View source for Astronomy:2011 XC2

{{Short description|Near-Earth asteroid}}
{{DISPLAYTITLE:2011 XC<sub>2</sub>}}
{{Infobox planet
| minorplanet = yes
| background = #FFC2E0
| name = {{mp|2011 XC|2}}
| discovery_ref = <ref name="MPEC2011-X35"/>
| discoverer = [[Astronomy:Lincoln Near-Earth Asteroid Research|LINEAR]] (704)
| discovered = 8 December 2011
| mpc_name = {{mp|2011 XC|2}}
| mp_category = {{mpcat|Apollo}}<br/>[[Astronomy:Near-Earth object|NEO]]<ref name="jpldata"/>
| orbit_ref = <ref name="jpldata"/>
| epoch = 13 January 2016 ([[Astronomy:Julian day|JD]] 2457400.5)
| observation_arc = 22 days
| aphelion = {{Convert|3.1579|AU|Gm|abbr=on|lk=on}} (Q)
| perihelion = {{Convert|0.83844|AU|Gm|abbr=on}} (q)
| semimajor = {{Convert|1.9982|AU|Gm|abbr=on}} (a)
| eccentricity = 0.58040 (e)
| period = 2.82 [[Astronomy:Julian year|yr]] (1031.7 [[Astronomy:Julian year|d]])
| inclination = 28.768° (i)
| asc_node = 70.686° (Ω)
| mean_anomaly = 176.76[[Degree (angle)|°]] (M)
| arg_peri = 306.58° (ω)
| dimensions = ~{{convert|85|m|sp=us}}<ref name=summary/><br />60–140 meters<ref name="h"/>
| mass = 8.4{{e|8}} kg (assumed)<ref name=summary/>
| magnitude = 
| abs_magnitude = 23.2<ref name="jpldata"/>
| mean_motion = {{Deg2DMS|0.34894|sup=ms}} /day (n)
| uncertainty = 7
| moid = {{Convert|0.00132534|AU|km|abbr=on}}
| jupiter_moid = {{Convert|2.67756|AU|Gm|abbr=on}}
}}
'''{{mp|2011 XC|2}}''' (also written [[Astronomy:Astronomical naming conventions#Minor planets|2011 XC2]]) is a [[Astronomy:Near-Earth asteroid|near-Earth asteroid]] roughly {{convert|60|-|140|m|sp=us}} in diameter that passed less than 1 [[Astronomy:Lunar distance|lunar distance]] from Earth on 3 December 2011.<ref name=jpl-close/>

From mid October 2011 until 3 December 2011 15:00&nbsp;[[Astronomy:Universal Time|UT]] the small dim asteroid had an [[Astronomy:Elongation|elongation]] less than 60 degrees from the Sun.<ref name="NEODyS2011"/> (While less than 18 degrees from the Sun any dim asteroid can be lost in astronomical twilight, and many [[Astronomy:Observatory|observatories]] can not see below ~40 degrees from the [[Horizon|horizon]].) On 3 December 2011 at 15:20&nbsp;UT the asteroid passed {{convert|0.0023|AU|km mi|abbr=on|lk=on}} from Earth and at 16:20&nbsp;UT passed {{convert|0.0016|AU|km mi|abbr=on|lk=off}} from the Moon.<ref name=jpl-close/> The asteroid was then discovered on 8 December 2011 by [[Astronomy:Lincoln Near-Earth Asteroid Research|Lincoln Near-Earth Asteroid Research]] (LINEAR) at an [[Astronomy:Apparent magnitude|apparent magnitude]] of 19 using a {{convert|1.0|m|in|adj=on|sp=us}} [[Astronomy:Reflecting telescope|reflecting telescope]].<ref name="MPEC2011-X35"/> At the time of discovery the asteroid was near [[Astronomy:Opposition (planets)|opposition]] to the Sun.<ref name="NEODyS2011"/>

It has an observation arc of 22 days with an uncertainty parameter of 7.<ref name=jpldata/> Virtual clones of the asteroid that fit the uncertainty region in the known trajectory show a 1 in 455,000 chance that the asteroid will [[Astronomy:Impact event|impact]] Earth on 2 December 2056.<ref name="summary"/> With a 2056 Palermo Technical Scale of −4.35,<ref name=summary/> the odds of impact by {{mp|2011 XC|2}} in 2056 are about 22387 times less<ref name=math/> than the background hazard level of Earth impacts which is defined as the average risk posed by objects of the same size or larger over the years until the date of the potential impact.<ref name="palermo"/> Using the [[Curve fitting|nominal]] orbit, [[Astronomy:JPL Horizons On-Line Ephemeris System|JPL Horizons]] shows that the asteroid will be {{convert|3.8|AU|km mi|abbr=on|lk=off}} from Earth on 2 December 2056.<ref name=Horizons/>

