.85 kilometers with an absolute magnitude of 14.0.
7187 Isobe | Classification and orbit
The S-type asteroid is a member of the Koronis family, a group consisting of about 200 known bodies. It orbits the Sun in the outer main-belt at a distance of 2.6–3.2 AU once every 4 years and 11 months (1,810 days). Its orbit has an eccentricity of 0.09 and an inclination of 3° with respect to the ecliptic.
1912 Anubis | Orbit and classification
Under the SMASS classification taxonomy, this asteroid is listed as a B-type; a group that combines both the Tholen B and F types. The spectrum of this object suggests the presence of magnetite (FeO), which gives it the spectrally-blue coloration that is a characteristic of this SMASS class. The spectrum of this asteroid also displays a band feature near 2.9 μm that indicate the presence of a hydrated mineral. This suggests that the asteroid has undergone significant water-based alteration.
335 Roberta | Introduction
The Tholen taxonomy also has additional notations, appended to the spectral type. The letter "U" is a qualifying flag, used for asteroids with an "unusual" spectrum, that falls far from the determined cluster center in the numerical analysis. The notation ":" (single colon) and "::" (two colons) are appended when the spectral data is "noisy" or "very noisy", respectively. For example, the Mars-crosser 1747 Wright has an "AU:" class, which means that it is an A-type asteroid, though with an unusual and noisy spectrum.
Asteroid spectral types | Taxonomic features
The Bus-DeMeo classification is an asteroid taxonomic system designed by Francesca DeMeo, Schelte Bus and Stephen Slivan in 2009. It is based on reflectance spectrum characteristics for 371 asteroids measured over the wavelength 0.45–2.45 micrometers. This system of 24 classes introduces a new "Sv"-type and is based upon a principal component analysis, in accordance with the SMASS taxonomy, which itself is based upon the Tholen classification.
Asteroid spectral types | Bus–DeMeo classification
These classification schemes are expected to be refined and/or replaced as further research progresses. However, for now the spectral classification based on the two above coarse resolution spectroscopic surveys from the 1990s is still the standard. Scientists have been unable to agree on a better taxonomic system, 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). Some groupings of asteroids have been correlated with meteorite types:
Asteroid spectral types | Appraisal
The objects in the Himalia group have semi-major axes (distances from Jupiter) in the range of 11.15 and 11.75 Gm, inclinations between 26.6° and 28.3°, and eccentricities of between 0.11 and 0.25. All orbit prograde. In physical appearance, the group is very homogenous, all satellites displaying neutral colours (colour indices B−V = 0.66 and V−R = 0.36) similar to those of C-type asteroids. Given the limited dispersion of the orbital parameters and the spectral homogeneity, it has been suggested that the group could be a remnant of the break-up of an asteroid from the main asteroid belt. The radius of the parent asteroid was probably about 89 km, only slightly larger than that of Himalia, which retains approximately 87% of the mass of the original body.
Himalia group | Characteristics and origin
Originally, spectral designations were based on inferences of an asteroid's composition. However, the correspondence between spectral class and composition is not always very good, and a variety of classifications are in use. This has led to significant confusion. Although asteroids of different spectral classifications are likely to be composed of different materials, there are no assurances that asteroids within the same taxonomic class are composed of the same (or similar) materials.
Asteroid | Problems
The S-type asteroid is a member of the Flora family, one of the largest groups of stony asteroids in the main-belt. It orbit has an eccentricity of 0.13 and an inclination of 2° with respect to the ecliptic. As no precovery were taken, and no prior identifications were made, the body's observation arc begins with its official discovery observation at Palomar in 1960.
6615 Plutarchos | Orbit and classification
It is a member of the Flora family, one of the largest families of stony asteroids in the asteroid belt. It orbits the Sun in the inner main-belt at a distance of 2.0–2.5 AU once every 3 years and 5 months (1,233 days). Its orbit has an eccentricity of 0.13 and an inclination of 4° with respect to the ecliptic.
1850 Kohoutek | Classification and orbit
In the Tholen classification, the S-type is a very broad grouping which includes all the types in the SMASS S-group except for the A, Q, and R, which have particularly strong "stony" absorption features around 1 μm.
S-type asteroid | Tholen classification
The abundance of olivine in the surface of suggests that it could be a mantle asteroid formed as a fragment from the rocky mantles of large, internally differentiated bodies. The absorption features in 's spectrum appear to be intermediate between the S-type and A-type spectral classes, hence it is classified as an Sa-type asteroid. Assuming an average albedo of 0.22 for S-type asteroids, 's diameter can be constrained to approximately .
