B-type asteroids are a relatively uncommon type of

carbon Carbon () is a chemical element; it has chemical symbol, symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—meaning that its atoms are able to form up to four covalent bonds due to its valence shell exhibiting 4 ...

aceous

asteroid An asteroid is a minor planet—an object larger than a meteoroid that is neither a planet nor an identified comet—that orbits within the Solar System#Inner Solar System, inner Solar System or is co-orbital with Jupiter (Trojan asteroids). As ...

, falling into the wider

C-group The C-Group culture is an archaeological culture found in Nubia, Lower Nubia, which dates from 2400 BCE to 1550 BCE. It was named by George A. Reisner. With no central site and no written evidence about what these people called themselves, Re ...

; the 'B' indicates these objects are spectrally blue. In the asteroid population, B-class objects can be found in the outer

asteroid belt The asteroid belt is a torus-shaped region in the Solar System, centered on the Sun and roughly spanning the space between the orbits of the planets Jupiter and Mars. It contains a great many solid, irregularly shaped bodies called asteroids ...

, and also dominate the high-

inclination Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a reference plane and the orbital plane or axis of direction of the orbiting object. For a satellite orbiting the Eart ...

Pallas family The Pallas family (''adj. Palladian''; ) is a small asteroid family of B-type asteroids at very high Orbital inclination, inclinations in the intermediate asteroid belt. The family was identified by Kiyotsugu Hirayama in 1928. The namesake of the ...

which includes the third-largest asteroid

2 Pallas Pallas (minor-planet designation: 2 Pallas) is the List of largest asteroids, third-largest asteroid in the Solar System by volume and mass. It is the second asteroid to have been discovered, after 1 Ceres, Ceres, and is likely a remnant ...

. They are thought to be primitive, volatile-rich remnants from the early

Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sola ...

. There are 65 known B-type asteroids in the SMASS classification, and 9 in the Tholen classification as of March 2015.

Characteristics

Generally similar to the C-type objects, but differing in that the

ultraviolet Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of ...

absorption below 0.5 μm is small or absent, and the

spectrum A spectrum (: spectra or spectrums) is a set of related ideas, objects, or properties whose features overlap such that they blend to form a continuum. The word ''spectrum'' was first used scientifically in optics to describe the rainbow of co ...

is rather slightly bluish than reddish. The

albedo Albedo ( ; ) is the fraction of sunlight that is Diffuse reflection, diffusely reflected by a body. It is measured on a scale from 0 (corresponding to a black body that absorbs all incident radiation) to 1 (corresponding to a body that reflects ...

also tends to be greater than in the generally very dark C type.

Spectroscopy Spectroscopy is the field of study that measures and interprets electromagnetic spectra. In narrower contexts, spectroscopy is the precise study of color as generalized from visible light to all bands of the electromagnetic spectrum. Spectro ...

of B-class objects suggests major surface constituents of

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 achie ...

silicates A silicate is any member of a family of polyatomic anions consisting of silicon and oxygen, usually with the general formula , where . The family includes orthosilicate (), metasilicate (), and pyrosilicate (, ). The name is also used for an ...

hydrated In chemistry, a hydrate is a substance that contains water or its constituent elements. The chemical state of the water varies widely between different classes of hydrates, some of which were so labeled before their chemical structure was understo ...

clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolinite, ). Most pure clay minerals are white or light-coloured, but natural clays show a variety of colours from impuriti ...

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2011): Mi ...

organic polymer A polymer () is a substance or material that consists of very large molecules, or macromolecules, that are constituted by many repeating subunits derived from one or more species of monomers. Due to their broad spectrum of properties, bot ...

magnetite Magnetite is a mineral and one of the main iron ores, with the chemical formula . It is one of the iron oxide, oxides of iron, and is ferrimagnetism, ferrimagnetic; it is attracted to a magnet and can be magnetization, magnetized to become a ...

, and

sulfide Sulfide (also sulphide in British English) is an inorganic anion of sulfur with the chemical formula S2− or a compound containing one or more S2− ions. Solutions of sulfide salts are corrosive. ''Sulfide'' also refers to large families o ...

s. The closest matches to B-class asteroids have been obtained on carbonaceous

chondrite A chondrite is a stony (non-metallic) meteorite that has not been modified by either melting or planetary differentiation, differentiation of the parent body. They are formed when various types of dust and small grains in the early Solar Syste ...

meteorite A meteorite is a rock (geology), rock that originated in outer space and has fallen to the surface of a planet or Natural satellite, moon. When the original object enters the atmosphere, various factors such as friction, pressure, and chemical ...

s that have been gently heated in the

laboratory A laboratory (; ; colloquially lab) is a facility that provides controlled conditions in which scientific or technological research, experiments, and measurement may be performed. Laboratories are found in a variety of settings such as schools ...