{|class="wikitable collapsible collapsed sortable"
|+H < 24 asteroids passing less than 1 LD from Earth
!Asteroid
!Date
!Nominal approach distance (LD)
!Min. distance (LD)
!Max. distance (LD)
![[Astronomy:Absolute magnitude|Absolute magnitude]] (H)
!Size (meters)
|-bgcolor=#c2c2c2
|{{mpl|(152680) 1998 KJ|9}} || 1914-12-31 || 0.606 || 0.604 || 0.608 || 19.4 || 279–900
|-bgcolor=#c2c2c2
|{{mpl|(458732) 2011 MD|5}} || 1918-09-17 || 0.911 || 0.909 || 0.913 || 17.9 || 556–1795
|-bgcolor=#c2c2c2
|{{mpl|(163132) 2002 CU|11}} || 1925-08-30 || 0.903 || 0.901 || 0.905 || 18.5 || ''443–477''
|-bgcolor=#c2c2c2
|{{mpl|2010 VB|1}} || 1936-01-06 || 0.553 || 0.553 || 0.553 || 23.2 || 48–156
|-bgcolor=#c2c2c2
|{{mpl|2002 JE|9}} || 1971-04-11 || 0.616 || 0.587 || 0.651 || 21.2 || 122–393
|-bgcolor=#c2c2c2
|{{mpl|2013 UG|1}} || 1976-10-17 || 0.854 || 0.853 || 0.855 || 22.3 || 73–237
|-bgcolor=#c2c2c2
|{{mpl|2012 TY|52}} || 1981-11-04 || 0.818 || 0.813 || 0.823 || 21.4 || 111–358
|-bgcolor=#c2c2c2
|{{mpl|2012 UE|34}} || 1991-04-08 || 0.847 || 0.676 || 1.027 || 23.3 || 46–149
|-bgcolor=#c2c2c2
|{{mpl|2017 VW|13}} || 2001-11-08 || 0.454 || 0.318 || 3.436 || 20.7 || 153–494
|-
|[[Astronomy:2002 MN|2002 MN]] || 2002-06-14 || 0.312 || 0.312 || 0.312 || 23.6 || 40–130
|-
|{{mpl|(308635) 2005 YU|55}} || 2011-11-08 || 0.845 || 0.845 || 0.845 || 21.9 || ''320–400''
|-
|'''{{mp|2011 XC|2}}''' || '''2011-12-03''' || '''0.904''' || '''0.901''' || '''0.907''' || '''23.2''' || '''48–156'''
|-
|[[Astronomy:2018 AH|2018 AH]] || 2018-01-02 || 0.773 || 0.772 || 0.773 || 22.5 || 67–216
|-
|{{mpl|2018 GE|3}} || 2018-04-15 || 0.502 || 0.501 || 0.503 || 23.7 || 35–135
|-bgcolor=#e2e2e2
|{{mpl|(153814) 2001 WN|5}} || 2028-06-26 || 0.647 || 0.647 || 0.647 || 18.2 || ''921–943''
|-bgcolor=#e2e2e2
|[[Astronomy:99942 Apophis|99942 Apophis]] || 2029-04-13 || 0.0981 || 0.0963 || 0.1000 || 19.7 || ''310–340''
|-bgcolor=#e2e2e2
|{{mp|2012 UE|34}} || 2041-04-08 || 0.283 || 0.274 || 0.354 || 23.3 || 46–149
|-bgcolor=#e2e2e2
|{{mpl|2015 XJ|351}} || 2047-06-06 || 0.789 || 0.251 || 38.135 || 22.4 || 70–226
|-bgcolor=#e2e2e2
|{{mpl|2007 TV|18}} || 2058-09-22 || 0.918 || 0.917 || 0.919 || 23.8 || 37–119
|-bgcolor=#e2e2e2
|{{mpl|2005 WY|55}} || 2065-05-28 || 0.865 || 0.856 || 0.874 || 20.7 || 153–494
|-bgcolor=#e2e2e2
|{{mp|(308635) 2005 YU|55}} || 2075-11-08 || 0.592 || 0.499 || 0.752 || 21.9 || ''320–400''
|-bgcolor=#e2e2e2
|{{mpl|(456938) 2007 YV|56}} || 2101-01-02 || 0.621 || 0.615 || 0.628 || 21.0 || 133–431
|-bgcolor=#e2e2e2
|{{mpl|2007 UW|1}} || 2129-10-19 || 0.239 || 0.155 || 0.381 || 22.7 || 61–197
|-bgcolor=#e2e2e2
|[[Astronomy:101955 Bennu|101955 Bennu]] || 2135-09-25 || 0.780 || 0.308 || 1.406 || 20.19 || ''472–512''
|-bgcolor=#e2e2e2
|{{mpl|(153201) 2000 WO|107}} || 2140-12-01 || 0.634 || 0.631 || 0.637 || 19.3 || ''427–593''
|-bgcolor=#e2e2e2
|{{mpl|2009 DO|111}} || 2146-03-23 || 0.896 || 0.744 || 1.288 || 22.8 || 58–188
|-bgcolor=#e2e2e2
|{{mpl|(85640) 1998 OX|4}} || 2148-01-22 || 0.771 || 0.770 || 0.771 || 21.1 || 127–411
|-bgcolor=#e2e2e2
|{{mpl|2007 UY|1}} || 2156-02-13 || 0.685 || 0.652 || 6.856 || 22.9 || 56–179
|-bgcolor=#e2e2e2
|{{mpl|2011 LT|17}} || 2156-12-16 || 0.998 || 0.955 || 1.215 || 21.6 || 101–327
|}

