(415029) 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]

(415029) 2011 UL21 (former is 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] (415029) 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. The 2029 impact date has been ruled out. The asteroid will be farther than 0.9. AU in 2029. 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. Retrieved 2012-05-17. 2012-04-18 last obs (arc=22 years) 
  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. Retrieved 2012-05-17. 2012 04 18 (arc=22 years) 
  8. ^ "JPL Close-Approach Data: (2011 UL21)". Retrieved 2012-05-17. 2012-04-18 last obs (arc=22 years) 
  9. ^ a b "JPL Small-Body Database Search Engine: PHAs and H < 17 (mag)". JPL Solar System Dynamics. Retrieved 2011-11-20.