List of dwarf planet candidates

List of dwarf planet candidates

At present, the International Astronomical Union classifies five objects as dwarf planets: Ceres, Pluto, Eris, Haumea, and Makemake, though dozens of others are thought likely to be classified as such in the future. The qualifying feature of dwarf planets is that they must "have sufficient mass for their self-gravity to overcome rigid body forces so that they assume a hydrostatic equilibrium (near-spherical shape)."[1][2][3] Those dwarf planets lying beyond the orbit of Neptune are termed "plutoids", after Pluto. Except for Pluto and Ceres, observations are insufficient for direct classification. However, based on present knowledge of how icy bodies gravitationally relax into equilibrium shapes, there are currently about 73 potential candidates amongst the population of trans-Neptunian objects (TNOs).[4] It is estimated that there are around 200 dwarf planets in the Kuiper belt and up to 2000 in the region beyond.[4] The first trans-Neptunian object discovered since Pluto that is a solid dwarf planet candidate is (15874) 1996 TL66, and is estimated by the Spitzer Space Telescope to be about 575 km in diameter.[5]

Contents

Changes to IAU naming procedures

See also: IAU definition of planet

The IAU has modified its nomenclature procedures such that objects considered highly likely to be plutoids receive differing treatment when receiving names than other TNOs. Objects that have an absolute magnitude less than +1 (and hence a mathematically-delimited minimum diameter of 838 km[6]) will be overseen by two naming committees rather than one. Once named, the objects are declared to be dwarf planets by the IAU. Makemake and Haumea are the only TNOs to have proceeded through the naming process as presumed plutoids.

Candidates

Colours of the Transneptunians

Mike Brown estimates that at a diameter somewhere between 200 and 400 km, an icy body relaxes into hydrostatic equilibrium.[4] Thus, all TNOs listed are those known or suspected to be 400 km or above in diameter.[4] However, diameter estimates vary widely, and they are therefore ordered here by their absolute magnitudes, H, rather than diameter. Theoretical minimum diameters correspond to a maximum albedo of 1. But many borderline candidates are thought to be dark, and therefore substantially larger than this lower limit due to tholins causing a red-sloped reflectance spectrum. Eris has a high albedo of 0.8–0.9, and the Haumea family are also thought to be bright.

The list is also further complicated by smaller candidates such as 1999 TC36 that are discovered to be binary or triple systems. Plutino 1999 TC36 was resolved as a triple system by the Hubble since the system is currently only 30.7 AU[7] from the Sun (just beyond the orbit of Neptune).

At present, Ceres is the only identified dwarf planet in the asteroid belt. At the time it announced the term "plutoid", the IAU noted that "current scientific knowledge lends credence to the belief that Ceres is the only object of its kind. Therefore, a separate category of Ceres-like dwarf planets will not be proposed at this time."[3] The likeliest exception would be 4 Vesta, the asteroid belt's second-most massive body; Vesta appears to have a fully differentiated interior and was therefore at least in equilibrium at some point in its history.[8] The third-most massive object, 2 Pallas, has a somewhat irregular surface, and is thought to have only a partially differentiated interior. Mike Brown estimates that, since rocky objects become rounded far less easily than icy objects, rocky objects below 900 km in diameter may not be in hydrostatic equilibrium.[4]

Spitzer alpha candidates

The following alpha list only contains candidates that the Spitzer Space Telescope has estimated to have diameters greater than 600 km.[5] 2007 OR10 is not included on this alpha list since it has not been observed by Spitzer. Even though (84522) 2002 TC302 has a dimmer absolute magnitude (H) than other objects on this list, it has a low albedo.

Calculation of the diameter of Ixion depends on the albedo (the fraction of light that it reflects).
Name (H) Spitzer
Size (km)		 Spitzer
Albedo		 V–R
Sedna 1.6 <1600 >0.16 0.78
(84522) 2002 TC302 3.8 1150 0.03+0.03
−0.01		 0.67
Orcus 2.3 946 0.28±0.04 0.37
Quaoar 2.5 844 0.199+0.13
−0.07		 0.64
(55565) 2002 AW197 3.2 734 0.117+.04
−.03		 0.56
(84922) 2003 VS2 4.0 725 0.058+.04
−.02		 0.59
2002 MS4 3.8 726 0.084+.03
−.02		 0.38
(208996) 2003 AZ84 4.0 686 0.12+.04
−.03		 0.36
(55637) 2002 UX25 3.6 681 0.115+0.05
−0.03		 0.57
(90568) 2004 GV9 3.9 677 0.08±0.02 0.52
Ixion 3.2 650 0.12+.14
−.06		 0.61

List by absolute magnitude (H)

Under 3

The Earth Dysnomia Eris Charon Pluto Makemake Haumea Sedna Orcus 2007 OR10 Quaoar File:EightTNOs.png
Artistic comparison of Eris, Pluto, Makemake, Haumea, Sedna, Orcus, 2007 OR10, Quaoar, and Earth (scales are outdated)

These TNOs are over a thousand km across when assuming a generic albedo of 0.09, and have theoretical minimum diameters greater than 334 km.

