(152680) 1998 KJ9

(152680) 1998 KJ9 is a sub-kilometer asteroid, classified as near-Earth object and potentially hazardous asteroid of the Apollo group.[2] Based on absolute magnitude, it is the third largest asteroid known to have passed closer than the Moon.[5]

(152680) 1998 KJ9
Discovery[1]
Discovered byLINEAR (704)
1.0-m Reflector
Discovery siteLincoln Lab's ETS
Discovery date27 May 1998
Designations
(152680) 1998 KJ9
NEO · PHA · Apollo [2]
Orbital characteristics[2]
Epoch 13 January 2016 (JD 2457400.5)
Uncertainty parameter 0
Observation arc7706 days (21.10 yr)
Aphelion2.3742 AU (355.18 Gm) (Q)
Perihelion0.52125 AU (77.978 Gm) (q)
1.4477 AU (216.57 Gm) (a)
Eccentricity0.63995 (e)
1.74 yr (636.25 d)
6.2670° (M)
0° 33m 56.952s / day (n)
Inclination10.932° (i)
98.675° (Ω)
259.95° (ω)
Earth MOID0.00552 AU (826,000 km)
Physical characteristics
Dimensions~500 meters[3]
Mass7.87×1010 kg[4]
19.4[2]

    Description

    It was discovered on 27 May 1998, by astronomers of the Lincoln Near-Earth Asteroid Research (LINEAR) at Lincoln Laboratory's ETS near Socorro, New Mexico, at an apparent magnitude of 17.6 using a 1.0-meter (39 in) reflector.[1] It was tracked through 9 June 1998.[6] It was recovered on 28 December 2003 which extended the observation arc by 5 years.[7] Two precovery images from January 1990 extended the observation arc by 8 years.[6]

    Based on an absolute magnitude of 19.4,[2] the asteroid has an estimated diameter of about 500 metres (1,600 ft).[3] (152680) 1998 KJ9 is noted for a close approach to the Earth on 31 December 1914 at a distance of 0.00155 AU (232,000 km; 144,000 mi).[8] It is one of the largest objects known to have come inside the orbit of the moon. During the 1914 close approach the asteroid reached about apparent magnitude 7.7.[9]

    History of close approaches of large near-Earth objects since 1908 (A)
    PHA 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
    69230 Hermes1937-10-301.9261.9261.92717.5700-900[10]data
    69230 Hermes1942-04-261.6511.6511.65117.5700-900[10]data
    (27002) 1998 DV91975-01-311.7621.7611.76218.1507–1637data
    2002 NY402002-08-181.3711.3711.37119.0335–1082data
    2004 XP142006-07-031.1251.1251.12519.3292–942data
    2015 TB1452015-10-311.2661.2661.26620.0620-690data
    (137108) 1999 AN102027-08-071.0141.0101.01917.9556–1793data
    (153814) 2001 WN52028-06-260.6470.6470.64718.2921–943data
    99942 Apophis2029-04-130.09810.09630.100019.7310–340data
    2017 MB12072-07-261.2161.2152.75918.8367–1186data
    2011 SM682072-10-171.8751.8651.88619.6254–820data
    (163132) 2002 CU112080-08-311.6551.6541.65618.5443–477data
    (416801) 1998 MZ2116-11-261.0681.0681.06919.2305–986data
    (153201) 2000 WO1072140-12-010.6340.6310.63719.3427–593data
    (276033) 2002 AJ1292172-02-081.7831.7751.79218.7385–1242data
    (290772) 2005 VC2198-05-051.9511.7912.13417.6638–2061data
    (A) This list includes near-Earth approaches of less than 2 lunar distances (LD) of objects with H brighter than 20.
    (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

    References
    1. "MPEC 1998-K31 : 1998 KJ9". IAU Minor Planet Center. 29 May 1998. Retrieved 15 November 2011. (J98K09J)
    2. "JPL Small-Body Database Browser: 152680 (1998 KJ9)" (last observation: 2011-02-06; arc: 21.1 years). Jet Propulsion Laboratory. Retrieved 7 April 2016.
    3. "Near Earth Asteroids (NEAs)" (Version 20.1). International Astronomical Union. 13 October 2011. Retrieved 30 October 2011.
    4. "Asteroid General Data - 1998 KJ9 (152680)". Catalogue of the Solar System Small Bodies Orbital Evolution. Retrieved 15 November 2011.
    5. NEO Earth Close Approaches @ JPL CNEOS
      Select "Nominal dist <= 1 LD", "Past only", Sort by "H (mag)"
    6. "(152680) = 1998 KJ9 Orbit" (2011-02-06; arc=7706 days). Minor Planet Center. Retrieved 24 September 2013.
    7. "MPEC 2003-Y87 : 1998 KJ9". IAU Minor Planet Center. 29 December 2003. Retrieved 24 September 2013.
    8. "JPL Close-Approach Data: 152680 (1998 KJ9)" (last observation: 2011-02-06; arc: 21.1 years). Retrieved 15 November 2011.
    9. "1998KJ9 Ephemerides for 31 December 1914". NEODyS (Near Earth Objects - Dynamic Site). Retrieved 15 November 2011.
    10. Marchis, F.; et al. "Multiple asteroid systems: Dimensions and thermal properties from Spitzer Space Telescope and ground-based observations". Icarus. 221 (2): 1130–1161. Bibcode:2012Icar..221.1130M. doi:10.1016/j.icarus.2012.09.013. Retrieved 24 August 2018.
    Preceded by
    		 Large NEO Earth close approach
    (inside the orbit of the Moon)
    31 December 1914    		 Succeeded by
    (163132) 2002 CU11
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