2020 AV2 | Physical characteristics
The Tholen taxonomy may encompass up to four letters (e.g. "SCTU"). The classification scheme uses the letter "I" for "inconsistent" spectral data, and should not be confused with a spectral type. An example is the Themistian asteroid 515 Athalia, which, at the time of classification was inconsistent, as the body's spectrum and albedo was that of a stony and carbonaceous asteroid, respectively. When the underlying numerical color analysis was ambiguous, objects were assigned two or three types rather than just one (e.g. "CG" or "SCT"), whereby the sequence of types reflects the order of increasing numerical standard deviation, with the best fitting spectral type mentioned first.
Asteroid spectral types | Taxonomic features
Ceres, the only object in the asteroid belt large enough to be a dwarf planet, is about 950 km in diameter, whereas Vesta, Pallas, and Hygiea have mean diameters of less than 600 km. The remaining bodies range down to the size of a dust particle. The asteroid material is so thinly distributed that numerous unmanned spacecraft have traversed it without incident. Nonetheless, collisions between large asteroids do occur, and these can produce an asteroid family whose members have similar orbital characteristics and compositions. Individual asteroids within the asteroid belt are categorized by their spectra, with most falling into three basic groups: carbonaceous (C-type), silicate (S-type), and metal-rich (M-type).
Asteroid belt | Introduction
is a bright core member of the Hungaria family (), a large family of three thousand asteroids located within the dynamical group with the same name. Hungarias form the innermost dense concentration of asteroids in the Solar System; they are inside the asteroid belt's core region, sometimes considered a completely independent population. The asteroid orbits the Sun in the innermost asteroid belt at a distance of 1.7–2.1 AU once every 2 years and 8 months (977 days; semi-major axis of 1.93 AU). Its orbit has an eccentricity of 0.10 and an inclination of 23° with respect to the ecliptic. The body's observation arc begins with a precovery found in the Digitized Sky Survey and taken at the Siding Spring Observatory in November 1977, almost 7 years prior to its official discovery observation at Palomar.
(15692) 1984 RA | Orbit and classification
is a member of the Athen group of asteroids. It orbits the Sun at a distance of 0.3–1.2 AU once every 8 months (243 days; semi-major axis of 0.76 AU). Its orbit has an eccentricity of 0.60 and an inclination of 20° with respect to the ecliptic. The body's observation arc begins with its official discovery observation at Socorro.
(163243) 2002 FB3 | Orbit and classification
The spectral type of the asteroid is that of a rare A-type in the SMASS taxonomy, with its surface consisting of almost pure olivine, which gives the body a very reddish color. As of November 2015, only 17 minor planets of this type are known. As a spectroscopic A-type asteroid, it belongs to the larger group of bodies with a silicaceous composition. However, the Collaborative Asteroid Lightcurve Link classifies the asteroid into the carbonaceous group, despite the fact that is assumes a relatively high geometric albedo of 0.20, which is rather typical for stony asteroids.
2423 Ibarruri | Physical characteristics
The S-type asteroid is a member of the Flora family, one of the largest groups of stony asteroids in the main-belt. It orbits the Sun in the inner main-belt at a distance of 1.9–2.6 AU once every 3 years and 5 months (1,238 days). Its orbit has an eccentricity of 0.15 and an inclination of 8° with respect to the ecliptic.
3212 Agricola | Orbit and classification
The X-group of asteroids collects together several types with similar spectra, but probably quite different compositions.
X-type asteroid | Introduction
" is a member of the Apollo group, which are Earth-crossing asteroids and the largest group of near-Earth asteroids. It orbits the Sun at a distance of 0.3–2.4 AU once every 19 months (583 days; semi-major axis of 1.37 AU). Its orbit has a high eccentricity of 0.78 and an inclination of 12° with respect to the ecliptic. As no precoveries were taken, the body's observation arc begins with its discovery observation in 2006.
(388188) 2006 DP14 | Classification and orbit
The S-type asteroid is a member of the Flora family, one of the largest groups of stony asteroids in the main-belt. It orbits the Sun in the inner main-belt at a distance of 2.0–2.4 AU once every 3 years and 2 months (1,161 days). Its orbit has an eccentricity of 0.09 and an inclination of 2° with respect to the ecliptic.
6267 Rozhen | Orbit and classification
A newer chemical classification scheme based on the proportions of the trace elements Ga, Ge and Ir separates the iron meteorites into classes corresponding to distinct asteroid parent bodies. This classification is based on diagrams that plot nickel content against different trace elements (e.g. Ga, Ge and Ir). The different iron meteorite groups appear as data point clusters. There were originally four of these groups designated by the Roman numerals I, II, III, IV. When more chemical data became available these were split, e.g. Group IV was split into IVA and IVB meteorites. Even later some groups got joined again when intermediate meteorites were discovered, e.g.
Iron meteorite | Chemical classification
A spectroscopic survey of the small near-Earth asteroid population conducted by European astronomers determined that "" is an X-type asteroid. Because of the objects low albedo "(see below)", it would be considered a primitive P-type asteroid in the Tholen classification.
