IAU definition of planet - Knowledge (XXG)

4957: 804:(2) According to point (1), the eight classical planets discovered before 1900, which move in nearly circular orbits close to the ecliptic plane, are the only planets of the Solar System. All the other objects in orbit around the Sun are smaller than Mercury. We recognize that there are objects that fulfill the criteria (b) and (c) but not criterion (a). Those objects are defined as "dwarf" planets. Ceres, as well as Pluto and several other large Trans-Neptunian objects, belongs to this category. In contrast to the planets, these objects typically have highly inclined orbits and/or large eccentricities. 181: 41: 384: 959: 1061: 987: 376: 484: 496:" (SSSB) and a new classification of "pluton". The former would have described those objects underneath the "spherical" threshold. The latter would have been applied to those planets with highly inclined orbits, large eccentricities and an orbital period of more than 200 earth years (that is, those orbiting beyond Neptune). Pluto would have been the prototype for this class. The term " 5097: 5121: 4933: 5085: 4945: 5109: 138:, it would not have enough mass to clear out a neighbourhood that size and meet criterion 3. The requirement for hydrostatic equilibrium (criterion 2) is also universally treated loosely as simply a requirement for roundedness; Mercury is not actually in hydrostatic equilibrium, but is explicitly included by the IAU definition as a planet. 1244:), these bodies only exist in Jupiter's orbit because they are in the sway of the planet's huge gravity. Earth accretes or ejects near-Earth asteroids on million-year time scales, thereby clearing its orbit. Similarly, Pluto may cross the orbit of Neptune, but Neptune long ago locked Pluto and its attendant Kuiper belt objects, called 714:) could not have been called a planet, even if it fit all other criteria. However, a similar situation already applies to the term 'moon'—such bodies ceasing to be moons on being ejected from planetary orbit—and this usage has widespread acceptance. Another criticism was that the definition did not differentiate between planets and 942:(2) A "dwarf planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape , (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite. 1039:

sought to insert an additional sentence at the end of the statement in 6A: "This category is to be called 'plutonian objects'." There was no debate on the question, and in the vote the proposed name was defeated by 186–183; a proposal to conduct a re-vote was rejected. An IAU process was then to be

733:) and could eventually become situated outside of both bodies. This development would then upgrade the Moon to planetary status at that time, according to the definition. The time taken for this to occur, however, would be billions of years, long after many astronomers expect the Sun to expand into a 894:

The second change was a redrawing of the planetary definition in the case of a double planet system. There had been a concern that, in extreme cases where a double body had its secondary component in a highly eccentric orbit, there could have been a drift of the barycenter in and out of the primary

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was discovered. By measuring Charon's orbital period, astronomers could accurately calculate Pluto's mass for the first time, which they found to be much smaller than expected. Pluto's mass was roughly one twenty-fifth of Mercury's, making it by far the smallest planet, smaller even than the Earth's

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on January 1, 1801. Astronomers immediately declared the tiny object to be the "missing planet" between Mars and Jupiter. Within four years, however, the discovery of two more objects with comparable sizes and orbits had cast doubt on this new thinking. By 1851, the number of planets had grown to 23

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which have been identified in orbit around other stars. A separate "working" definition for extrasolar planets was, however, recommended by a working group of the IAU in 2003 and includes the criterion: "The minimum mass/size required for an extrasolar object to be considered a planet should be the

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exerted by Saturn and the moon's gravity, its tiny 3 km diameter suggests Methone is composed of icy fluff. The IAU's stated radius and mass limit are not too far off from what as of 2019 is believed to be the approximate limit for objects beyond Neptune that are fully compact, solid bodies,

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A further twelve bodies, pending refinements of knowledge regarding their physical properties, were possible candidates to join the list under this definition. Some objects in this second list were more likely eventually to be adopted as 'planets' than others. Despite what had been claimed in the

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and, thus, cast no vote. Only 424 astronomers were present for the vote, which is less than 5% of the astronomer community. However, sampling 400 representative members out of a population of 9,000 statistically yields a result with good accuracy (confidence interval better than 5%). Astronomer

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The final vote was criticized because of the relatively small percentage of the 9000-strong IAU membership who participated. Besides the fact that most members do not attend the General Assemblies, this lack was also due to the timing of the vote: the final vote was taken on the last day of the

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proposed a statement concerning Pluto: "Pluto is a dwarf planet by the above definition and is recognized as the prototype of a new category of trans-Neptunian objects." After a little quibbling over the grammar involved and questions of exactly what constituted a "trans-Neptunian object", the

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Voting on the definition took place at the Assembly plenary session during the afternoon. Following a reversion to the previous rules on 15 August, as a planetary definition is a primarily scientific matter, every individual member of the Union attending the Assembly was eligible to vote. The

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physics; the main sticking point was whether or not to include a body's orbital characteristics among the definition criteria. In an indicative vote, members heavily defeated the proposals on Pluto-like objects and double planet systems, and were evenly divided on the question of hydrostatic

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gained the upper hand among the members attending and was described as unlikely to lose its hold by August 24. This position would result in only eight major planets, with Pluto ranking as a "dwarf planet". The discussion at the first meeting was heated and lively, with IAU members in vocal

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in paragraph (1) and footnote . This represented a choice between having a set of three distinct categories of body (planet, "dwarf planet" and SSSB) and the opening of an umbrella of 'planets' over the first two such categories. The Resolution proposed the latter option; it was defeated

275:. Pluto came to be seen as the largest member of a new class of objects, and some astronomers stopped referring to Pluto as a planet. Pluto's eccentric and inclined orbit, while very unusual for a planet in the Solar System, fits in well with the other KBOs. New York City's newly renovated 302:, it became clear that either they all had to be called planets or Pluto would have to be reclassified. Astronomers also thought it likely that more objects as large as Pluto would be discovered, and the number of planets would start growing quickly. They were also concerned about the 1685:"The real answer here is to not get too hung up on definitions, which I admit is hard when the IAU tries to make them sound official and clear, but, really, we all understand the intent of the hydrostatic equilibrium point, and the intent is clearly to include Mercury & the moon" 247:

wrote a column in 1956 titled "The Demotion of Pluto", stating that it "simply failed to live up to the advance publicity it received as 'Planet X' before its discovery. It has been a disappointment all along, for it did not turn out to be what one could reasonably have expected".

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The decision generated cultural and societal implications, affecting the "industry of astronomical artifacts and toys." Most educational books that included the definition were printed after 2006. The decision was important enough to prompt the editors of the 2007 edition of the

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Some astronomers counter this opinion by saying that, far from not having cleared their orbits, the major planets completely control the orbits of the other bodies within their orbital zone. Although Jupiter does coexist with a large number of small bodies in its orbit (the

1096:" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape , (c) has not cleared the neighbourhood around its orbit, and (d) is not a 500:" would have been available to describe all planets smaller than the eight "classical planets" in orbit around the Sun, though would not have been an official IAU classification. The IAU did not make recommendations in the draft resolution on what separated a planet from a 1002:

constituted the definition itself as stated above. There was much discussion among members about the appropriateness of using the expression "cleared the neighbourhood" instead of the earlier reference to "dominant body", and about the implications of the definition for

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objects reach hydrostatic equilibrium at much smaller sizes, probably somewhere between 200 and 400 km in diameter. It all depends on the rigidity of the material that makes up the body, which is in turn strongly influenced by its internal temperature. Assuming that

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The proposed definition found support among many astronomers as it used the presence of a physical qualitative factor (the object being round) as its defining feature. Most other potential definitions depended on a limiting quantity (e.g., a minimum size or maximum

197:(the 8 major planets, plus 15 minor planets between Mars and Jupiter), and it was clear that hundreds more would eventually be discovered. Astronomers began cataloguing them separately and began calling them "asteroids" instead of "planets". With the discovery of 3374: 750:". You know, the word "continent" has no scientific definition ... they're just cultural definitions, and I think the geologists are wise to leave that one alone and not try to redefine things so that the word "continent" has a big, strict definition." 899:

and planet depending on where the system was in its orbit. Thus the definition was reformulated so as to consider a double planet system in existence if its barycenter lay outside both bodies for a majority of the system's orbital period.

