(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][lower-alpha 1]

(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][lower-alpha 1] 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]

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

References

External links

• Arecibo images from 2012
• Asteroid Lightcurve Database (LCDB), query form (info Archived 16 December 2017 at the Wayback Machine)
• Dictionary of Minor Planet Names, Google books
• Asteroids and comets rotation curves, CdR – Observatoire de Genève, Raoul Behrend
• (192642) 1999 RD32 at NeoDyS-2, Near Earth Objects—Dynamic Site
  • Ephemeris · Obs prediction · Orbital info · MOID · Proper elements · Obs info · Close · Physical info · NEOCC
• RD32 (192642) 1999 RD32 at ESA–space situational awareness
  • RD32&tab=eph Ephemerides · RD32&tab=obs Observations · RD32&tab=orbprop Orbit · RD32&tab=physprops Physical Properties · RD32&tab=summary Summary
• (192642) 1999 RD32 at the JPL Small-Body Database
  • Close approach · Discovery · Ephemeris · Orbit diagram · Orbital elements · Physical parameters