Name H Category Diameter (km) Min.
diam.[9]		 Mass
(1020 kg)		 Average distance
from the Sun (AU)[4]
by [4] by [10] others
Sedna 1.58 detached object 1800 1700 < 1600[5] 650 8.3–70? 486.0
2007 OR10 2.00 SDO 1834 900–1400 532 67
Orcus 2.30 plutino 1100 901 875–1020[5] 460 6.32[11] 39.34
Quaoar 2.48 cubewano 1290 842 820–960[12] 426 13–19[12] 43.58

Between 3 and 4

These minor planets have theoretical minimum diameters of 213–336 km.

Name H Category Diameter (km) Mass
(1020 kg)		 Average distance
from the Sun (AU)[4]
by [4] by [10] others
(55636) 2002 TX300 3.19 haumeid 800 709 286[13] 0.2 43.11
Vesta 3.20 asteroid 578×560×458 km[14] 2.59 [15] 2.361
Ixion 3.20 plutino 980 727 430–910;[5] 900–1230 [16] ~3? 39.65
(55565) 2002 AW197 3.26 cubewano 940 766 625–850;[5] 770–1010 [16] ~4? 47.30
2005 QU182 3.40 SDO 919 925[6][17] (550–1240)[18] 113
(202421) 2005 UQ513 3.40 cubewano 919 925[6][17] (550–1240)[18] 43
(229762) 2007 UK126 3.40 SDO 919 530–1190[18] 73
(174567) 2003 MW12 3.40 cubewano 740 838 45.94
(55637) 2002 UX25 3.60 cubewano 810 649 570–795 [5] ~3? 42.53
Varuna 3.70 cubewano 780 785 755–1025;[19] 480–800 [5] 42.90
(278361) 2007 JJ43 3.70 cubewano 1008 1015[6][17] 47.99
2002 MS4 3.77 cubewano 740 728 600–850 [5] 41.90
2006 QH181 3.80 semi-detached 765 67.3
2010 EK139 3.81 SDO 765 462–1033[18] 69.4
(84522) 2002 TC302 3.87 5:2 SDO 710 1150 920–1480[5] ~15? 55.02
(145452) 2005 RN43 3.90 cubewano 740 730 41.53
(90568) 2004 GV9 3.90 cubewano 680 681 610–750 [5] ~3? 42.23
2010 KZ39 3.90 SDO 697 421-942[18] 184.4
(120178) 2003 OP32 3.95 haumeid 650 666 230 km 43.24
(84922) 2003 VS2 3.99 plutino 610 636 540–925 [5] 39.27

Between 4 and 5

Name H Category Diameter (km) Mass
(1020 kg)		 Average distance
from the Sun (AU)[4]
by [4] by [10] others
(145453) 2005 RR43 4.0 haumeid 697 252 km 43
(208996) 2003 AZ84 4.0 plutino 710 686 590–785 km[5] 39.45
(230965) 2004 XA192 4.0 cubewano 696 46.98
(42301) 2001 UR163 4.05 9:4 SDO 620 636 51.40
Pallas 4.13 asteroid 582×556×500±9 km[8] 2.11±0.26[20] 2.772
2010 RE64 4.2 cubewano 380-860[18] 45.8
120347 Salacia 4.3 cubewano 560 548 41.97
2003 UZ413 4.3 plutino 591
(120348) 2004 TY364 4.3 other TNO 540 554 38.72
210-584 54.2
2008 ST291 4.4 SDO 583 350-784[18] 106
(145451) 2005 RM43 4.4 SDO 560 580 89.73
2004 NT33 4.4 cubewano 580
2004 XR190 (Buffy) 4.47 SDO 540 572 57.36
haumeid 540 900 200 km 43.19
lost 520 522 ~45
2:5 TNO 490 461 461±45[5] 1? 55.72
38628 Huya 4.7 plutino 480 506 532±25[5] 1.6? 39.76
(145480) 2005 TB190 4.7 detached 505 76.38
haumeid 470 702 174 km 41.64
(120132) 2003 FY128 4.8 detached 430 440 49.77
(82075) 2000 YW134 4.8 8:3 TNO 430 431 57.77
19521 Chaos 4.9 cubewano 450 745 45.56
2002 XV93 4.9 plutino 430 457 39.22
edit] Above 5
Name H Category Diameter (km) Average distance
from the Sun (AU)[4]
(119979) 2002 WC19 5.0 twotino 410,[4] 400[10] 47.67
(79360) 1997 CS29 5.1 cubewano 410,[4] 305[10] 43.87
1999 CD158 5.1 SDO 410,[4] 426[10] 43.69
(26181) 1996 GQ21 5.2 SDO 401 94.88
2006 HH123 5.2 lost 400[10] ~56
(15874) 1996 TL66 5.4 SDO 632,[4] 460-690 [5] 83
2003 QW90 5.4 cubewano 560,[4] 396[10] 43.65
Hygiea 5.43 asteroid 500×385×350[20] 3.139
absolute magnitudes (H) dimmer than H=6, are not included since even assuming a dark albedo of 0.04 results in an estimated size less than 400 km.[6]