(163348) 2002 NN4 | Physical characteristics
The asteroid is characterized as both a carbonaceous C-type and metallic M-type asteroid. The density of the primary was calculated using the orbital elements of the binary system, the primary-to-secondary mass ratio, and estimates of the primary size. The primary has a low density of 1.7 g/cm, which may indicate a "rubble pile" structure containing rocks and voids.
(185851) 2000 DP107 | Physical characteristics
Asteroids in the asteroid belt are divided into asteroid groups and families based on their orbital characteristics. Asteroid moons are asteroids that orbit larger asteroids. They are not as clearly distinguished as planetary moons, sometimes being almost as large as their partners. The asteroid belt also contains main-belt comets, which may have been the source of Earth's water. Jupiter trojans are located in either of Jupiter's L or L points (gravitationally stable regions leading and trailing a planet in its orbit); the term is also used for small bodies in any other planetary or satellite Lagrange point. Hilda asteroids are in a 2:3 resonance with Jupiter; that is, they go around the Sun three times for every two Jupiter orbits.
Solar System | Asteroid groups
Generally similar to the C-type objects, but contain a strong ultraviolet absorption feature below 0.5 μm. An absorption feature around 0.7 μm may also be present, which is indicative of phyllosilicate minerals such as clays or mica. In the SMASS classification the G-type corresponds to the Cgh and Cg types, depending on the presence or absence (respectively) of the absorption feature at 0.7 μm. The G-type, C-type and some rare types are sometimes collected together into a wider C-group of carbonaceous asteroids.
G-type asteroid | Characteristics
In 1918, the Japanese astronomer Kiyotsugu Hirayama noticed that the orbits of some of the asteroids had similar parameters, forming families or groups. Approximately one-third of the asteroids in the asteroid belt are members of an asteroid family. These share similar orbital elements, such as semi-major 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 asteroid belt, show concentrations indicating the presence of an asteroid family. There are about 20 to 30 associations that are almost certainly asteroid families.
Asteroid belt | Families and groups
The overwhelming majority of known asteroids have orbits lying between the orbits of Mars and Jupiter, roughly between 2 and 4 AU. These could not form a planet due to the gravitational influence of Jupiter. Jupiter's gravitational influence, through orbital resonance, clears Kirkwood gaps in the asteroid belt, first recognised by Daniel Kirkwood in 1874. The region with the densest concentration (lying between the Kirkwood gaps at 2.06 and 3.27 AU, with eccentricities below about 0.3, and inclinations smaller than 30°) is called the asteroid belt. It can be further subdivided by the Kirkwood Gaps into the:
List of minor-planet groups | The asteroid belt
is a member of the dynamical Amor group of near-Earth asteroids, and therefore does not currently cross Earth's orbit. The asteroid's closest approach to the Sun is just outside Earth's farthest distance from the Sun. When the asteroid has a perihelion point less than 1.017 AU (Earth's aphelion), it is classified an Apollo asteroid. This asteroid's category flips back and forth as time passes, due to minor perturbations of its orbit. It orbits the Sun at a distance of 1.0–3.7 AU once every 3 years and 8 months (1,344 days; semi-major axis of 2.38 AU). Its orbit has a high eccentricity of 0.57 and an inclination of ° with respect to the ecliptic.
(52768) 1998 OR2 | Orbit and classification
The term "cluster" is also used to describe a small asteroid family, such as the Karin cluster. "Clumps" are groupings which have relatively few members but are clearly distinct from the background (e.g. the Juno clump). "Clans" are groupings which merge very gradually into the background density and/or have a complex internal structure making it difficult to decide whether they are one complex group or several unrelated overlapping groups (e.g. the Flora family has been called a clan). "Tribes" are groups that are less certain to be statistically significant against the background either because of small density or large uncertainty in the orbital parameters of the members.
Asteroid family | Clusters, clumps, clans and tribes
The S-type asteroid is a member of the Flora family, one of the largest groups of stony asteroids in the main-belt. It orbits the Sun at a distance of 2.0–2.4 AU once every 3 years and 4 months (1,211 days). Its orbit has an eccentricity of 0.09 and an inclination of 4° with respect to the ecliptic. The body's observation arc begins with its official discovery observation, as the previous identifications, and , made at Johannesburg and Uccle in 1942 and 1950, respectively, remained unused.
1810 Epimetheus | Classification and orbit
is a member of the dynamical Apollo group, which are Earth-crossing asteroids. Apollo asteroids are the largest subgroup of near-Earth objects. Unlike many Apollo asteroids, this asteroid is not a Mars-crosser, as its aphelion is smaller than the orbit of the Red Planet at 1.66 AU. This asteroid orbits the Sun at a distance of 0.97–1.59 AU once every 17 months (531 days; semi-major axis of 1.28 AU). Its orbit has an eccentricity of 0.24 and an inclination of 0° with respect to the ecliptic. The body's observation arc begins with a precovery found in ESO's Astrovirtel data archive , in August 2000, less than 5 months prior to its official discovery observation at Socorro.