. The majority of asteroids that have been observed to display cometary-like activity are B-types. 1. Introduction: "the majority of asteroids that have been observed to display cometary-like activity are B-types" Some of these objects display indications of aqueous alteration in the past, and they may have incorporated significant amounts of water ice.

Well studied B-type asteroids

Asteroid

101955 Bennu 101955 Bennu ( provisional designation ) is a carbonaceous asteroid in the Apollo group discovered by the LINEAR Project on 11 September 1999. It is a potentially hazardous object that is listed on the Sentry Risk Table and has the second hig ...

is a B-type asteroid which is the target of the

OSIRIS-REx OSIRIS-REx was a NASA asteroid-study and sample-return mission that visited and collected samples from 101955 Bennu, a C-type asteroid, carbonaceous near-Earth object, near-Earth asteroid. The material, returned in September 2023, is expected ...

mission. The mission seeks to characterize the asteroid by mapping the surface, studying the

Yarkovsky effect The Yarkovsky effect is a force acting on a rotating body in space caused by the anisotropic emission of thermal photons, which carry momentum. It is usually considered in relation to meteoroids or small asteroids (about 10 cm to 10 km ...

, and retrieving a sample of the asteroid to return in 2023. The spacecraft was launched in 2016 and has been at Bennu since December 2018. Other B-type asteroids include: *

* 24 Themis *

47 Aglaja 47 Aglaja is a large, dark main belt asteroid. It was discovered by Robert Luther on 15 September 1857 from Düsseldorf. The name was chosen by the Philosophical Faculty of the University of Bonn and refers to Aglaea, one of the Charites in ...

* 59 Elpis *

85 Io 85 Io is a carbonaceous asteroid in the central region of the asteroid belt, approximately 170 kilometers in diameter. It is an identified Eunomian interloper. Discovery and naming It was discovered by C. H. F. Peters on 19 September 186 ...

88 Thisbe 88 Thisbe is the 13th largest main-belt asteroid. It was discovered by C. H. F. Peters on 15 June 1866, and named after Thisbe, heroine of a Roman fable. This asteroid is orbiting the Sun at a distance of with a period of and an orbital ...

* 142 Polana * 213 Lilaea * 241 Germania * 282 Clorinde * 335 Roberta * 372 Palma *

383 Janina 383 Janina is a Themistian asteroid, approximately in diameter. It is spectral B-type and is probably composed of primitive carbonaceous chondritic material. It was discovered by Auguste Charlois on 29 January 1894 in Nice. The reference of ...

* 431 Nephele * 531 Zerlina * 541 Deborah * 555 Norma * 560 Delila * 702 Alauda * 704 Interamnia * 767 Bondia * 895 Helio * 1021 Flammario * 1331 Solvejg *

1474 Beira 1474 Beira, provisional designation , is a bright carbonaceous asteroid and large Mars-crosser on an eccentric orbit from the asteroid belt, approximately 15 kilometers in diameter. It was discovered on 20 August 1935, by South African astronome ...

* 1484 Postrema * 1539 Borrelly * 1655 Comas Sola * 1705 Tapio * 1724 Vladimir * 2382 Nonie * 2446 Lunacharsky * 2527 Gregory * 2629 Rudra * 2659 Millis *

2708 Burns 2708 Burns ( ''prov. designation'': ) is a carbonaceous Themistian asteroid from the outer regions of the asteroid belt, approximately in diameter. It was discovered on 24 November 1981, by American astronomer Edward Bowell at the Anderson Me ...

* 2772 Dugan * 2809 Vernadskij * 2816 Pien * 2973 Paola * 3000 Leonardo * 3074 Popov *

3200 Phaethon 3200 Phaethon (; previously sometimes spelled Phæton), provisionally designated , is an active Apollo asteroid with an orbit that brings it closer to the Sun than any other named asteroid (though there are numerous unnamed asteroids with sm ...

* 3566 Levitan * 3579 Rockholt * 3581 Alvarez * 3627 Sayers * 3647 Dermott * 4124 Herriot * 4396 Gressmann * 4686 Maisica * 4997 Ksana * 5079 Brubeck * 5102 Benfranklin * 5133 Phillipadams * 5222 Ioffe * 5234 Sechenov * 5330 Senrikyu * 5344 Ryabov * (5690) 1992 EU * 6500 Kodaira * (7753) 1988 XB * * (65679) 1989 UQ *

References

{{Small Solar System bodies Asteroid spectral classes

Characteristics

Well studied B-type asteroids

See also

References