List of possible dwarf planets

Illustration of the relative sizes, albedos, and colours of the largest trans-Neptunian objects

It is estimated that there may be 200 dwarf planets in the Kuiper belt of the outer Solar System and up to 10,000 in the region beyond.[1][2] The International Astronomical Union (IAU) has accepted four of these: Pluto, Eris, Haumea, and Makemake, as well as Ceres in the inner Solar System. This article lists these and the more likely of the remaining known possibilities.

IAU naming procedures

In 2008, the IAU modified its naming procedures such that objects considered most likely to be dwarf planets receive differing treatment than others. Objects that have an absolute magnitude (H) less than +1 (and hence a mathematically delimited minimum diameter of 838 kilometres (521 mi)[3]) are overseen by two naming committees, one for minor planets and one for planets. Once named, the objects are declared to be dwarf planets. Makemake and Haumea are the only objects to have proceeded through the naming process as presumed dwarf planets; currently there are no other bodies which meet this requirement. All other bodies are named by the minor-planet naming committee alone, and the IAU has not stated how or if they will be accepted as dwarf planets.

Limiting values

Calculation of the diameter of Ixion depends on the albedo (the fraction of light that it reflects), which is currently unknown.

The qualifying feature of a dwarf planet is that it "has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape".[4][5][6] Except for Pluto and Ceres, current observations are insufficient for a direct determination if a body meets this definition. However, Michael Brown estimates that an icy body relaxes into hydrostatic equilibrium at a diameter somewhere between 200 and 400 km.[1] Thus, all the trans-Neptunian objects (TNOs) listed below are estimated to be at least 400 kilometres (250 mi) in diameter, though not all bodies estimated to be that size are included. The lists are further complicated by bodies such as (47171) 1999 TC36 that were at first assumed to be large single objects but were later discovered to be smaller binary or triple systems.[7]

Ceres is the only identified dwarf planet in the asteroid belt. 4 Vesta, the second-most-massive asteroid, appears to have a fully differentiated interior and was therefore in equilibrium at some point in its history, but it is not today.[8] The third-most massive object, 2 Pallas, has a somewhat irregular surface and is thought to have only a partially differentiated interior. Brown estimates that, since rocky objects are more rigid than icy objects, rocky objects below 900 kilometres (560 mi) in diameter may not be in hydrostatic equilibrium and thus not dwarf planets.[1]

Probable per Brown

Mike Brown considers a large number of trans-Neptunian bodies, ranked by estimated size, to be "probably" dwarf planets.[9] He did not consider asteroids, stating "In the asteroid belt Ceres, with a diameter of 900 km, is the only object large enough to be round".[9]

The terms for varying degrees of likelihood he split these into:

• Near certainty: diameter estimated/measured to be over 900 kilometres (560 mi). Sufficient confidence to say these must be in hydrostatic equilibrium, even if predominantly rocky.
• Highly likely: diameter estimated/measured to be over 600 kilometres (370 mi). The size would have to be "grossly in error" or they would have to be primarily rocky to not be dwarf planets.
• Likely: diameter estimated/measured to be over 500 kilometres (310 mi). Uncertainties in measurement mean that some of these will be significantly smaller and thus doubtful.
• Probable: diameter estimated/measured to be over 400 kilometres (250 mi). Expected to be dwarf planets, if they are icy, and that figure is correct.
• Possible: diameter estimated/measured to be over 200 kilometres (120 mi). Icy moons transition from a round to irregular shape in the 200–400 km range, suggesting that the same figure holds true for KBOs. Thus, some of these objects could be dwarf planets.
• Probably not: diameter estimated/measured to be under 200 km. No icy moon under 200 km is round, suggesting that the same figure holds true for KBOs. The estimated size of these objects would have to be in error for them to be dwarf planets.