2001 AV43 | Orbit and classification
The asteroid is a member of the Eunomia family, a large group of S-type asteroids and the most prominent family in the intermediate main-belt. It orbits the Sun in the central main-belt at a distance of 2.2–3.1 AU once every 4 years and 3 months (1,550 days). Its orbit has an eccentricity of 0.17 and an inclination of 12° with respect to the ecliptic. As no precoveries were taken, the asteroid's observation arc begins with its discovery in 1973.
2005 Hencke | Orbit and classification
The relatively bright S-type asteroid is a member of the Flora family, one of the largest collisional groups in the main-belt. It orbits the Sun in the inner main-belt at a distance of 1.8–2.6 AU once every 3 years and 4 months (1,204 days). Its orbit has an eccentricity of 0.17 and an inclination of 5° with respect to the ecliptic. Its observation arc begins with its official discovery observation at Heidelberg.
1703 Barry | Orbit and classification
The orbital characteristics that define an asteroid as being in the Amor group are:
Amor asteroid | Definition
The S-type asteroid is a member of the Koronis family, a group consisting of about 200 known stony bodies with nearly ecliptical orbits. It orbits the Sun in the outer main-belt at a distance of 2.6–3.1 AU once every 4 years and 10 months (1,761 days). Its orbit has an eccentricity of 0.08 and an inclination of 1° with respect to the ecliptic. The first precovery was obtained at Lowell Observatory in 1929, extending the asteroid's observation arc by 48 years prior to its discovery.
3409 Abramov | Orbit and classification
The very low dispersion of the mean orbital elements among the core members (the group is separated by less than 700,000 km in semi major axis and less than 0.7° in inclination) suggests that the Carme group may once have been a single body that was broken apart by an impact. The dispersion can be explained by a very small velocity impulse (5 < δV < 50 m/s). The parent body was probably about the size of Carme, 46 km in diameter; 99% of the group's mass is still located in Carme. Further support to the single body origin comes from the known colours: all the satellites appear light red, with colour indices B-V= 0.76 and V-R= 0.47 and infrared spectra, similar to D-type asteroids.
Carme group | Origin
It is a member of the Themis family, a dynamical group of outer-belt asteroids with nearly coplanar ecliptical orbits. The C-type asteroid is also classified as a rather rare L-type asteroid by Pan-STARRS large-scale survey. It orbits the Sun in the outer main-belt at a distance of 2.7–3.5 AU once every 5 years and 6 months (2,000 days). Its orbit has an eccentricity of 0.13 and an inclination of 2° with respect to the ecliptic.
12621 Alsufi | Classification and orbit
An early system of asteroid taxonomy was established in 1975 from the doctoral thesis work of David J. Tholen. This was based upon observations of a group of 110 asteroids. The U-type classification was used as a miscellaneous class for asteroids with unusual spectra that didn't fit into the C and S-type asteroid classifications. In 1976, some of these U-type asteroids with unusual moderate albedo levels were labeled as M-type. Around 1981, an offshoot of the M-type asteroid branch appeared for minor planets that have spectra that are indistinguishable from M-type, but that also have low albedo not consistent with the M type.
P-type asteroid | Taxonomy
Additionally, some interlopers from the heterogeneous background asteroid population are expected even in the central regions of a family. Since the true family members caused by the collision are expected to have similar compositions, most such interlopers can in principle be recognised by spectral properties which do not match those of the bulk of family members. A prominent example is 1 Ceres, the largest asteroid, which is an interloper in the family once named after it (the Ceres family, now the Gefion family).
Asteroid family | Hierarchical clustering method
"Spahr" is a non-family asteroid of the main belt's background population when applying the hierarchical clustering method to its proper orbital elements. Based on osculating Keplerian orbital elements, the asteroid has also been classified as a member of the Flora family (), a giant asteroid family and the largest family of stony asteroids in the main-belt. It orbits the Sun in the inner asteroid belt at a distance of 2.0–2.5 AU once every 3 years and 4 months (1,232 days; semi-major axis of 2.25 AU). Its orbit has an eccentricity of 0.09 and an inclination of 7° with respect to the ecliptic.
2975 Spahr | Orbit and classification
The former was proposed in 1984 by David J. Tholen, and was based on data collected from an eight-color asteroid survey performed in the 1980s. This resulted in 14 asteroid categories. In 2002, the Small Main-Belt Asteroid Spectroscopic Survey resulted in a modified version of the Tholen taxonomy with 24 different types. Both systems have three broad categories of C, S, and X asteroids, where X consists of mostly metallic asteroids, such as the M-type. There are also several smaller classes. The proportion of known asteroids falling into the various spectral types does not necessarily reflect the proportion of all asteroids that are of that type; some types are easier to detect than others, biasing the totals.
