(415029)_2011_UL21

<span class="nowrap">(415029) 2011 UL<sub>21</sub></span>

(415029) 2011 UL21

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(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]

Quick Facts Discovery, Discovered by ...

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 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]

On 27 June 2024 it will have a relatively close fly-by with the Earth, reaching a minimum distance of 6,000,000 km from it[10]

More information PHA, Date ...
Chronology of close approaches of large near-Earth objects since 1981 (A)

References

  1. [1]
    "MPEC 2011-U39 : 2011 UL21". IAU Minor Planet Center. 28 October 2011. Retrieved 1 November 2011.
  2. [2]
    "JPL Small-Body Database Browser: (2011 UL21)". Jet Propulsion Laboratory. Retrieved 8 April 2016. 2012-04-18 last obs (arc=22 years)
  3. [3]
    "Earth Impact Risk Summary: 2011 UL21". NASA/JPL Near-Earth Object Program Office. Archived from the original on 2 November 2011. Retrieved 1 November 2011.
  4. [4]
    "Observations of small Solar-System bodies". hohmanntransfer. 27 October 2011. Archived from the original on 29 November 2014. Retrieved 4 September 2013. (1.5e-06 = 1 in 667,000 chance)
  5. [5]
    David Morrison (26 October 2011). "Should we be concerned about 2011 UL21". NASA Ask An Astrobiologist. Retrieved 6 November 2011.[dead link]
  6. [6]
    "Date/Time Removed". NASA/JPL Near-Earth Object Program Office. Retrieved 6 November 2011.
  7. [7]
    "2011 UL21 Orbit". Minor Planet Center. Retrieved 17 May 2012. 2012 04 18 (arc=22 years)
  8. [8]
    "JPL Close-Approach Data: (2011 UL21)". Retrieved 17 May 2012. 2012-04-18 last obs (arc=22 years)
  9. [9]
    "JPL Small-Body Database Search Engine: PHAs and H < 17 (mag)". JPL Solar System Dynamics. Retrieved 20 November 2011.
  10. [10]
    Masi, Gianluca (27 May 2024). "The large potentially hazardous asteroid 2011 UL21 is safely approaching, no risk for our Earth - 27 May 2024". The Virtual Telescope Project 2.0. Retrieved 28 May 2024.
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