==References==
{{Reflist
| refs =
<ref name=jpldata>{{cite web
  |type=last observation: 2011-12-30; [[Astronomy:Observation arc|arc]]: 22 days
  |title=JPL Small-Body Database Browser: (2011 XC2)
  |url=http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2011XC2
  |archive-url=https://web.archive.org/web/20190528050534/https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2011XC2
  |url-status=dead
  |archive-date=28 May 2019
  |publisher=[[Organization:Jet Propulsion Laboratory|Jet Propulsion Laboratory]]
  |accessdate=1 April 2016}}</ref>

<ref name="MPEC2011-X35">{{cite web
  |title=MPEC 2011-X35 : 2011 XC2
  |publisher=IAU Minor Planet Center
  |date=2011-12-11
  |url=http://www.minorplanetcenter.net/mpec/K11/K11X35.html
  |accessdate=2014-02-20}} (K11X02C)</ref>

<ref name=jpl-close>{{cite web
  |type=last observation: 2011-12-30; [[Astronomy:Observation arc|arc]]: 22 days
  |title=JPL Close-Approach Data: (2011 XC2)
  |url=http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2011XC2;cad=1#cad
  |accessdate=2014-02-20}}</ref>

<ref name=summary>{{cite web
  |title=Earth Impact Risk Summary: 2011 XC2
  |publisher=NASA/JPL Near-Earth Object Program Office
  |url=https://cneos.jpl.nasa.gov/sentry/details.html#?des=2011%20XC2
  |accessdate=2014-02-20}}</ref>

<ref name=math>Math: 10<sup>4.35</sup>&nbsp;=&nbsp;22387</ref>

<ref name="palermo">{{cite web
  |date=31 Aug 2005
  |title=The Palermo Technical Impact Hazard Scale
  |publisher=NASA/JPL Near-Earth Object Program Office
  |url=http://neo.jpl.nasa.gov/risk/doc/palermo.html
  |archive-url=https://web.archive.org/web/20020321092747/http://neo.jpl.nasa.gov/risk/doc/palermo.html
  |url-status=dead
  |archive-date=21 March 2002
  |accessdate=2014-02-20}}</ref>

<ref name="h">{{cite web
  |title=Absolute Magnitude (H)
  |publisher=NASA/JPL
  |url=http://neo.jpl.nasa.gov/glossary/h.html
  |archive-url=https://web.archive.org/web/20010302182040/http://neo.jpl.nasa.gov/glossary/h.html
  |url-status=dead
  |archive-date=2001-03-02
  |accessdate=2014-02-20}}</ref>

<ref name="NEODyS2011">{{cite web
  |title=2011XC2 Ephemerides for 11 October 2011 through 17 December 2011
  |publisher=[[Astronomy:NEODyS|NEODyS]] (Near Earth Objects – Dynamic Site)
  |url=http://newton.spacedys.com/neodys/index.php?pc=1.1.3.1&n=2011XC2&oc=500&y0=2011&m0=10&d0=11&h0=0&mi0=0&y1=2011&m1=12&d1=17&h1=0&mi1=0&ti=1.0&tiu=days
  |accessdate=2014-02-20}}</ref>

<ref name=Horizons>{{cite web
  |author=[[Astronomy:JPL Horizons On-Line Ephemeris System|Horizons]] output
  |url=http://ssd.jpl.nasa.gov/horizons.cgi?find_body=1&body_group=sb&sstr=2011XC2
  |title=Horizon Online Ephemeris System
  |accessdate=2014-02-20}} (Geocentric Solution)</ref>

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

== External links ==
* {{NeoDys|2011+XC2}}
* {{ESA-SSA|2011XC2}}
* {{JPL small body|id=3590911}}

{{s-start}}
{{s-bef|before={{mpl|(308635) 2005 YU|55}}}}
{{s-ttl|title=Large [[Astronomy:Near-Earth object|NEO]] Earth close approach<br />(inside the orbit of the Moon)|years=3 December 2011}}
{{s-aft|after=[[Astronomy:367943 Duende|367943 Duende]] ({{mp|2012 DA|14}})}}
{{end}}

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{{Small Solar System bodies}}
{{2011 in space}}

{{DEFAULTSORT:2011 XC2}}
[[Category:Apollo asteroids|#]]

{{Sourceattribution|2011 XC2}}