World Library  
Flag as Inappropriate
Email this Article

(55637) 2002 Ux25

(55637) 2002 UX25
2002 UX25 as seen by Hubble
Discovered by Spacewatch (291)
Discovery site Kitt Peak National Obs.
Discovery date 30 October 2002
MPC designation (55637) 2002 UX25
Cubewano (MPC)[2]
Extended (DES)[3]
Orbital characteristics[4]
Epoch 27 June 2015 (JD 2457200.5)
Uncertainty parameter 3
Observation arc 22.15 yr (8,090 days)
Aphelion 48.803 AU
Perihelion 36.509 AU
42.656 AU
Eccentricity 0.1441
278.60 yr (101,758 days)
Average orbital speed
4.54 km/s
Inclination 19.463°
Known satellites 1
(ø: ~ 190–260 km)[5][6]
Physical characteristics
Dimensions 665±29 km[7]
Mass (1.25±0.03)×1020 kg[6]
Mean density
0.82±0.11 g/cm3[6]
Equatorial surface gravity
0.075 m/s2
Equatorial escape velocity
0.227 km/s
Sidereal rotation period
14.382±0.001 h[8]
Temperature ≈ 43 K
(pushing red)

V−H=2.22 [8]
19.8 [13]
3.9 [4]

(55637) 2002 UX25 is a possible dwarf planet that orbits the Sun in the Kuiper belt beyond Neptune. Its orbit takes roughly 280 years, and it has one known moon. This moon makes it much easier to calculate mass, and when the size is known, also a density. The low density of about 0.82 g/cm3 has been a surprise to astronomers.[14]

It is a trans-Neptunian object with an absolute magnitude of 3.9,[4] making it highly likely to be a dwarf planet. The Spitzer Space Telescope results estimate it to be about 681 km in diameter.[9] It was discovered on 30 October 2002, by the Spacewatch program.[1] It is a mid-sized cubewano similar in size to 20000 Varuna.


  • Classification 1
    • Dwarf-planet status 1.1
  • Physical characteristics 2
    • Brightness and color 2.1
    • Composition 2.2
  • Satellite 3
  • References 4
  • External links 5


2002 UX25 (vmag 19.9) as viewed with a 24" telescope

(55637) 2002 UX25 has a perihelion (closest approach to the Sun) of 36.7 AU,[4] which it will next reach in 2065.[4] As of 2010, (55637) 2002 UX25 is 41 AU from the Sun.[13]

The Minor Planet Center (MPC) classifies (55637) 2002 UX25 as a cubewano[2] while the Deep Ecliptic Survey (DES) classifies it as scattered-extended.[3] The DES using a 10 My integration (last observation: 2009-10-22) shows it with a minimum perihelion (qmin) distance of 36.3 AU.[3]

(55637) 2002 UX25 has been observed 60 times with precovery images back to 1991.[4]

Dwarf-planet status

(55637) 2002 UX25 has an estimated diameter of 665±29 km,[7] and most icy objects around 400 km in diameter are believed to be spherical.[15] Michael Brown's website lists it as a highly likely dwarf planet.[16] However, light-curve analysis has questioned whether it is actually a dwarf planet.[17][18]

Physical characteristics

Brightness and color

A variability of the visual brightness was detected which could be fit to a period of 14.38 or 16.78 h (depending on a single-peaked or double peaked curve).[19]

The Spitzer Space Telescope has estimated it to have a size of 681+116
.[9] It is redder than Varuna, unlike its neutral-colored "twin" 2002 TX300, in spite of similar brightness and orbit elements. The light-curve amplitude is ΔM = 0.21±0.06.[8]


(55637) 2002 UX25 is one of the largest known solid objects in the Solar System that is less dense than water. Why this should be is not well understood: objects of its size in the Kuiper belt are typically rocky and dense, and to have a similar composition to others of its kind, it would have to be exceptionally porous, which is unlikely given the compactability of water ice.[6] Its density of 0.82 g/cm3 astonished astronomers.[14]

Density comparison
What Density
Settled snow 0.2–0.3 [20]
Slush/ firn 0.7–0.8 [20]
2002 UX25 0.82 [6]
Glacier ice 0.83–0.92 [20]
Tethys 0.984 [21]
Liquid water 1 [20]


The discovery of a satellite of (55637) 2002 UX25 was reported in IAUC 8812 on 22 February 2007.[5] The satellite was detected using the Hubble Space Telescope in August 2005.[5] The satellite was found at 0.16 arcsec from the primary with an apparent magnitude difference of 2.5.[22] It orbits the primary in 8.309±0.0002 days,[8] at a distance of 4770±40 km, yielding a system mass of (1.25±0.03)×1020 kg.[6][8] The eccentricity of the orbit is 0.17±0.03.[8]