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The twelve "candidate planets" that were possibilities for inclusion under the originally proposed definition. Note that all but the last three are trans-Neptunian objects. The smallest three (Vesta, Pallas, Hygeia) are in the asteroid

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Boss, Alan P; Butler, R. Paul; Hubbard, William B; Ianna, Philip A; Kürster, Martin; Lissauer, Jack J; Mayor, Michel; Meech, Karen J; Mignard, Francois; Penny, Alan J; Quirrenbach, Andreas; Tarter, Jill C; Vidal-Madjar, Alfred (2007).

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On 22 August 2006 the draft proposal was rewritten with two changes from the previous draft. The first was a generalisation of the name of the new class of planets (previously the draft resolution had explicitly opted for the term

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Some aspects of the definition are as yet difficult to apply outside the Solar System. Techniques for identifying extrasolar objects generally cannot determine whether an object has "cleared its orbit", except indirectly via an

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It also had the advantage of measuring an observable quality. Suggested criteria involving the nature of formation would have been more likely to see accepted planets later declassified as scientific understanding improved.

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are addressed in a 2003 position statement issued by a now-defunct IAU Working Group on Extrasolar Planets. However, this position statement was never proposed as an official IAU resolution and was never voted on by IAU

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both wrote about why they thought the definition was not, in general, a good one. It defined a planet as orbiting a star, which would have meant that any planet ejected from its star system or formed outside of one (a

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The IAU Executive Committee presented four Resolutions to the Assembly, each concerning a different aspect of the debate over the definition. Minor amendments were made on the floor for the purposes of clarification.

1248:, into a 3:2 resonance (i.e., they orbit the Sun twice for every three Neptune orbits). Since the orbits of these objects are entirely dictated by Neptune's gravity, Neptune is therefore gravitationally dominant. 119:(SSSB). An alternate proposal included dwarf planets as a subcategory of planets, but IAU members voted against this proposal. The decision was a controversial one, and has drawn both support and criticism from 1510:

as "to demote or devalue someone or something, as happened to the former planet Pluto when the General Assembly of the International Astronomical Union decided Pluto no longer met its definition of a planet."

113:. According to the IAU, "planets and dwarf planets are two distinct classes of objects" – in other words, "dwarf planets" are not planets. A non-satellite body fulfilling only the first criterion is termed a 674:) tailored for the Solar System. According to members of the IAU committee this definition did not use human-made limits but instead deferred to "nature" in deciding whether or not an object was a planet. 387:

The original proposal would have immediately added three planets, shown here in a size comparison to Earth. Leftmost is Pluto (shown in lieu of Eris, which is about the same size), then Charon, Ceres, and

1465:, highlights that the actual celestial body is unaffected by the naming arguments and remains impressive in its own right, and extending the metaphor to loving one's self regardless of internal doubts. 875:; such formations are fairly common balls of rock. Confusion was thought undesirable due to the status of planetology as a field closely allied to geology. Further concerns surrounded use of the word 4860: 4434: 1414:, part of his release "50-vc. Doberman." About Pluto's reclassification, remembered as a 9th planet from the times of the singer's youth, and re-presents Pluto as an unforgotten monarch of the 575:

endorsed the draft proposal. The DPS Committee represents a small subset of the DPS members, and no resolution in support of the IAU definition was considered or approved by the DPS membership.

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Additionally, the definition kept Pluto as a planet. Pluto's planetary status was and is fondly thought of by many, especially in the United States since Pluto was found by American astronomer

4830: 793:(1) A planet is a celestial body that (a) is by far the largest object in its local population, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a 1369:

The impact of the revised definition, particularly the change in the status of Pluto, has been reflected in popular culture. A number of musical contributions have commemorated the change:

4631: 1802: 2768: 979:. During this session, IAU members cast votes on each resolution by raising yellow cards. A team of students counted the votes in each section of the auditorium, and astronomer 1888:

Buie, Marc W.; Grundy, William M.; Young, Eliot F.; Young, Leslie A.; Stern, S. Alan (2006). "Orbits and Photometry of Pluto's Satellites: Charon, S/2005 P1, and S/2005 P2".

243:, and Tombaugh had been searching for Planet X when he found Pluto. Almost immediately after its discovery, however, astronomers questioned whether Pluto could be Planet X. 920:

At the second meeting of the day, following "secret" negotiations, a compromise began to emerge after the Executive Committee moved explicitly to exclude consideration of

2628: 4867: 1236:. Jupiter, meanwhile, is accompanied by 100,000 Trojan asteroids on its orbital path. Stern has asserted: "If Neptune had cleared its zone, Pluto wouldn't be there." 2719: 2353: 865:), with a decision on the name to be used postponed. Many geologists had been critical of the choice of name for Pluto-like planets, being concerned about the term 1518:: "Our members believe the great emotional reaction of the public to the demotion of Pluto shows the importance of Pluto as a name. We may no longer believe in the 447:

and Eris, has said that at least 53 known bodies in the Solar System probably fit the definition, and that a complete survey would probably reveal more than 200.

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has clarified that not all members of the Union were needed to vote on the classification issue: only those whose work is directly related to planetary studies.

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The process of new discoveries spurring a contentious refinement of Pluto's categorization echoed a debate in the 19th century that began with the discovery of

4564: 1572: 480:, but would still not have been defined as a component of a double planet, since the barycenter of the system lies within the more massive celestial body. 146:

Objects with true masses below the limiting mass for thermonuclear fusion of deuterium (currently calculated to be 13 Jupiter masses for objects of solar

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is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a

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interview, Mike Brown expressed doubt that a scientific definition was even necessary. He stated, "The analogy that I always like to use is the word "

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On a literal reading of the Resolution, "dwarf planets" are by implication of paragraph (1) excluded from the status of "planet". Use of the word

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Later on August 22, two open meetings were held which ended in an abrupt about-face on the basic planetary definition. The position of astronomer

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definition proposal on August 16, 2006. Its form followed loosely the second of three options proposed by the original committee. It stated that:

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10-day event, after many participants had left or were preparing to leave. Many astronomers were also unable or chose not to make the trip to

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on the draft proposal: Only 18 were in favour of it, with over 50 against. The 50 in opposition preferred an alternative proposal drawn up by

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Because new planets are discovered infrequently, the IAU did not have any mechanism for their definition and naming. After the discovery of

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Resolution was approved by a vote of 237–157, with 30 abstentions. A new category of dwarf planet was thus established. It would be named "

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equilibrium. The debate was said to be "still open", with private meetings being held ahead of a vote scheduled for the following day.

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This definition would have led to three more celestial bodies being recognized as planets, in addition to the previously accepted nine:

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The minimum mass/size required for an extrasolar object to be considered a planet should be the same as that used in our Solar System.

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The IAU...resolves that planets and other bodies in the Solar System be defined into three distinct categories in the following way:

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mission to Pluto) showed it to be slightly larger than Pluto, and so was thought to be equally deserving of the status of "planet".

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A planet is a celestial body that (a) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a

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who led the committee which generated the original definition, and consisting of five planetary scientists and the science writer

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These currently include most of the Solar System asteroids, most Trans-Neptunian Objects (TNOs), comets, and other small bodies.

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These currently include most of the Solar System asteroids, most Trans-Neptunian Objects (TNOs), comets, and other small bodies.

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in the Solar System. It has been argued that the definition is problematic because it depends on the location of the body: if a

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Cronología de los hechos relativos a la Definición de Planeta adoptada por la Asamblea de la Unión Astronómica Internacional

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On June 11, 2008, the IAU announced that the subcategory of dwarf planets with trans-Neptunian orbits would be known as "

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The local population is the collection of objects that cross or closely approach the orbit of the body in consideration.

