(15810) 1994 JR1

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(15810) 1994 JR1
Discovered by M. J. Irwin, A. Zytkow
Discovery date May 12, 1994
MPC designation (15810) 1994 JR1
Orbital characteristics[3]
Epoch April 18, 2013 (JD 2456400.5)
Aphelion 43.6977721 AU
Perihelion 34.7394915 AU
39.2186318 AU
Eccentricity 0.1142095
245.61 y (89709.1181843 d)
Inclination 3.80462 °
Physical characteristics
Dimensions 127 km[4]
Albedo 0.09 (assumed)

(15810) 1994 JR1, also written (15810) 1994 JR1, is a minor planet that moves around the Sun in an orbit entirely located beyond Neptune. It is the first object that was confirmed to be a quasi-satellite of Pluto.[5]

Discovery, orbit and physical properties[edit]

(15810) 1994 JR1 was discovered on May 12, 1994, by M. J. Irwin and A. Zytkow with the 2.5 m Isaac Newton Telescope at the Roque de los Muchachos Observatory in the island of La Palma.[3] It is a plutino, so it is trapped in a 2:3 mean motion resonance with Neptune, similarly to dwarf planet Pluto (the largest known plutino). It has a perihelion (closest approach to the Sun) of 34.753 AU and an aphelion (farthest distance from the Sun) of 43.722 AU, so it is moving in a relatively eccentric orbit entirely beyond Neptune. It is about 127 km in diameter.[4]

Quasi-satellite dynamical state and orbital evolution[edit]

(15810) 1994 JR1 is currently following a quasi-satellite loop around Pluto.[5] In contrast with the cases of 2002 VE68 or (309239) 2007 RW10, the quasi-satellite state of (15810) 1994 JR1 is mainly the result of resonances with Neptune not caused by a discrete close encounter with another body. This dynamical behavior is recurrent: the object becomes a Plutonian quasi-satellite every 2 Myr and remains in that phase for nearly 350,000 years.[5][6]


(15810) 1994 JR1 is moving in a very stable orbit, likely as stable as Pluto's. This suggests that it may be a primordial plutino formed around the same time Pluto itself and Charon came into existence. It is unlikely to be relatively recent debris originated in collisions within Pluto’s system or a captured object.[5]

Possible New Horizons flyby[edit]

(15810) 1994 JR1 is currently a relatively close neighbor of Pluto's. In 2017, it will be only 2.7 AU from Pluto.[7] Around 2011 it was the best known target for a flyby by the New Horizons spacecraft after its Pluto flyby in 2015, but it is hoped that still better targets will be found.[8][9]


  1. ^ Marc W. Buie (2006-10-14). "Orbit Fit and Astrometric record for 15810". SwRI (Space Science Department). Retrieved 2008-10-02. 
  2. ^ Brian G. Marsden (2008-07-17). "MPEC 2008-O05 : Distant Minor Planets (2008 Aug. 2.0 TT)". IAU Minor Planet Center. Harvard-Smithsonian Center for Astrophysics. Archived from the original on 7 December 2008. Retrieved 2008-10-02. 
  3. ^ a b c "JPL Small-Body Database Browser: 15810 (1994 JR1)" (2000-06-25 last obs). Retrieved 2008-10-02. 
  4. ^ a b "List of Known Trans-Neptunian Objects". Johnston's Archive. Archived from the original on 18 February 2007. Retrieved 2007-01-25. 
  5. ^ a b c d de la Fuente Marcos, C.; de la Fuente Marcos, R. (November 2012). "Plutino 15810 (1994 JR1), an accidental quasi-satellite of Pluto". Monthly Notices of the Royal Astronomical Society: Letters 427 (1): L85–L89. arXiv:1209.3116. Bibcode:2012MNRAS.427L..85D. doi:10.1111/j.1745-3933.2012.01350.x. 
  6. ^ "Pluto's fake moon". Archived from the original on 2015-03-25. Retrieved 2012-09-24. 
  7. ^ "50000 Quaoar distance (AU) from Pluto". Retrieved 2007-12-18. 
  8. ^ Ted Stryk / Emily Lakdawalla (January 24, 2011). "Ted Stryk: Report from the 2011 New Horizons Science Team Meeting". The Planetary Society Blog. Retrieved 2011-01-25. 
  9. ^ "25 closer candidates". Retrieved 2012-09-30. 

External links[edit]