Probable per Brown

Mike Brown considers the following bodies, ranked by estimated size, to be "probably" plutoids. Asteroids are not considered.

The terms for varying degrees of likelihood are:

Near certainty: Sufficient confidence to say these must be in hydrostatic equilibrium even if predominantly rocky.
Highly likely: Estimated/measured to be over 600 km. The size would have to be "grossly in error" or they would have to be primarily rocky to not be dwarf planets.
Likely: Estimated/measured to be over 500 km. Uncertainties in measurement mean that some of these will be significantly smaller and thus doubtful.
Probable: Estimated/measured to be over 400 km. Expected to be dwarf planets if they are icy and that figure is correct.
Probable plutoids (as of 2011 Aug 24)[22]
rank name diameter
(km)		 albedo
(%)		 absolute
magnitude
(H)		 comments likelihood
1 Eris 2330 99 −1.1 (measured) near certainty
2 Pluto 2330 66 −0.7 (measured) near certainty
3 Haumea 1500 69 0.2 (measured) near certainty
4 Makemake 1440 79 0.1 (measured) near certainty
5 2007 OR10 1420 19 1.7 (estimate) near certainty
6 Sedna 1400 22 1.6 (estimate) near certainty
7 2002 TC302 1150 4 3.8 (very large uncertainty:
likely smaller)		 highly likely
8 Quaoar 980 18 2.6 (measured) near certainty
9 Orcus 950 25 2.3 (measured) near certainty
10 2007 UK126 748 15 3.4 highly likely
11 2005 QU182 748 15 3.4 highly likely
12 2003 MW12 748 15 3.4 highly likely
13 2005 UQ513 748 15 3.4 highly likely
14 2002 AW197 734 15 3.4 (measured) highly likely
15 2002 MS4 726 12 3.7 (measured) highly likely
16 2007 JJ43 694 13 3.7 highly likely
17 2003 AZ84 685 15 3.6 (measured) highly likely
18 2002 UX25 681 13 3.7 (measured) highly likely
19 2006 QH181 677 12 3.8 highly likely
20 2010 EK139 677 12 3.8 highly likely
21 2004 GV9 677 10 4.0 (measured) highly likely
22 2005 RN43 661 12 3.9 highly likely
23 2010 KZ39 661 12 3.9 highly likely
24 Ixion 650 21 3.3 (measured) highly likely
25 2004 XA192 644 11 4.0 highly likely
26 2003 VS2 629 11 4.1 highly likely
27 2001 UR163 613 10 4.2 highly likely
28 Salacia 613 10 4.2 highly likely
29 2004 PF115 613 10 4.2 highly likely
30 2010 RF43 613 10 4.2 highly likely
31 2010 RE64 613 10 4.2 highly likely
32 2008 ST291 598 10 4.3 likely
33 2003 UZ413 598 10 4.3 likely
34 2010 FX86 598 10 4.3 likely
35 2005 RM43 584 10 4.4 likely
