(308635) 2005 YU55
Goldstone radar image of asteroid 2005 YU55
taken 7 November 2011.
Discovery[1]
Discovered byR. S. McMillan
Steward Observatory
Kitt Peak (691)
Discovery date28 December 2005
Designations
(308635) 2005 YU55
2005 YU55
Orbital characteristics[2]
Epoch 13 January 2016 (JD 2457400.5)
Uncertainty parameter 0
Observation arc2,183 days (5.98 yr)
Aphelion1.65562913 AU (247.678593 Gm) (Q)
Perihelion0.659003712 AU (98.5855521 Gm) (q)
1.15731642 AU (173.132072 Gm) (a)
Eccentricity0.430576028 (e)
1.25 Jyr (454.75 d)
175.227687° (M)
0° 47m 29.892s / day (n)
Inclination0.340553512° (i)
35.9073158° (Ω)
273.628156° (ω)
Known satellitesnone[3]
Earth MOID0.000433476 AU (64,847.1 km)
(0.17 LD)[2]
Venus MOID0.0017 AU
(0.66 LD)[4]
Mars MOID0.03884 AU
(15.11 LD)[4]
Jupiter MOID3.60813 AU (539.769 Gm)
TJupiter5.347
Physical characteristics
Dimensions360±40 m[5][6][7][8]
Mean radius
0.2 km
18 h (0.75 d)
19.31±0.02 h[2][9]
0.042±0.008
C-type[6][9][10]
21.9[2][9]

    (308635) 2005 YU55, provisionally named 2005 YU55, is a potentially hazardous asteroid[2] 360±40 meters in diameter, as measured after its Earth flyby.[8] Previously it was estimated to be 310 meters[5] or about 400 m (1,300 feet) in diameter.[6][7] It was discovered on 28 December 2005 by Robert S. McMillan at Steward Observatory, Kitt Peak.[1] On 8 November 2011 it passed 0.85 lunar distances (324,900 kilometers; 201,900 miles)[11] from Earth.

    8 November 2011 flyby

    Animation of the trajectory of asteroid 2005 YU55 compared with the orbits of Earth and the Moon on 8–9 November 2011.
    Trajectory of asteroid 2005 YU55 compared with the orbits of Earth and the Moon on 8–9 November 2011.
    Skymap showing apparent trajectory of 2005 YU55.
    Apparent trajectory on 8–9 November 2011.

    In February 2010, (308635) 2005 YU55 was rated 1 on the Torino Scale for a potential pass near Earth on 10 November 2103,[12] that posed no unusual level of danger. On 19 April 2010, radar ranging by the Arecibo radio telescope reduced uncertainties about the orbit by 50%.[7] This improvement eliminated any possibility of an impact with Earth within the next 100 years.[7] It was removed from the Sentry Risk Table on 22 April 2010 and as such it now has a rating of 0 on the Torino Scale.[13] It is now known that on 10 November 2103 (308635) 2005 YU55 will be roughly 2 AU from Earth.[14]

    On 8 November 2011 at 23:28 UT the asteroid passed 0.85 LD (330,000 km; 200,000 mi) from Earth.[11] On 9 November 2011 at 07:13 UT the asteroid passed 0.6231 LD (239,500 km; 148,800 mi) from the Moon.[15] During the close approach the asteroid reached about apparent magnitude 11,[6][16] and would have been visible to experienced observers using high-end binoculars with an objective lens of 80+ mm if it were not for bright moonlight preventing a true dark sky. Since the gibbous moon did interfere with the viewing,[3] observers trying to visually locate the asteroid required a telescope with an aperture of 6 inches (15 centimeters) or larger.[3][11]

    The next few times a known asteroid this large will come this close to Earth will be in 2028[3] when (153814) 2001 WN5 passes 0.65 LD from Earth,[17] and in 2029 when the 325-meter 99942 Apophis comes even closer at just 0.10 LD.[18]

    According to Jay Melosh, if an asteroid the size of (308635) 2005 YU55 (~400 m across) were to hit land, it would create a crater 6.3 km (3.9 mi) across, 518 m (1,699 ft) deep and generate a seven-magnitude-equivalent-earthquake.[19] The chances of an actual collision with an asteroid like (308635) 2005 YU55 is about 1 percent in the next thousand years.[19]

