List of possible dwarf planets

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The number of dwarf planets in the Solar System is unknown. Estimates have run as high as 200 in the Kuiper belt[1] and over 10,000 in the region beyond.[2] However, consideration of the surprisingly low densities of many dwarf-planet candidates suggests that the numbers may be much lower (e.g. at most 10 among bodies known so far).[3] The International Astronomical Union (IAU) notes five in particular: Ceres in the inner Solar System and four in the trans-Neptunian region: Pluto, Eris, Haumea, and Makemake, the last two of which were accepted as dwarf planets for naming purposes. Only Pluto is confirmed as a dwarf planet, and it has also been declared one by the IAU independently of whether it meets the IAU definition of a dwarf planet.

Limiting values

Calculation of the diameter of Ixion depends on the albedo (the fraction of light that it reflects). Current estimates are that the albedo is 13–15%, a bit under the midpoint of the range shown here and corresponding to a diameter of 620 km.

Beside directly orbiting the Sun, the qualifying feature of a dwarf planet is that it have "sufficient mass for its self-gravity to overcome rigid-body forces so that it assumes a hydrostatic equilibrium (nearly round) shape".[4][5][6] Current observations are generally insufficient for a direct determination as to whether a body meets this definition. Often the only clues for trans-Neptunian objects (TNO) is a crude estimate of their diameters and albedos. Icy satellites as large as 1500 km in diameter have proven to not be in equilibrium, whereas dark objects in the outer solar system often have low densities that imply they are not even solid bodies, much less gravitationally controlled dwarf planets.

Ceres, which has a significant amount of ice in its composition, is the only confirmed dwarf planet in the asteroid belt, though the question remains open for 10 Hygiea.[7][8] 4 Vesta, the second-most-massive asteroid and one that is basaltic in composition, appears to have a fully differentiated interior and was therefore in equilibrium at some point in its history, but no longer is today.[9] The third-most massive object, 2 Pallas, has a somewhat irregular surface and is thought to have only a partially differentiated interior; it is also less icy than Ceres. Michael Brown has estimated that, because rocky objects such as Vesta 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][10]

Based on a comparison with the icy moons that have been visited by spacecraft, such as Mimas (round at 400 km in diameter) and Proteus (irregular at 410–440 km in diameter), Brown estimated that an icy body relaxes into hydrostatic equilibrium at a diameter somewhere between 200 and 400 km.[1] However, after Brown and Tancredi made their calculations, better determination of their shapes showed that Mimas and the other mid-sized ellipsoidal moons of Saturn up to at least Iapetus (which is of the approximate size of Haumea and Makemake) are no longer in hydrostatic equilibrium; they are also icier than TNOs are likely to be. They have equilibrium shapes that froze in place some time ago, and do not match the shapes that equilibrium bodies would have at their current rotation rates.[11] Thus Ceres, at 950 km in diameter, is the smallest body for which gravitational measurements indicate current hydrostatic equilibrium.[12] Much larger objects, such as Earth's moon, are not near hydrostatic equilibrium today,[13][14][15] though the Moon is composed primarily of silicate rock (in contrast to most dwarf planet candidates, which are ice and rock). Saturn's moons may have been subject to a thermal history that would have produced equilibrium-like shapes in bodies too small for gravity alone to do so. Thus, at present it is unknown whether any trans-Neptunian objects smaller than Pluto and Eris are in hydrostatic equilibrium.[3]

The majority of mid-sized TNOs up to about 900–1000 km in diameter have significantly lower densities (~ 1.0–1.2 g/ml) than larger bodies such as Pluto (1.86 g/ml). Brown had speculated that this was due to their composition, that they were almost entirely icy. However, Grundy et al.[3] point out that there is no known mechanism or evolutionary pathway for mid-sized bodies to be icy while both larger and smaller objects are partially rocky. They demonstrated that at the prevailing temperatures of the Kuiper Belt, water ice is strong enough to support open interior spaces (interstices) in objects of this size; they concluded that mid-size TNOs have low densities for the same reason that smaller objects do—because they have not compacted under self-gravity into fully solid objects, and thus the typical TNO smaller than 900–1000 km in diameter is (pending some other formative mechanism) unlikely to be a dwarf planet.

