2011 UL21

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2011 UL21
Discovery[1]
Discovered by Catalina Sky Survey (703)
0.68-m Schmidt + CCD
Discovery date 2011, October 17
Designations
MPC designation 2011 UL21
Minor planet category Apollo NEO,
PHA[2]
Orbital characteristics[2]
Epoch 2012-Mar-14
(Uncertainty=0)[2]
Aphelion 3.508 AU (Q)
Perihelion 0.7359 AU (q)
2.122 AU (a)
Eccentricity 0.6532
3.09 yr
23.77° (M)
Inclination 34.84°
275.6°
284.7°
Physical characteristics
Dimensions ~2500 meters[3]
Mass 2.1×1013 kg (assumed)[3]
15.8[2]

2011 UL21 is an Apollo class potentially hazardous asteroid (PHA) discovered on October 17, 2011 by the Catalina Sky Survey project.[1] The asteroid is estimated to have a diameter of 2.5 kilometres (1.6 mi). It was rated at Torino Scale 1 on October 27, 2011 with an observation arc of 9.6 days.[4] 2011 UL21 briefly had about a 1 in a million chance of impacting in 2029.[5] Its cumulative impact probability was dropped to 1 in 71 million by 2 November 2011 with an observation arc of 15 days. It was removed from the Sentry Risk Table on 4 November 2011.[6] Palomar Observatory precovery images from 1989 and 1990 have extended the observation arc to 22 years.[7] Its next notable close approach to the Earth will be on June 27, 2024 at a distance of 0.044 AU (6,600,000 km; 4,100,000 mi).[8]

With an absolute magnitude (H) of 15.8,[2] it is potentially the largest/brightest potentially hazardous asteroid detected since (242450) 2004 QY2.[9] The next largest PHA (based on absolute magnitude) discovered in 2011 is 2011 WO41 with an absolute magnitude of 16.8.[9]

References[edit]

  1. ^ a b "MPEC 2011-U39 : 2011 UL21". IAU Minor Planet Center. 2011-10-28. Retrieved November 1, 2011. 
  2. ^ a b c d e "JPL Small-Body Database Browser: (2011 UL21)". Jet Propulsion Laboratory. 2012-04-18 last obs (arc=22 years). Retrieved 2012-05-17. 
  3. ^ a b "Earth Impact Risk Summary: 2011 UL21". NASA/JPL Near-Earth Object Program Office. Retrieved November 1, 2011.  (Wayback Machine)
  4. ^ "Observations of small Solar-System bodies". hohmanntransfer. 2011-10-27. Retrieved 2013-09-04.  (1.5e-06 = 1 in 667,000 chance)
  5. ^ David Morrison (October 27, 2011). "Should we be concerned about 2011 UL21". NASA Ask An Astrobiologist. Retrieved 2011-11-06. 
  6. ^ "Date/Time Removed". NASA/JPL Near-Earth Object Program Office. Retrieved 2011-11-06. 
  7. ^ "2011 UL21 Orbit". Minor Planet Center. 2012 04 18 (arc=22 years). Retrieved 2012-05-17. 
  8. ^ "JPL Close-Approach Data: (2011 UL21)". 2012-04-18 last obs (arc=22 years). Retrieved 2012-05-17. 
  9. ^ a b "JPL Small-Body Database Search Engine: PHAs and H < 17 (mag)". JPL Solar System Dynamics. Retrieved 2011-11-20.