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2010 WC9

2010 WC9, unofficially designated ZJ99C60, is a sub-kilometer near-Earth asteroid of the Apollo group, approximately 100 meters (330 feet) in diameter. First observed for eleven days by the Catalina Sky Survey in 2010, the asteroid was recovered in May 2018 during its sub-lunar close encounter with Earth.[4]

2010 WC9
Orbit of 2010 WC9 with positions before 2018 flyby
Discovery[1]
Discovered byCatalina Sky Srvy.
Discovery siteCatalina Stn.
(first observed only)
Discovery date30 November 2010
Designations
2010 WC9
ZJ99C60[2][3]
Orbital characteristics
Epoch 23 March 2018 (JD 2458200.5)
Uncertainty parameter 0
Observation arc7.45 yr (2,721 d)
Aphelion1.3797 AU
Perihelion0.7784 AU
1.0791 AU
Eccentricity0.2786
1.12 yr (409 d)
251.06°
0° 52m 45.48s / day
Inclination17.994°
54.655°
273.53°
Earth MOID0.00138 AU (0.5454 LD)
Venus MOID0.158 AU (23,600,000 km)[1]
Physical characteristics
8–20 minutes
23.5[4]

First observation and recovery

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2010 WC9 was first observed by astronomers with the Catalina Sky Survey on 30 November 2010 with a 1-day observation arc[6] and was observed through 10 December 2010.[7] By 10 December 2010, the asteroid was more than 24 million kilometers from Earth[6] at apparent magnitude 21.8[1] and was becoming too faint to be practical to track.

The preliminary 10-day observation arc generated a line of variation roughly 15 million km long for May 2018 that did not intersect Earth's orbit and thus was not a 2018 impact threat.[8] The 10-day observation arc showed the asteroid would pass about 0.026 AU (3,900,000 km; 2,400,000 mi) from Earth around late 14 May 2018. The asteroid was recovered on 8 May 2018 when it was 8 million kilometers from Earth and given the temporary NEOCP designation ZJ99C60.[2] It was removed from the Sentry Risk Table on 10 May 2018[9] and is not an impact threat for the next 100 years or more. The asteroid now has a secure 7-year observation arc.[4]

Orbit and classification

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2010 WC9 is an Apollo asteroid, the largest dynamical group of near-Earth objects with nearly 10,000 known members. It orbits the Sun at a distance of 0.78–1.4 AU once every 13 months (409 days; semi-major axis of 1.08 AU). Its orbit has an eccentricity of 0.28 and an inclination of 18° with respect to the ecliptic.[4]

Using an epoch of 23 March 2018, the object had a minimum orbital intersection distance with Earth of 206,000 km (0.00138 AU), or 0.55 lunar distances (LD).[4]

2018 approach

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On 15 May 2018, 22:05 UT, the asteroid approached Earth at just over 0.5 LD, the closest approach of this asteroid in nearly 300 years.[3] It was expected to reach apparent magnitude +11 at closest approach,[10] bright enough to be seen in a small telescope if you have a custom ephemeris for your location. At closest approach, it was best seen from the Southern hemisphere such as South Africa and southern South America. The asteroid passed Earth going 12.81 km/s (28,700 mph).[4]

This was the third closest approach ever observed by an asteroid with absolute magnitude (H) brighter than 24.[11]

 
 
Flyby in 2018: geocentric trajectory in the sky (top) and flyby from north to south, shown with hourly motion (bottom)
Animation of 2010 WC9's orbit
 