Tancredi's assessment

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 a calculation that the object was more than 450 kilometres (280 mi) in diameter. Some diameters were measured, some were best-fit estimates, and others used an assumed albedo of 0.10 to calculate the diameter. Of these, he identified 15 as dwarf planets by his criteria (including the 4 accepted by the IAU), with another 9 being considered possible. To be cautious, he advised the IAU to "officially" accept as dwarf planets the top three not yet accepted: Sedna, Orcus, and Quaoar.[16] Although the IAU had anticipated Tancredi's recommendations, a decade later the IAU had never responded.

Brown's assessment

EarthMoonCharonCharonNixNixKerberosKerberosStyxStyxHydraHydraPlutoPlutoDysnomiaDysnomiaErisErisNamakaNamakaHi'iakaHi'iakaHaumeaHaumeaMakemakeMakemakeMK2MK2XiangliuXiangliuGonggongGonggongWeywotWeywotQuaoarQuaoarSednaSednaVanthVanthOrcusOrcusActaeaActaeaSalaciaSalacia2002 MS42002 MS4File:10 Largest Trans-Neptunian objects (TNOS).png
Artistic comparison of Pluto, Eris, Makemake, Haumea, Gonggong (2007 OR10), Sedna, Quaoar, Orcus, 2002 MS4, and Salacia.
Brown's categories Min. ⌀ Number of objects
nearly certainly >900 km 10
highly likely 600–900 km 17 (27 total)
likely 500–600 km 41 (68 total)
probably 400–500 km 62 (130 total)
possibly 200–400 km 611 (741 total)
Source: Mike Brown,[17] as of 2020 October 22

Mike Brown considers 130 trans-Neptunian bodies to be "probably" dwarf planets, ranked them by estimated size.[17] He does not consider asteroids, stating "in the asteroid belt Ceres, with a diameter of 900 km, is the only object large enough to be round."[17]

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. 10 objects as of 2020.
  • 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. 17 objects as of 2020.
  • 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. 41 objects as of 2020.
  • Probably: diameter estimated/measured to be over 400 kilometres (250 mi). Expected to be dwarf planets, if they are icy, and that figure is correct. 62 objects as of 2020.
  • Possibly: 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. 611 objects as of 2020.
  • Probably not: diameter estimated/measured to be under 200 km. No icy moon under 200 km is round, and the same may be true of KBOs. The estimated size of these objects would have to be in error for them to be dwarf planets.

Beside the five accepted by the IAU, the 'nearly certain' category includes Gonggong, Quaoar, Sedna, Orcus, 2002 MS4 and Salacia.

Grundy et al.’s assessment

Grundy et al. propose that dark, low-density TNOs in the size range of approximately 400–1000 km are transitional between smaller, porous (and thus low-density) bodies and larger, denser, brighter and geologically differentiated planetary bodies (such as dwarf planets). Bodies in this size range should have begun to collapse the interstitial spaces left over from their formation, but not fully, leaving some residual porosity.[3]

Many TNOs in the size range of about 400–1000 km have oddly low densities, in the range of about 1.0–1.2 g/cm3, that are substantially less than dwarf planets such as Pluto, Eris and Ceres, which have densities closer to 2. Brown has suggested that large low-density bodies must be composed almost entirely of water ice, since he presumed that bodies of this size would necessarily be solid. However, this leaves unexplained why TNOs both larger than 1000 km and smaller than 400 km, and indeed comets, are composed of a substantial fraction of rock, leaving only this size range to be primarily icy. Experiments with water ice at the relevant pressures and temperatures suggest that substantial porosity could remain in this size range, and it is possible that adding rock to the mix would further increase resistance to collapsing into a solid body. Bodies with internal porosity remaining from their formation could be at best only partially differentiated, in their deep interiors. (If a body had begun to collapse into a solid body, there should be evidence in the form of fault systems from when its surface contracted.) The higher albedos of larger bodies is also evidence of full differentiation, as such bodies were presumably resurfaced with ice from their interiors. Grundy et al.[3] propose therefore that mid-size (< 1000 km), low-density (< 1.4 g/ml) and low-albedo (< ~0.2) bodies such as Salacia, Varda, Gǃkúnǁʼhòmdímà and (55637) 2002 UX25 are not differentiated planetary bodies like Orcus, Quaoar and Charon. The boundary between the two populations would appear to be in the range of about 900–1000 km.[3]

