(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 by	LINEAR (704) 1.0-m Reflector
Discovery site	Lincoln Lab's ETS
Discovery date	27 May 1998
Designations
MPC designation	(152680) 1998 KJ9
Minor planet category	NEO · PHA · Apollo [2]
Orbital characteristics[2]
Epoch 13 January 2016 (JD 2457400.5)
Uncertainty parameter 0
Observation arc	7706 days (21.10 yr)
Aphelion	2.3742 AU (355.18 Gm) (Q)
Perihelion	0.52125 AU (77.978 Gm) (q)
Semi-major axis	1.4477 AU (216.57 Gm) (a)
Eccentricity	0.63995 (e)
Orbital period	1.74 yr (636.25 d)
Mean anomaly	6.2670° (M)
Mean motion	0° 33^m 56.952^s / day (n)
Inclination	10.932° (i)
Longitude of ascending node	98.675° (Ω)
Argument of perihelion	259.95° (ω)
Earth MOID	0.00552 AU (826,000 km)
Physical characteristics
Dimensions	~500 meters[3]
Mass	7.87×10^10 kg[4]
Absolute magnitude (H)	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 KJ9	1914-12-31	0.606	0.604	0.608	19.4	279–900	data
(458732) 2011 MD5	1918-09-17	0.911	0.909	0.913	17.9	556–1795	data
(163132) 2002 CU11	1925-08-30	0.903	0.901	0.905	18.5	443–477	data
69230 Hermes	1937-10-30	1.926	1.926	1.927	17.5	700-900[10]	data
69230 Hermes	1942-04-26	1.651	1.651	1.651	17.5	700-900[10]	data
(27002) 1998 DV9	1975-01-31	1.762	1.761	1.762	18.1	507–1637	data
2002 NY40	2002-08-18	1.371	1.371	1.371	19.0	335–1082	data
2004 XP14	2006-07-03	1.125	1.125	1.125	19.3	292–942	data
2015 TB145	2015-10-31	1.266	1.266	1.266	20.0	620-690	data
(137108) 1999 AN10	2027-08-07	1.014	1.010	1.019	17.9	556–1793	data
(153814) 2001 WN5	2028-06-26	0.647	0.647	0.647	18.2	921–943	data
99942 Apophis	2029-04-13	0.0981	0.0963	0.1000	19.7	310–340	data
2017 MB1	2072-07-26	1.216	1.215	2.759	18.8	367–1186	data
2011 SM68	2072-10-17	1.875	1.865	1.886	19.6	254–820	data
(163132) 2002 CU11	2080-08-31	1.655	1.654	1.656	18.5	443–477	data
(416801) 1998 MZ	2116-11-26	1.068	1.068	1.069	19.2	305–986	data
(153201) 2000 WO107	2140-12-01	0.634	0.631	0.637	19.3	427–593	data
(276033) 2002 AJ129	2172-02-08	1.783	1.775	1.792	18.7	385–1242	data
(290772) 2005 VC	2198-05-05	1.951	1.791	2.134	17.6	638–2061	data
^(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.

External links

• (152680) 1998 KJ9 at NeoDyS-2, Near Earth Objects—Dynamic Site
  • Ephemeris · Obs prediction · Orbital info · MOID · Proper elements · Obs info · Close · Physical info · NEOCC
• (152680) 1998 KJ9 at the JPL Small-Body Database
  • Close approach · Discovery · Ephemeris · Orbit diagram · Orbital elements · Physical parameters

Preceded by

Large NEO Earth close approach (inside the orbit of the Moon) 31 December 1914

Succeeded by (163132) 2002 CU11