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are two distinct classes of objects", meaning that dwarf planets, despite their name, would not be considered planets.

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and Charon would have been the only known double planet in the Solar System. Other planetary satellites (such as the

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According to an IAU draft resolution, the roundness condition generally results in the need for a mass of at least 5

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This generally applies to objects with sizes above several hundred kilometers, depending on the material strength.

150:) that orbit stars, brown dwarfs or stellar remnants and that have a mass ratio with the central object below the 4683: 4658: 4468: 1394:. Featured a song "I'm Your Moon", from Charon's point of view, about Pluto being reclassified as a dwarf planet. 1086: 808: 303: 1421:"134340 Pluto" (2014), by Cojum Dip, a song from the point of view of Pluto asking what it did to anger the IAU. 657:

unknown) being borderline cases both for the 2006 Q&A expectations and in more recent evaluations, and with

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An IAU process will be established to assign borderline objects into either dwarf planet and other categories.

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An IAU process will be established to assign borderline objects into either dwarf planet and other categories.

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The final definition, as passed on 24 August 2006 under the Resolution 5A of the 26th General Assembly, is:

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in the chair, to consider the definition of a planet. It proposed three definitions that could be adopted:

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IAU 2006 General Assembly: video-records of the discussion and of the final vote on the Planet definition.

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Plenary session of the IAU General Assembly on August 24, 2006. Votes were cast by raising yellow cards.

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and to bring into the definition a criterion concerning the dominance of a body in its neighbourhood.

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that have sufficient mass for their self-gravity to overcome rigid body forces so that they assume a

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is a "dwarf planet" by the above definition and is recognized as the prototype of a new category of

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claimed that these numbers are only right for rocky bodies like asteroids, and that icy bodies like

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Such a definition of the term "planet" could also have led to changes in classification for the

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said that correspondence he had received had been evenly divided for and against the proposal.

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In the 1990s, astronomers began finding other objects at least as far away as Pluto, known as

100: 3008:(Press release). Paris: International Astronomical Union (News Release – IAU0804). 2008-06-11 5153: 5089: 4949: 4753: 4743: 4636: 4611: 4021: 3991: 3862: 3842: 3741: 3716: 3556: 3421: 3048: 2692: 2684: 2470: 2448: 2266: 2030: 1915: 1832: 1775: 1651: 1577: 1503: 1391: 1381: 1119: 980: 884: 782: 583: 440: 307: 222: 135: 3398: 3377: 3221: 2563:"The IAU Committee Presents Today in Prague the new Proposals for the Definition of Planet" 1655: 725:: at present the Moon is defined as a satellite of the Earth, but over time the Earth-Moon 17: 4820: 4718: 4626: 4517: 4495: 4292: 4236: 4226: 4016: 3996: 3971: 3959: 3913: 3901: 3835: 3805: 3798: 3788: 3748: 3726: 3721: 3381: 3379: 3327: 2877: 1947: 1403: 1374: 1241: 1060: 958: 948:

The eight planets are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.

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This criterion allows the distinction between gas giant planets and brown dwarfs or stars.

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showing the IAU Executive Committee conception of the types of bodies in the Solar System.

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media, the proposal did not necessarily leave the Solar System with only twelve planets.

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Society president Cleveland Evans stated the reason for the organization's selection of

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Grundy, W.M.; Noll, K.S.; Buie, M.W.; Benecchi, S.D.; Ragozzine, D.; Roe, H.G. (2019).

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system if each component independently satisfied the planetary criteria and the common

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Thomas, P. C.; Burns, J. A.; Tiscareno, M. S.; Hedman, M. M.; Helfenstein, P. (2013).

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have not fully cleared their orbital zones, just like Pluto. Earth orbits with 10,000

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stars. Any attempt to clarify this differentiation was to be left until a later date.

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This article is about the formal definition established in 2006. For other uses, see

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the object is large enough to cause all other objects to eventually leave its orbit.

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Dwarf planet discoverer Mike Brown explains the concept behind the new definition

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The term "minor planet" would have been abandoned, replaced by the categories "

5041: 4988: 4728: 4307: 3891: 3196: 3130: 3122: 3076: 3053: 3028: 2466: 2349: 2325: 2248:"The Mutual Orbit, Mass, and Density of Transneptunian Binary Gǃkúnǁʼhòmdímà ( 1483: 1445:) are anthropomorphized, and Pluto is "uninvited to the interplanetary dance." 1432: 1398: 1343: 1209: 1004: 774: 726: 698: 571:

On 18 August the Committee of the Division of Planetary Sciences (DPS) of the

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body, leading to a shift in the classification of the secondary body between

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The IAU...resolves that planets and other bodies, except satellites, in the

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did not include Pluto in its exhibit of the planets when it reopened as the

244: 214: 2890: 2840: 1844: 1033:" and more narrowly defined by the IAU Executive Committee on 11 June 2008. 260:, although it was still over ten times as massive as the largest asteroid, 3266: 2813: 236:, one of many astronomers who had theorized on the existence of the large 5055: 4893: 4512: 4360: 4216: 4201: 3942: 3649: 3497: 2696: 1902: 1819: 1638: 908:

disagreement with one another over such issues as the relative merits of

561: 515: 272: 240: 2870: 1377:. A good-natured protest against suggestions that Pluto is not a planet. 421:, a moon of Pluto; the Pluto-Charon system would have been considered a 4297: 4285: 4211: 3610: 3588: 3463: 3448: 1692: 1431:

Pluto's demotion is alluded to in "The Lonesome Friends of Science" on

1264: 1252: 1245: 1229: 1225: 1147: 1135: 1030: 909: 778: 557: 323:, it set up a 19-member committee in 2005, with the British astronomer 2937:(Press release). Prague: IAU (News Release – IAU0603). August 24, 2006 1183:

An IAU process will be established to select a name for this category.

4738: 4031: 4026: 3935: 3930: 3644: 3639: 3605: 3593: 3538: 3490: 3483: 3458: 3453: 1561: 1338: 1143: 1139: 1115: 1078: 867: 511: 218: 210: 127: 61: 1428:'s self-titled debut album, mentioning the change of classification. 3182:"Korean Scientists Commend BTS For Integration Science On "134340"" 1919: 1762: 1522:, but we still have a sense of connection with the former planet". 1007:. The Resolution was ultimately approved by a near-unanimous vote. 932:

The final, third draft definition proposed on 24 August 2006 read:

4055: 3634: 3566: 3561: 3476: 3431: 3426: 1280: 1217: 1169: 1127: 1123: 1059: 1013:

sought to amend the above definition by the insertion of the word

985: 957: 831:

This class currently includes most of the Solar System asteroids,

482: 465: 382: 374: 299: 198: 179: 107:, which had hitherto been considered a planet) is classified as a 104: 74: 39: 3687: 3571: 3436: 2166:"Planetary Scientists Support Proposed Redefinition Of A Planet" 1494:

in the aftermath of the 2006 IAU decision. In January 2007, the

1315: 1221: 1131: 697:

The proposed definition was criticised as ambiguous: Astronomer

469: 257: 131: 3336: 3332: 2935:"IAU 2006 General Assembly: Result of the IAU Resolution votes" 2858:"IAU 2006 General Assembly: Result of the IAU Resolution votes" 1072:

be defined into three distinct categories in the following way:

450:

The definition would have considered a pair of objects to be a

286:

Starting in 2000, with the discovery of at least three bodies (

3416: 2387:"Wherein I argue emotionally about the definition of "planet"" 1705:

Sean Solomon, Larry Nittler & Brian Anderson, eds. (2018)

1449: 1309: 1260: 797:(nearly round) shape , and (c) does not produce energy by any 103:

body fulfilling only the first two of these criteria (such as

78: 3290:

IAU 2006 General Assembly: Result of the IAU Resolution votes

2003:(Press release). International Astronomical Union. 2006-08-16 3372: 3006:"Plutoid chosen as name for Solar System objects like Pluto" 1361:

to hold off printing until a final result had been reached.

