2011 UL21

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]
Epoch 2011-Oct-23
(Uncertainty=7)[2]
Aphelion 3.51 AU (Q)
Perihelion 0.736 AU (q)
Semi-major axis 2.12 AU (a)
Eccentricity 0.653
Orbital period 3.09 yr
Mean anomaly 338.2° (M)
Inclination 34.84°
Longitude of ascending node 275.6°
Argument of perihelion 284.7°
Physical characteristics
Dimensions ~2500 meters[3]
Mass 2.1×1013 kg (assumed)[3]
Absolute magnitude (H) 15.6[2]

2011 UL21 is an Apollo asteroid discovered on October 17, 2011 by the Catalina Sky Survey project.[1] The asteroid is estimated to have a diameter of 2.5 km. It was rated at Torino Scale 1 on October 27, 2011.[3] 2011 UL21 briefly had about a 1 in a million chance of impacting in 2029.[4] It's cumulative impact probability was dropped to 1 in 71 million by 02 November 2011 with an observation arc of 15 days. It was removed from the Sentry Risk Table on 04 November 2011.[5]

With a preliminary absolute magnitude (H) of 15.6,[2] it is potentially the largest/brightest potentially hazardous object detected in years.[6]

References

  1. ^ a b "MPEC 2011-U39 : 2011 UL21". IAU Minor Planet Center. 2011-10-28. http://www.minorplanetcenter.net/mpec/K11/K11U39.html. Retrieved 2011, Nov 1. 
  2. ^ a b c d e "JPL Small-Body Database Browser: (2011 UL21)". Jet Propulsion Laboratory. 2011-10-31 last obs (arc=13 days). http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2011UL21. Retrieved 2011, Nov 1. 
  3. ^ a b c "Earth Impact Risk Summary: 2011 UL21". NASA/JPL Near-Earth Object Program Office. http://neo.jpl.nasa.gov/risk/2011ul21.html. Retrieved 2011, Nov 1. 
  4. ^ David Morrison (October 27, 2011). "Should we be concerned about 2011 UL21". NASA Ask An Astrobiologist. http://astrobiology.nasa.gov/ask-an-astrobiologist/question/?id=18090. Retrieved 2011-11-06. 
  5. ^ "Date/Time Removed". NASA/JPL Near-Earth Object Program Office. http://neo.jpl.nasa.gov/risk/removed.html. Retrieved 2011-11-06. 
  6. ^ "JPL Small-Body Database Search Engine: PHAs and H < 17 (mag)". JPL Solar System Dynamics. http://ssd.jpl.nasa.gov/sbdb_query.cgi?obj_group=pha;obj_kind=all;obj_numbered=all;OBJ_field=0;ORB_field=0;c1_group=OBJ;c1_item=Ai;c1_op=%3C;c1_value=17;table_format=HTML;max_rows=100;format_option=comp;c_fields=AcBhBgBjBkBlBiBnBsCkCqAi;.cgifields=format_option;.cgifields=obj_kind;.cgifields=obj_group;.cgifields=obj_numbered;.cgifields=ast_orbit_class;.cgifields=table_format;.cgifields=com_orbit_class&query=1&c_sort=AcA. Retrieved 2011-11-20.