Astronomy:(415029) 2011 UL21

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(415029) 2011 UL21
Discovery[1]
Discovered byCatalina Sky Srvy.
Discovery siteCatalina Stn.
Discovery date17 October 2011
Designations
(415029) 2011 UL21
2011 UL21
Minor planet categoryApollo · NEO · PHA[2]
Orbital characteristics[2]
Epoch 13 January 2016 (JD 2457400.5)
Uncertainty parameter 0
Observation arc9379 days (25.68 yr)
|{{{apsis}}}|helion}}3.5091 astronomical unit|AU (524.95 Gm)
|{{{apsis}}}|helion}}0.73606 AU (110.113 Gm)
2.1226 AU (317.54 Gm)
Eccentricity0.65323
Orbital period3.09 yr (1129.5 d)
Mean anomaly110.19°
Mean motion0° 19m 7.392s / day
Inclination34.845°
Longitude of ascending node275.60°
284.74°
Earth MOID0.0185982 AU (2.78225 Gm)
Physical characteristics
Mean diameter2.5 km[3]
Mass2.1×1013 kg (assumed)[3]
Absolute magnitude (H)15.8[2]


(415029) 2011 UL21, provisional designation 2011 UL21, is an Apollo class potentially hazardous asteroid 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]

Description

2011 UL21 briefly had about a 1 in a million chance of impacting in 2029.[5] Its cumulative impact probability dropped to 1 in 71 million by 2 November 2011 when the observation arc reached 15 days. It was removed from the Sentry Risk Table on 4 November 2011 when all impact scenarios for the next 100 years or more were ruled out.[6] During 2029, the closest approach to Earth is 1.6 AU. 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 astronomical unit|AU (6,600,000 km; 4,100,000 mi).[8]

With an absolute magnitude of 15.8,[2] it is one of the brightest and therefore largest potentially hazardous asteroids (PHA) 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

  1. ↑ 1.0 1.1 "MPEC 2011-U39 : 2011 UL21". IAU Minor Planet Center. 2011-10-28. https://www.minorplanetcenter.net/mpec/K11/K11U39.html. Retrieved November 1, 2011. 
  2. ↑ 2.0 2.1 2.2 2.3 "JPL Small-Body Database Browser: (2011 UL21)". Jet Propulsion Laboratory. https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2011UL21. Retrieved 8 April 2016. "2012-04-18 last obs (arc=22 years)" 
  3. ↑ 3.0 3.1 "Earth Impact Risk Summary: 2011 UL21". NASA/JPL Near-Earth Object Program Office. http://neo.jpl.nasa.gov/risk/2011ul21.html. Retrieved November 1, 2011. 
  4. ↑ "Observations of small Solar-System bodies". hohmanntransfer. 2011-10-27. http://www.hohmanntransfer.com/mn/11/11300_1027.htm#2011UL21. Retrieved 2013-09-04.  (1.5e-06 = 1 in 667,000 chance)
  5. ↑ David Morrison (October 26, 2011). "Should we be concerned about 2011 UL21". NASA Ask An Astrobiologist. https://www.astrobiology.nasa.gov/ask-an-astrobiologist/answered/2011/10/27/2058/. Retrieved 2011-11-06. 
  6. ↑ "Date/Time Removed". NASA/JPL Near-Earth Object Program Office. https://cneos.jpl.nasa.gov/sentry/removed.html. Retrieved 2011-11-06. 
  7. ↑ "2011 UL21 Orbit". Minor Planet Center. https://www.minorplanetcenter.net/db_search/show_object?object_id=2011+UL21. Retrieved 2012-05-17. "2012 04 18 (arc=22 years)" 
  8. ↑ "JPL Close-Approach Data: (2011 UL21)". https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2011UL21;cad=1#cad. Retrieved 2012-05-17. "2012-04-18 last obs (arc=22 years)" 
  9. ↑ 9.0 9.1 "JPL Small-Body Database Search Engine: PHAs and H < 17 (mag)". JPL Solar System Dynamics. https://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=AcBhBgBjBiBnBsCkCqAi;.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. 

External links



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