721:

There had also been criticism of the proposed definition of

504:. A vote on the proposal was scheduled for August 24, 2006. 2584:"The IAU's Definition of Planet develops further – Draft c" 835:(NEOs), Mars-, Jupiter- and Neptune-Trojan asteroids, most 773:, a subgroup of the IAU met on August 18, 2006, and held a 2301:"Nine Planets Become 12 with Controversial New Definition" 2081:"Nine Planets Become 12 with Controversial New Definition" 1744:

Lecavelier des Etangs, A.; Lissauer, Jack J. (June 2022).

2192:"Saturn's Mysterious Arc-Embedded Moons: Recycled Fluff?" 1040:

put in motion to determine the name for the new category.

2108:"Draft Resolution 5 for GA-XXVI: Definition of a Planet" 1255:". In an accompanying press release, the IAU said that: 1022:

convincingly, with only 91 members voting in its favour.

848:

Under this proposal, Pluto would have been demoted to a

350:

Another committee, chaired by a historian of astronomy,

2419:"Moon Mechanics: What Really Makes Our World Go 'Round" 1384:. An impassioned defense of Pluto's status as a planet. 141:

The working definition of an exoplanet is as follows:

5073: 2771:. Deutsche Presse-Agentur. 2006-08-22. Archived from 2102: 2100: 582:

10 kg, or diameter of at least 800 km. However,

3312:

Q&A article on the new definition from SPACE.com

3069:"Position statement on the Definition of a "Planet"" 2629:"Geologists Force Astronomers To Rethink Pluto Plan" 2001:"The IAU draft definition of "planet" and "plutons"" 4876: 4813: 4563: 4399: 4329: 4040: 3982: 3675: 3537: 3033:

