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T-type Asteroids (SMASS)
T-type asteroids are rare inner-belt asteroids of unknown composition with dark, featureless and moderately red spectra, and a moderate absorption feature shortwards of 0.85 μm. No direct meteorite analog has been found to date. Thought to be anhydrous, they are considered to be related to P-types or D-types, or possibly a highly altered C-type. Examples of T-type asteroids include 96 Aegle, 114 Kassandra, 233 Asterope, and 308 Polyxo. The infrared spectrum of the first three are similar to the mineral troilite, while 308 Polyxo is modified with hydration features. In 2010, the asteroid 596 Scheila was impacted by a projectile. The impact changed its spectrum from T-type to D-type, likely by exposing fresh material that was not weathered. See also *Asteroid spectral types 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 s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Asteroid
An asteroid is a minor planet of the inner Solar System. Sizes and shapes of asteroids vary significantly, ranging from 1-meter rocks to a dwarf planet almost 1000 km in diameter; they are rocky, metallic or icy bodies with no atmosphere. 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 the main asteroid belt. Asteroids are generally classified to be of three types: C-type, M-type, and S-type. These were named after and are generally identified with carbonaceous, metallic, and silicaceous compositions, respectively. The size of asteroids varies greatly; the largest, Ceres, is almost across and qualifies as a dwarf planet. The total mass of all the asteroids combined 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 comple ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electromagnetic Spectrum
The electromagnetic spectrum is the range of frequencies (the spectrum) of electromagnetic radiation and their respective wavelengths and photon energies. The electromagnetic spectrum covers electromagnetic waves with frequencies ranging from below one hertz to above 1025 hertz, corresponding to wavelengths from thousands of kilometers down to a fraction of the size of an atomic nucleus. This frequency range is divided into separate bands, and the electromagnetic waves within each frequency band are called by different names; beginning at the low frequency (long wavelength) end of the spectrum these are: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays at the high-frequency (short wavelength) end. The electromagnetic waves in each of these bands have different characteristics, such as how they are produced, how they interact with matter, and their practical applications. There is no known limit for long and short wavelengths. Extreme ultr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Meteorite
A meteorite is a solid piece of debris from an object, such as a comet, asteroid, or meteoroid, that originates in outer space and survives its passage through the atmosphere to reach the surface of a planet or Natural satellite, moon. When the original object enters the atmosphere, various factors such as friction, pressure, and chemical interactions with the atmospheric gases cause it to heat up and radiate energy. It then becomes a meteor and forms a Meteoroid#Fireball, fireball, also known as a shooting star; astronomers call the brightest examples "Bolide#Astronomy, bolides". Once it settles on the larger body's surface, the meteor becomes a meteorite. Meteorites vary greatly in size. For geologists, a bolide is a meteorite large enough to create an impact crater. Meteorites that are recovered after being observed as they transit the atmosphere and Impact event, impact the Earth are called meteorite falls. All others are known as meteorite finds. Meteorites have traditiona ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anhydrous
A substance is anhydrous if it contains no water. Many processes in chemistry can be impeded by the presence of water; therefore, it is important that water-free reagents and techniques are used. In practice, however, it is very difficult to achieve perfect dryness; anhydrous compounds gradually absorb water from the atmosphere so they must be stored carefully. Solids Many salts and solids can be dried using heat, or under vacuum. Desiccators can also be used to store reagents in dry conditions. Common desiccants include phosphorus pentoxide and silica gel. Chemists may also require dry glassware for sensitive reactions. This can be achieved by drying glassware in an oven, by flame, or under vacuum. Dry solids can be produced by freeze-drying, which is also known as lyophilization. Liquids or solvents In many cases, the presence of water can prevent a reaction from happening, or cause undesirable products to form. To prevent this, anhydrous solvents must be used when performi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
P-type Asteroid
P-type asteroids are asteroids that have low albedo and a featureless reddish spectrum. It has been suggested that they have a composition of organic rich silicates, carbon and anhydrous silicates, possibly with water ice in their interior. P-type asteroids are found in the outer asteroid belt and beyond. There are in the neighborhood of 33 known P-type asteroids, depending on the classification, including 46 Hestia, 65 Cybele, 76 Freia, 87 Sylvia, 153 Hilda, 476 Hedwig and, in some classifications, 107 Camilla. Taxonomy 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
D-type Asteroid
D-type asteroids have a very low albedo and a featureless reddish Asteroid spectral types, spectrum. It has been suggested that they have a composition of organic-rich silicates, carbon and anhydrous silicates, possibly with water ice in their interiors. D-type asteroids are found in the outer asteroid belt and beyond; examples are 152 Atala, and 944 Hidalgo as well as the majority of Jupiter Trojan, Jupiter trojans. It has been suggested that the Tagish Lake (meteorite), Tagish Lake meteorite was a fragment from a D-type asteroid, and that the Martian moon Phobos (moon), Phobos is closely related. The Nice model suggests that D-type asteroids may have originated in the Kuiper belt. 46 D-type asteroids are known, including: 3552 Don Quixote, 944 Hidalgo, 624 Hektor, and 10199 Chariklo. Examples A list of some of the largest D-type asteroids. See also * Asteroid spectral types * Tagish Lake (meteorite) References Asteroid spectral classes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