    History of closest approaches of large near-Earth objects since 1914
    (less than H 24 and 1 LD)(A)
    NEO Date Approach distance in lunar distances Abs. mag
    (H)    		 Diameter (C)
    (m)    		 Ref (D)
    Nominal(B) Minimum Maximum
    (152680) 1998 KJ91914-12-310.6060.6040.60819.4279–900data
    (458732) 2011 MD51918-09-170.9110.9090.91317.9556–1795data
    (163132) 2002 CU111925-08-300.9030.9010.90518.5443–477data
    2010 VB11936-01-060.5530.5530.55323.248–156data
    2002 JE91971-04-110.6160.5870.65121.2122–393data
    2013 UG11976-10-170.8540.8530.85522.373–237data
    2012 TY521982-11-040.8180.8130.82221.4111–358data
    2012 UE341991-04-080.8470.6761.02723.346–149data
    2017 VW132001-11-080.3730.3163.23620.7153–494data
    2002 MN2002-06-140.3120.3120.31223.640–130data
    (308635) 2005 YU552011-11-080.8450.8450.84521.9320–400data
    2011 XC22011-12-030.9040.9010.90723.248–156data
    2018 AH2018-01-020.7730.7720.77322.567–216data
    2018 GE32018-04-150.5020.5010.50323.735–135data
    2010 WC92018-05-150.5280.5280.52823.542–136data
    (153814) 2001 WN52028-06-260.6470.6470.64718.2921–943data
    99942 Apophis2029-04-130.09890.09890.098919.7310–340data
    2012 UE342041-04-080.2830.2740.35423.346–149data
    2015 XJ3512047-06-060.7890.25138.13522.470–226data
    2007 TV182058-09-220.9180.9170.91923.837–119data
    2005 WY552065-05-280.8650.8560.87420.7153–494data
    (308635) 2005 YU552075-11-080.5920.4990.75221.9320–400data
    (456938) 2007 YV562101-01-020.6210.6150.62821.0133–431data
    2007 UW12129-10-190.2390.1550.38122.761–197data
    101955 Bennu2135-09-250.5310.5070.55520.19472–512data
    (153201) 2000 WO1072140-12-010.6340.6310.63719.3427–593data
    2009 DO1112146-03-230.8960.7441.28822.858–188data
    (85640) 1998 OX42148-01-220.7710.7700.77121.1127–411data
    2011 LT172156-12-160.9980.9551.21521.6101–327data
    (A) This list includes near-Earth approaches of less than 1 lunar distances (LD) of objects with H brighter than 24.
    (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 0.05 and 0.25.
    (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
    Note: All close approaches between 1900 and 2200 are listed (with H<24 at less than 1 LD). Objects not observed during the approach,
    and simply estimated to have approached on this date, are colored grey. Generically estimated asteroid diameters are given in italics.

    Study

    During the 2011 passage (308635) 2005 YU55 was studied with radar using Goldstone, Arecibo, the Very Long Baseline Array, and the Green Bank Telescope.[3] The Herschel Space Observatory has made far-infrared measurements of (308635) 2005 YU55 on 10 November, helping determine its temperature and composition.[20]

    Radar analysis has also helped to pin down the asteroid's albedo, or diffuse reflectivity. Although radar measurements do not detect visible light they can determine the distance and size of an object with a high degree of accuracy. This information, coupled with visible light measurements, provides a more accurate measure of an object's absolute magnitude, and therefore its albedo.

    On 8 November 2011, NASA released a statement mentioning a number of structures on the surface of the asteroid, which were detected as it passed near Earth.[21] On 11 November 2011, higher-resolution images showed concavities, a ridge near the asteroid's equator, and numerous features interpreted as decameter-scale boulders.[8][22] Shape modeling based on the radar images shows that YU55's shape is close to spheroidal, with maximum dimensions of 360±40 m, and an equator-aligned ridge. A 150–200 meter-long, ~20 meter-high rise forms a portion of the ridge-line, and the number of boulders on the surface is comparable to that seen on the asteroid 25143 Itokawa by the Hayabusa spacecraft.[8]

    Optical lightcurve measurements during the flyby provided a more accurate estimate of the asteroid's spin period – about 19.3 hours.[9] Because (308635) 2005 YU55 is so nearly spheroidal, it was not significantly torqued by Earth's tides during the flyby, and there is no evidence of non-principal-axis rotation. Optical, near-infrared,[10] and ultraviolet[23] spectroscopy confirmed that 2005 YU55 is a C-type asteroid.

    Future trajectory

    On 19 January 2029, (308635) 2005 YU55 will pass 0.0023 AU (340,000 km; 210,000 mi) from Venus.[15] The close approach distance to Venus in 2029 will determine how close the asteroid will pass to Earth in 2041.[3] Before the November 2011 observations, the uncertainties in the post-2029 trajectory showed that the asteroid would pass somewhere between 0.002 AU (300,000 km; 190,000 mi) and 0.3 AU (45,000,000 km; 28,000,000 mi) of Earth in 2041.[3] Radar astrometry in November 2011 clarified the Earth passage in 2041 and beyond.[3] As a result of the November 2011 radar observations, it is now known that (308635) 2005 YU55 will pass between 0.1017 AU (15,210,000 km; 9,450,000 mi) and 0.1020 AU of Earth on 12 November 2041.[15] Using the current uncertainty region integrated until the future, the 2075 approach will be between 0.0013 AU (190,000 km; 120,000 mi) and 0.0021 AU (310,000 km; 200,000 mi).[15]