36 2004 XR190 584 10 4.4 likely
37 2002 KX14 584 10 4.4 likely
38 2004 NT33 584 10 4.4 likely
39 1996 TL66 575 4 5.4 (measured) likely
40 2004 TY364 569 9 4.5 likely
41 2004 UX10 569 9 4.5 likely
42 2008 AP129 569 9 4.5 likely
43 2010 VK201 569 9 4.5 likely
44 2004 PR107 555 9 4.6 likely
45 2005 TB190 542 8 4.7 likely
46 2003 QX113 542 8 4.7 likely
47 2007 JH43 542 8 4.7 likely
48 Huya 532 7 4.9 (measured) likely
49 2010 VZ98 528 8 4.8 likely
50 Chaos 528 8 4.8 likely
51 2000 YW134 515 8 4.9 likely
52 2004 PG115 515 8 4.9 likely
53 2008 QY40 515 8 4.9 likely
54 2003 FY128 515 8 4.9 likely
55 2008 OG19 503 7 5.0 likely
56 2001 KA77 503 7 5.0 likely
57 2002 KW14 503 7 5.0 likely
58 2002 XV93 503 7 5.0 likely
59 2007 XV50 503 7 5.0 likely
60 2011 FW62 503 7 5.0 likely
61 Varuna 500 27 3.6 (measured) probable
62 2002 WC19 490 7 5.1 probable
63 1999 CD158 490 7 5.1 probable
64 2001 QF298 490 7 5.1 probable
65 2010 EL139 490 7 5.1 probable
66 2010 RO64 490 7 5.1 probable
67 2011 GM27 490 7 5.1 probable
68 1996 GQ21 478 7 5.2 probable
69 2006 HH123 478 7 5.2 probable
70 2010 ET65 478 7 5.2 probable
71 2010 TY53 478 7 5.2 probable
72 2008 UA332 478 7 5.2 probable
73 2010 HE79 478 7 5.2 probable
74 2002 PJ149 467 7 5.3 probable
75 2003 UA414 467 7 5.3 probable
76 2005 RS43 467 7 5.3 probable
77 2010 JK124 467 7 5.3 probable
78 2010 PU75 467 7 5.3 probable
79 1999 DE9 461 8 5.1 (measured) probable
80 1998 SN165 460 5 5.6 (measured) probable
81 1995 TL8 455 6 5.4 probable
82 2008 CT190 455 6 5.4 probable
83 2010 ER65 455 6 5.4 probable
84 2010 TR19 455 6 5.4 probable
85 2002 GJ32 455 6 5.4 probable
86 2001 QS297 455 6 5.4 probable
87 2002 CY248 455 6 5.4 probable
88 2003 QW90 455 6 5.4 probable
89 2007 PS45 455 6 5.4 probable
90 2002 JR146 444 6 5.5 probable
91 2010 TJ 444 6 5.5 probable
92 2002 XW93 444 6 5.5 probable
93 2001 YH140 444 6 5.5 probable
94 2001 XD255 444 6 5.5 probable
95 2002 GH32 444 6 5.5 probable
96 2002 XH91 444 6 5.5 probable
97 2010 EP65 444 6 5.5 probable
98 1999 TC36 415 12 4.9 (measured) probable
99 2001 FP185 411 4 6.0 (blue) probable
100 2000 CQ105 411 4 6.0 (blue) probable
101 2001 QX322 411 4 6.0 (blue) probable
102 1999 CL119 411 4 6.0 (blue) probable

Another 288 objects were listed as "possible" dwarfs, depending on composition and the accuracy of size and mass estimates.

