View source for Astronomy:50000 Quaoar

{{Short description|Cold classical Kuiper belt object}}
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{{Infobox planet
 | minorplanet             = yes
 | name                    = 50000 Quaoar
 | symbol                  = [[File:Quaoar symbol (bold).svg|24px|🝾]] (mostly astrological)
 | background              = #C2E0FF
 | image                   = quaoar-weywot_hst.jpg
 | image_scale              =
 | caption                 = Quaoar with its moon Weywot imaged by the [[Astronomy:Hubble Space Telescope|Hubble Space Telescope]] in 2006
 | discovery_ref           = <ref name="MPC-object"/>
 | discoverer              = {{ubl|Chadwick A. Trujillo|[[Biography:Michael E. Brown|Michael E. Brown]]}}
 | discovery_site          = [[Organization:Palomar Observatory|Palomar Observatory]]
 | discovered              = 4 June 2002
 | earliest_precovery_date = 25 May 1954
 | mpc_name                = (50000) Quaoar
 | alt_names               = {{mp|2002 LM|60}}
 | pronounced              = {{IPAc-en|ˈ|k|w|ɑː|w|ɑːr}}, {{IPAc-en|ˈ|k|w|ɑː|oʊ|.|ɑːr}}
 | named_after             = Qua-o-ar / Kwawar<ref name="Schmadel2006"/><br/>(deity of the Tongva people)
 | adjective               = Quaoarian
 | mp_category             = {{ubl|[[Astronomy:Trans-Neptunian object|TNO]]<ref name="jpldata"/>{{·}}[[Astronomy:Classical Kuiper belt object|cubewano]]<ref name="Buie"/><ref name="MPEC-2008-O05"/>|[[Astronomy:Distant minor planet|distant]]<ref name="MPC-object"/> [[Astronomy:Dwarf planet|dwarf planet]]}}
 | orbit_ref               = <ref name="jpldata"/>
 | epoch                   = 31 May 2020 ([[Astronomy:Julian day|JD]] 2459000.5)
 | uncertainty             = 3
 | observation_arc         = 65.27 yr (23,839 d)
 | aphelion                = 45.488 [[Astronomy:Astronomical unit|AU]] ({{val|6.805|ul=Tm}})
 | perihelion              = 41.900 AU ({{val|6.268|u=Tm}})
 | time_periastron         = ≈ 11 February 2075<ref name=perihelion>[http://ssd.jpl.nasa.gov/horizons.cgi?find_body=1&body_group=sb&sstr=2002LM60 JPL Horizons] {{Webarchive|url=https://web.archive.org/web/20210509231607/https://ssd.jpl.nasa.gov/horizons.cgi?find_body=1&body_group=sb&sstr=2002LM60 |date=9 May 2021 }} Observer Location: @sun (Perihelion occurs when deldot changes from negative to positive. Uncertainty in time of perihelion is 3-sigma.)</ref><br/>±17 days
 | semimajor               = 43.694 AU ({{val|6.537|u=Tm}})
 | eccentricity            = 0.04106
 | period                  = 288.83 [[Astronomy:Julian year|yr]] (105,495 [[Day|d]])
 | mean_anomaly            = 301.104[[Degree (angle)|°]]
 | mean_motion             = {{Deg2DMS|0.0034125|sup=ms}} / day
 | inclination             = 7.9895°
 | asc_node                = 188.927°
 | arg_peri                = 147.480°
 | satellites              = 1 (Weywot)
 | dimensions              = {{val|1159|8|u=km|fmt=commas}} (2023; equatorial)<ref name="Pereira2023"/><br/>{{nowrap|{{val|1138|48|34|fmt=commas}} × {{val|1036|44|31|u=km|fmt=commas}}}} (2013; equatorial and polar){{efn|Polar dimension calculated by multiplying the measured equatorial diameter {{val|1138|48|34|u=km|fmt=commas}} with the oblateness 0.0897 obtained from the occultation in 2013.<ref name="Braga-Ribas2013"/>}}
 | mean_diameter           = {{val|1086|4|u=km|fmt=commas}} (2023; area equivalent)<ref name="Pereira2023"/><br/>{{val|1110|5|u=km|fmt=commas}} (2013; volume equivalent)<ref name="Braga-Ribas2013"/>
 | mean_radius             = {{val|543|2|u=km}} (2023; area equivalent)<ref name="Pereira2023"/><br/>{{val|555|2.5|u=km}} (2013; volume equivalent)<ref name="Braga-Ribas2013"/>
 | flattening              = {{val|0.12|0.01}} (2023; projected)<ref name="Pereira2023"/><br/>{{val|0.0897|0.006}} (2013)<ref name="Braga-Ribas2013"/>
 | surface_area            = {{val|3.83|e=6|u=km2}}<ref name="Wolfram1"/>
 | volume                  = {{val|7.16|0.10|e=8|u=km3}}{{efn|name=volume|Calculated given a mean radius of {{val|555|2.5|u=km}}<ref name="Braga-Ribas2013"/>}}