Proceedings of the International Astronomical Union

1048:in their title may, however, cause some ambiguity. 2137:"Planet Definition" Questions & Answers Sheet" 1619:"Planetesimals to Brown Dwarfs: What is a Planet?" 1259:Plutoids are celestial bodies in orbit around the 213:, along with thousands of smaller bodies such as 3306:, International Astronomical Union Official Site 2918:"IAU 2006 General Assembly: Resolutions 5 and 6" 2891:"IAU General Assembly Newspaper, 25 August 2006" 334:a planet is a planet if enough people say it is; 221:. Pluto was initially thought to be larger than 27:2006 International Astronomical Union definition 3376: 3304:Planet Definition Questions & Answers Sheet 1441:, in which the planets (including non-existent 1257: 1167: 1058: 934: 791: 398: 298:) all comparable to Pluto in terms of size and 228:Tombaugh discovered Pluto while working at the 143: 2841:IAU General Assembly Newspaper, 24 August 2006 2769:"Astronomers divided over 'planet' definition" 2749:"Pluto Seems Poised to Lose Its Planet Status" 1960:Pluto at 75: Still Crazy After All These Years 3348: 3310:Q&A: The IAU's Proposed Planet Definition 2507: 2505: 2049: 2047: 2019: 2017: 1720:"Official Working Definition of an Exoplanet" 1626:Annual Review of Earth and Planetary Sciences 1612: 1610: 1608: 1606: 1323:, and is thus not applicable to the numerous 188:(green), set against the outer planets (blue) 167:)) are "planets" (no matter how they formed). 8: 2953: 2951: 2221:"Saturn's egg moon Methone is made of fluff" 1746:"The IAU working definition of an exoplanet" 3246:"Pluto's revenge: 'Word of the Year' award" 3227:. American Dialect Society. January 5, 2007 2199:44th Lunar and Planetary Science Conference 2026:"Nine no longer: Panel declares 12 planets" 1995: 1993: 1573:How I Killed Pluto and Why It Had It Coming 4326: 3534: 3530: 3355: 3341: 3333: 3267:"'Plutoed' chosen as '06 Word of the Year" 2852: 2850: 2848: 1271:(near-spherical) shape, and that have not 975:plenary session was chaired by astronomer 340:a planet is large enough to form a sphere; 55:(IAU) defined in August 2006 that, in the 3073:Working Group on Extrasolar Planets (IAU) 3052: 1901: 1818: 1761: 1637: 354:, a historian and astronomer emeritus at 4868:Interstellar and circumstellar molecules 2535:"Details Emerge on Plan to Demote Pluto" 1328:same as that used in the Solar System." 1303:. The wording of the 2006 definition is 5080: 5064:) may be read as "within" or "part of". 4092:Planetary orbit-crossing minor planets 3222:""Plutoed" Voted 2006 Word of the Year" 2786:Tresch Fienberg, Richard (2006-08-22). 2475:"Pluto's Planet Status / String Theory" 1589: 1064:Illustration of the outcome of the vote 595:shape reflects the balance between the 3149: 3147: 1656:10.1146/annurev.earth.34.031405.125058 1617:Gibor Basri; Michael E. Brown (2006). 983:compiled and tallied the vote counts. 464:) was located outside of both bodies. 362:, was set up to make a firm proposal. 2830:. Orange County Register. 2006-09-01. 2790:. Sky & Telescope. Archived from 1424:"Ode to Pluto" is the final track on 661:being just above the expected limit. 7: 3156:"Pluto is demoted to 'dwarf planet'" 2449:"Earth's moon could become a planet" 205:in 1930, astronomers considered the 1397:"Bring Back Pluto" (2007), song by 1263:at a distance greater than that of 891:, potentially adding to confusion. 184:Plot of the positions of all known 134:-sized body were discovered in the 2288:from the original on 7 April 2019. 1683:Brown, Mike (February 10, 2023). 1085:(nearly round) shape, and (c) has 962:Illustration of the final proposal 771:Carnegie Institution of Washington 379:Illustration of the draft proposal 126:The IAU has stated that there are 25: 2960:"Pluto vote 'hijacked' in revolt" 2720:"Congratulations! It's a planet!" 2514:"Pluto May Get Demoted After All" 2354:"Congratulations! It's a planet!" 1837:10.1038/scientificamerican0107-34 1707:Mercury: The View after MESSENGER 737:and destroy both Earth and Moon. 5119: 5107: 5095: 5083: 4955: 4943: 4931: 3293:International Astronomical Union 2512:Britt, Robert Roy (2006-08-18). 2141:International Astronomical Union 2112:International Astronomical Union 53:International Astronomical Union 4831:Gravitationally rounded objects 3269:. Associated Press. Jan 8, 2007 3129:. thenation.com. Archived from 2582:Günther Wuchterl (2006-08-23). 2561:Günther Wuchterl (2006-08-22). 1214:NASA's robotic mission to Pluto 281:Rose Center for Earth and Space 2747:Overbye, Dennis (2006-08-22). 2604:"Star-gazers puzzled by Pluto" 879:as in major languages such as 815:Definitions and clarifications 84:has sufficient mass to assume 1: 3154:Dennis Overbye (2006-08-24). 2683:Geoff Brumfiel (2006-08-21). 2056:"How Many Planets Are There?" 1542:Geophysical planet definition 1390:, August 25, 2006 podcast by 573:American Astronomical Society 3075:. 2003-02-28. Archived from 2814:"Diary of a planet's demise" 2271:10.1016/j.icarus.2018.12.037 2219:Battersby, S. (2013-05-17). 1547:List of Solar System objects 1188:The IAU also resolved that " 458:of the system (known as the 4926:Outline of the Solar System 4689:Interplanetary medium/space 2812:Hogan, Jenny (2008-08-24). 1780:10.1016/j.newar.2022.101641 1448:"134340" (2018), a song by 1373:"Planet X" (1996), song by 88:(a nearly round shape), and 18:2006 redefinition of planet 5190: 4642:Extraterrestrial materials 2958:Paul Rincon (2006-08-25). 2324:Pearson education (2006). 2024:Gareth Cook (2006-08-16). 1869:Ley, Willy (August 1956). 1532:Clearing the neighbourhood 1279:This subcategory includes 1165:The IAU further resolves: 29: 4962:Earth sciences portal 4921: 4684:Interplanetary dust cloud 3528: 3370: 3097:Margot, Jean-Luc (2006). 3054:10.1017/S1743921306004509 2980:Michael E. Brown (2006). 2718:Phil Plait (2006-08-15). 2655:"Planet, pluton or rock?" 2447:Robert Roy Britt (2006). 2417:Robert Roy Britt (2006). 2299:Robert Roy Britt (2006). 2079:Robert Roy Britt (2006). 1273:cleared the neighbourhood 1105:Small Solar System Bodies 1087:cleared the neighbourhood 887:, Pluto is itself called 809:Small Solar System Bodies 729:will drift outwards (see 434:of the outer Solar System 304:classification of planets 93:cleared the neighbourhood 4975:Local Interstellar Cloud 3693:other near-Earth objects 3029:"Definition of a planet" 1890:The Astronomical Journal 1873:. For Your Information. 