(42301) 2001 UR163

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(42301) 2001 UR163
Discovered by Kitt Peak (695)
Discovery date October 21, 2001
MPC designation (42301) 2001 UR163

TNO (SDO)[2]

4:9 resonance[3]
Orbital characteristics[4]
Epoch December 31, 2006 (JD 2454100.5)
Aphelion 66.106 AU (9889.356 Gm)
Perihelion 36.756 AU (5498.582 Gm)
51.431 AU (7693.969 Gm)
Eccentricity 0.285
368.85 a (134721.208 d)
4.07 km/s
Inclination 0.752°
Physical characteristics
Dimensions 636 km (assumed)[5]
Albedo 0.09? (assumed)
Temperature ≈39 K
Spectral type
(Super red; highest B−R)
B−V=1.44; V−R=0.84;

(42301) 2001 UR163, also written as (42301) 2001 UR163, is a likely dwarf planet[7] that resides in the scattered disc. It was discovered on October 21, 2001 by the Deep Ecliptic Survey (DES) program at Kitt Peak. Light-curve-amplitude analysis shows only small deviations, suggesting that 2001 UR163 is a spheroid with small albedo spots.[8] Mike Brown's website lists it as a highly likely dwarf planet, but the diameter of the object has never been measured.[9]

2001 UR163 has the reddest color index of any object in the Solar System. On October 31, 2002, the 3.6-meter Canada–France–Hawaii Telescope observed 2001 UR163 set a record red reading of B−R=2.28. This makes 2001 UR163 even redder than 5145 Pholus, (119070) 2001 KP77, 90377 Sedna and comet C/2001 T4.

Reddening of the spectrum is caused by cosmic irradiation by ultraviolet radiation and charged particles. Becoming bluer in the spectrum is caused by impact collisions exposing the interior of an object. In the visible spectrum, 2001 UR163 would appear orange-brown, depending on its albedo.

It came to perihelion around 1937.[4] In 2006, it moved beyond 50 AU from the Sun. It is currently 51.9 AU from the Sun.[6]


  1. ^ Marsden, Brian G. (2001-11-14). "MPEC 2001-V57: 2001 QX322, 2001 UR163, 2001 VN71". IAU Minor Planet Center. Harvard-Smithsonian Center for Astrophysics. Retrieved 2010-01-06.  (K01UG3R*)
  2. ^ "List Of Centaurs and Scattered-Disk Objects". Minor Planet Center. Retrieved 2008-09-25. 
  3. ^ Marc W. Buie (2003-10-23). "Orbit Fit and Astrometric record for 42301". SwRI (Space Science Department). Retrieved 2008-09-25. 
  4. ^ a b c "JPL Small-Body Database Browser: 42301 (2001 UR163)" (2003-10-23 last obs). Retrieved 2009-03-22. 
  5. ^ Wm. Robert Johnston. "List of Known Trans-Neptunian Objects". Johnston's Archive. Archived from the original on 24 June 2009. Retrieved 2009-08-28. 
  6. ^ a b "AstDyS (42301) 2001UR163 Ephemerides". Department of Mathematics, University of Pisa, Italy. Archived from the original on 2009-04-18. Retrieved 2009-03-19. 
  7. ^ Gonzalo Tancredi and Sofía Favre (October 13, 2008). "Dwarf Planet & Plutoid Headquarters". Portal Uruguayo de Astronomía. Retrieved 2010-09-22.  (Which are the dwarfs in the Solar System?)
  8. ^ Tancredi, G., & Favre, S. (2008) Which are the dwarfs in the Solar System?. Depto. Astronomía, Fac. Ciencias, Montevideo, Uruguay; Observatorio Astronómico Los Molinos, MEC, Uruguay. Retrieved 10-08-2011
  9. ^ Michael E. Brown. "How many dwarf planets are there in the outer solar system? (updates daily)". California Institute of Technology. Retrieved 2011-08-25. 

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