Asteroid | Spectral classification
Present day computer-assisted searches have identified more than a hundred asteroid families. The most prominent algorithms have been the hierarchical clustering method (HCM), which looks for groupings with small nearest-neighbour distances in orbital element space, and wavelet analysis, which builds a density-of-asteroids map in orbital element space, and looks for density peaks. The boundaries of the families are somewhat vague because at the edges they blend into the background density of asteroids in the main belt. For this reason the number of members even among discovered asteroids is usually only known approximately, and membership is uncertain for asteroids near the edges.
Asteroid family | Hierarchical clustering method
An asteroid family is a population of asteroids that share similar proper orbital elements, such as semimajor axis, eccentricity, and orbital inclination. The members of the families are thought to be fragments of past asteroid collisions. An asteroid family is a more specific term than asteroid group whose members, while sharing some broad orbital characteristics, may be otherwise unrelated to each other.
Asteroid family | Introduction
Although the asteroid's spectral type is unknown, its albedo indicates a carbonaceous composition, which agrees with C-type classification for the Themistian asteroids.
3054 Strugatskia | Physical characteristics
With a semi-major axis (average orbit distance) greater than 1 AU and a perihelion distance within that of Earth's, is formally classified under the Apollo group of near-Earth asteroids. The asteroid's minimum orbital intersection distance (MOID) from Earth is approximately , or about 0.78 lunar distances. Having such a small Earth MOID, is considered a potentially hazardous asteroid (PHA) by the Minor Planet Center, under the definition that PHAs have Earth MOIDs less than 0.05 AU and absolute magnitudes under 22. Despite this, will not make any close Earth encounters within 15 lunar distances or over the next 200 years, and the asteroid has not been listed by the JPL Sentry Risk Table .
2020 BX12 | Orbit and classification
"Dientzenhofer" is a non-family asteroid of the main belt's background population when applying the hierarchical clustering method to its proper orbital elements. Based on osculating Keplerian orbital elements, the asteroid has also been classified as a member of the Flora family (), a giant asteroid family and the largest family of stony asteroids in the main-belt. The asteroid orbits the Sun in the inner main-belt at a distance of 2.0–2.6 AU once every 3 years and 6 months (1,266 days; semi-major axis of 2.29 AU). Its orbit has an eccentricity of 0.13 and an inclination of 3° with respect to the ecliptic.
5318 Dientzenhofer | Orbit and classification
"Volkonskaya" is a member of the Vesta family (), when applying the hierarchical clustering method to its proper orbital elements. Vestian asteroids have a composition akin to cumulate eucrites (HED meteorites) and are thought to have originated deep within 4 Vesta's crust, possibly from the Rheasilvia crater, a large impact crater on its southern hemisphere near the South pole, formed as a result of a subcatastrophic collision. Vesta is the main belt's second-largest and second-most-massive body after . Based on osculating Keplerian orbital elements, the asteroid has also been classified as a member of the Flora family (), a giant asteroid family and the largest family of stony asteroids in the main-belt.
3703 Volkonskaya | Orbit and classification
This is a more recent taxonomy introduced by American astronomers Schelte Bus and Richard Binzel in 2002, based on the Small Main-Belt Asteroid Spectroscopic Survey (SMASS) of 1,447 asteroids. This survey produced spectra of a far higher resolution than ECAS "(see Tholen classification above)", and was able to resolve a variety of narrow spectral features. However, a somewhat smaller range of wavelengths (0.44 μm to 0.92 μm) was observed. Also, albedos were not considered. Attempting to keep to the Tholen taxonomy as much as possible given the differing data, asteroids were sorted into the 26 types given below. As for the Tholen taxonomy, the majority of bodies fall into the three broad C, S, and X categories, with a few unusual bodies categorized into several smaller types "(also see above)": A significant number of small asteroids were found to fall in the Q, R, and V types, which were represented by only a single body in the Tholen scheme.
Asteroid spectral types | SMASS classification
The asteroid is a member of the Koronis family, a collisional group consisting of a few hundred known bodies with nearly ecliptical orbits. It orbits the Sun in the outer main-belt at a distance of 2.6–3.0 AU once every 4 years and 9 months (1,747 days). Its orbit has an eccentricity of 0.07 and an inclination of 3° with respect to the ecliptic.
9999 Wiles | Classification and orbit
Based upon its spectral characteristics, this object is classified as a K-type asteroid. The orbital properties show it to be a member of the extensive Eos asteroid family, which is named after it. The spectral properties of the asteroid suggest it may have come from a partially differentiated parent body.
221 Eos | Introduction
The Ananke group is believed to have been formed when an asteroid was captured by Jupiter and subsequently fragmented by a collision. This belief is founded on the fact that the dispersion of the mean orbital parameters of the core members is very small and can be accounted for by a small velocity impulse (15 < δV < 80 m/s), compatible with a single collision and breakup. Based on the sizes of the satellites, the original asteroid may have been about 28 km in diameter. Since this value is near the approximate diameter of Ananke itself, it is likely the parent body was not heavily disrupted.
