52246 Donaldjohanson
Asteroid From Wikipedia, the free encyclopedia
52246 Donaldjohanson (provisional designation 1981 EQ5) is a carbonaceous asteroid from the inner regions of the asteroid belt, approximately 8 kilometers (5.0 miles) long and 3.5 kilometers (2.2 miles) at its widest point. It was discovered on 2 March 1981, by American astronomer Schelte Bus at the Siding Spring Observatory in Australia. The C-type asteroid was the 2nd target of the Lucy mission, with the spacecraft flying 960 km (600 mi) from the surface on 20 April 2025, revealing the asteroid to be a contact binary.[8] It was named after American paleoanthropologist Donald Johanson, the discoverer of the "Lucy" hominid fossil.[1]
Donaldjohanson photographed by the Lucy spacecraft on 20 April 2025 | |
| Discovery[1] | |
|---|---|
| Discovered by | S. J. Bus |
| Discovery site | Siding Spring Obs. |
| Discovery date | 2 March 1981 |
| Designations | |
| (52246) Donaldjohanson | |
Named after | Donald Johanson [1] (paleoanthropologist) |
| 1981 EQ5 · 1998 YF26 | |
| main-belt [1][2] · (inner) Erigone [3][4] | |
| Orbital characteristics[2] | |
| Epoch 25 February 2023 (JD 2460000.5) | |
| Uncertainty parameter 0 | |
| Earliest precovery date | 14 February 1981[1] |
| Aphelion | 2.830 AU |
| Perihelion | 1.936 AU |
| 2.383 AU | |
| Eccentricity | 0.1876 |
| 3.68 yr (1,343 d) | |
| 186.269° | |
| 0° 16m 4.79s / day | |
| Inclination | 4.424° |
| 262.809° | |
| 213.016° | |
| Physical characteristics | |
| Dimensions | 8 km × 3.5 km[5] |
| 3.895±0.013 km[6] | |
| 251±1 hr[7] | |
| 0.103±0.019[6] | |
| C [3] | |
| 15.69[2] | |
Orbit and classification
Lucy · Sun · Earth · 52246 Donaldjohanson · 3548 Eurybates · 21900 Orus · 617 Patroclus
Donaldjohanson is a member of the Erigone family (406),[3][4] a large carbonaceous asteroid family of nearly 2,000 known members, which is named after its parent body 163 Erigone.[9] The Erigone family is a relatively old family that was created by an asteroid collision approximately 150 million years ago. Since Donaldjohanson belongs to this family, it likely has the same age of 150 million years.[10]
It orbits the Sun in the inner asteroid belt at a distance of 1.9–2.8 AU once every 3 years and 8 months (1,345 days; semi-major axis of 2.38 AU). Its orbit has an eccentricity of 0.19 and an inclination of 4° with respect to the ecliptic.[2] A first precovery was taken at the discovering observatory in February 1981, extending the body's observation arc by 2 weeks prior to its official discovery observation.[1]
Physical characteristics
Donaldjohanson has been characterized as a carbonaceous C-type asteroid,[3] in-line with the C and X overall spectral type for Erigonian asteroids.[9]: 23 It has an absolute magnitude of 15.5.[2]
Lightcurve
Photometric observations of Donaldjohanson in August 2020 revealed that it is a slow rotator with an exceptionally high lightcurve amplitude of 1.0[10] to 1.7 magnitude.[11][7] The lightcurve suggested that Donaldjohanson must either be highly elongated in shape, or possibly a synchronous binary system.[11] Extensive photometric observations by the two TRAPPIST telescopes from November 2020 to February 2021 determined the rotation period of Donaldjohanson to be approximately 252 hours.[12]
Diameter and albedo
According to the survey carried out by NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, Donaldjohanson measures 3.895 kilometers in diameter and its surface has an albedo of 0.103.[6] The Lucy spacecraft found the asteroid to be larger then predicted, measuring around 8 kilometers long and 3.5 kilometers wide at its largest point.[5]
Exploration
Donaldjohanson was visited by the Lucy spacecraft that was launched on 16 October 2021. The flyby took place on 20 April 2025, with a closest approach distance of 960 kilometers (600 mi) at a relative velocity of 13.4 kilometers (8.3 mi) per second.[8]
Naming
The Lucy probe is named after the "Lucy" hominid fossil, while Donaldjohanson is named for that fossil's co-discoverer Donald Johanson (born 1943), an American paleoanthropologist. The approved naming citation was published by the Minor Planet Center on 25 December 2015 (M.P.C. 97569).[1][13]
See also
- Discovery program
- List of minor planets and comets visited by spacecraft
- 152830 Dinkinesh – Binary asteroid and Lucy's first target
References
External links
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