(367789) 2011 AG5

(367789) 2011 AG5, provisional designation 2011 AG5, is a sub-kilometer asteroid, classified as near-Earth object and potentially hazardous asteroid of the Apollo group.[1] It has a diameter of about 140 meters (460 ft).[4] It was removed from the Sentry Risk Table on 21 December 2012 and as such it now has a rating of 0 on the Torino Scale.[5]

(367789) 2011 AG5
Orbital diagram of 2011 AG5 (green) passing the Earth-Moon system in February 2040 (orbital solution from 2011)
Discovery [1][2]
Discovered byMount Lemmon Srvy.
Discovery siteMount Lemon Obs.
Discovery date8 January 2011
Designations
(367789) 2011 AG5
2011 AG5
Apollo · NEO · PHA [1][3]
Orbital characteristics [1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 1
Observation arc2.84 yr (1,038 days)
Earliest precovery date8 November 2010
Aphelion1.9893 AU
Perihelion0.8724 AU
1.4308 AU
Eccentricity0.3903
1.71 yr (625 days)
276.67°
0° 34m 33.24s / day
Inclination3.6822°
135.67°
53.556°
Earth MOID0.0001 AU · 0 LD
Physical characteristics
Dimensions140 m[4]
Mass4×109 kg (assumed)[4]
21.8[1]

    Description

    2011 AG5 was discovered on 8 January 2011 by the Mount Lemmon Survey at an apparent magnitude of 19.6 using a 1.52-meter (60 in) reflecting telescope.[3][2] Pan-STARRS precovery images from 8 November 2010 extended the observation arc to 317 days. Observations by the Gemini 8.2-metre (320 in) telescope at Mauna Kea recovered the asteroid on October 20, 21 and 27, 2012,[6] and extended the observation arc to 719 days.[3]

    The October 2012 observations have reduced the orbit uncertainties by more than a factor of 60, meaning that the Earth's position in February 2040 no longer falls within the range of possible future paths for the asteroid.[6] On 4 February 2040 the asteroid will pass no closer than 0.006 AU (900,000 km; 560,000 mi) (~2.3 LD) from Earth.[7] Until 21 December 2012 it was listed on the Sentry Risk Table with a rating on the Torino Scale of Level 1.[5] A Torino rating of 1 is a routine discovery in which a pass near the Earth is predicted that poses no unusual level of danger.[8] It is estimated that an impact would produce the equivalent of 100 megatons of TNT,[4] roughly twice that of the most powerful nuclear weapon ever detonated (Tsar Bomba). This is powerful enough to damage a region at least a hundred miles wide.

    Older risks

    Virtual clones of the asteroid that fit the mid-2012 uncertainty region in the known trajectory showed four potential impacts between 2040 and 2047.[4] It had a 1 in 500 chance of impacting the Earth on 5 February 2040.[4] In September 2013, there was an opportunity to make additional observations of 2011 AG5 when it came within 0.98 AU (147,000,000 km; 91,000,000 mi) of Earth.[9] The 2013 observations allowed a further refinement to the known trajectory. The asteroid will also pass 0.0121 AU (1,810,000 km; 1,120,000 mi) from the Earth on 3 February 2023.[7][10] The 2023 gravitational keyhole was 227 miles (365 kilometers) wide.[11] With a Palermo Technical Scale of -1.00,[4] the odds of impact by 2011 AG5 were about 10 times less[12] than the background hazard level of Earth impacts which is defined as the average risk posed by objects of the same size or larger over the years until the date of the potential impact.[13]

    References
    1. "JPL Small-Body Database Browser: 367789 (2011 AG5)" (2013-09-11 last obs.). Jet Propulsion Laboratory. Retrieved 17 January 2018.
    2. "MPEC 2011-A31 : 2011 AG5". IAU Minor Planet Center. 9 January 2011. Retrieved 17 October 2011. (K11A05G)
    3. "367789 (2011 AG5)". Minor Planet Center. Retrieved 17 January 2018.
    4. "Earth Impact Risk Summary: 2011 AG5". Wayback Machine: NASA/JPL Near-Earth Object Program Office. Archived from the original on 18 November 2012. Retrieved 12 December 2012.
    5. "Date/Time Removed". NASA/JPL Near-Earth Object Program Office. Retrieved 21 December 2012.
    6. ""All Clear" Given on Potential 2040 Impact of Asteroid 2011 AG5". NASA/JPL Near-Earth Object Program Office. 21 December 2012. Retrieved 21 December 2012.
    7. "JPL Close-Approach Data: (2011 AG5)" (last observation: 2013-09-11; arc: 2.84 years). Retrieved 21 September 2013.
    8. "The Torino Impact Hazard Scale". NASA/JPL Near-Earth Object Program Office. 13 April 2005. Retrieved 5 November 2011.
    9. "Asteroid 2011 AG5 - A Reality Check". NASA/JPL Near-Earth Object Program Office. 28 February 2012. Retrieved 29 February 2012.
    10. "NEODyS-2 Close Approaches for 2011AG5". Near Earth Objects - Dynamic Site. Retrieved 21 September 2013.
    11. "NASA Releases Workshop Data and Findings on Asteroid 2011 AG5". NASA/JPL. 15 June 2012. Retrieved 16 June 2012. (2012-178)
    12. Math: 101.00 = 10
    13. "The Palermo Technical Impact Hazard Scale". NASA/JPL Near-Earth Object Program Office. 31 August 2005. Retrieved 14 October 2011.
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