Ananke group | Origin
Asteroids can be classified into three major types according to their spectra. The original categories were created by Clark R. Chapman, David Morrison, and Ben Zellner in 1975, and further expanded by David J. Tholen in 1984. In what is now known as the Tholen classification, the C-types are made of carbonaceous material, S-types consist mainly of silicates, and X-types are 'metallic'. There are other classifications for unusual asteroids. C- and S-type asteroids are the most common asteroids. In 2002 the Tholen classification was further "evolved" into the SMASS classification, expanding the number of categories from 14 to 26 to account for more precise spectroscopic analysis of the asteroids.
Astronomical spectroscopy | Asteroids
The asteroid belongs to the Taurid Complex "(also see Taurids)", a group of near-Earth asteroids thought to be extinct cometary nuclei, that are associated with four meteor showers on Earth, due to their disintegration. The Taurid Complex includes several other Apollo asteroids such as 4183 Cuno, 4341 Poseidon, 5143 Heracles, and 5731 Zeus.
2201 Oljato | Orbit and classification
The C-type asteroid is a non-family asteroid that belongs to the background population of the main belt. It orbits the Sun in the outer asteroid belt at a distance of 2.9–3.2 AU once every 5 years and 4 months (1,939 days; semi-major axis of 3.04 AU). Its orbit has an eccentricity of 0.05 and an inclination of 10° with respect to the ecliptic.
1910 Mikhailov | Orbit and classification
When applying the hierarchical clustering method to its proper orbital elements, "Aivazovskij" is a member of the Itha family, a very small family of asteroids, named after its parent body 918 Itha. It orbits the Sun in the outer main belt at a distance of 2.5–3.2 AU once every 4 years and 10 months (1,759 days; semi-major axis of 2.85 AU). Its orbit has an eccentricity of 0.13 and an inclination of 12° with respect to the ecliptic. The first precovery was taken at Lowell Observatory in 1931, extending the asteroid's observation arc by 46 years prior to its discovery.
3787 Aivazovskij | Orbit and classification
The S-type asteroid is a member of the Flora family, one of the largest groups of stony asteroids in the main-belt. It orbits the Sun in the inner main-belt at a distance of 2.1–2.4 AU once every 3 years and 4 months (1,216 days). Its orbit has an eccentricity of 0.07 and an inclination of 4° with respect to the ecliptic. The first precovery was obtained at Lowell Observatory in 1931, extending the asteroid's observation arc by 33 years prior to its discovery.
3181 Ahnert | Orbit and classification
The stony S-type asteroid is a member of the Phocaea family (), a group of asteroids with similar orbital characteristics, named after its largest member, 25 Phocaea. It orbits the Sun in the inner main-belt at a distance of 1.9–3.0 AU once every 3 years and 9 months (1,373 days). Its orbit has an eccentricity of 0.23 and an inclination of 24° with respect to the ecliptic. A first precovery was taken at the discovering observatory in 1971, extending the body's observation arc by one year prior to its official discovery observation.
5040 Rabinowitz | Orbit and classification
is an Apollo asteroid, the largest group of near-Earth objects and Earth-crossing asteroids with approximately 10 thousand known members. It orbits the Sun at a distance of 0.72–1.55 AU once every 15 months (440 days; semi-major axis of 1.13 AU). Its orbit has an eccentricity of 0.36 and an inclination of 15° with respect to the ecliptic. The asteroid has a notably low minimum orbital intersection distance with Earth of , or 0.11 LD.
2017 XO2 | Orbit and classification
When applying the hierarchical clustering method to its proper orbital elements according to Nesvorný, "Bradfield" is a member of the Agnia family (), a very large family of stony asteroids with more than 2000 known members. They most likely formed from the breakup of a basalt object, which in turn was spawned from a larger parent body that underwent igneous differentiation. The family's parent body and namesake is the asteroid 847 Agnia. In the 1995-HCM analysis by Zappalà, however, it is a member of the Liberatrix family (also described as Nemesis family by Nesvorný). It orbits the Sun in the central main-belt at a distance of 2.5–3.0 AU once every 4 years and 7 months (1,674 days; semi-major axis of 2.76 AU).
3430 Bradfield | Orbit and classification
The asteroid's spectral type is unknown. Typically, members of the Eos family are K-type asteroids. "Mikeanderson"s measured albedo also agrees with this spectral classification "(see below)".
51824 Mikeanderson | Physical characteristics
The S-type asteroid is a member of the Flora family, one of the largest groups of stony asteroids in the main-belt. It orbits the Sun in the inner main-belt at a distance of 2.0–2.6 AU once every 3 years and 5 months (1,254 days). Its orbit has an eccentricity of 0.13 and an inclination of 6° with respect to the ecliptic. The first precovery was obtained at the U.S. Goethe Link Observatory in 1950, extending the asteroid's observation arc by 35 years prior to its discovery.
