Editing B-type asteroid

{{short description|Asteroid spectral class; uncommon type of carbonaceous asteroid}}
[[File:Bennu mosaic OSIRIS-REx (square).png|thumb|B-type asteroid Bennu imaged by ''[[OSIRIS-REx]]'' from a range of {{convert|24|km|mi|abbr=on}}]]

'''B-type asteroids''' are a relatively uncommon type of [[carbon]]aceous [[asteroid]], falling into the wider [[C-type asteroid#C-group asteroids|C-group]]; the 'B' indicates these objects are spectrally blue.<ref name=Yang2010/> In the asteroid population, B-class objects can be found in the outer [[asteroid belt]], and also dominate the high-[[inclination]] [[Pallas family]] which includes the third-largest asteroid [[2 Pallas]]. They are thought to be [[:wikt:primitive|primitive]], [[Volatile (astrogeology)|volatile]]-rich remnants from the early [[Solar System]]. There are 65 known B-type asteroids in the SMASS classification,<ref name="SBDB"/> and 9 in the Tholen classification as of March 2015.

==Characteristics==
Generally similar to the [[C-type asteroid#Characteristics|C-type]] objects, but differing in that the [[ultraviolet]] absorption below 0.5 μm is small or absent, and the [[spectrum]] is rather slightly bluish than reddish. The [[albedo]] also tends to be greater than in the generally very dark C type. [[Spectroscopy]] of B-class objects suggests major surface constituents of [[anhydrous]] [[silicates]], [[hydrated]] [[clay]] [[mineral]]s, [[organic polymer]]s, [[magnetite]], and [[sulfide]]s. The closest matches to B-class asteroids have been obtained on carbonaceous [[chondrite]] [[meteorite]]s that have been gently heated in the [[laboratory]].

The majority of asteroids that have been observed to display [[Active asteroid|cometary-like activity]] are B-types.<ref>{{cite journal |last1=Licandro |first1=J |last2=Hargrove |first2=K |last3=Kelley |first3=M |last4=Campins |first4=H |title=5–14 μm Spitzer spectra of Themis family asteroids |journal=Astronomy & Astrophysics |date=Jan 2012 |volume=537 |page=A73 |doi=10.1051/0004-6361/201118142|bibcode=2012A&A...537A..73L |doi-access=free }}</ref><ref>{{cite journal |last1=Alí-Lagoa |first1=V |last2=De León |first2=J |last3=Licandro |first3=J |last4=Delbo |first4=M |last5=Campins |first5=H |last6=Pinilla-Alonso |first6=N |last7=Kelley |first7=M |title=Physical properties of B-type asteroids from WISE data |journal=Astronomy & Astrophysics |date=Mar 2013 |volume=554 |page=A71 |doi=10.1051/0004-6361/201220680|arxiv=1303.5487 |bibcode=2013A&A...554A..71A |doi-access=free }} 1. Introduction: "the majority of asteroids
that have been observed to display cometary-like activity are B-types" </ref> Some of these objects display indications of aqueous alteration in the past, and they may have incorporated significant amounts of water ice.<ref name=Yang2010/>

== Well studied B-type asteroids ==
[[File:Potw1749a_Pallas_crop.png|thumb|right|[[2 Pallas|Pallas]], the largest B-type asteroid]]

Asteroid [[101955 Bennu]] is a B-type asteroid which is the target of the [[OSIRIS-REx]] mission. The mission seeks to characterize the asteroid by mapping the surface, studying the [[Yarkovsky effect]], 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:
{{Div col|colwidth=16em}}
* [[2 Pallas]]
* [[24 Themis]]
* [[47 Aglaja]]
* [[59 Elpis]]
* [[85 Io]]
* [[88 Thisbe]]
* [[142 Polana]]
* [[213 Lilaea]]
* [[241 Germania]]
* [[282 Clorinde]]
* [[335 Roberta]]
* [[372 Palma]]
* [[383 Janina]]
* [[431 Nephele]]
* [[531 Zerlina]]
* [[541 Deborah]]
* [[555 Norma]]
* [[560 Delila]]
* [[702 Alauda]]
* [[704 Interamnia]]
* [[767 Bondia]]
* [[895 Helio]]
* [[1021 Flammario]]
* [[1331 Solvejg]]
* [[1474 Beira]]
* [[1484 Postrema]]
* [[1539 Borrelly]]
* [[1655 Comas Sola]]
* [[1705 Tapio]]
* [[1724 Vladimir]]
* [[2382 Nonie]]
* [[2446 Lunacharsky]]
* [[2527 Gregory]]
* [[2629 Rudra]]
* [[2659 Millis]]
* [[2708 Burns]]
* [[2772 Dugan]]
* [[2809 Vernadskij]]
* [[2816 Pien]]
* [[2973 Paola]]
* [[3000 Leonardo]]
* [[3074 Popov]]
* [[3200 Phaethon]]
* [[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]]
* {{mpl|(25330) 1999 KV|4}}
* [[(65679) 1989 UQ]]
* {{mpl|(523972) 1999 CW|8}}
{{Div col end}}

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

== References ==
{{reflist
| refs =

<ref name="SBDB">{{cite web
  |title      = JPL Small-Body Database Search Engine: spec. type <nowiki>=</nowiki> B (SMASSII)
  |publisher  = [[JPL Solar System Dynamics]]
  |url        = http://ssd.jpl.nasa.gov/sbdb_query.cgi?obj_group=all;obj_kind=all;obj_numbered=all;OBJ_field=0;ORB_field=0;c1_group=OBJ;c1_item=Ax;c1_op=%3D;c1_value=B;table_format=HTML;max_rows=100;format_option=comp;c_fields=AcBhBgBjBiBnBsAiApAyAx;.cgifields=format_option;.cgifields=obj_kind;.cgifields=obj_group;.cgifields=obj_numbered;.cgifields=ast_orbit_class;.cgifields=table_format;.cgifields=com_orbit_class&query=1&c_sort=AxA  |access-date = 2015-06-17}}</ref>

<ref name=Yang2010>{{cite journal
 | title=Identification of Magnetite in B-type Asteroids
 | last1=Yang | first1=Bin | last2=Jewitt | first2=David
 | journal=The Astronomical Journal
 | volume=140 | issue=3 | pages=692–698 | date=September 2010
 | arxiv=1006.5110 | bibcode=2010AJ....140..692Y 
 | doi=10.1088/0004-6256/140/3/692 | s2cid=724871 }}</ref>

}} <!-- end of reflist -->


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

[[Category:Asteroid spectral classes]]
[[Category:B-type asteroids| ]]