1496:American Dialect Society 1410:"Pluto" (2009), song by 1380:"Pluto" (1998), song by 1301:orbit-clearing criterion 1212:, the lead scientist on 4938:Solar System portal 4664:Giant-impact hypothesis 4271:Trans-Neptunian objects 2788:"The Day We Lost Pluto" 1871:"The Demotion of Pluto" 1576:- Memoir by astronomer 1567:Small Solar System body 1438:The Tree of Forgiveness 1358:World Book Encyclopedia 1307:in its use of the word 1269:hydrostatic equilibrium 1174:Trans-Neptunian Objects 1083:hydrostatic equilibrium 841:Trans-Neptunian Objects 795:hydrostatic equilibrium 687:trans-Neptunian objects 509:trans-Neptunian objects 494:small Solar System body 478:hydrostatic equilibrium 402:hydrostatic equilibrium 116:small Solar System body 86:hydrostatic equilibrium 4826:Possible dwarf planets 4669:Gravitational collapse 4607:Circumstellar envelope 3412: 3248:. CNN. January 7, 2007 3099:"What makes a planet?" 2828:"Pluto in perspective" 2653:Elise Kleeman (2006). 2631:. 2006. Archived from 2143:. 2006. Archived from 2114:. 2006. Archived from 1975:, p.p.31-34 (May 2007) 1875:Galaxy Science Fiction 1801:Soter, Steven (2007). 1724:IAU position statement 1552:List of former planets 1277: 1186: 1163: 1065: 991: 970:Plenary session debate 963: 956: 856:Revised draft proposal 846: 489: 406: 392:The IAU published the 389: 380: 251:In 1978, Pluto's moon 238:trans-Neptunian object 189: 173: 48: 5035:Laniakea Supercluster 4652:Sample-return mission 3411: 3127:"A Passion For Pluto" 2485:National Public Radio 2326:"The Flap over Pluto" 1750:New Astronomy Reviews 1063: 989: 961: 905:Julio Ángel Fernández 787:Julio Ángel Fernández 740:In an 18 August 2006 486: 386: 378: 183: 43: 5169:Definition of planet 5164:History of astronomy 4950:Astronomy portal 4851:Solar System objects 4597:Circumplanetary disk 3184:. September 3, 2018. 2697:10.1038/news060821-4 2054:Brown, Mike (2006). 1941:Much Ado about Pluto 1234:near-Earth asteroids 977:Jocelyn Bell Burnell 928:Final draft proposal 761:Alternative proposal 556:, and the asteroids 443:, the discoverer of 371:First draft proposal 5049:Observable universe 4846:Solar System models 4776:Protoplanetary disk 4699:Interstellar medium 4659:Frost/Ice/Snow line 3045:2007IAUTA..26..183B 2982:"The Eight Planets" 1912:2006AJ....132..290B 1829:2007SciAm.296a..34S 1807:Scientific American 1803:"What Is a Planet?" 1772:2022NewAR..9401641L 1648:2006AREPS..34..193B 1455:Love Yourself: Tear 1275:around their orbit. 922:extra-solar planets 843:(TNOs), and comets. 672:orbital inclination 269:Kuiper Belt objects 186:Kuiper belt objects 128:eight known planets 95:" around its orbit. 5174:Pluto's planethood 5029:Virgo Supercluster 5010:Milky Way subgroup 4841:Natural satellites 4724:Nebular hypothesis 4704:Interstellar space 4694:Interstellar cloud 4602:Circumstellar disc 4192:Near-Earth objects 4076:names and meanings 3413: 3326:2020-07-25 at the 3161:The New York Times 2923:. IAU. 2006-08-24. 2876:2007-01-03 at the 2754:The New York Times 2659:Pasadena Star News 2608:Independent Online 2147:on August 22, 2006 2118:on August 22, 2006 1946:2008-01-25 at the 1089:around its orbit. 1066: 992: 964: 833:Near-Earth objects 731:tidal acceleration 490: 390: 381: 356:Harvard University 277:Hayden Planetarium 230:Lowell Observatory 190: 49: 5071: 5070: 4916: 4915: 4912: 4911: 4889:Lagrangian points 4861:by discovery date 4459:Human spaceflight 4430:historical models 4323: 4322: 3948:S/2015 (136472) 1 2392:The Panda's Thumb 1950:plutopetition.com 1877:. pp. 79–91. 1537:Fusor (astronomy) 1461:"H.S" (2023), by 1216:, contended that 456:center of gravity 308:planetary systems 152:L4/L5 instability 16:(Redirected from 5181: 5124: 5123: 5122: 5112: 5111: 5110: 5100: 5099: 5098: 5088: 5087: 5086: 5079: 5065: 5063: 5054: 5047: 5040: 5033: 5027: 5021: 5015: 5008: 5001: 4994: 4987: 4980: 4973: 4960: 4959: 4958: 4948: 4947: 4946: 4936: 4935: 4934: 4637:Exozodiacal dust 4327: 4293:Detached objects 3535: 3531: 3375: 3357: 3350: 3343: 3334: 3278: 3277: 3275: 3274: 3263: 3257: 3256: 3254: 3253: 3242: 3236: 3235: 3233: 3232: 3226: 3218: 3212: 3211: 3209: 3207: 3192: 3186: 3185: 3178: 3172: 3171: 3169: 3168: 3151: 3142: 3141: 3139: 3138: 3119: 3113: 3112: 3110: 3109: 3094: 3088: 3087: 3085: 3084: 3065: 3059: 3058: 3056: 3023: 3017: 3016: 3014: 3013: 3002: 2996: 2995: 2993: 2992: 2977: 2971: 2970: 2968: 2967: 2955: 2946: 2945: 2943: 2942: 2931: 2925: 2924: 2922: 2914: 2908: 2907: 2905: 2904: 2895: 2887: 2881: 2868: 2866: 2865: 2854: 2843: 2838: 2832: 2831: 2824: 2818: 2817: 2809: 2803: 2802: 2800: 2799: 2783: 2777: 2776: 2765: 2759: 2758: 2744: 2738: 2737: 2735: 2734: 2728: 2722:. 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Brown 1504:Word of the Year 1392:Jonathan Coulton 1242:Trojan asteroids 1052:Final definition 1017:before the word 981:Virginia Trimble 783:Gonzalo Tancredi 652: 650: 640: 631: 629: 625: 615: 613: 581: 555: 542: 430:, a body in the 166: 165: 164: 136:inner Oort cloud 21: 5189: 5188: 5184: 5183: 5182: 5180: 5179: 5178: 5149:2006 in science 5134: 5133: 5130: 5120: 5118: 5108: 5106: 5096: 5094: 5084: 5082: 5074: 5072: 5067: 5061: 5059: 5058: 5052: 5045: 5038: 5031: 5025: 5019: 5013: 5006: 4999: 4992: 4985: 4978: 4971: 4956: 4954: 4944: 4942: 4932: 4930: 4917: 4908: 4872: 4809: 4793:vs. Hill sphere 4719:Molecular cloud 4647:Sample curation 4627:Detached object 4566: 4559: 4403: 4395: 4332: 4319: 4264:Neptune trojans 4047: 4045: 4043: 4036: 3978: 3671: 3542: 3524: 3410: 3373: 3366: 3361: 3328:Wayback Machine 3286: 3281: 3272: 3270: 3265: 3264: 3260: 3251: 3249: 3244: 3243: 3239: 3230: 3228: 3224: 3220: 3219: 3215: 3205: 3203: 3194: 3193: 3189: 3180: 3179: 3175: 3166: 3164: 3153: 3152: 3145: 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3608: 3598: 3597: 3596: 3591: 3576: 3575: 3574: 3569: 3564: 3559: 3548: 3546: 3529: 3526: 3525: 3523: 3522: 3515: 3508: 3501: 3494: 3487: 3480: 3473: 3466: 3461: 3456: 3451: 3446: 3439: 3434: 3429: 3424: 3419: 3371: 3368: 3367: 3362: 3360: 3359: 3352: 3345: 3337: 3331: 3330: 3318: 3313: 3307: 3301: 3296: 3295:official site. 3285: 3284:External links 3282: 3280: 3279: 3258: 3237: 3213: 3187: 3173: 3143: 3114: 3089: 3060: 3018: 2997: 2972: 2947: 2926: 2909: 2882: 2844: 2833: 2819: 2804: 2778: 2775:on 2006-08-30. 2760: 2739: 2710: 2675: 2645: 2620: 2595: 2574: 2553: 2526: 2501: 2480:Science Friday 2473:(2006-08-18). 2458: 2439: 2409: 2374: 2341: 2330:infoplease.com 2316: 2291: 2251: 2238: 2211: 2201:. p. 1598 2182: 2157: 2128: 2096: 2071: 2043: 2013: 1989: 1977: 1964: 1952: 1933: 1920:10.1086/504422 1896:(1): 290–298. 