If Grundy et al.[3] are correct, then among known bodies in the outer Solar System only Pluto–Charon, Eris, Haumea, Gonggong, Makemake, Quaoar, Orcus, Sedna and perhaps Salacia (which if it were spherical and had the same albedo as its moon would have a density of between 1.4 and 1.6 g/cm3, calculated a few months after Grundy et al's initial assessment, though still an albedo of only 0.04)[18] are likely to have compacted into fully solid bodies, and thus to possibly have become dwarf planets at some point in their past or to still be dwarf planets at present.

Likeliest dwarf planets

The assessments of the IAU, Tancredi et al., Brown and Grundy et al. for the dozen largest potential dwarf planets are as follows. For the IAU, the acceptance criteria were for naming purposes. Several of these objects had not yet been discovered when Tancredi et al. did their analysis. Brown's sole criterion is diameter; he accepts a great many more as highly likely to be dwarf planets (see below). Grundy et al. did not determine which bodies were dwarf planets, but rather which could not be. A red No marks objects too dark or not dense enough to be solid bodies, a question mark the smaller bodies consistent with being differentiated (the question of current equilibrium was not addressed).

Mercury, Iapetus, Earth's moon and Phoebe are included for comparison, as none of these objects are in equilibrium today. Triton (which formed as a TNO and is likely still in equilibrium) and Charon are included as well.

Designation Measured mean
diameter (km) 		Density
(g/cm3) 		Albedo Per IAU Per Tancredi
et al.[16] 		Per Brown[17] Per Grundy
et al.[3][18] 		Category
No Mercury 4880 5.427 0.142 (no longer in equilibrium)[19] (planet)
No The Moon 3475 3.344 0.136 (no longer in equilibrium)[20][21] (moon of Earth)
N I Triton 2707±2 2.06 0.76 (likely in equilibrium)[22] (moon of Neptune)
134340 Pluto 2376±3 1.854±0.006 0.49 to 0.66 Yes Yes Yes 2:3 resonant
136199 Eris 2326±12 2.43±0.05 0.96 Yes Yes Yes SDO
136108 Haumea ≈ 1560 ≈ 2.018 0.51 Yes
(naming rules)		 Yes Yes cubewano
No S VIII Iapetus 1469±6 1.09±0.01 0.05 to 0.5 (no longer in equilibrium)[23] (moon of Saturn)
136472 Makemake 1430+38
−22		 1.9±0.2 0.81 Yes
(naming rules)		 Yes Yes cubewano
225088 Gonggong 1230±50 1.74±0.16 0.14 NA Yes Maybe 3:10 resonant
P I Charon 1212±1 1.70±0.02 0.2 to 0.5 (possibly in equilibrium)[24] (moon of Pluto)
50000 Quaoar 1110±5 2.0±0.5 0.11 Yes Yes Maybe cubewano
90377 Sedna 995±80 ? 0.32 Yes Yes Maybe detached
1 Ceres 946±2 2.16±0.01 0.09 Yes (close to equilibrium)[25] asteroid
90482 Orcus 910+50
−40		 1.53±0.14 0.23 Yes Yes Maybe 2:3 resonant
120347 Salacia 846±21 1.5±0.12 0.04 Maybe Yes Maybe cubewano
(307261) 2002 MS4 778±11 ? 0.10 NA Yes No cubewano
(55565) 2002 AW197 768±39 ? 0.11 Yes Maybe No cubewano
174567 Varda 749±18 1.27±0.06 0.10 Maybe Maybe No 4:7 resonant
(532037) 2013 FY27 742+78
−83		 ? 0.17 NA Maybe No SDO
(208996) 2003 AZ84 707±24 0.87±0.01? 0.10 Yes Maybe No 2:3 resonant
No S IX Phoebe 213±2 1.64±0.03 0.06 (no longer in equilibrium)[26] (moon of Saturn)