See also

References

  1. ^ "IAU 2006 General Assembly: Result of the IAU Resolution votes". International Astronomical Union. 2006. http://www.iau.org/iau0603.414.0.html. Retrieved 2008-01-26. 
  2. ^ "Dwarf Planets". NASA. http://solarsystem.nasa.gov/planets/profile.cfm?Object=Dwarf&Display=OverviewLong. Retrieved 2008-01-22. 
  3. ^ a b "Plutoid chosen as name for Solar System objects like Pluto" (Press release). http://www.iau.org/public_press/news/release/iau0804/. 
  4. ^ a b c d e f g h i j k l m n o p q r Mike Brown. "The Dwarf Planets". http://web.gps.caltech.edu/~mbrown/dwarfplanets/. Retrieved 2008-01-20. 
  5. ^ a b c d e f g h i j k l m n o p q r Barucci, M.A.; John Stansberry, Will Grundy, Mike Brown, Dale Cruikshank, John Spencer, David Trilling, Jean-Luc Margot (2007). "Physical Properties of Kuiper Belt and Centaur Objects: Constraints from Spitzer Space Telescope". Kuiper Belt. arXiv:astro-ph/0702538. Bibcode 2008ssbn.book..161S. 
  6. ^ a b c d e Dan Bruton. "Conversion of Absolute Magnitude to Diameter for Minor Planets". Department of Physics & Astronomy (Stephen F. Austin State University). http://www.physics.sfasu.edu/astro/asteroids/sizemagnitude.html. Retrieved 2008-06-13. 
  7. ^ "AstDys (47171) 1999TC36 Ephemerides". Department of Mathematics, University of Pisa, Italy. http://hamilton.dm.unipi.it/astdys/index.php?pc=1.1.3.0&n=47171. Retrieved 2009-12-07. 
  8. ^ a b Savage, Don; Jones, Tammy; and Villard, Ray (1995-04-19). "Asteroid or Mini-Planet? Hubble Maps the Ancient Surface of Vesta". Hubble Site News Release STScI-1995-20. http://hubblesite.org/newscenter/archive/releases/1995/20/image/c. Retrieved 2006-10-17. 
  9. ^ Minimum diameter = 1329*10(−H/5)
  10. ^ a b c d e f g h i Robert Johnston. "List of Known Trans-Neptunian Objects". http://www.johnstonsarchive.net/astro/tnoslist.html. Retrieved 2010-08-07. 
  11. ^ Brown, M.E.; Ragozzine, D.; Stansberry, J.; Fraser, W.C. (2009). "The size, density, and formation of the Orcus-Vanth system in the Kuiper belt". AJ. arXiv:0910.4784. Bibcode 2010AJ....139.2700B. doi:10.1088/0004-6256/139/6/2700. 
  12. ^ a b Brown, Michael E.; Fraser, Wesley C. (2010). "Quaoar: A Rock in the Kuiper belt". The Astrophysical Journal 714: 1547. Bibcode 2010ApJ...714.1547F. doi:10.1088/0004-637X/714/2/1547. http://arxiv4.library.cornell.edu/abs/1003.5911. Retrieved 2010-04-01. 
  13. ^ Clara Moskowitz (2010-06-16). "Scientists size up a bright mini-world". MSNBC. http://www.msnbc.msn.com/id/37735465/ns/technology_and_science-space/. Retrieved 2010-06-16. 
  14. ^ Thomas, P. C.; et al. (1997). "Impact excavation on asteroid 4 Vesta: Hubble Space Telescope results". Science 277 (5331): 1492. Bibcode 1997Sci...277.1492T. doi:10.1126/science.277.5331.1492. 
  15. ^ Baer, James; Chesley, Steven R. (2008). "Astrometric masses of 21 asteroids, and an integrated asteroid ephemeris" (PDF). Celestial Mechanics and Dynamical Astronomy (Springer Science+Business Media B.V. 2007) 100 (2008): 27–42. Bibcode 2008CeMDA.100...27B. doi:10.1007/s10569-007-9103-8. http://www.springerlink.com/content/h747307j43863228/fulltext.pdf. Retrieved 2008-11-11. 
  16. ^ a b David C. Jewitt. "Kuiper Belt". http://www2.ess.ucla.edu/~jewitt/kb.html. Retrieved 2008-01-22. 
  17. ^ a b c Assuming an albedo of 0.09.
  18. ^ a b c d e f g h i j k l "Absolute Magnitude (H)". NASA/JPL. http://neo.jpl.nasa.gov/glossary/h.html. Retrieved 2008-12-09. 
  19. ^ Dave Jewitt: Size and Albedo of Kuiper Belt Object (20000) Varuna
  20. ^ a b Baer, James; Steven R. Chesley (2008). "Astrometric masses of 21 asteroids, and an integrated asteroid ephemeris" (PDF). Celestial Mechanics and Dynamical Astronomy (Springer Science+Business Media B.V. 2007) 100 (2008): 27–42. Bibcode 2008CeMDA.100...27B. doi:10.1007/s10569-007-9103-8. http://www.springerlink.com/content/h747307j43863228/fulltext.pdf. Retrieved 2008-11-11. 
  21. ^ Benecchi, S.D; Noll, K. S.; Grundy, W. M.; Levison, H. F. (2009). "(47171) 1999 TC36, A Transneptunian Triple". Icarus. arXiv:0912.2074. Bibcode 2010Icar..207..978B. doi:10.1016/j.icarus.2009.12.017. 
  22. ^ Mike Brown, How many dwarf planets are there in the outer solar system?[1]

External links

v · d · eOfficial and potential plutoids (Trans-Neptunian dwarf planets)
Kuiper belt
Scattered disc
Kuiper-belt candidates
Scattered-disc candidates
Other candidates

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