Probable per Tancredi

In 2010, Gonzalo Tancredi presented a report to the IAU evaluating a list of 46 candidates for dwarf-planet status based on light curve amplitude analysis and the assumption that the object was more than 450 kilometres (280 mi) in diameter. Some diameters are measured, some are best-fit estimates, and others use an assumed albedo of 0.10. Of these, he identified 15 as dwarf planets by his criteria, with another nine being considered possible. To be cautious, he advised the IAU to "officially" accept as dwarf planets the top three: Sedna, Orcus, and Quaoar.[10] Although the IAU had anticipated Tancredi's recommendations, as of 2013, they had not responded.

Likeliest possible dwarf planets

Brown's categories
near certainty
highly likely
likely
probably
possibly
probably not

This is a list of the largest objects in the Solar System that are possible dwarf planets. Excepting Ceres, all are trans-Neptunian objects.

The default sort is per Brown's size estimate. The IAU recognised dwarf planets have bold names. Brown's diameter estimates are in red when they are based upon an assumed albedo. Explanations and sources for the measured masses and diameters can be found on the bodies' linked pages.

Body Per Brown[9] Measured per
measured
Diameter
per assumed albedo
Result
per Tancredi[10]
Category Best[a]
Diameter
km
H
Diameter[b]
(km)
Albedo
%
Mass
(Zg)
H Diameter
(km)
Albedo[c]
%
Small
albedo=100%
(km)
Large
albedo=4%
(km)
Eris −1.1 2330 99 16700 −1.2 2326 99 2310 11548 accepted (measured) SDO 2326
Pluto −0.7 2329 64 13100 −0.8 2368 66 1921 9605 accepted (measured) 2:3 resonant 2368
Makemake 0.1 1426 81 −0.4 1430 125 1598 7989 accepted cubewano 1430
(225088) 2007 OR10 2 1290 19 2 1280 17 529 2645 SDO 1280
Haumea 0.4 1252 80 4000 0.1 1430 79 1269 6346 accepted cubewano 1430
Quaoar 2.7 1092 13 1400 2.4 1074 17 440 2200 accepted (and recommended) cubewano 1074
Sedna 1.8 1041 32 1.5 995 45 666 3330 accepted (and recommended) detached 995
Orcus 2.3 983 23 580 2.2 917 28 483 2413 accepted (and recommended) 2:3 resonant 917
(307261) 2002 MS4 4 960 5 3.7 934 7 242 1209 cubewano 934
Ceres 943 3.3 952 9 291 1454 main belt 952
Salacia 4.2 921 4 450 4.2 854 5 192 960 possible cubewano 854
Varuna 3.9 770 9 3.6 757 11 253 1266 accepted cubewano 757
2013 FY27 3.3 765 15 3 334 1669 SDO 765
(208996) 2003 AZ84 3.7 747 11 3.8 727 10 231 1155 accepted 2:3 resonant 727
(55637) 2002 UX25 3.9 704 11 125 3.8 697 11 231 1155 cubewano 697
(55565) 2002 AW197 3.8 704 12 3.5 768 12 265 1326 accepted cubewano 768
(90568) 2004 GV9 4.2 703 8 4 680 10 211 1053 accepted 3:5 resonant 680
(145452) 2005 RN43 3.9 697 11 3.9 679 11 221 1103 possible cubewano 679
(202421) 2005 UQ513 3.7 695 13 3.4 498 31 278 1388 cubewano 498
Varda 3.7 695 13 265 3.4 705 16 278 1388 possible cubewano 705
Ixion 3.8 674 12 3.6 650 15 253 1266 accepted 2:3 resonant 650
(278361) 2007 JJ43 4.2 617 11 3.9 221 1103 cubewano 617
(229762) 2007 UK126 3.7 612 17 3.4 599 21 278 1388 SDO 599
Chaos 5 612 5 4.8 600 6 146 729 cubewano 600
