13963 Euphrates

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13963 Euphrates
Discovery [1]
Discovered by E. W. Elst
Discovery site La Silla Obs.
Discovery date 3 August 1991
MPC designation (13963) Euphrates
Pronunciation /jˈfrtz/
Named after
(river in Mesopotamia)
1991 PT4 · 1997 TO10
main-belt · (outer)[1]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc 45.98 yr (16,793 days)
Aphelion 4.1853 AU
Perihelion 2.4762 AU
3.3307 AU
Eccentricity 0.2566
6.08 yr (2,220 days)
0° 9m 43.56s / day
Inclination 0.9360°
TJupiter 3.1090
Physical characteristics
Dimensions 9±1 km (est. at 0.06)[4]

13963 Euphrates (/jˈfrtz/), 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]

Orbit and classification[edit]

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[edit]

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]


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]


  1. ^ a b c d e f "JPL Small-Body Database Browser: 13963 Euphrates (1991 PT4)" (2017-03-17 last obs.). Jet Propulsion Laboratory. Retrieved 5 July 2017. 
  2. ^ a b c d Schmadel, Lutz D. (2006). Dictionary of Minor Planet Names – (13963) Euphrates, Addendum to Fifth Edition: 2003–2005. Springer Berlin Heidelberg. p. 82. ISBN 978-3-540-34360-8. Retrieved 7 April 2016. 
  3. ^ a b 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. ^ a b "Absolute Magnitude (H)". NASA/JPL. Retrieved 7 April 2016. 
  5. ^ a b "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. 

External links[edit]