52246 Donaldjohanson

52246 Donaldjohanson, provisional designation 1981 EQ5, is a carbonaceous Erigonian asteroid from the inner regions of the asteroid belt, approximately 4 kilometers (2.5 miles) in diameter. It was discovered on 2 March 1981, by American astronomer Schelte Bus at the Siding Spring Observatory in Australia. The C-type asteroid is a target of the Lucy mission and was aptly named after American paleoanthropologist Donald Johanson.[1]

52246 Donaldjohanson
Discovery [1]
Discovered byS. J. Bus
Discovery siteSiding Spring Obs.
Discovery date2 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 23 March 2018 (JD 2458200.5)
Uncertainty parameter 0
Observation arc18.12 yr (6,619 d)
Aphelion2.8274 AU
Perihelion1.9415 AU
2.3844 AU
Eccentricity0.1858
3.68 yr (1,345 d)
64.092°
0° 16m 3.72s / day
Inclination4.4195°
262.84°
213.10°
Physical characteristics
Mean diameter
3.895±0.013 km[5]
0.103±0.019[5]
C [3]
15.5[2]

    Orbit and classification

    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. It is a relatively old family that was created approximately 130 million years ago.[6]

    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]

    Lucy mission target

    Donaldjohanson is planned to be visited by the Lucy spacecraft which will launch in 2021. The flyby is scheduled for 20 April 2025, and will approach the asteroid to a distance of 922 kilometers at a velocity of 13.4 kilometers per second.[3] The mission's targets with their flyby dates are:[3][7][8]

    • 52246 Donaldjohanson — 20 April 2025: 4 km diameter C-type asteroid in the inner main-belt, member of the Erigone family;
    • 3548 Eurybates — 12 August 2027: 64 km diameter C-type Jupiter Trojan in the Greek camp at L4, largest member of the only confirmed disruptive collisional family in the Trojans;
    • 15094 Polymele — 15 September 2027: 21 km diameter P-type Trojan at L4, likely collisional fragment;
    • 11351 Leucus — 18 April 2028: 34 km diameter D-type slow rotator Trojan at L4;
    • 21900 Orus — 11 November 2028: 51 km diameter D-type Trojan at L4;
    • 617 Patroclus — 2 March 2033: P-type binary Trojan. The primary, Patroclus, has a mean diameter of 113 km and its companion, Menoetius, has a diameter of 104 km. The pair orbit at a separation of 680 km. The binary resides in the Trojan camp at L5.

    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.[6]:23 It has an absolute magnitude of 15.5.[2] As of 2018, the asteroid's period, pole and shape remain unknown.[2][9]

    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.[5]

    Naming

    This minor planet is planned to be visited by the Lucy spacecraft, which would observe it en route to its main target of several Jupiter trojans.[7] 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][10]

    See also

    References
    1. "52246 Donaldjohanson (1981 EQ5)". Minor Planet Center. Retrieved 28 April 2018.
    2. "JPL Small-Body Database Browser: 52246 Donaldjohanson (1981 EQ5)" (2017-01-29 last obs.). Jet Propulsion Laboratory. Retrieved 28 April 2018.
    3. Levison, H. F.; Olkin, C.; Noll, K. S.; Marchi, S.; Lucy Team (March 2017). "Lucy: Surveying the Diversity of the Trojan Asteroids: The Fossils of Planet Formation" (PDF). 48th Lunar and Planetary Science Conference (1964): 2025. Bibcode:2017LPI....48.2025L. Retrieved 13 April 2017.
    4. "Asteroid 52246 Donaldjohanson – Nesvorny HCM Asteroid Families V3.0". Small Bodies Data Ferret. Retrieved 27 October 2019.
    5. Masiero, Joseph R.; Mainzer, A. K.; Grav, T.; Bauer, J. M.; Cutri, R. M.; Dailey, J.; et al. (November 2011). "Main Belt Asteroids with WISE/NEOWISE. I. Preliminary Albedos and Diameters". The Astrophysical Journal. 741 (2): 20. arXiv:1109.4096. Bibcode:2011ApJ...741...68M. doi:10.1088/0004-637X/741/2/68.
    6. Nesvorný, D.; Broz, M.; Carruba, V. (December 2014). Identification and Dynamical Properties of Asteroid Families. Asteroids IV. pp. 297–321. arXiv:1502.01628. Bibcode:2015aste.book..297N. doi:10.2458/azu_uapress_9780816532131-ch016. ISBN 9780816532131.
    7. Casey Dreier; Emily Lakdawalla (30 September 2015). "NASA announces five Discovery proposals selected for further study". The Planetary Society. Retrieved 12 April 2017.
    8. https://www.hou.usra.edu/meetings/lpsc2017/pdf/2025.pdf
    9. "LCDB Data for (52246) Donaldjohanson". Asteroid Lightcurve Database (LCDB). Retrieved 12 April 2017.
    10. "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 28 April 2018.

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