2011 XC₂

2011 XC₂ (also written 2011 XC2) is a near-Earth asteroid roughly 60–140 meters (200–460 ft) in diameter that passed less than 1 lunar distance from Earth on 3 December 2011.[5]

2011 XC₂

Discovery[1]
Discovered by	LINEAR (704)
Discovery date	8 December 2011
Designations
MPC designation	2011 XC2
Minor planet category	Apollo NEO[2]
Orbital characteristics[2]
Epoch 13 January 2016 (JD 2457400.5)
Uncertainty parameter 7
Observation arc	22 days
Aphelion	3.1579 AU (472.42 Gm) (Q)
Perihelion	0.83844 AU (125.429 Gm) (q)
Semi-major axis	1.9982 AU (298.93 Gm) (a)
Eccentricity	0.58040 (e)
Orbital period	2.82 yr (1031.7 d)
Mean anomaly	176.76° (M)
Mean motion	0° 20^m 56.184^s /day (n)
Inclination	28.768° (i)
Longitude of ascending node	70.686° (Ω)
Argument of perihelion	306.58° (ω)
Earth MOID	0.00132534 AU (198,268 km)
Jupiter MOID	2.67756 AU (400.557 Gm)
Physical characteristics
Dimensions	~85 meters (279 ft)[3] 60–140 meters[4]
Mass	8.4×10^8 kg (assumed)[3]
Absolute magnitude (H)	23.2[2]

From mid October 2011 until 3 December 2011 15:00 UT the small dim asteroid had an elongation less than 60 degrees from the Sun.[6] (While less than 18 degrees from the Sun any dim asteroid can be lost in astronomical twilight, and many observatories can not see below ~40 degrees from the horizon.) On 3 December 2011 at 15:20 UT the asteroid passed 0.0023 AU (340,000 km; 210,000 mi) from Earth and at 16:20 UT passed 0.0016 AU (240,000 km; 150,000 mi) from the Moon.[5] The asteroid was then discovered on 8 December 2011 by Lincoln Near-Earth Asteroid Research (LINEAR) at an apparent magnitude of 19 using a 1.0-meter (39 in) reflecting telescope.[1] At the time of discovery the asteroid was near opposition to the Sun.[6]

It has an observation arc of 22 days with an uncertainty parameter of 7.[2] 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 impact Earth on 2 December 2056.[3] With a 2056 Palermo Technical Scale of −4.35,[3] the odds of impact by 2011 XC₂ in 2056 are about 22387 times less[7] 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.[8] Using the nominal orbit, JPL Horizons shows that the asteroid will be 3.8 AU (570,000,000 km; 350,000,000 mi) from Earth on 2 December 2056.[9]

H < 24 asteroids passing less than 1 LD from Earth

Asteroid	Date	Nominal approach distance (LD)	Min. distance (LD)	Max. distance (LD)	Absolute magnitude (H)	Size (meters)
(152680) 1998 KJ9	1914-12-31	0.606	0.604	0.608	19.4	279–900
(458732) 2011 MD5	1918-09-17	0.911	0.909	0.913	17.9	556–1795
(163132) 2002 CU11	1925-08-30	0.903	0.901	0.905	18.5	443–477
2010 VB1	1936-01-06	0.553	0.553	0.553	23.2	48–156
2002 JE9	1971-04-11	0.616	0.587	0.651	21.2	122–393
2013 UG1	1976-10-17	0.854	0.853	0.855	22.3	73–237
2012 TY52	1981-11-04	0.818	0.813	0.823	21.4	111–358
2012 UE34	1991-04-08	0.847	0.676	1.027	23.3	46–149
2017 VW13	2001-11-08	0.454	0.318	3.436	20.7	153–494
2002 MN	2002-06-14	0.312	0.312	0.312	23.6	40–130
(308635) 2005 YU55	2011-11-08	0.845	0.845	0.845	21.9	320–400
2011 XC2	2011-12-03	0.904	0.901	0.907	23.2	48–156
2018 AH	2018-01-02	0.773	0.772	0.773	22.5	67–216
2018 GE3	2018-04-15	0.502	0.501	0.503	23.7	35–135
(153814) 2001 WN5	2028-06-26	0.647	0.647	0.647	18.2	921–943
99942 Apophis	2029-04-13	0.0981	0.0963	0.1000	19.7	310–340
2012 UE34	2041-04-08	0.283	0.274	0.354	23.3	46–149
2015 XJ351	2047-06-06	0.789	0.251	38.135	22.4	70–226
2007 TV18	2058-09-22	0.918	0.917	0.919	23.8	37–119
2005 WY55	2065-05-28	0.865	0.856	0.874	20.7	153–494
(308635) 2005 YU55	2075-11-08	0.592	0.499	0.752	21.9	320–400
(456938) 2007 YV56	2101-01-02	0.621	0.615	0.628	21.0	133–431
2007 UW1	2129-10-19	0.239	0.155	0.381	22.7	61–197
101955 Bennu	2135-09-25	0.780	0.308	1.406	20.19	472–512
(153201) 2000 WO107	2140-12-01	0.634	0.631	0.637	19.3	427–593
2009 DO111	2146-03-23	0.896	0.744	1.288	22.8	58–188
(85640) 1998 OX4	2148-01-22	0.771	0.770	0.771	21.1	127–411
2007 UY1	2156-02-13	0.685	0.652	6.856	22.9	56–179
2011 LT17	2156-12-16	0.998	0.955	1.215	21.6	101–327

References

1. "MPEC 2011-X35 : 2011 XC2". IAU Minor Planet Center. 11 December 2011. Retrieved 20 February 2014. (K11X02C)
2. "JPL Small-Body Database Browser: (2011 XC2)" (last observation: 2011-12-30; arc: 22 days). Jet Propulsion Laboratory. Retrieved 1 April 2016.
3. "Earth Impact Risk Summary: 2011 XC2". NASA/JPL Near-Earth Object Program Office. Retrieved 20 February 2014.
4. "Absolute Magnitude (H)". NASA/JPL. Retrieved 20 February 2014.
5. "JPL Close-Approach Data: (2011 XC2)" (last observation: 2011-12-30; arc: 22 days). Retrieved 20 February 2014.
6. "2011XC2 Ephemerides for 11 October 2011 through 17 December 2011". NEODyS (Near Earth Objects – Dynamic Site). Retrieved 20 February 2014.
7. Math: 10^4.35 = 22387
8. "The Palermo Technical Impact Hazard Scale". NASA/JPL Near-Earth Object Program Office. 31 August 2005. Retrieved 20 February 2014.
9. Horizons output. "Horizon Online Ephemeris System". Retrieved 20 February 2014. (Geocentric Solution)

External links

• 2011 XC2 at NeoDyS-2, Near Earth Objects—Dynamic Site
  • Ephemeris · Obs prediction · Orbital info · MOID · Proper elements · Obs info · Close · Physical info · NEOCC
• 2011 XC2 at ESA–space situational awareness
  • Ephemerides · Observations · Orbit · Physical Properties · Summary
• 2011 XC2 at the JPL Small-Body Database
  • Close approach · Discovery · Ephemeris · Orbit diagram · Orbital elements · Physical parameters