(230965) 2004 XA192 4.3 603 10 4 339 39 211 1053 1:2 resonant 339
2013 FZ27 4.3 603 10 4 211 1053 cubewano 603
2012 VP113 4.3 603 10 4 211 1053 detached 603
2010 KZ39 4.3 603 10 4 211 1053 cubewano 603
(84522) 2002 TC302 4.2 591 12 3.8 584 16 231 1155 2:5 resonant 584
2010 RF43 4.4 588 10 4.1 201 1006 SDO 588
(78799) 2002 XW93 5.4 584 4 5.5 106 528 SDO 584
2003 UZ413 4.5 574 9 4.2 192 960 2:3 resonant 574
(42301) 2001 UR163 4.5 574 9 4.2 192 960 possible SDO 574
2002 XV93 5.4 564 4 5 549 6 133 665 2:3 resonant 549
2010 FX86 4.6 561 9 4.3 183 917 cubewano 561
2010 RE64 4.6 561 9 4.3 183 917 SDO 561
2006 QH181 4.6 561 9 4.3 183 917 SDO 561
2008 ST291 4.6 561 9 4.3 183 917 detached 561
(145451) 2005 RM43 4.7 548 9 4.4 175 876 possible SDO 548
2004 XR190 4.7 548 9 4.4 175 876 detached 548
2004 NT33 4.7 548 9 4.4 423 17 175 876 cubewano 423
(84922) 2003 VS2 4.1 537 15 4.2 523 13 192 960 2:3 resonant 523
(120348) 2004 TY364 4.8 535 8 4.5 167 837 2:3 resonant 535
2008 OG19 4.8 522 8 4.6 160 799 SDO 522
2010 VK201 4.8 522 8 4.6 160 799 cubewano 522
(308379) 2005 RS43 5.5 513 4 5.3 116 579 1:2 resonant 513
2007 JH43 4.9 510 8 4.7 153 763 2:3 resonant 510
2003 QX113 4.9 510 8 4.7 153 763 SDO 510
(82075) 2000 YW134 5 498 7 4.8 146 729 detached 498
(307616) 2003 QW90 5.6 491 4 5.4 111 553 cubewano 491
(119979) 2002 WC19 5.1 486 7 4.9 139 696 1:2 resonant 486
2007 XV50 5.1 486 7 4.9 139 696 cubewano 486
(315530) 2008 AP129 5.1 486 7 4.9 139 696 3:5 resonant 486
(307982) 2004 PG115 5.1 486 7 4.9 139 696 SDO 486
(175113) 2004 PF115 4.5 482 12 4.4 406 19 175 876 2:3 resonant 406
2010 EK139 3.8 475 25 3.8 470 24 231 1155 SDO 470
2010 TJ 5.2 475 7 5 133 665 SDO 475
2010 RF64 5.2 475 7 5 133 665 cubewano 475
2010 VZ98 5.2 475 7 5 133 665 SDO 475
2011 FW62 5.2 475 7 5 133 665 2:3 resonant 475
(26375) 1999 DE9 5.2 474 7 5.1 461 8 127 635 possible SDO 461
(35671) 1998 SN165 5.7 473 4 5.6 393 7 101 504 cubewano 393
(145480) 2005 TB190 4.4 469 15 4.7 464 11 153 763 detached 464
(119951) 2002 KX14 4.9 468 10 4.4 175 876 2:3 resonant 468
(120132) 2003 FY128 5.1 467 8 4.9 460 9 139 696 SDO 460
Huya 5 466 8 4.9 458 9 139 696 accepted 2:3 resonant 458
1999 CD158 5.3 463 6 5.1 127 635 4:7 resonant 463
2010 EL139 5.3 463 6 5.1 127 635 2:3 resonant 463
2013 FC28 5.3 463 6 5.1 127 635 cubewano 463
(84719) 2002 VR128 5.6 459 5 5.7 449 5 96 481 2:3 resonant 449
2003 QX111 6.8 453 2 6.8 58 290 2:3 resonant 453
(26181) 1996 GQ21 5.4 452 6 5.2 121 606 SDO 452
2013 JW63 5.4 452 6 5.2 121 606 1:2 resonant 452
2011 GM27 5.4 452 6 5.2 121 606 cubewano 452
2010 HE79 5.4 452 6 5.2 121 606 2:3 resonant 452
2010 ET65 5.4 452 6 5.2 121 606 SDO 452
2008 NW4 5.4 452 6 5.2 121 606 cubewano 452
(305543) 2008 QY40 5.4 452 6 5.2 121 606 SDO 452
2008 UA332 5.4 452 6 5.2 121 606 cubewano 452
2006 HH123 5.4 452 6 5.2 121 606 2:5 resonant 452
2002 GD32 5.9 430 4 5.7 96 481 cubewano 430
2001 QF298 5.4 421 7 5.1 408 10 127 635 2:3 resonant 408
(303775) 2005 QU182 3.8 415 33 3.5 416 41 265 1326 SDO 416
(144897) 2004 UX10 4.8 409 14 4.5 361 21 167 837 possible 2:3 resonant 361