Largest candidates

The following trans-Neptunian objects have estimated diameters at least 400 kilometres (250 mi) and so are considered "probable" dwarf planets by Brown's assessment. Not all bodies estimated to be this size are included. The list is complicated by bodies such as 47171 Lempo that were at first assumed to be large single objects but later discovered to be binary or triple systems of smaller bodies.[27] The dwarf planet Ceres is added for comparison. Explanations and sources for the measured masses and diameters can be found in the corresponding articles linked in column "Designation" of the table.

The Best diameter column uses a measured diameter if one exists, otherwise it uses Brown's assumed-albedo diameter. If Brown does not list the body, the size is calculated from an assumed-albedo of 9% per Johnston.[28]

Designation Best[a]
diameter
km 		Measured per
measured 		Per Brown[17] Notes on shape Result
per Tancredi[16] 		Category
Mass[b]
(1018 kg) 		H

[29][30]

Diameter
(km) 		Method Geometric
albedo[c]
(%) 		H
 Diameter[d]
(km) 		Geometric
albedo
(%)
134340 Pluto 2377 13030 −0.76 2377±3 direct 63 −0.7 2329 64 spherical accepted (measured) 2:3 resonant
136199 Eris 2326 16466 −1.17 2326±12 occultation 96 −1.1 2330 99 spherical accepted (measured) SDO
136108 Haumea 1559 4006 0.43 1559 occultation 49 0.4 1252 80 Jacobi ellipsoid accepted cubewano
136472 Makemake 1429 3100 0.05 1429+38
−20 		occultation 83 0.1 1426 81 slightly oblate accepted cubewano
225088 Gonggong 1230 1750 2.34 1230±50 thermal 14 2 1290 19 3:10 resonant
50000 Quaoar 1103 1400 2.74 1103+47
−33 		occultation 11 2.7 1092 13 Maclaurin spheroid accepted (and recommended) cubewano
1 Ceres 939 939 3.36 939±2 direct 9 Maclaurin spheroid asteroid belt
90482 Orcus 910 641 2.31 910+50
−40 		thermal 25 2.3 983 23 accepted (and recommended) 2:3 resonant
90377 Sedna 906 1.83 906+314
−258 		thermal 40 1.8 1041 32 accepted (and recommended) detached
120347 Salacia 846 492 4.27 846±21 thermal 5 4.2 921 4 possible cubewano
(307261) 2002 MS4 787 3.5 787±13 occultation 11 4 960 5 Maclaurin spheroid cubewano
(55565) 2002 AW197 768 3.57 768+39
−38 		thermal 11 3.6 754 12 accepted cubewano
174567 Varda 749 245 3.61 749±18 occultation 11 3.7 689 13 Maclaurin spheroid possible cubewano
(532037) 2013 FY27 742 3.15 742+78
−83 		thermal 18 3.5 721 14 SDO
28978 Ixion 710 3.83 710±0.2 occultation 10 3.8 674 12 Maclaurin spheroid accepted 2:3 resonant
(208996) 2003 AZ84 707 3.74 707±24 occultation 11 3.9 747 11 Jacobi ellipsoid accepted 2:3 resonant
(90568) 2004 GV9 680 4.23 680±34 thermal 8 4.2 703 8 accepted cubewano
(145452) 2005 RN43 679 3.89 679+55
−73 		thermal 11 3.9 697 11 possible cubewano
(55637) 2002 UX25 659 125 3.87 659±38 thermal 12 3.9 704 11 cubewano