4936 Butakov | Orbit and classification
When applying the hierarchical clustering method to its proper orbital elements, "Adele" is a core member of the Eunomia family (), a prominent family of stony S-type asteroids and the largest one in the intermediate main belt with more than 5,000 known members. It orbits the Sun in the central asteroid belt at a distance of 2.2–3.1 AU once every 4 years and 4 months (1,585 days; semi-major axis of 2.66 AU). Its orbit has an eccentricity of 0.16 and an inclination of 13° with respect to the ecliptic.
812 Adele | Orbit and classification
A more recent study by Rivkin "et al." published in 2002 examined the dependence of spectral absorption on the asteroid's rotational phase. The study looked at the 0.7 μm band, which is also associated with hydrated silicates, and found that the reflectance changes as the asteroid rotates, suggesting that the surface is heterogeneous with some hydrated areas intermixed with dry areas.
135 Hertha | Spectral classification
is a member of the dynamical Aten group, which are Earth-crossing asteroids and one of the smaller subgroups of near-Earth objects. It orbits the Sun at a distance of 0.60–1.08 AU once every 9 months (279 days; semi-major axis of 0.84 AU). Its orbit has an eccentricity of 0.29 and an inclination of nearly 0° with respect to the ecliptic. The body's observation arc begins with a precovery taken by DECam at the Chilean Víctor M. Blanco Telescope on 1 April 2013, just two nights prior to its first official observation at Mount Lemmon.
2013 GM3 | Orbit and classification
" is non-family asteroid of the main belt's background population. It orbits the Sun in the central asteroid belt at a distance of 2.1–3.3 AU once every 4 years and 5 months (1,602 days; semi-major axis of 2.68 AU). Its orbit has an eccentricity of 0.23 and an inclination of 13° with respect to the ecliptic.
(7563) 1988 BC | Classification and orbit
These observations did not indicate a binary asteroid type, but did add to the data set available for this asteroid; this asteroid is part of the Hungaria group.
2131 Mayall | Introduction
When applying the hierarchical clustering method to its proper orbital elements, "Vecherka" has both been considered a non-family asteroid of the main belt's background population (according to Nesvorný), and core member of the Maria family (according to Milani and Knežević). It orbits the Sun in the central asteroid belt at a distance of 2.2–3.0 AU once every 4 years and 3 months (1,537 days). Its orbit has an eccentricity of 0.15 and an inclination of 15° with respect to the ecliptic. The body's observation arc begins with its first observation as at Uccle Observatory in October 1952, or 21 years prior to its official discovery observation at Nauchnij.
4962 Vecherka | Orbit and classification
is a member of the dynamical Apollo group, which are Earth-crossing asteroids. Apollo asteroids are the largest subgroup of near-Earth objects. It orbits the Sun at a distance of 0.31–4.1 AU once every 3 years and 3 months (1,194 days; semi-major axis of 2.20 AU). Its orbit has an exceptionally high eccentricity of 0.86 and an inclination of 18° with respect to the ecliptic. The body's observation arc begins with a precovery taken at the Siding Spring Observatory in June 1983, more than 15 years prior to its official discovery observation at Socorro.
(16960) 1998 QS52 | Orbit and classification
Skirting the inner edge of the belt (ranging between 1.78 and 2.0 AU, with a mean semi-major axis of 1.9 AU) is the Hungaria family of minor planets. They are named after the main member, 434 Hungaria; the group contains at least 52 named asteroids. The Hungaria group is separated from the main body by the 4:1 Kirkwood gap and their orbits have a high inclination. Some members belong to the Mars-crossing category of asteroids, and gravitational perturbations by Mars are likely a factor in reducing the total population of this group. Another high-inclination group in the inner part of the asteroid belt is the Phocaea family.
Asteroid belt | Periphery
Apart from a few asteroids whose densities have been investigated, one has to resort to enlightened guesswork. See Carry for a summary. For many asteroids a value of "ρ"~2 g/cm has been assumed. However, density depends on the asteroid's spectral type. Krasinsky "et al." gives calculations for the mean densities of C, S, and M class asteroids as 1.38, 2.71, and 5.32 g/cm. (Here "C" included Tholen classes C, D, P, T, B, G, and F, while "S" included Tholen classes S, K, Q, V, R, A, and E). Assuming these values (rather than the present ~2 g/cm) is a better guess.