2003 UA414 5.5 381 8 5.3 116 579 cubewano 381
2002 PJ149 5.5 381 8 5.3 116 579 cubewano 381
2002 CY248 5.5 381 8 5.3 116 579 cubewano 381
2010 JK124 5.5 381 8 5.3 116 579 2:3 resonant 381
2010 RO64 5.5 381 8 5.3 116 579 cubewano 381
2011 JF31 5.5 381 8 5.3 116 579 cubewano 381
2001 QX322 6.2 376 4 6 84 419 SDO 376
1999 CL119 6.2 376 4 6 84 419 cubewano 376
2000 CQ105 6.2 376 4 6 84 419 SDO 376
(48639) 1995 TL8 5.6 364 8 5.4 111 553 detached 364
2001 QS297 5.6 364 8 5.4 111 553 cubewano 364
(126154) 2001 YH140 5.6 364 8 5.4 111 553 cubewano 364
2010 TR19 5.6 364 8 5.4 111 553 SDO 364
2010 TY53 5.6 364 8 5.4 111 553 2:3 resonant 364
2010 VW11 5.6 364 8 5.4 111 553 SDO 364
2010 ER65 5.6 364 8 5.4 111 553 detached 364
2008 CT190 5.6 364 8 5.4 111 553 SDO 364
(82155) 2001 FZ173 6.3 360 4 6.1 80 400 SDO 360
2000 KK4 6.3 360 4 6.1 80 400 cubewano 360
2000 PE30 6.3 360 4 6.1 80 400 SDO 360
2001 XD255 5.7 348 8 5.5 106 528 2:3 resonant 348
2002 GH32 5.7 348 8 5.5 106 528 3:5 resonant 348
2002 XH91 5.7 348 8 5.5 106 528 cubewano 348
2007 PS45 5.7 348 8 5.5 106 528 cubewano 348
(312645) 2010 EP65 5.7 348 8 5.5 106 528 1:2 resonant 348
2010 VR11 5.7 348 8 5.5 106 528 cubewano 348
2013 FB28 5.7 348 8 5.5 106 528 cubewano 348
2007 TG422 6.4 345 4 6.2 76 382 SDO 345
(15874) 1996 TL66 5.4 344 11 5.4 339 11 111 553 accepted SDO 339
(135182) 2001 QT322 6.4 342 4 6.2 76 382 cubewano 342
(82158) 2001 FP185 6.4 336 5 6 84 419 SDO 336
2010 AH2 5.8 333 8 5.6 101 504 1:2 resonant 333
2007 JF43 5.8 333 8 5.6 101 504 2:3 resonant 333
2012 XR157 5.8 333 8 5.6 101 504 1:2 resonant 333
2011 HP83 5.8 333 8 5.6 101 504 SDO 333
2010 RN64 5.8 333 8 5.6 101 504 cubewano 333
2010 PK66 5.8 333 8 5.6 101 504 cubewano 333
2010 PU75 5.8 333 8 5.6 101 504 SDO 333
2001 QC298 6.5 330 4 6.3 73 365 cubewano 330
(148209) 2000 CR105 6.5 330 4 6.3 73 365 detached 330
2001 KA77 5.6 324 10 5 133 665 cubewano 324
(307251) 2002 KW14 5.9 322 8 5 133 665 cubewano 322
2003 UB292 5.9 319 8 5.7 96 481 cubewano 319
2002 GF32 5.9 319 8 5.7 96 481 2:3 resonant 319
2010 VQ11 5.9 319 8 5.7 96 481 cubewano 319
2007 OC10 5.4 315 13 5.7 96 481 SDO 315
2004 VN112 6.6 315 4 6.4 70 349 detached 315
2004 OJ14 6.6 315 4 6.4 70 349 2:5 resonant 315
(150642) 2001 CZ31 6 305 8 5.8 92 460 cubewano 305
(79978) 1999 CC158 6 305 8 5.8 92 460 SDO 305
2005 CA79 6 305 8 5.8 92 460 1:2 resonant 305
2008 SP266 6 305 8 5.8 92 460 cubewano 305
2007 TB418 6 305 8 5.8 92 460 2:5 resonant 305
2007 VK305 6 305 8 5.8 92 460 SDO 305
2010 JC80 6 305 8 5.8 92 460 SDO 305
2013 JV63 6 305 8 5.8 92 460 cubewano 305
2005 SD278 6.7 302 4 6.5 67 333 2:5 resonant 302
2000 CP104 6.7 302 4 6.5 67 333 cubewano 302
1. ^ The measured diameter, else Brown's estimated diameter, else the diameter calculated from H using an assumed albedo of 8%.
2. ^ Diameters in red indicate that Brown derived them from an assumed albedo.
3. ^ The albedo $A$ is calculated from the measured absolute magnitude $H$ and measured diameter $D$ via the formula: $A =\left ( \frac{1329\times10^{-H/5}}{D} \right ) ^2$

