13963 Euphrates

13963 Euphrates (/juːˈfreɪtiːz/), provisional designation 1991 PT4, is a resonant Griqua asteroid from the outer region of the asteroid belt, approximately 9 kilometers in diameter. It was discovered on 3 August 1991, by Belgian astronomer Eric Elst at ESO's La Silla Observatory site in Chile.[5] The asteroid was named after the Euphrates River in the Middle East.[2]

13963 Euphrates
Discovery[1]
Discovered byE. W. Elst
Discovery siteLa Silla Obs.
Discovery date3 August 1991
Designations
(13963) Euphrates
Pronunciation/juːˈfreɪtiːz/
Named after
Euphrates[2]
(river in Mesopotamia)
1991 PT4 · 1997 TO10
main-belt · (outer)[1]
Griqua[3]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc45.98 yr (16,793 days)
Aphelion4.1853 AU
Perihelion2.4762 AU
3.3307 AU
Eccentricity0.2566
6.08 yr (2,220 days)
84.506°
0° 9m 43.56s / day
Inclination0.9360°
227.18°
129.72°
TJupiter3.1090
Physical characteristics
Dimensions9±1 km (est. at 0.06)[4]
13.9[1]

    Orbit and classification

    Euphrates is one of very few bodies located in the 2:1 mean motion resonance with the gas giant Jupiter and belongs to the "marginally unstable" Griqua group.[3]

    It orbits the Sun in the outer main-belt at a distance of 2.5–4.2 AU once every 6 years and 1 month (2,220 days). Its orbit has an eccentricity of 0.26 and an inclination of 1° with respect to the ecliptic.[1] A first precovery was taken at Palomar Observatory in 1971, extending the asteroid's observation arc by 20 years prior to its official discovery observation.[5]

    Physical characteristics

    Based on an absolute magnitude of 13.9, it measures between 4 and 10 kilometers in diameter, assuming an albedo in the range of 0.05 to 0.25. Since asteroids in the outer main-belt are mostly of a carbonaceous rather than of a silicaceous composition, with low albedos, typically around 0.06, its diameter is likely to be between 8 and 10 kilometers.[4]

    As of 2017, Euphrates' effective size, its composition and albedo, as well as its rotation period and shape remain unknown.[1][6]

    Naming

    This minor planet was named after the Euphrates river, that flows through northern Syria and Iraq.[2]

    It is one of the most historically important rivers of Western Asia. The Tigris–Euphrates river system, a major river system, is formed when the two rivers combine at Al Qurnah. The minor planet 13096 Tigris is named after the other river of this system.[2] The approved naming citation was published by the Minor Planet Center on 6 August 2003 (M.P.C. 49280).[7]

    References
    1. "JPL Small-Body Database Browser: 13963 Euphrates (1991 PT4)" (2017-03-17 last obs.). Jet Propulsion Laboratory. Retrieved 5 July 2017.
    2. Schmadel, Lutz D. (2006). "(13963) Euphrates [3.32, 0.26, 0.9]". Dictionary of Minor Planet Names – (13963) Euphrates, Addendum to Fifth Edition: 2003–2005. Springer Berlin Heidelberg. p. 82. doi:10.1007/978-3-540-34361-5_818. ISBN 978-3-540-34360-8.
    3. Roig, F.; Nesvorný, D.; Ferraz-Mello, S. (September 2002). "Asteroids in the 2 : 1 resonance with Jupiter: dynamics and size distribution". Monthly Notices of the Royal Astronomical Society. 335 (2): 417–431. Bibcode:2002MNRAS.335..417R. doi:10.1046/j.1365-8711.2002.05635.x. Retrieved 7 April 2016.
    4. "Absolute Magnitude (H)". NASA/JPL. Archived from the original on 2 March 2001. Retrieved 7 April 2016.
    5. "13963 Euphrates (1991 PT4)". Minor Planet Center. Retrieved 7 April 2016.
    6. "LCDB Data for (13963) Euphrates". Asteroid Lightcurve Database (LCDB). Retrieved 5 July 2017.
    7. "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 19 May 2016.

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