486958 Arrokoth
486958 Arrokoth (provisional designation 2014 MU69; formerly nicknamed Ultima Thule) is a trans-Neptunian object located in the Kuiper belt. Arrokoth became the farthest and most primitive object in the Solar System visited by a spacecraft when the NASA space probe New Horizons conducted a flyby on 1 January 2019. Arrokoth is a contact binary 36 km (22 mi) long, composed of two planetesimals 21 and 15 km (13 and 9 mi) across, that are joined along their major axes. With an orbital period of about 298 years and a low orbital inclination and eccentricity, Arrokoth is classified as a cold classical Kuiper belt object.
Grayscale composite image of Arrokoth | |||||||||
| Discovery | |||||||||
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| Discovered by |
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| Discovery site | Hubble Space Telescope | ||||||||
| Discovery date | 26 June 2014 | ||||||||
| Designations | |||||||||
MPC designation | (486958) Arrokoth | ||||||||
| Pronunciation | /ˈærəkɒθ/ | ||||||||
Named after | Powhatan word arrokoth, glossed 'sky' but probably meaning 'cloud' | ||||||||
Alternative designations |
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Minor planet category | |||||||||
| Orbital characteristics | |||||||||
| Epoch 27 April 2019 (JD 2458600.5) | |||||||||
| Uncertainty parameter 2 | |||||||||
| Observation arc | 2.33 yr (851 days) | ||||||||
| Aphelion | 46.442 AU | ||||||||
| Perihelion | 42.721 AU | ||||||||
Semi-major axis | 44.581 AU | ||||||||
| Eccentricity | 0.04172 | ||||||||
Orbital period (sidereal) | 297.67 yr | ||||||||
Mean anomaly | 316.551° | ||||||||
Mean motion | 0° 0m 11.92s / day | ||||||||
| Inclination | 2.4512° | ||||||||
Longitude of ascending node | 158.998° | ||||||||
| 174.418° | |||||||||
| Physical characteristics | |||||||||
| Dimensions | Overall best fit: 35.95 × 19.90 × 9.75 km Wenu 21.20 × 19.90 × 9.05 km Weeyo 15.75 × 13.85 × 9.75 km | ||||||||
Mean diameter | Overall volume equivalent: 18.26 km Wenu 15.86 km Weeyo 12.79 km | ||||||||
| Volume | 3185 km3 | ||||||||
| Mass | ~ 7.485×1014 kg (assumed nominal density) | ||||||||
Mean density | ~ 0.235 g/cm3 (nominal) 1-sigma range: 0.155–0.600 g/cm3 | ||||||||
Equatorial surface gravity | ~ 0.0001 g ~ 0.001 m/s2: 28:45 | ||||||||
Synodic rotation period | 15.9380±0.0005 h | ||||||||
| 99.3° | |||||||||
North pole right ascension | 317.5°±1° | ||||||||
North pole declination | −24.89°±1° | ||||||||
| 0.21+0.05 −0.04 (geometric) 0.062±0.015 (Bond) | |||||||||
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| V−I=1.35 G−I=1.42±0.14 G−R=0.95±0.14 | |||||||||
| 26.6 | |||||||||
10.4 (V-band)
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Arrokoth was discovered on 26 June 2014 by astronomer Marc Buie and the New Horizons Search Team using the Hubble Space Telescope as part of a search for a Kuiper-belt object for New Horizons to target in its first extended mission; it was chosen over two other candidates, 2014 OS393 and 2014 PN70, to become the primary target of the mission.