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(415029) 2011 UL21

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Title::apollo    Category::removed    November::morrison    Years::asteroid    Object::format    October::sentry

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(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.<ref name="MPEC2011-U39"/> The asteroid is estimated to have a diameter of {{safesubst:#invoke:convert|convert}}. It was rated at Torino Scale 1 on October 27, 2011 with an observation arc of 9.6 days.<ref name="hohmanntransfer1027"/> (415029) 2011 UL21 briefly had about a 1 in a million chance of impacting in 2029.<ref name="Morrison"/> 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.<ref name="removed"/> Palomar Observatory precovery images from 1989 and 1990 have extended the observation arc to 22 years.<ref name=mpc/> Its next notable close approach to the Earth will be on June 27, 2024 at a distance of {{safesubst:#invoke:convert|convert}}.<ref name=jpl-close/>

With an absolute magnitude (H) of 15.8,<ref name=jpl/> it is potentially the largest/brightest potentially hazardous asteroid detected since (242450) 2004 QY2.<ref name="jpl-search"/> The next largest PHA (based on absolute magnitude) discovered in 2011 is 2011 WO41 with an absolute magnitude of 16.8.<ref name="jpl-search"/>


(415029) 2011 UL21 sections
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