Editing C-type asteroid

{{short description|Asteroid spectral type; most common variety, forming around 75% of known asteroids}}
{{More citations needed|date=June 2010}}
[[File:(253) mathilde.jpg|thumb|right|[[253 Mathilde]], a C-type asteroid]]

'''C-type''' ([[carbon]]aceous {{IPAc-en|ˌ|k|ɑːr|b|ə|ˈ|n|eɪ|ʃ|ə|s}}) '''asteroids''' are the most common variety, forming around 75% of known [[asteroid]]s.<ref>{{Cite book |last1=Gradie |first1=J. C. |url=https://archive.org/details/asteroidsii0000unse |title=Asteroids II |last2=Chapman |first2=C. R. |last3=Tedesco |first3=E. F. |publisher=[[University of Arizona Press]] |year=1989 |isbn=0-8165-1123-3 |editor-last=Binzel |editor-first=R. P. |location=[[Tucson]] |pages=316–335 |chapter=Distribution of taxonomic classes and the compositional structure of the asteroid belt |ol=OL2199416M |editor-last2=Gehrels |editor-first2=T. |editor-last3=Matthews |editor-first3=M. S. |chapter-url=https://archive.org/details/asteroidsii0000unse/page/316 |url-access=registration}}</ref> 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. They have an average density of about {{val|1.7|u=g/cm3}}.

They lie most often at the outer edge of the [[asteroid belt]], {{convert|3.5|au|e6km e6mi |abbr=unit |lk=on}} from the [[Sun]], where 80% of the asteroids are of this type, whereas only 40% of asteroids at {{convert|2|au|e6km e6mi |abbr=unit}} from the Sun are C-type.<ref>{{cite web |url=https://esa.int/Our_Activities/Space_Science/Asteroids_Structure_and_composition_of_asteroids |title=Asteroids: Structure and composition of asteroids |publisher=[[European Space Agency|ESA]]}}</ref> The proportion of C-types may actually be greater than this, since C-types are much darker (and hence [[sampling bias|less detectable]]) than most other asteroid types, except for [[D-type asteroid|D-types]] and others that lie mostly at the extreme outer edge of the asteroid belt.

==Characteristics==
Asteroids of this class have [[spectrum|spectra]] very similar to those of [[carbonaceous chondrite]] [[meteorite]]s (types CI and CM). The latter are very close in chemical composition to the [[Sun]] and the primitive [[solar nebula]] minus [[hydrogen]], [[helium]] and other volatiles. [[Hydrate]]d (water-containing) minerals are present.<ref name=norton>{{cite book |title=The Cambridge Encyclopedia of Meteorites |last=Norton |first=O. Richard |year=2002 |publisher=[[Cambridge University Press]] |location=Cambridge |isbn=0-521-62143-7 |pages=121–124}}</ref>

C-type asteroids are extremely dark, with [[albedo]]s typically in the 0.03 to 0.10 range. Consequently, whereas a number of [[S-type asteroid]]s can normally be viewed with [[binoculars]] at [[opposition (astronomy)|opposition]], even the largest C-type asteroids require a small [[telescope]]. The potentially brightest C-type asteroid is [[324 Bamberga]], but that object's very high [[Orbital eccentricity|eccentricity]] means it rarely reaches its maximum [[apparent magnitude|magnitude]].

Their [[electromagnetic spectrum|spectra]] contain moderately strong [[ultraviolet]] absorption at wavelengths below about 0.4 μm to 0.5 μm, while at longer wavelengths they are largely featureless but slightly reddish. The so-called "water" absorption feature of around 3 μm, which can be an indication of water content in minerals, is also present.

Due to their volatile-rich (icy) composition, C-type asteroids have relatively low density. A survey of 20 C-type asteroids found an average density of {{val|1.7|u=g/cm3}}.<ref name="VLT">{{Cite journal |last1=Vernazza |first1=P. |last2=Ferrais |first2=M. |last3=Jorda |first3=L. |last4=Hanuš |first4=J. |last5=Carry |first5=B. |last6=Marsset |first6=M. |last7=Brož |first7=M. |last8=Fetick |first8=R. |last9=Viikinkoski |first9=M. |last10=Marchis |first10=F. |last11=Vachier |first11=F. |last12=Drouard |first12=A. |last13=Fusco |first13=T. |last14=Birlan |first14=M. |last15=Podlewska-Gaca |first15=E. |display-authors=1 |date=2021 |title=VLT/SPHERE imaging survey of the largest main-belt asteroids: Final results and synthesis |url=https://www.aanda.org/articles/aa/abs/2021/10/aa41781-21/aa41781-21.html |journal=Astronomy & Astrophysics |volume=654 |doi=10.1051/0004-6361/202141781 |issn=0004-6361 |doi-access=free |bibcode=2021A&A...654A..56V |article-number=A56|hdl=10261/263281 |hdl-access=free }}</ref>

The largest unequivocally C-type asteroid is [[10 Hygiea]], although the [[asteroid spectral types#SMASS classification|SMASS classification]] places the largest asteroid, [[Ceres (dwarf planet)|1 Ceres]], here as well, because that scheme lacks a [[G-type asteroid|G-type]].

== C-group classifications ==

=== C-group (Tholen) ===

In the [[asteroid spectral types#Tholen classification|Tholen classification]], the C-type is grouped along with three less numerous types into a wider C-group of carbonaceous asteroids which contains:{{citation needed|date=February 2012}}
* [[B-type asteroid|B-type]]
* C-type
* [[F-type asteroid|F-type]]
* [[G-type asteroid|G-type]]

=== C-group (SMASS) ===

In the [[asteroid spectral types#SMASS classification|SMASS classification]], the wider C-group contains the types:{{citation needed|date=February 2012}}
* B-type corresponding to the Tholen B and F-types
* a core C-type for asteroids having the most "typical" spectra in the group
* Cg and Cgh types corresponding to the Tholen [[G-type asteroid|G-type]]
* Ch type with an absorption feature around 0.7μm
* Cb type corresponding to transition objects between the SMASS C and B types

==See also==
*[[Asteroid spectral types]]

==References==
{{reflist}}
*<div id="Bus2002">{{Cite journal |last1=Bus |first1=S. J. |last2=Binzel |first2=R. P. |date=2002 |title=Phase II of the Small Main-Belt Asteroid Spectroscopic Survey A Feature-Based Taxonomy |url=https://picture.iczhiku.com/resource/paper/SyiwUawiiRzekMmN.pdf |journal=Icarus |volume=158 |issue=1 |pages=146–177 |doi=10.1006/icar.2002.6856 |bibcode=2002Icar..158..146B |issn=0019-1035}} </div>

{{Asteroids}}
{{Small Solar System bodies}}

{{DEFAULTSORT:C-Type Asteroid}}
[[Category:Asteroid spectral classes]]
[[Category:C-type asteroids (SMASS)|*]]
[[Category:C-type asteroids (Tholen)|*]]