1880: 1861: 1793: 1736: 1711: 1698: 1691:) – via 1675: 1602: 1588: 1586: 1583: 1582: 1581: 1569: 1564: 1559: 1554: 1549: 1544: 1539: 1534: 1527: 1524: 1471: 1468: 1467: 1466: 1459: 1446: 1429: 1422: 1419: 1408: 1395: 1385: 1378: 1366: 1363: 1351: 1348: 1333: 1330: 1206: 1203: 1201: 1200:Closing issues 1198: 1053: 1050: 1042: 1041: 1034: 1023: 1008: 971: 968: 929: 926: 857: 854: 845: 844: 829: 826: 823: 819: 818: 816: 799:nuclear fusion 762: 759: 755:Owen Gingerich 753:On 18 August, 743:Science Friday 694: 691: 683:Clyde Tombaugh 666: 663: 636: 551: 538: 476:) might be in 436: 435: 432:scattered disk 425: 416: 372: 369: 367: 364: 352:Owen Gingerich 348: 347: 344: 341: 338: 335: 332: 203:Clyde Tombaugh 177: 174: 172: 171: 168: 155: 97: 96: 89: 82: 67:celestial body 32:Definition of 26: 24: 14: 13: 10: 9: 6: 4: 3: 2: 5186: 5175: 5172: 5170: 5167: 5165: 5162: 5160: 5159:Dwarf planets 5157: 5155: 5152: 5150: 5147: 5145: 5142: 5141: 5139: 5132: 5127: 5117: 5115: 5105: 5103: 5093: 5091: 5081: 5077: 5066: 5057: 5050: 5043: 5036: 5030: 5024: 5018: 5011: 5004: 4997: 4990: 4983: 4976: 4969: 4963: 4953: 4951: 4941: 4939: 4929: 4927: 4924: 4923: 4920: 4905: 4904:Tidal locking 4902: 4900: 4897: 4895: 4892: 4890: 4887: 4885: 4884:Double planet 4882: 4881: 4879: 4875: 4869: 4866: 4862: 4859: 4857: 4854: 4853: 4852: 4849: 4847: 4844: 4842: 4839: 4837: 4836:Minor planets 4834: 4832: 4829: 4827: 4824: 4822: 4819: 4818: 4816: 4812: 4806: 4803: 4801: 4798: 4794: 4791: 4790: 4789: 4786: 4784: 4781: 4777: 4774: 4770: 4769:Merging stars 4767: 4766: 4765: 4762: 4760: 4757: 4755: 4752: 4750: 4747: 4745: 4742: 4741: 4740: 4737: 4735: 4732: 4730: 4727: 4725: 4722: 4720: 4717: 4715: 4712: 4710: 4707: 4705: 4702: 4700: 4697: 4695: 4692: 4690: 4687: 4685: 4682: 4680: 4677: 4675: 4672: 4670: 4667: 4665: 4662: 4660: 4657: 4653: 4650: 4648: 4645: 4644: 4643: 4640: 4638: 4635: 4633: 4630: 4628: 4625: 4623: 4620: 4618: 4615: 4613: 4610: 4608: 4605: 4603: 4600: 4598: 4595: 4591: 4588: 4587: 4586: 4583: 4581: 4578: 4576: 4573: 4572: 4570: 4568: 4562: 4556: 4553: 4551: 4548: 4546: 4543: 4541: 4538: 4536: 4533: 4531: 4528: 4526: 4523: 4519: 4516: 4515: 4514: 4511: 4509: 4506: 4504: 4501: 4497: 4494: 4493: 4492: 4489: 4487: 4484: 4482: 4479: 4475: 4472: 4470: 4467: 4465: 4462: 4461: 4460: 4457: 4453: 4450: 4448: 4445: 4444: 4443: 4440: 4436: 4433: 4431: 4428: 4426: 4423: 4422: 4421: 4418: 4416: 4413: 4412: 4410: 4407: 4402: 4398: 4392: 4389: 4387: 4384: 4382: 4379: 4377: 4374: 4372: 4371:Subsatellites 4369: 4367: 4364: 4362: 4359: 4357: 4354: 4352: 4349: 4347: 4344: 4342: 4339: 4338: 4336: 4334: 4331:Hypothetical 4328: 4325: 4316: 4313: 4309: 4306: 4304: 4301: 4299: 4296: 4294: 4291: 4287: 4284: 4282: 4279: 4278: 4277: 4274: 4273: 4272: 4269: 4265: 4262: 4260: 4257: 4256: 4255: 4252: 4248: 4245: 4243: 4240: 4238: 4235: 4233: 4230: 4228: 4225: 4223: 4220: 4218: 4215: 4213: 4210: 4208: 4205: 4204: 4203: 4200: 4198: 4197:Asteroid belt 4195: 4193: 4190: 4186: 4183: 4181: 4178: 4176: 4173: 4169: 4166: 4164: 4161: 4160: 4159: 4156: 4154: 4151: 4149: 4146: 4144: 4141: 4140: 4139: 4136: 4132: 4129: 4127: 4124: 4122: 4119: 4117: 4114: 4112: 4109: 4107: 4104: 4102: 4099: 4097: 4094: 4093: 4091: 4089: 4086: 4082: 4079: 4077: 4074: 4073: 4072: 4071:Minor planets 4069: 4067: 4064: 4062: 4059: 4057: 4054: 4053: 4051: 4049: 4039: 4033: 4030: 4028: 4025: 4023: 4020: 4018: 4015: 4013: 4010: 4008: 4005: 4002: 3998: 3995: 3993: 3990: 3989: 3987: 3985: 3981: 3973: 3970: 3969: 3968: 3965: 3961: 3958: 3957: 3956: 3953: 3949: 3946: 3945: 3944: 3941: 3937: 3934: 3933: 3932: 3929: 3925: 3922: 3920: 3917: 3916: 3915: 3912: 3908: 3905: 3903: 3900: 3898: 3895: 3893: 3890: 3888: 3885: 3884: 3883: 3880: 3876: 3873: 3872: 3871: 3868: 3864: 3861: 3859: 3856: 3854: 3851: 3849: 3846: 3845: 3844: 3841: 3837: 3834: 3832: 3829: 3827: 3824: 3822: 3819: 3817: 3814: 3812: 3809: 3808: 3807: 3804: 3800: 3797: 3795: 3792: 3790: 3787: 3785: 3782: 3780: 3777: 3775: 3772: 3770: 3767: 3765: 3762: 3760: 3757: 3755: 3752: 3751: 3750: 3747: 3743: 3740: 3738: 3735: 3733: 3730: 3728: 3725: 3723: 3720: 3719: 3718: 3715: 3711: 3708: 3706: 3703: 3702: 3701: 3698: 3694: 3691: 3689: 3686: 3685: 3683: 3682: 3680: 3678: 3674: 3666: 3663: 3661: 3658: 3656: 3653: 3651: 3648: 3646: 3643: 3641: 3638: 3636: 3633: 3631: 3628: 3626: 3623: 3622: 3621: 3618: 3612: 3609: 3607: 3604: 3603: 3602: 3599: 3595: 3592: 3590: 3587: 3586: 3585: 3582: 3581: 3580: 3577: 3573: 3570: 3568: 3565: 3563: 3560: 3558: 3555: 3554: 3553: 3550: 3549: 3547: 3545: 3540: 3536: 3533: 3532: 3527: 3521: 3520: 3516: 3514: 3513: 3509: 3507: 3506: 3502: 3500: 3499: 3495: 3493: 3492: 3488: 3486: 3485: 3481: 3479: 3478: 3474: 3472: 3471: 3467: 3465: 3462: 3460: 3457: 3455: 3452: 3450: 3447: 3445: 3444: 3440: 3438: 3435: 3433: 3430: 3428: 3425: 3423: 3420: 3418: 3415: 3414: 3369: 3365: 3358: 3353: 3351: 3346: 3344: 3339: 3338: 3335: 3329: 3325: 3322: 3319: 3317: 3314: 3311: 3308: 3305: 3302: 3300: 3297: 3294: 3291: 3288: 3287: 3283: 3268: 3262: 3259: 3247: 3241: 3238: 3223: 3217: 3214: 3202: 3198: 3191: 3188: 3183: 3177: 3174: 3163: 3162: 3157: 3150: 3148: 3144: 3133:on 2006-11-30 3132: 3128: 3124: 3118: 3115: 3104: 3100: 3093: 3090: 3079:on 2006-09-16 3078: 3074: 3070: 3064: 3061: 3055: 3050: 3046: 3042: 3038: 3034: 3030: 3022: 3019: 3007: 3001: 2998: 2987: 2983: 2976: 2973: 2961: 2954: 2952: 2948: 2936: 2930: 2927: 2919: 2913: 2910: 2899: 2892: 2886: 2883: 2879: 2875: 2872: 2859: 2853: 2851: 2849: 2845: 2842: 2837: 2834: 2829: 2823: 2820: 2815: 2808: 2805: 2794:on 2009-01-07 2793: 2789: 2782: 2779: 2774: 2770: 2764: 2761: 2756: 2755: 2750: 2743: 2740: 2729:on 2011-10-03 2725: 2721: 2714: 2711: 2706: 2702: 2698: 2694: 2690: 2686: 2679: 2676: 2665:on 2007-09-28 2664: 2660: 2656: 2649: 2646: 2635:on 2007-05-17 2634: 2630: 2624: 2621: 2609: 2605: 2599: 2596: 2585: 2578: 2575: 2564: 2557: 2554: 2542: 2541: 2536: 2530: 2527: 2515: 2508: 2506: 2502: 2491:on 2006-08-30 2490: 2486: 2482: 2481: 2476: 2472: 2468: 2462: 2459: 2454: 2450: 2443: 2440: 2429:on 2010-08-22 2428: 2424: 2420: 2413: 2410: 2399:on 2006-09-08 2398: 2394: 2393: 2388: 2384: 2378: 2375: 2364:on 2011-10-03 2363: 2359: 2358:Bad Astronomy 2355: 2351: 2345: 2342: 2331: 2327: 2320: 2317: 2306: 2302: 2295: 2292: 2284: 2280: 2276: 2272: 2268: 2264: 2260: 2256: 2242: 2239: 2228: 2227: 2226:New Scientist 2222: 2215: 2212: 2200: 2193: 2186: 2183: 2171: 2167: 2161: 2158: 2146: 2142: 2138: 2132: 2129: 2117: 2113: 2109: 2103: 2101: 2097: 2086: 2082: 2075: 2072: 2061: 2057: 2050: 2048: 2044: 2033: 2032: 2027: 2020: 2018: 2014: 2002: 1996: 1994: 1990: 1987: 1981: 1978: 1974: 1968: 1965: 1961: 1956: 1953: 1949: 1945: 1942: 1937: 1934: 1929: 1925: 1921: 1917: 1913: 1909: 1904: 1899: 1895: 1891: 1884: 1881: 1876: 1872: 1865: 1862: 1851:on 2007-10-13 1850: 1846: 1842: 1838: 1834: 1830: 1826: 1821: 1816: 1812: 1808: 1804: 1797: 1794: 1789: 1785: 1781: 1777: 1773: 1769: 1764: 1759: 1755: 1751: 1747: 1740: 1737: 1725: 1721: 1715: 1712: 1708: 1702: 1699: 1694: 1690: 1686: 1679: 1676: 1665: 1661: 1657: 1653: 1649: 1645: 1640: 1635: 1631: 1627: 1620: 1613: 1611: 1609: 1607: 1603: 1598: 1593: 1590: 1584: 1579: 1575: 1574: 1570: 1568: 1565: 1563: 1560: 1558: 1555: 1553: 1550: 1548: 1545: 1543: 1540: 1538: 1535: 1533: 1530: 1529: 1525: 1523: 1521: 1517: 1512: 1509: 1505: 1501: 1497: 1493: 1489: 1485: 1481: 1477: 1469: 1464: 1460: 1457: 1456: 1451: 1447: 1444: 