(192642) 1999 RD32

(192642) 1999 RD₃₂, provisional designation: 1999 RD₃₂, is an asteroid and suspected contact binary on an eccentric orbit, classified as a large near-Earth object and potentially hazardous asteroid of the Apollo group, approximately 5 kilometers (3 miles) in diameter. It was discovered on 8 September 1999, at a magnitude of 18, by astronomers of the LINEAR program using its 1-meter telescope at the Lincoln Laboratory's Experimental Test Site near Socorro, New Mexico, United States.^[3][2] The asteroid is likely of carbonaceous composition and has a rotation period of 17.08 hours.^[4][a]

(192642) 1999 RD₃₂

Goldstone radar image showing the two lobes of suspected contact binary 1999 RD32.
Discovery[1][2][3]
Discovered by	LINEAR
Discovery site	Lincoln Lab's ETS
Discovery date	8 September 1999
Designations
MPC designation	(192642) 1999 RD32
Alternative designations	1999 RD32
Minor planet category	Apollo · NEO · PHA[1][3]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc	21.92 yr (8,007 days)
Aphelion	4.6801 AU
Perihelion	0.6093 AU
Semi-major axis	2.6447 AU
Eccentricity	0.7696
Orbital period (sidereal)	4.30 yr (1,571 days)
Mean anomaly	89.009°
Mean motion	0° 13m 45.12s / day
Inclination	6.7914°
Longitude of ascending node	310.04°
Argument of perihelion	299.89°
Earth MOID	0.0495 AU · 19.3 LD
Jupiter MOID	0.6702 AU
Physical characteristics
Mean diameter	1.63 km (calculated–dated)[4] 5 km (est.–radiometric)[5]
Synodic rotation period	17.08±0.03 h[6][a] 17.1±0.5 h[7]
Geometric albedo	0.04 (est.–radiometric)[5] 0.20 (assumed–dated)[4]
Spectral type	C[4][5][8][9]
Absolute magnitude (H)	16.00[8] · 16.23±0.01[9] · 16.3[1][4]

Description

1999 RD₃₂ orbits the Sun at a distance of 0.6–4.7 AU once every 4 years and 4 months (1,571 days; semi-major axis of 2.64 AU). Its orbit has a high eccentricity of 0.77 and an inclination of 7° with respect to the ecliptic.^[1]

The asteroid's observation arc begins with a precovery taken at Palomar Observatory in January 1995.^[3] It is known that 1999 RD₃₂ passed 0.0093 AU (1,390,000 km; 860,000 mi) from Earth on 27 August 1969.^[10] During the 1969 close approach the asteroid reached about apparent magnitude 8.8.^[11] The similarly sized 4179 Toutatis also reached that brightness in September 2004. It passed less than 0.007 AU (1,000,000 km; 650,000 mi) from asteroid 29 Amphitrite on 17 January 1939.^[1]

Arecibo radar observations on 5–6 March 2012 showed that 1999 RD₃₂ is approximately 5 kilometers (3 mi) in diameter^[5] and has an estimated albedo of only 0.04.^[5] Other sources calculate a smaller diameter of 1.63 kilometers based on a dated assumption, that the object is a stony rather than a carbonaceous asteroid.^[4] The two visible lobes suggest that 1999 RD₃₂ is a tight binary asteroid or contact binary.^[5] About 10–15% of near-Earth asteroids larger than 200 meters are expected to be contact binary asteroids with two lobes in mutual contact.^[12]

Close-approaches to Earth^[10]

Date	Distance from Earth
1969-08-27	0.0093 AU (1,390,000 km; 860,000 mi)
2012-03-14	0.1487 AU (22,250,000 km; 13,820,000 mi)
2042-03-11	0.1428 AU (21,360,000 km; 13,270,000 mi)
2046-09-04	0.1071 AU (16,020,000 km; 9,960,000 mi)

History of close approaches of large near-Earth objects since 1908 ^(A)

• v
• t
• e

PHA	Date	Approach distance (lunar dist.)			Abs. mag (H)	Diameter (C) (m)	Ref (D)
		Nomi- nal(B)	Mini- mum	Maxi- mum
(33342) 1998 WT24	1908-12-16	3.542	3.537	3.547	17.9	556–1795	data
(458732) 2011 MD5	1918-09-17	0.911	0.909	0.913	17.9	556–1795	data
(7482) 1994 PC1	1933-01-17	2.927	2.927	2.928	16.8	749–1357	data
69230 Hermes	1937-10-30	1.926	1.926	1.927	17.5	668–2158	data
69230 Hermes	1942-04-26	1.651	1.651	1.651	17.5	668–2158	data
(137108) 1999 AN10	1946-08-07	2.432	2.429	2.435	17.9	556–1795	data
(33342) 1998 WT24	1956-12-16	3.523	3.523	3.523	17.9	556–1795	data
(163243) 2002 FB3	1961-04-12	4.903	4.900	4.906	16.4	1669–1695	data
(192642) 1999 RD32	1969-08-27	3.627	3.625	3.630	16.3	1161–3750	data
(143651) 2003 QO104	1981-05-18	2.761	2.760	2.761	16.0	1333–4306	data
2017 CH1	1992-06-05	4.691	3.391	6.037	17.9	556–1795	data
(170086) 2002 XR14	1995-06-24	4.259	4.259	4.260	18.0	531–1714	data
(33342) 1998 WT24	2001-12-16	4.859	4.859	4.859	17.9	556–1795	data
4179 Toutatis	2004-09-29	4.031	4.031	4.031	15.3	2440–2450	data
2014 JO25	2017-04-19	4.573	4.573	4.573	17.8	582–1879	data
(137108) 1999 AN10	2027-08-07	1.014	1.010	1.019	17.9	556–1795	data
(35396) 1997 XF11	2028-10-26	2.417	2.417	2.418	16.9	881–2845	data
(154276) 2002 SY50	2071-10-30	3.415	3.412	3.418	17.6	714–1406	data
(164121) 2003 YT1	2073-04-29	4.409	4.409	4.409	16.2	1167–2267	data
(385343) 2002 LV	2076-08-04	4.184	4.183	4.185	16.6	1011–3266	data
(52768) 1998 OR2	2079-04-16	4.611	4.611	4.612	15.8	1462–4721	data
(33342) 1998 WT24	2099-12-18	4.919	4.919	4.919	17.9	556–1795	data
(85182) 1991 AQ	2130-01-27	4.140	4.139	4.141	17.1	1100	data
314082 Dryope	2186-07-16	3.709	2.996	4.786	17.5	668–2158	data
(137126) 1999 CF9	2192-08-21	4.970	4.967	4.973	18.0	531–1714	data
(290772) 2005 VC	2198-05-05	1.951	1.791	2.134	17.6	638–2061	data
(A) List includes near-Earth approaches of less than 5 lunar distances (LD) of objects with H brighter than 18. (B) Nominal geocentric distance from the Earth's center to the object's center (Earth radius≈0.017 LD). (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

Numbering and naming

This minor planet was numbered by the Minor Planet Center on 13 November 2008.^[13] As of 2018, it has not been named.^[3]

Notes

1. Lightcurve plot of (192642) 1999 RD32, Palmer Divide Observatory, B. D. Warner (2012): rotation period 17.08±0.03 hours with a brightness amplitude of 0.28±0.02 mag. Summary figures at the LCDB