(85989) 1999 JD6

(85989) 1999 JD₆ (provisional designation 1999 JD₆) is an Aten asteroid, near-Earth object, and potentially hazardous object in the inner Solar System that makes frequent close approaches to Earth and Venus. On the Earth approach in 2015, it was observed by the Goldstone Solar System Radar and found to be a contact binary with the largest axis approximately 2 kilometers wide, and each lobe about 200–300 meters large.^[2] Although 1999 JD₆ in its current orbit never passes closer than 0.047 AU to Earth, it is listed as a potentially hazardous object because it is large and might pose a threat in the future.

(85989) 1999 JD₆

Goldstone Solar System radar image showing 1999 JD6 as a contact binary
Discovery
Discovered by	LONEOS
Discovery date	12 May 1999
Designations
Minor planet category	Aten NEA PHO
Orbital characteristics[1]
Epoch 13 January 2016 (JD 2457400.5)
Uncertainty parameter 0
Observation arc	9167 days (25.10 yr)
Aphelion	1.44183 AU (215.695 Gm)
Perihelion	0.32425 AU (48.507 Gm)
Semi-major axis	0.88304 AU (132.101 Gm)
Eccentricity	0.63280
Orbital period (sidereal)	0.83 yr (303.1 d)
Mean anomaly	137.83229°
Mean motion	1.18778°/day
Inclination	17.05701°
Longitude of ascending node	130.21399°
Argument of perihelion	309.18377°
Earth MOID	0.0487023 AU (7.28576 Gm)
Jupiter MOID	3.86909 AU (578.808 Gm)
Physical characteristics
Dimensions	~0.7 km × 2 km (contact binary)
Synodic rotation period	7.6638 h (0.31933 d)
Geometric albedo	~0.15
Spectral type	K (SMASS)
Apparent magnitude	~16–18
Absolute magnitude (H)	17.1

The asteroid is well-observed, having been observed over 2,000 times over a length of over 25 years, and was assigned a numeric designation in August 2004.^[3]

July 2015 Earth passage

Series of Goldstone Solar System radar images showing the rotation of 1999 JD₆

On 24 July 2015 1999 JD₆ came as close as 19 lunar distances to Earth.^[4] It was imaged by radar, and shown to be a contact binary, about 2 kilometers (1.2 miles) on its long axis.^[4]

See also

• Contact binary (asteroid)