Standard asteroid physical characteristics | Density
When applying the synthetic hierarchical clustering method (HCM) by Nesvorný, "Elisa" is a member of the Flora family (), a giant asteroid family and the largest family of stony asteroids in the main-belt. However, according to another HCM-analysis by Milani and Knežević (AstDys), it is a background asteroid as this analysis does not recognize the Flora asteroid clan. "Elisa" orbits the Sun in the inner asteroid belt at a distance of 1.8–2.8 AU once every 3 years and 6 months (1,273 days; semi-major axis of 2.3 AU). Its orbit has an eccentricity of 0.20 and an inclination of 6° with respect to the ecliptic.
956 Elisa | Orbit and classification
In the Tholen classification, this object is an uncommon Q-type asteroid, that falls into the larger stony S-complex. As of 2018, no rotational lightcurve of this asteroid has been obtained from photometric observations. The body's rotation period, pole and shape remain unknown. It has a brightness variation of 0.69 magnitude, indicative for an elongated, non-spherical shape.
(85182) 1991 AQ | Physical characteristics
This arrangement was referred to as the "asteroid hypothesis", in analogy to asteroids occupying a single orbit in the solar system. Before this time the lanthanides were generally (and unsuccessfully) placed throughout groups I to VIII of the older 8-column form of periodic table. Although predecessors of Brauner's 1902 arrangement are recorded from as early as 1895, he is known to have referred to the "chemistry of asteroids" in an 1881 letter to Mendeleev. Other authors assigned all of the lanthanides to either group 3, groups 3 and 4, or groups 2, 3 and 4. In 1922 Niels Bohr continued the detachment process by locating the lanthanides between the s- and d-blocks.
Group 3 element | Composition of group 3
The S-type asteroid is a member of the Flora family, one of the largest groups of stony asteroids in the main-belt. It orbits the Sun in the inner main-belt at a distance of 2.0–2.3 AU once every 3 years and 3 months (1,171 days). Its orbit has an eccentricity of 0.06 and an inclination of 5° with respect to the ecliptic. The first precovery was taken at La Plata Astronomical Observatory in 1950, extending the asteroid's observation arc by 36 years prior to its discovery.
3851 Alhambra | Orbit and classification
is a member of the dynamical Apollo group, which are Earth-crossing asteroids. Conversely, it is classified as a non-Earth crossing Amor asteroid by the Minor Planet Center, due to its near-threshold perihelion of 1.011 AU. It orbits the Sun at a distance of 1.01–1.94 AU once every 21 months (655 days; semi-major axis of 1.48 AU). Its orbit has an eccentricity of 0.31 and an inclination of 13° with respect to the ecliptic. The body's observation arc begins with its official discovery observation by Spacewatch on 16 August 1993.
(7025) 1993 QA | Orbit and classification
"De Sanctis" a member of the Vesta family () when applying the hierarchical clustering method to its proper orbital elements. Vestian asteroids have a composition akin to cumulate eucrites and are thought to have originated deep within 4 Vesta's crust, possibly from the Rheasilvia crater, a large impact crater on its southern hemisphere near the South pole, formed as a result of a subcatastrophic collision. Based on osculating Keplerian orbital elements, "De Sanctis" has also been classified as a member of the Flora family (), a giant asteroid family and the largest family of stony asteroids in the main-belt. The asteroid orbits the Sun in the inner main-belt at a distance of 2.0–2.6 AU once every 3 years and 7 months (1,313 days; semi-major axis of 2.35 AU).
3268 De Sanctis | Orbit and classification
9 km), 1131 Porzia (7 km), 1235 Schorria (est. 9 km), 985 Rosina (8 km) 1310 Villigera (15 km), and 1468 Zomba (7 km); and significantly smaller than the largest members of this dynamical group, namely, 132 Aethra, 323 Brucia, 2204 Lyyli and 512 Taurinensis, which are all larger than 20 kilometers in diameter.
3343 Nedzel | Diameter and albedo
"Alexisrodrz" has been characterized as a LS-subtype by Pan-STARRS large-scale survey. This subtype is a transitional group from the common stony S-type to the rare and reddish L-type asteroids.
17119 Alexisrodrz | Physical characteristics
is a member of the Apollo group of asteroids, which are Earth-crossing asteroids. They are the largest group of near-Earth objects with approximately 10,000 known members. It orbits the Sun at a distance of 0.91–1.29 AU once every 14 months (424 days; semi-major axis of 1.1 AU). Its orbit has an eccentricity of 0.18 and an inclination of 1° with respect to the ecliptic. The body's observation arc begins with its first observation by the Mount Lemmon Survey on 31 March 2019, just a few days prior to its potential discovery observation by the Catalina Sky Survey.
2019 GC6 | Orbit and classification
The asteroid is a member of the Adeona family (), a large family of carbonaceous asteroids. In 1997, "Járacimrman"s orbit was calculated more precisely by additional observatories and it could therefore be numbered as asteroid 7796, the 312th recognized (numbered) asteroid discovered at the Kleť Observatory. Moravec suggested naming it after the fictional Czech polymath Jára Cimrman.
7796 Járacimrman | Classification and orbit