2018 VG18 656 3.6 3.9 656 12 SDO
229762 Gǃkúnǁʼhòmdímà 655 136 3.69 655+14
−13 		occultation 14 3.7 612 17 Maclaurin spheroid SDO
20000 Varuna 654 3.76 654+154
−102 		thermal 12 3.9 756 9 Jacobi ellipsoid accepted cubewano
2018 AG37 645 4.19 SDO
2014 UZ224 635 3.4 635+65
−72 		thermal 14 3.7 688 11 SDO
(523794) 2015 RR245 626 3.8 4.1 626 11 SDO
(523692) 2014 EZ51 626 3.8 4.1 626 11 detached
2010 RF43 611 3.9 4.2 611 10 SDO
19521 Chaos 600 4.8 600+140
−130 		thermal 5 5 612 5 cubewano
2010 JO179 597 4 4.3 597 10 SDO
2012 VP113 597 4 4.3 597 10 detached
2010 KZ39 597 4 4.3 597 10 detached
(303775) 2005 QU182 584 3.8 584+155
−144 		thermal 13 3.8 415 33 cubewano
(543354) 2014 AN55 583 4.1 4.4 583 10 SDO
2015 KH162 583 4.1 4.4 583 10 detached
(78799) 2002 XW93 565 5.5 565+71
−73 		thermal 4 5.4 584 4 SDO
2006 QH181 556 4.3 4.6 556 9 SDO
2002 XV93 549 5.42 549+22
−23 		thermal 4 5.4 564 4 2:3 resonant
(84922) 2003 VS2 548 4.1 548+30
−45 		occultation 15 4.1 537 15 triaxial ellipsoid not accepted 2:3 resonant
(523639) 2010 RE64 543 4.4 4.7 543 8 SDO
(523759) 2014 WK509 543 4.4 4.7 543 8 detached
(528381) 2008 ST291 543 4.4 4.7 543 8 detached
(470443) 2007 XV50 543 4.4 4.7 543 8 cubewano
(482824) 2013 XC26 543 4.4 4.7 543 8 cubewano
(523671) 2013 FZ27 543 4.4 4.7 543 8 1:2 resonant
2004 XR190 538 4.3 538 occultation 12 4.6 556 9 oblate detached
2015 BP519 530 4.5 4.8 530 8 SDO
(278361) 2007 JJ43 530 4.5 4.8 530 8 cubewano
(470308) 2007 JH43 530 4.5 4.8 530 8 2:3 resonant
2014 WP509 530 4.5 4.8 530 8 cubewano
(145451) 2005 RM43 524 4.4 524+96
−103 		thermal 11 4.7 543 8 possible SDO
2013 AT183 518 4.6 4.9 518 8 SDO
2014 FC69 518 4.6 4.9 518 8 detached
(499514) 2010 OO127 518 4.6 4.9 518 8 cubewano
2014 YA50 518 4.6 4.8 518 8 cubewano
2017 OF69 518 4.6 4.9 518 8 2:3 resonant
2020 FY30 517 4.67 SDO
(84522) 2002 TC302 514 3.9 514±15 occultation 14 4.2 591 12 oblate 2:5 resonant
(120348) 2004 TY364 512 4.52 512+37
−40 		thermal 10 4.7 536 8 not accepted 2:3 resonant
(145480) 2005 TB190 507 4.4 507+127
−116 		thermal 15 4.4 469 15 detached
(470599) 2008 OG19 506 4.7 5 506 7 elongated SDO
2014 FC72 506 4.7 5 506 7 detached
2014 HA200 506 4.7 5 506 7 SDO
(315530) 2008 AP129 506 4.7 5 506 7 cubewano
(472271) 2014 UM33 506 4.7 5 506 7 cubewano
(523681) 2014 BV64 506 4.7 5 506 7 cubewano
2010 FX86 506 4.7 5 506 7 cubewano
2015 BZ518 506 4.7 5 506 7 cubewano
(202421) 2005 UQ513 498 3.6 498+63
−75 		thermal 26 3.8 643 11 cubewano
(523742) 2014 TZ85 494 4.8 5.1 494 7 4:7 resonant
(523635) 2010 DN93 490 4.8 5.1 490 7 detached
2003 QX113 490 5.1 5.1 490 7 SDO
2003 UA414 490 5 5.1 490 7 SDO
(523693) 2014 FT71 490 5 5.1 490 7 4:7 resonant
2014 HZ199 479 5 5.2 479 7 cubewano