    References

    1. 1 2 "MPEC 2005 Y47 : 2005 YU55". IAU Minor Planet Center. 29 December 2005. Retrieved 5 May 2011.
    2. 1 2 3 4 5 6 "last observation: 2011-12-16; arc: 5.98 years". JPL Small-Body Database Browser: 308635 (2005 YU55). Retrieved 7 April 2016.
    3. 1 2 3 4 5 6 7 8 Dr. Lance A. M. Benner (29 October 2011). "2005 YU55 Goldstone Radar Observations Planning". NASA/JPL Asteroid Radar Research. Retrieved 30 October 2011.
    4. 1 2 "Minor Planet Center – 2005 YU55". Minor Planet Center. Retrieved 19 November 2014.
    5. 1 2 The Herschel Space Observatory catches a glimpse of the minor planet during its rendezvous with Earth (17 November 2011)
    6. 1 2 3 4 Don Yeomans; Lance Benner & Jon Giorgini (10 March 2011). "Asteroid 2005 YU55 to approach Earth on November 8, 2011". NASA/JPL Near-Earth Object Program Office. Archived from the original on 24 April 2011. Retrieved 5 May 2011.
    7. 1 2 3 4 Blaine Friedlander, Jr. (30 April 2010). "Arecibo telescope tracks 'potentially dangerous' asteroid within 1.5 million miles of Earth". Cornell Chronicle @ Cornell University. Archived from the original on 23 May 2011. Retrieved 5 May 2011.
    8. 1 2 3 4 M.W. Busch; et al. (31 March 2012). "Shape and spin of near-Earth asteroid 308635 (2005 YU55) from radar images and speckle tracking" (PDF). LPI. Retrieved 9 April 2012.
    9. 1 2 3 4 B.D. Warner; et al. (31 March 2012). "CCD photometric observations of 2005 YU55 during the 2011 November flyby" (PDF). LPI. Retrieved 9 April 2012.
    10. 1 2 N.A. Moskovitz (31 March 2012). "The near-Earth encounter of 2005 YU55: Time-resolved visible and near-infrared spectroscopy" (PDF). LPI. Retrieved 9 April 2012.
    11. 1 2 3 "NASA in Final Preparations for Nov. 8 Asteroid Flyby". NASA/JPL. 26 October 2011. Archived from the original on 13 January 2012. Retrieved 26 October 2011.
    12. ↑ "Earth impact risk summary: 2005 YU55". NASA/JPL Near-Earth Object program office. 25 March 2010. Archived from the original on 25 March 2010. Retrieved 23 October 2013 – via Wayback Machine.
      "6.1e-04 = 1 in 1,640 chance". jpl.nasa.gov. Archived from the original on 2013-10-24. Retrieved 2013-10-23.
    13. ↑ "Date/Time Removed". NASA/JPL Near-Earth Object Program Office. Archived from the original on 26 April 2011. Retrieved 6 May 2011.
    14. ↑ "(308635) 2005YU55 Ephemerides for 10 November 2103". NEODyS (Near Earth Objects – Dynamic Site). Retrieved 23 October 2013.
    15. 1 2 3 4 "last observation: 2011-12-16; arc: 5.98 years". JPL close-approach data: (2005 YU55). Retrieved 7 September 2013.
    16. ↑ "2005 YU55 Ephemerides for 9 Nov 2011". Near Earth Objects – Dynamics (NEODyS). Retrieved 5 May 2011.
    17. ↑ "Last observation: 2011-01-04; arc: 14.9 years". JPL close-approach data: 153814 (2001 WN5). Retrieved 16 October 2011.
    18. ↑ "NEO Earth Close-Approaches (Between 1900 A.D. and 2200 A.D., NEOs with H <=22, nominal distance within 5 LD)". Near-Earth Object Program Office. NASA/JPL. Archived from the original on 13 December 2012. Retrieved 17 May 2015.
    19. 1 2 Elizabeth K. Gardner (31 October 2011). "Large asteroid to pass by Earth Nov. 8, but what if it didn't?". Purdue University. Retrieved 7 November 2011.
    20. ↑ Chris North (6 November 2011). "Herschel to observe near-Earth asteroid". UK outreach site for the Herschel Space Observatory. Retrieved 7 November 2011.
    21. ↑ "NASA releases radar movie of Asteroid 2005 YU55". NASA. 8 November 2011. Retrieved 6 December 2011.
    22. ↑ "NASA releases updated radar movie of asteroid 2005 YU55 (2011–351)". NASA/JPL. 11 November 2011. Retrieved 6 December 2011.
    23. ↑ Bodewits, Dennis; et al. (5 December 2011). "2005 YU_55". Central Bureau for Astronomical Telegrams. Electronic Telegram. Retrieved 14 November 2018.
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