This moon is estimated to be 210±30 km in diameter.[7] Assuming the same albedo as the primary, it would have a diameter of 190 km, assuming an albedo of 0.05 (typical of other cold, classical KBOs of similar size) a diameter of 260 km.[6]


  1. ^ a b Marsden, Brian G. (2002-11-01). "MPEC 2002-V08 : 2002 UX25". IAU Minor Planet Center. Harvard-Smithsonian Center for Astrophysics. Retrieved 2011-07-05. 
  2. ^ a b "MPEC 2009-C70 :Distant Minor Planets (2009 FEB. 28.0 TT)". Minor Planet Center. 2009-02-10. Retrieved 2011-07-05. 
  3. ^ a b c  
  4. ^ a b c d e f "JPL Small-Body Database Browser: 55637 (2002 UX25)" (2013-12-05 last obs.). Jet Propulsion Laboratory. Retrieved October 2015. 
  5. ^ a b c Daniel W. E. Green (2007-02-22). "IAUC 8812: Sats OF 2003 AZ_84, (50000), (55637), (90482)". International Astronomical Union Circular. Archived from the original on 19 July 2011. Retrieved 2011-07-05. 
  6. ^ a b c d e f g M.E. Brown, 2013, "The density of mid-sized Kuiper belt object 2002 UX25 and the formation of the dwarf planets"
  7. ^ a b c S. Fornasier, E. Lellouch, T. Müller, P. Santos-Sanz, P. Panuzzo, C. Kiss, T. Lim, M. Mommert, D. Bockelée-Morvan, E. Vilenius, J. Stansberry, G.P. Tozzi, S. Mottola, A. Delsanti, J. Crovisier, R. Duffard, F. Henry, P. Lacerda, A. Barucci, & A. Gicquel (2013). m.µTNOs are Cool: A survey of the trans-Neptunian region. VIII. Combined Herschel PACS and SPIRE observations of 9 bright targets at 70–500
  8. ^ a b c d e f g h (55637) 2002 UX25Johnston's Archive for
  9. ^ a b c John Stansberry; Will Grundy; Mike Brown; Dale Cruikshank; John Spencer; David Trilling; et al. (2007). "Physical Properties of Kuiper Belt and Centaur Objects: Constraints from Spitzer Space Telescope".  
  10. ^ TNO Colors
  11. ^ Tegler, Stephen C. (2007-02-01). "Kuiper Belt Object Magnitudes and Surface Colors". Retrieved 2009-12-30. 
  12. ^ Doressoundiram (2004). "The Meudon Multicolor Survey (2MS) of Centraurs and Trans-Neptunian objects" (PDF). Retrieved 2006-11-06. 
  13. ^ a b "AstDys (55637) 2002UX25 Ephemerides". Department of Mathematics, University of Pisa, Italy. Retrieved 2009-11-19. 
  14. ^ a b Ron Cowen - Nature - Astronomers surprised by large space rock less dense than water Kuiper belt object challenges planet-formation theories. (13 November 2013)
  15. ^  
  16. ^  
  17. ^ Gonzalo Tancredi & Sofía Favre (13 October 2008). "Dwarf Planet & Plutoid Headquarters". Portal Uruguayo de Astronomía. Retrieved 2010-09-22.  (Which are the dwarfs in the Solar System?)
  18. ^ Tancredi, Gonzalo (2009). "Physical and dynamical characteristics of icy "dwarf planets" (plutoids)". Proceedings of the International Astronomical Union Symposium S263 5: 173–185.  
  19. ^ Rousselot, P.; Petit, J.-M.; Poulet, F.; Sergeev, A. Photometric study of Centaur (60558) 2000 EC98 and trans-neptunian object (55637) 2002 UX25 at different phase angles, Icarus, 176, (2005) pp. 478–491.Abstract.
  20. ^ a b c d Typical densities of snow and ice (kg/m³)
  21. ^ Roatsch Jaumann et al. 2009, p. 765, Tables 24.1–2
  22. ^ Distant EKO The Kuiper Belt Electronic newsletter, March 2007

External links

  • Orbital simulation from JPL (Java) / Ephemeris
  • MPEC 2002-V08
  • Strange Object Boosts Kuiper Belt Mystery (Discovery 13 Nov 2013)
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.

Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.