(15810) 1994 JR1

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(15810) 1994 JR1
1994 JR1 close-up from New Horizons.gif
A distant view of 1994 JR1 from New Horizons in November 2015.[a]
Discovered by M. J. Irwin, A. Zytkow
Discovery date 12 May 1994
MPC designation (15810) 1994 JR1
Orbital characteristics[3]
Epoch 13 January 2016 (JD 2457400.5)
Uncertainty parameter 3
Observation arc 7701 days (21.08 yr)
Aphelion 44.0242786 AU (6.58593834 Tm)
Perihelion 34.7065029 AU (5.19201893 Tm)
39.3653908 AU (5.88897864 Tm)
Eccentricity 0.1183498
246.99 yr (90213.2 d)
0° 0m 14.366s / day
Inclination 3.8084099°
Earth MOID 33.6944 AU (5.04061 Tm)
Jupiter MOID 29.3494 AU (4.39061 Tm)
Physical characteristics
Dimensions 127 km[4]
5.4 h[5]

(15810) 1994 JR1, also written (15810) 1994 JR1, is a minor planet that orbits around the Sun in an orbit entirely located beyond Neptune.

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]

In 2012, (15810) 1994 JR1 was hypothesized to be in a quasi-satellite loop around Pluto, as part of a recurring pattern, becoming a Plutonian quasi-satellite every 2 Myr and remaining in that phase for nearly 350,000 years.[6][7] This idea was argued against when the New Horizons probe measured its motion more accurately,[5][8] but new calculations using both the pre- and post-New Horizons encounter orbital solutions show that this object exhibits quasi-satellite behavior with respect to Pluto.[9]


(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.[6]


Orbit of 1994 JR1 near Pluto

(15810) 1994 JR1 is currently relatively close to Pluto. In 2017, it will be only 2.7 AU from Pluto.[10] Before 2014 MU69 was discovered in 2014, (15810) 1994 JR1 was the best known target for a flyby by the New Horizons spacecraft after its Pluto flyby in 2015.[11][12]

1994 JR1 was one of the first objects targeted for distant observations by New Horizons, which were taken on 2 November 2015.[13] More observations were made in April 2016.

On 2 November 2015, 1994 JR1 was imaged by the LORRI instrument aboard New Horizons, making it the closest observation of a Kuiper belt object other than the Pluto-Charon system by a factor of 15.[14]

Between 7–8 April 2016, New Horizons imaged 1994 JR1 from a new record distance of about 111 million kilometers, using the LORRI instrument. The new images allowed the science team at Southwest Research Institute (SwRI) in Boulder, Colorado to further pinpoint the location of 1994 JR1 to within 1000 kilometers. The new data also made it possible for scientists to observe 1994 JR1's rotation period, which was determined to be 5.4 hours.[15]


  1. ^ This four-frame animation depicting 1994 JR1 was taken on November 2, 2015 by New Horizons, when the spacecraft was 270 million kilometers (170 million miles) away. 1994 JR1 is the white dot, just left of center, moving from right to left.
  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 5 April 2016. 
  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 "New Horizons Collects First Science on a Post-Pluto Object". 
  6. ^ a b 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. 
  7. ^ "Pluto's fake moon". Archived from the original on 2015-03-25. Retrieved 2012-09-24. 
  8. ^ Porter, Simon B.; et al. (2016). "Red, Rough, Fast, and Perturbed: New Horizons Observations of KBO (15810) 1994 JR1 from the Kuiper Belt". The Astrophysical Journal Letters. arXiv:1605.05376. Bibcode:2016arXiv160505376P. 
  9. ^ de la Fuente Marcos, Carlos; de la Fuente Marcos, Raúl (2016). "The analemma criterion: accidental quasi-satellites are indeed true quasi-satellites". Monthly Notices of the Royal Astronomical Society. arXiv:1607.06686. Bibcode:2016arXiv160706686D. doi:10.1093/mnras/stw1833. 
  10. ^ "50000 Quaoar distance (AU) from Pluto". Retrieved 2007-12-18. 
  11. ^ 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. 
  12. ^ "25 closer candidates". Retrieved 2012-09-30. 
  13. ^ "A Distant Close-up: New Horizons’ Camera Captures a Wandering Kuiper Belt Object". New Horizons. NASA/JHUAPL. December 4, 2015. Retrieved December 5, 2015. 
  14. ^ "New Horizons' catches a wandering Kuiper Belt Object not far off". SpaceDaily. 7 December 2015. 
  15. ^ "New Horizons Collects First Science on a Post-Pluto Object". New Horizons. NASA/JHUAPL/SwRI. May 17, 2016. Retrieved May 19, 2016. 

External links[edit]