1440: 1439: 1434: 1430: 1427: 1423: 1420: 1417: 1413: 1409: 1406: 1405: 1401:on the album 1400: 1396: 1393: 1389: 1386: 1383: 1382:2 Skinnee J's 1379: 1376: 1372: 1371: 1370: 1364: 1362: 1360: 1359: 1349: 1347: 1345: 1340: 1331: 1329: 1326: 1322: 1321: 1317: 1312: 1311: 1306: 1302: 1296: 1294: 1290: 1286: 1282: 1276: 1274: 1270: 1266: 1262: 1256: 1254: 1249: 1247: 1243: 1237: 1235: 1231: 1227: 1223: 1219: 1215: 1211: 1204: 1199: 1197: 1195: 1194:dwarf planets 1191: 1185: 1184: 1180: 1177: 1175: 1171: 1166: 1162: 1161: 1157: 1155: 1151: 1149: 1145: 1141: 1137: 1133: 1129: 1125: 1121: 1117: 1116:eight planets 1111: 1108: 1106: 1101: 1099: 1095: 1090: 1088: 1084: 1080: 1075: 1074: 1071: 1062: 1057: 1051: 1049: 1047: 1038: 1037:Resolution 6B 1035: 1032: 1027: 1026:Resolution 6A 1024: 1020: 1016: 1012: 1011:Resolution 5B 1009: 1006: 1001: 1000:Resolution 5A 998: 997: 996: 988: 984: 982: 978: 969: 967: 960: 955: 952: 949: 946: 943: 940: 937: 933: 927: 925: 923: 918: 915: 911: 906: 901: 898: 892: 890: 886: 882: 878: 874: 870: 869: 864: 855: 853: 851: 842: 838: 834: 830: 827: 824: 821: 820: 817: 814: 813: 812: 810: 805: 802: 800: 796: 790: 788: 784: 780: 776: 772: 768: 765:According to 760: 758: 756: 751: 749: 745: 744: 738: 736: 732: 728: 724: 723:double planet 719: 717: 713: 708: 704: 700: 692: 690: 688: 684: 679: 675: 673: 664: 662: 660: 656: 644: 639: 619: 607: 603: 598: 594: 589: 585: 576: 574: 569: 567: 563: 559: 554: 546: 541: 533: 529: 525: 521: 517: 513: 510: 505: 503: 499: 495: 485: 481: 479: 475: 471: 467: 463: 462: 457: 453: 452:double planet 448: 446: 442: 433: 429: 426: 424: 423:double planet 420: 417: 414: 411: 410: 409: 405: 403: 397: 395: 385: 377: 370: 365: 363: 361: 357: 353: 345: 342: 339: 336: 333: 330: 329: 328: 326: 325:Iwan Williams 322: 317: 315: 314: 309: 305: 301: 297: 293: 289: 284: 282: 278: 274: 270: 265: 263: 259: 254: 249: 246: 242: 239: 235: 231: 226: 224: 220: 216: 212: 209:to have nine 208: 204: 200: 195: 187: 182: 175: 169: 153: 149: 145: 144: 142: 139: 137: 133: 129: 124: 122: 118: 117: 112: 111: 106: 102: 94: 90: 87: 83: 80: 76: 72: 71: 70: 68: 64: 63: 58: 54: 46: 45:Euler diagram 42: 36: 35: 19: 5144:Solar System 5131: 5126:Solar System 5060:Each arrow ( 4982:Local Bubble 4968:Solar System 4966: 4759:Planetesimal 4714:Kuiper cliff 4442:Space probes 4415:Colonization 4254:Kirkwood gap 4175:Saturn Moons 4088:Planetesimal 3552:Terrestrials 3517: 3510: 3503: 3496: 3489: 3482: 3475: 3468: 3441: 3364:Solar System 3271:. Retrieved 3261: 3250:. Retrieved 3240: 3229:. Retrieved 3216: 3206:17 September 3204:. Retrieved 3200: 3195:Cardy, Tom. 3190: 3176: 3165:. Retrieved 3159: 3135:. Retrieved 3131:the original 3117: 3106:. Retrieved 3102: 3092: 3081:. Retrieved 3077:the original 3072: 3063: 3036: 3032: 3021: 3010:. Retrieved 3000: 2989:. Retrieved 2985: 2975: 2964:. Retrieved 2939:. Retrieved 2929: 2912: 2901:. Retrieved 2897: 2885: 2862:. Retrieved 2836: 2822: 2807: 2796:. Retrieved 2792:the original 2781: 2773:the original 2763: 2752: 2742: 2731:. Retrieved 2724:the original 2713: 2688: 2678: 2667:. Retrieved 2663:the original 2658: 2648: 2637:. Retrieved 2633:the original 2623: 2612:. Retrieved 2607: 2598: 2587:. Retrieved 2577: 2566:. Retrieved 2556: 2545:. Retrieved 2538: 2529: 2518:. Retrieved 2493:. Retrieved 2489:the original 2478: 2461: 2452: 2442: 2431:. Retrieved 2427:the original 2422: 2412: 2401:. Retrieved 2397:the original 2390: 2377: 2366:. Retrieved 2362:the original 2357: 2344: 2333:. 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Retrieved 1629: 1625: 1592: 1571: 1557:Minor planet 1515: 1513: 1507: 1502:as its 2006 1499: 1487: 1475: 1473: 1453: 1436: 1426:Terra Lumina 1412:Robbie Fulks 1402: 1388:Thing a Week 1387: 1368: 1356: 1353: 1335: 1314: 1308: 1305:heliocentric 1297: 1278: 1258: 1250: 1238: 1208: 1193: 1189: 1187: 1182: 1181: 1178: 1168: 1164: 1159: 1158: 1153: 1113: 1112: 1109: 1102: 1094:dwarf planet 1091: 1076: 1073: 1070:Solar System 1067: 1055: 1045: 1043: 1036: 1025: 1018: 1014: 1010: 999: 993: 973: 965: 953: 950: 947: 944: 941: 938: 935: 931: 919: 902: 893: 888: 876: 866: 862: 859: 850:dwarf planet 847: 806: 803: 801:mechanism . 792: 781:astronomers 764: 752: 741: 739: 720: 712:rogue planet 696: 680: 676: 668: 654: 642: 617: 605: 577: 570: 506: 498:dwarf planet 491: 459: 449: 437: 407: 399: 393: 391: 349: 318: 313:New Horizons 311: 285: 266: 250: 227: 207:Solar System 191: 140: 125: 114: 110:dwarf planet 108: 98: 60: 57:Solar System 50: 33: 5114:Outer space 5102:Spaceflight 5023:Local Sheet 5017:Local Group 4800:Rubble pile 4788:Roche limit 4783:Ring system 4734:Outer space 4709:Kuiper belt 4679:Hill sphere 4674:Hills cloud 4622:Debris disk 4617:Cosmic dust 4401:Exploration 4356:Planet Nine 4341:Fifth giant 4315:Hills cloud 4276:Kuiper belt 4247:exceptional 4163:Trojan camp 3123:Geha, Marla 3039:: 183–186. 2689:Nature News 2516:. Space.com 2383:Nick Matzke 1729:29 November 1632:: 193–216. 1506:, defining 1452:from album 1416:Kuiper Belt 1313:instead of 1110:Footnotes: 716:brown dwarf 707:Nick Matzke 689:uniformly. 597:tidal force 588:Kuiper Belt 502:brown dwarf 232:founded by 158:< 2/(25+ 148:metallicity 121:astronomers 77:around the 5138:Categories 5042:Local Hole 4989:Gould Belt 4729:Oort cloud 4565:Formation, 4555:Deep space 4391:Vulcanoids 4308:Oort cloud 4232:first 1000 4168:Greek camp 4066:Meteoroids 4061:Damocloids 4007:Charikloan 3273:2007-01-10 3252:2007-01-20 3231:2007-01-07 3167:2006-08-27 3137:2006-09-13 3108:2013-08-28 3083:2008-08-04 3012:2008-06-11 2991:2007-02-21 2966:2008-08-01 2941:2008-08-04 2903:2014-07-03 2864:2007-12-31 2798:2006-08-23 2733:2008-08-04 2669:2006-08-20 2639:2006-08-18 2614:2006-08-18 2589:2008-08-04 2568:2008-08-04 2547:2006-08-18 2520:2006-08-24 2495:2006-08-22 2471:Mike Brown 2467:Ira Flatow 2433:2010-08-24 2403:2006-08-18 2368:2006-08-18 2350:Phil Plait 2335:2006-08-19 2310:2006-08-19 2232:2013-05-21 2205:2013-05-21 2176:2006-08-19 2170:SpaceDaily 2151:2006-08-16 2122:2006-08-16 2090:2006-08-16 2065:2006-08-16 2037:2006-08-16 2007:2008-08-16 1855:2007-01-11 1763:2203.09520 1756:: 101641. 1669:2008-08-04 1597:Exoplanets 1585:References 1433:John Prine 1399:Aesop Rock 1344:Marla Geha 1210:Alan Stern 1179:Footnote: 1005:satellites 775:straw poll 727:barycenter 699:Phil Plait 665:Advantages 651:12 km 630:10 kg 614:11 km 584:Mike Brown 461:barycenter 441:Mike Brown 360:Dava Sobel 337:Structural 176:Background 5090:Astronomy 5003:Milky Way 4996:Orion Arm 4764:Formation 4749:Migration 4744:Disrupted 4612:Coatlicue 4580:Accretion 4567:evolution 4513:Asteroids 4425:astronomy 4420:Discovery 4281:Cubewanos 4202:Asteroids 4032:Quaoarian 4022:Neptunian 4012:Chironean 3997:Saturnian 3779:Enceladus 2871:orig link 2816:. 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