C-type Asteroid
C-type (carbonaceous) asteroids are the most common variety, forming around 75% of known asteroids. They are volatile-rich and distinguished by a very low albedo because their composition includes a large amount of carbon, in addition to rocks and minerals. Their density averages at about . They occur most frequently at the outer edge of the asteroid belt, 3.5 astronomical units (AU) from the Sun, where 80% of the asteroids are of this type, whereas only 40% of asteroids at 2 AU from the Sun are C-type. The proportion of C-types may actually be greater than this, because C-types are much darker (and therefore less detectable) than most other asteroid types except for D-types and others that are mostly at the extreme outer edge of the asteroid belt. Characteristics Asteroids of this class have spectra very similar to those of carbonaceous chondrite meteorites (types CI and CM). The latter are very close in chemical composition to the Sun and the primitive solar nebula minus h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
96 Aegle
Aegle (minor planet designation: 96 Aegle) is a carbonaceous asteroid and the namesake of the Aegle family located in the outer regions of the asteroid belt, approximately in diameter. It was discovered on 17 February 1868, by French astronomer Jérôme Coggia at the Marseille Observatory in southeastern France. The rare T-type asteroid has a rotation period of 13.8 hours and has been observed several times during occultation events. It was named after Aegle, one of the Hesperides (nymphs of the evening) from Greek mythology. Orbit and classification ''Aegle'' is the parent body of the Aegle family (), a very small asteroid family of less than a hundred known members. It orbits the Sun in the outer asteroid belt at a distance of 2.6–3.5 AU once every 5 years and 4 months (1,948 days; semi-major axis of 3.05 AU). Its orbit has an eccentricity of 0.14 and an inclination of 16 ° with respect to the ecliptic. The body's observation arc begins at Litchfield Observat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
114 Kassandra
Kassandra (minor planet designation: 114 Kassandra) is a large and dark main-belt asteroid. It belongs to the rare class T. It was discovered by C. H. F. Peters on July 23, 1871, and is named after Cassandra, the prophetess in the tales of the Trojan War. The asteroid is featured in the 2009 film ''Meteor'', in which it is split in two by a comet, and set on a collision course with Earth. This object is classified as a rare T-type asteroid, with parts of the spectrum displaying properties similar to the mineral troilite and to carbonaceous chondrite. The shape of the spectrum also appears similar to fine grain from the Ornans meteorite, which landed in France in 1868. The light curve for this asteroid displays a period of 10.758 ± 0.004 hours with a brightness variation of 0.25 ± 0.01 in magnitude. During 2001, 114 Kassandra was observed by radar from the Arecibo Observatory. The return signal matched an effective diameter of 100 ± 14 km. This is consistent with the as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
233 Asterope
Asterope ( minor planet designation: 233 Asterope) is a large main-belt asteroid that was discovered on 11 May 1883, by French astronomer Alphonse Borrelly at Marseille Observatory in Marseille, France. The asteroid was named after Asterope (or Sterope), one of the Pleiades. This asteroid is orbiting the Sun with a semimajor axis of , a period of 4.34 years, and an eccentricity of 0.10. The orbital plane is inclined by 7.68° to the plane of the ecliptic. It is a rare T-type asteroid and has a relatively dark surface. The spectrum of 233 Asterope bears a resemblance to Troilite, a sulfurous iron mineral found in most iron meteorites. Photometric observations during 1995 show a rotation period of 19.743 hours. Measurements made with the IRAS observatory give a diameter of 109.56 ± 5.04 km and a geometric albedo of 0.08 ± 0.01. By comparison, the MIPS photometer A photometer is an instrument that measures the strength of electromagnetic radiation in the range fro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
308 Polyxo
Polyxo ( minor planet designation: 308 Polyxo) is a main-belt asteroid that was discovered by A. Borrelly on March 31, 1891, in Marseilles. It is orbiting the Sun at a distance of with a low orbital eccentricity (ovalness) of 0.04 and a period of . The orbital plane is tilted at an angle of 4.36° to the plane of the ecliptic. 308 Polyxo is classified as a rare T-type asteroid, with a spectrum that bears some similarity to the Tagish Lake meteorite. A spectral feature at a wavelength of suggests aqueous alteration of some surface materials. Photometric measurements reported in 1983 give a rotation period of 12.03 hours and a brightness variation of 0.20 in magnitude. The adaptive optics instrument at the W. M. Keck Observatory shows an oblate object with a diameter of 130 km. The size ratio between the major and minor axes is 1.26 ± 0.11. Light curves for this object suggests it has a very irregular shape. Stellar occultation events were observed for this asteroid du ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Troilite
Troilite is a rare iron sulfide mineral with the simple formula of FeS. It is the iron-rich endmember of the pyrrhotite group. Pyrrhotite has the formula Fe(1-x)S (x = 0 to 0.2) which is iron deficient. As troilite lacks the iron deficiency which gives pyrrhotite its characteristic magnetism, troilite is non-magnetic. Troilite can be found as a native mineral on Earth but is more abundant in meteorites, in particular, those originating from the Moon and Mars. It is among the minerals found in samples of the meteorite that struck Russia in Chelyabinsk on February 15th, 2013. Uniform presence of troilite on the Moon and possibly on Mars has been confirmed by the Apollo, Viking and Phobos space probes. The relative intensities of isotopes of sulfur are rather constant in meteorites as compared to the Earth minerals, and therefore troilite from Canyon Diablo meteorite is chosen as the international sulfur isotope ratio standard, the Canyon Diablo Troilite (CDT). Structure Troilit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