2014 BZ57 479 5 5.2 479 7 cubewano
(523752) 2014 VU37 479 5.1 5.2 479 7 cubewano
(495603) 2015 AM281 479 4.8 5.2 479 7 detached
(455502) 2003 UZ413 472 4.38 472+122
−25 		thermal 15 4.7 536 8 2:3 resonant
(523645) 2010 VK201 471 5 5.3 471 7 cubewano
2015 AJ281 468 5 5.3 468 7 4:7 resonant
(523757) 2014 WH509 468 5.2 5.3 468 7 cubewano
2014 JP80 468 5 5.3 468 7 2:3 resonant
2014 JR80 468 5.1 5.3 468 7 2:3 resonant
(523750) 2014 US224 468 5 5.3 468 7 cubewano
2013 FS28 468 4.9 5.3 468 7 SDO
2010 RF188 468 5.2 5.3 468 7 SDO
2011 WJ157 468 5 5.3 468 7 SDO
(120132) 2003 FY128 460 4.6 460±21 thermal 12 5.1 467 8 SDO
2010 ER65 457 5.2 5.4 457 6 detached
(445473) 2010 VZ98 457 4.8 5.4 457 6 SDO
2010 RF64 457 5.7 5.4 457 6 cubewano
(523640) 2010 RO64 457 5.2 5.4 457 6 cubewano
2010 TJ 457 5.7 5.4 457 6 SDO
2014 OJ394 457 5.1 5.4 457 6 detached
2014 QW441 457 5.2 5.4 457 6 cubewano
2014 AM55 457 5.2 5.4 457 6 cubewano
(523772) 2014 XR40 457 5.2 5.4 457 6 cubewano
(523653) 2011 OA60 457 5.1 5.4 457 6 cubewano
(26181) 1996 GQ21 456 4.9 456+89
−105 		thermal 6 5.3 468 7 SDO
(84719) 2002 VR128 449 5.58 449+42
−43 		thermal 5 5.6 459 5 2:3 resonant
2013 SF106 451 4.96 SDO
2012 VB116 449 5.2 5.4 449 6 cubewano
(471137) 2010 ET65 447 5.1 5.5 447 6 SDO
(471165) 2010 HE79 447 5.1 5.5 447 6 2:3 resonant
2010 EL139 447 5.6 5.5 447 6 2:3 resonant
(523773) 2014 XS40 447 5.4 5.5 447 6 cubewano
2014 XY40 447 5.1 5.5 447 6 cubewano
2015 AH281 447 5.1 5.5 447 6 cubewano
2014 CO23 447 5.3 5.5 447 6 cubewano
(523690) 2014 DN143 447 5.3 5.5 447 6 cubewano
(523738) 2014 SH349 447 5.4 5.5 447 6 cubewano
2014 FY71 447 5.4 5.5 447 6 4:7 resonant
(471288) 2011 GM27 447 5.1 5.5 447 6 cubewano
(532093) 2013 HV156 447 5.2 5.5 447 6 1:2 resonant
471143 Dziewanna 433 3.8 433+63
−64 		thermal 30 3.8 475 25 SDO
(444030) 2004 NT33 423 4.8 423+87
−80 		thermal 12 5.1 490 7 4:7 resonant
(182934) 2002 GJ32 416 6.16 416+81
−73 		thermal 3 6.1 235 12 SDO
(469372) 2001 QF298 408 5.43 408+40
−45 		thermal 7 5.4 421 7 2:3 resonant
(175113) 2004 PF115 406 4.54 406+98
−85 		thermal 12 4.5 482 12 2:3 resonant
38628 Huya 406 5.04 406±16 thermal 10 5 466 8 Maclaurin spheroid accepted 2:3 resonant
(307616) 2003 QW90 401 5 401+63
−48 		thermal 8 5.4 457 6 cubewano
(469615) 2004 PT107 400 6.33 400+45
−51 		thermal 3 6 302 8 cubewano
  1. ^ The measured diameter, else Brown's estimated diameter, else the diameter calculated from H using an assumed albedo of 9%.
  2. ^ This is the total system mass (including moons), except for Pluto and Ceres.
  3. ^ The geometric albedo is calculated from the measured absolute magnitude and measured diameter via the formula:
  4. ^ Diameters with the text in red indicate that Brown's bot derived them from heuristically expected albedo.