Around the Sun
 
Around the Earth
  2010 WC9 ·   Sun ·   Earth ·   Moon
History of closest approaches of large near-Earth objects since 1914
(less than H 24 and 1 LD)(A)
NEO Date Approach distance in lunar distances Abs. mag
(H) 		Diameter (C)
(m) 		Ref (D)
Nominal(B) Minimum Maximum
(152680) 1998 KJ9 1914-12-31 0.606 0.604 0.608 19.4 279–900 data
(458732) 2011 MD5 1918-09-17 0.911 0.909 0.913 17.9 556–1795 data
(163132) 2002 CU11 1925-08-30 0.903 0.901 0.905 18.5 443–477 data
2010 VB1 1936-01-06 0.553 0.553 0.553 23.2 48–156 data
2002 JE9 1971-04-11 0.616 0.587 0.651 21.2 122–393 data
2013 UG1 1976-10-17 0.854 0.853 0.855 22.3 73–237 data
2012 TY52 1982-11-04 0.818 0.813 0.822 21.4 111–358 data
2012 UE34 1991-04-08 0.847 0.676 1.027 23.3 46–149 data
2017 VW13 2001-11-08 0.373 0.316 3.236 20.7 153–494 data
2002 MN 2002-06-14 0.312 0.312 0.312 23.6 40–130 data
(308635) 2005 YU55 2011-11-08 0.845 0.845 0.845 21.9 320–400 data
2011 XC2 2011-12-03 0.904 0.901 0.907 23.2 48–156 data
2018 AH 2018-01-02 0.773 0.772 0.773 22.5 67–216 data
2018 GE3 2018-04-15 0.502 0.501 0.503 23.7 35–135 data
2010 WC9 2018-05-15 0.528 0.528 0.528 23.5 42–136 data
(153814) 2001 WN5 2028-06-26 0.647 0.647 0.647 18.2 921–943 data
99942 Apophis 2029-04-13 0.0989 0.0989 0.0989 19.7 310–340 data
2012 UE34 2041-04-08 0.283 0.274 0.354 23.3 46–149 data
2015 XJ351 2047-06-06 0.789 0.251 38.135 22.4 70–226 data
2007 TV18 2058-09-22 0.918 0.917 0.919 23.8 37–119 data
2005 WY55 2065-05-28 0.865 0.856 0.874 20.7 153–494 data
(308635) 2005 YU55 2075-11-08 0.592 0.499 0.752 21.9 320–400 data
(456938) 2007 YV56 2101-01-02 0.621 0.615 0.628 21.0 133–431 data
2007 UW1 2129-10-19 0.239 0.155 0.381 22.7 61–197 data
101955 Bennu 2135-09-25 0.531 0.507 0.555 20.19 472–512 data
(153201) 2000 WO107 2140-12-01 0.634 0.631 0.637 19.3 427–593 data
2009 DO111 2146-03-23 0.896 0.744 1.288 22.8 58–188 data
(85640) 1998 OX4 2148-01-22 0.771 0.770 0.771 21.1 127–411 data
2011 LT17 2156-12-16 0.998 0.955 1.215 21.6 101–327 data
(A) This list includes near-Earth approaches of less than 1 lunar distances (LD) of objects with H brighter than 24.
(B) Nominal geocentric distance from the center of Earth to the center of the object (Earth has a radius of approximately 6,400 km).
(C) Diameter: estimated, theoretical mean-diameter based on H and albedo range between 0.05 and 0.25.
(D) Reference: data source from the JPL SBDB, with AU converted into LD (1 AU≈390 LD)
(E) Color codes:   unobserved at close approach   observed during close approach   upcoming approaches
Note: All close approaches between 1900 and 2200 are listed (with H<24 at less than 1 LD). Objects not observed during the approach,
and simply estimated to have approached on this date, are colored grey. Generically estimated asteroid diameters are given in italics.

Physical characteristics

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Diameter

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As the asteroid has not been directly resolved by telescope, its diameter can only be estimated based on the distance and brightness. Based on a generic magnitude-to-diameter conversion, it is estimated to measure between 60 and 130 meters in diameter, for an absolute magnitude of 23.5,[4] and an assumed albedo of 0.04–0.20.[3][5]

Numbering and naming

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As of 2018, this minor planet has neither been numbered nor named by the Minor Planet Center.[1]

See also

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References

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  1. ^ a b c d e "2010 WC9". Minor Planet Center. Retrieved 11 May 2018.
  2. ^ a b ""Pseudo-MPEC" for ZJ99C60". projectpluto.com. 10 May 2018. Archived from the original on 12 May 2018. Retrieved 14 May 2018.
  3. ^ a b c d Irizarry, Eddie (12 May 2018). ""Lost" asteroid to pass closely May 15". earthsky.org. Retrieved 12 May 2018.
  4. ^ a b c d e f g h "JPL Small-Body Database Browser: (2010 WC9)" (2018-05-13 last obs.). Jet Propulsion Laboratory. Archived from the original on 10 May 2018. Retrieved 11 May 2018.
  5. ^ a b c "Asteroid Size Estimator". CNEOS NASA/JPL. Retrieved 14 May 2018.
  6. ^ a b "MPEC 2010-X07 : 2010 WC9". IAU Minor Planet Center. 1 December 2010. Retrieved 13 May 2018. (K10W09C)
  7. ^ "MPC/MPO/MPS Archive: MPS 358671-362682" (PDF). IAU Minor Planet Center. 19 December 2010. Retrieved 13 May 2018. (pg 645)
  8. ^ Earth Impact Risk Summary: 2010 WC9 (10 day arc; computed on Sep 20, 2015) "2010 WC9 Impact Risk". Archived from the original on 15 December 2016. Retrieved 13 May 2018.
  9. ^ Removed Objects "Sentry: Earth Impact Monitoring". Archived from the original on 13 May 2018. Retrieved 14 May 2018.{{cite web}}: CS1 maint: bot: original URL status unknown (link)
  10. ^ "2010WC9 Ephemerides for 15–16 May 2018". NEODyS (Near Earth Objects – Dynamic Site). Retrieved 14 May 2018.
  11. ^ "Closest Approaches to the Earth by Minor Planets". Minor Planet Center. Retrieved 14 May 2018.
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