References

1. ^ a b c Mike Brown. "The Dwarf Planets". Retrieved 2008-01-20.
2. ^ "Today we know of more than a dozen dwarf planets in the solar system [and] it is estimated that the ultimate number of dwarf planets we will discover in the Kuiper Belt and beyond may well exceed 10,000".The PI's Perspective
3. ^ Dan Bruton. "Conversion of Absolute Magnitude to Diameter for Minor Planets". Department of Physics & Astronomy (Stephen F. Austin State University). Retrieved 2008-06-13.
4. ^ "IAU 2006 General Assembly: Result of the IAU Resolution votes". International Astronomical Union. 2006. Retrieved 2008-01-26.
5. ^ "Dwarf Planets". NASA. Retrieved 2008-01-22.
6. ^ "Plutoid chosen as name for Solar System objects like Pluto" (Press release).
7. ^ "AstDys (47171) 1999TC36 Ephemerides". Department of Mathematics, University of Pisa, Italy. Retrieved 2009-12-07.
8. ^ Savage, Don; Jones, Tammy; Villard, Ray (1995-04-19). "Asteroid or Mini-Planet? Hubble Maps the Ancient Surface of Vesta". Hubble Site News Release STScI-1995-20. Retrieved 2006-10-17.
9. ^ a b c
10. ^ a b Tancredi, G. (2010). "Physical and dynamical characteristics of icy "dwarf planets" (plutoids)". Icy Bodies of the Solar System: Proceedings IAU Symposium No. 263, 2009.
11. ^ "List Of Trans-Neptunian Objects". Minor Planet Center.
12. ^ "List Of Centaurs and Scattered-Disk Objects". Minor Planet Center.