See also

References

  1. ^ a b c Mike Brown. "The Dwarf Planets". Retrieved 20 January 2008.
  2. ^ Stern, Alan (24 August 2012). "The Kuiper Belt at 20: Paradigm Changes in Our Knowledge of the Solar System". Applied Physics Laboratory. 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.
  3. ^ a b c d e f g h Grundy, W.M.; Noll, K.S.; Buie, M.W.; Benecchi, S.D.; Ragozzine, D.; Roe, H.G. (December 2019). "The mutual orbit, mass, and density of transneptunian binary Gǃkúnǁʼhòmdímà ((229762) 2007 UK126)" (PDF). Icarus. 334: 30–38. doi:10.1016/j.icarus.2018.12.037. Archived from the original (PDF) on 7 April 2019.
  4. ^ "IAU 2006 General Assembly: Result of the IAU Resolution votes". International Astronomical Union. 24 August 2006. Archived from the original on 3 January 2007. Retrieved 26 January 2008.
  5. ^ "Dwarf Planets". NASA. Archived from the original on 4 July 2012. Retrieved 22 January 2008.
  6. ^ "Plutoid chosen as name for Solar System objects like Pluto" (Press release). 11 June 2008. Archived from the original on 2 July 2011. Retrieved 15 June 2008.
  7. ^ "ESO science paper 1918a" (PDF).[full citation needed]
  8. ^ Hanuš, J.; Vernazza, P.; Viikinkoski, M.; Ferrais, M.; Rambaux, N.; Podlewska-Gaca, E.; Drouard, A.; Jorda, L.; Jehin, E.; Carry, B.; Marsset, M.; Marchis, F.; Warner, B.; Behrend, R.; Asenjo, V.; Berger, N.; Bronikowska, M.; Brothers, T.; Charbonnel, S.; Colazo, C.; Coliac, J-F.; Duffard, R.; Jones, A.; Leroy, A.; Marciniak, A.; Melia, R.; Molina, D.; Nadolny, J.; Person, M.; et al. (2020). "arXiv paper 1911.13049". Astronomy & Astrophysics. A65: 633. arXiv:1911.13049. doi:10.1051/0004-6361/201936639. S2CID 208512707.[full citation needed]
  9. ^ Savage, Don; Jones, Tammy; Villard, Ray (19 April 1995). "Asteroid or mini-planet? Hubble maps the ancient surface of Vesta". HubbleSite (Press release). News Release STScI-1995-20. Retrieved 17 October 2006.
  10. ^ https://www.sciencenews.org/article/hygiea-may-be-solar-system-smallest-dwarf-planet
  11. ^ "Iapetus' peerless equatorial ridge". www.planetary.org. Retrieved 2 April 2018.
  12. ^ "DPS 2015: First reconnaissance of Ceres by Dawn". www.planetary.org. Retrieved 2 April 2018.
  13. ^ Garrick; Bethell; et al. (2014). "The tidal-rotational shape of the Moon and evidence for polar wander". Nature. 512 (7513): 181–184. Bibcode:2014Natur.512..181G. doi:10.1038/nature13639. PMID 25079322. S2CID 4452886.
  14. ^ Balogh, A.; Ksanfomality, Leonid; Steiger, Rudolf von (23 February 2008). Hydrostatic equilibrium of Mercury. ISBN 9780387775395 – via Google Books.[full citation needed]
  15. ^ "[no title cited]" (Document). doi:10.1002/2015GL065101. {{cite document}}: Cite document requires |publisher= (help)[full citation needed]
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External links


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