(415029) 2011 UL21

(Redirected from 2011 UL21)

(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]

(415029) 2011 UL21
Discovery[1]
Discovered byCatalina Sky Srvy.
Discovery siteCatalina Stn.
Discovery date17 October 2011
Designations
(415029) 2011 UL21
2011 UL21
Apollo · NEO · PHA[2]
Orbital characteristics[2]
Epoch 13 January 2016 (JD 2457400.5)
Uncertainty parameter 0
Observation arc9379 days (25.68 yr)
Aphelion3.5091 AU (524.95 Gm)
Perihelion0.73606 AU (110.113 Gm)
2.1226 AU (317.54 Gm)
Eccentricity0.65323
3.09 yr (1129.5 d)
110.19°
0° 19m 7.392s / day
Inclination34.845°
275.60°
284.74°
Known satellites1 moonlet discovered
Earth MOID0.0185982 AU (2.78225 Gm)
Physical characteristics
2.5 km[3]
Mass2.1×1013 kg (assumed)[3]
15.8[2]

Description

edit

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]

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.[8] The next largest PHA (based on absolute magnitude) discovered in 2011 is 2011 WO41 with an absolute magnitude of 16.8.[8]

On 27 June 2024 it had a relatively close fly-by with the Earth, reaching a minimum distance of 0.044 AU (6,600,000 km; 4,100,000 mi) from it.[9][10] It was revealed to be orbited by a moonlet.[11]

Chronology of close approaches of large near-Earth objects since 1981 (A)
PHA Date Approach distance in lunar distances Abs. mag
(H)
Diameter (C)
(m)
Ref (D)
Nominal (B) Minimum Maximum
(143651) 2003 QO104 1981-05-18 2.761 2.760 2.761 16.0 1333–4306 data
2014 LJ21 1989-08-01 7.034 6.843 7.224 16.0 1333–4306 data
4179 Toutatis 1992-12-08 9.399 9.399 9.399 15.30 2440–2450 data
4179 Toutatis 2004-09-29 4.031 4.031 4.031 15.30 2440–2450 data
(159857) 2004 LJ1 2038-11-16 7.719 7.719 7.719 15.4 1746–4394 data
(4953) 1990 MU 2058-06-05 8.986 8.984 8.988 14.1 3199–10329 data
4179 Toutatis 2069-11-05 7.725 7.724 7.725 15.30 2440–2450 data
(52768) 1998 OR2 2079-04-16 4.611 4.611 4.612 15.8 1462–4721 data
(415029) 2011 UL21 2089-06-25 6.936 6.935 6.938 15.7 1531–4944 data
3200 Phaethon 2093-12-14 7.714 7.709 7.718 14.6 4900–5300 data
(52768) 1998 OR2 2127-04-16 6.536 6.510 6.563 15.8 1462–4721 data
(A) This list includes near-Earth approaches of less than 10 lunar distances (LD) of objects with H brighter than 16.
(B) Nominal geocentric distance from the center of Earth to the center of the object (Earth has a radius of approximately 6,400 km).
(C) Diameter: estimated, theoretical mean-diameter based on H and albedo range between X and Y.
(D) Reference: data source from the JPL SBDB, with AU converted into LD (1 AU≈390 LD)
(E) Color codes:   unobserved at close approach   observed during close approach   upcoming approaches

See also

edit
  • 2024 MK - a near-Earth object that made close approach on 29 June 2024

References

edit
  1. ^ a b "MPEC 2011-U39 : 2011 UL21". IAU Minor Planet Center. 28 October 2011. Retrieved 1 November 2011.
  2. ^ a b c d "JPL Small-Body Database Browser: (2011 UL21)". Jet Propulsion Laboratory. Retrieved 8 April 2016. 2012-04-18 last obs (arc=22 years)
  3. ^ a b "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. ^ "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. ^ David Morrison (26 October 2011). "Should we be concerned about 2011 UL21". NASA Ask An Astrobiologist. Retrieved 6 November 2011.[dead link]
  6. ^ "Date/Time Removed". NASA/JPL Near-Earth Object Program Office. Retrieved 6 November 2011.
  7. ^ "2011 UL21 Orbit". Minor Planet Center. Retrieved 17 May 2012. 2012 04 18 (arc=22 years)
  8. ^ a b "JPL Small-Body Database Search Engine: PHAs and H < 17 (mag)". JPL Solar System Dynamics. Retrieved 20 November 2011.
  9. ^ "JPL Close-Approach Data: (2011 UL21)". Retrieved 17 May 2012. 2012-04-18 last obs (arc=22 years)
  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.
  11. ^ Carter, Jamie. "NASA Drops Stunning New Images Of Mile-Wide Asteroid With Its Own Moon". Forbes. Retrieved 5 July 2024.
edit