 | mass                    = {{val|1.20|0.05|e=21|u=kg}}<ref name="Morgado2023"/>{{rp|page=3}}
 | density                 = {{val|1.68|0.08|u=g/cm3}}{{efn|name=density|Calculated given a mass of {{val|1.20|0.05|e=21|u=kg}}<ref name="Morgado2023"/> and a radius of {{val|555|2.5|u=km}}<ref name="Braga-Ribas2013"/>}}
 | surface_grav            = {{Gr|1.2|555|2}} m/s<sup>2</sup>
 | escape_velocity         = {{V2|1.2|555|2}} km/s
 | spectral_type           = [[Astronomy:Trans-Neptunian object#Colors|IR]] (moderately red)<br/>B–V={{val|0.94|0.01}}<ref name="Tegler2007"/><ref name="Belskaya2015"/><br/>V−R={{val|0.64|0.01}}<ref name="Tegler2007"/><br/>V−I={{val|1.28|0.02}}<ref name="Belskaya2015"/><ref name="lcdb"/>
 | albedo                  = {{val|0.124|0.006}}<ref name="Pereira2023"/><br/>{{val|0.109|0.007}}<ref name="Braga-Ribas2013"/>
 | rotation                = {{val|17.6788|0.0004|u=h}}<ref name="Ortiz2003"/><ref name="Morgado2023"/>
 | axial_tilt              = 13.6°{{efn|name=Morgado-pole|Morgado et al. (2023) give the outer ring's north pole direction in terms of equatorial coordinates ({{mvar|α}}, {{mvar|δ}}) {{=}} (258.47°, +54.14°), where  {{mvar|α}}  is [[Right ascension|right ascension]] and  {{mvar|δ}}  is [[Declination|declination]].<ref name="Morgado2023"/>{{rp|page=3}} [[Astronomy:Astronomical coordinate systems#Equatorial ↔ ecliptic|Transforming]] these equatorial coordinates to ecliptic coordinates gives  {{mvar|λ}} ≈ 240.17° and  {{mvar|β}} ≈ +76.38°.<ref name="coordstransform"/> The ecliptic latitude,  {{mvar|β}},  is the angular offset from the ecliptic plane, whereas inclination  {{mvar|i}}  with respect to the ecliptic is the angular offset from the ecliptic north pole at {{nobr| {{mvar|β}} {{=}} +90° ;}}  {{mvar|i}}  with respect to the ecliptic would be the [[Angle#Combining angle pairs|complement]] of  {{mvar|β}}, which is expressed by the difference {{nobr| {{mvar|i}} {{=}} 90° – {{mvar|β}}}}. Thus, the axial tilt of Quaoar's outer ring is 13.62° with respect to the ecliptic. If the outer ring is coplanar to Quaoar's equator (having the same north pole orientation), then Quaoar would have the same axial tilt with respect to the ecliptic.}} or 14.0°{{efn|name=Pereira-pole|Pereira et al. (2023) give the outer ring's north pole direction in terms of equatorial coordinates ({{mvar|α}}, {{mvar|δ}}) {{=}} ({{RA|17|19|16}}, {{DEC|+53|27}}), where  {{mvar|α}}  is [[Right ascension|right ascension]] and  {{mvar|δ}}  is [[Declination|declination]].<ref name="Pereira2023"/>{{rp|page=4}} Converting these equatorial coordinates from sexagesimal to decimal degrees gives ({{mvar|α}}, {{mvar|δ}}) {{=}} (259.82°, +53.45°). Then, [[Astronomy:Astronomical coordinate systems#Equatorial ↔ ecliptic|transforming]] these equatorial coordinates to ecliptic coordinates gives  {{mvar|λ}} ≈ 64.26° (ecliptic longitude) and  {{mvar|β}} ≈ +75.98° (ecliptic latitude).<ref name="coordstransform"/> Subtracting this value of  {{mvar|β}}  from +90° gives the inclination of Quaoar's outer ring with respect to the ecliptic: {{nobr| {{mvar|i}} {{=}} 90° – {{mvar|β}} ≈ 14.02°}}. If the outer ring is coplanar to Quaoar's equator (having the same north pole orientation), then Quaoar would have the same axial tilt with respect to the ecliptic.}} to [[Astronomy:Ecliptic|ecliptic]] (if coplanar with rings)
 | right_asc_north_pole    = {{val|258.47|0.87|u=deg}}<ref name="Morgado2023" />{{rp|page=3}} or {{val|259.82|0.23|u=deg}}<ref name="Pereira2023"/>{{rp|page=4}} (outer ring)
 | declination             = +{{val|54.14|0.11|u=deg}}<ref name="Morgado2023" />{{rp|page=3}} or +{{val|53.45|0.30|u=deg}}<ref name="Pereira2023"/>{{rp|page=4}} (outer ring)
 | magnitude               = 19.0<ref name="Grundy-orbits"/>
 | abs_magnitude           = {{val|2.737|0.008}}<ref name="Grundy-orbits"/><br/>2.4 (assumed)<ref name="jpldata"/><ref name="MPC-object"/>
 | angular_size            = {{val|40.4|1.8}} milliarcseconds<ref name="Brown2004"/>
 | single_temperature      = ≈ 44 [[Kelvin|K]]<ref name="Fraser2013b"/>
}}

'''Quaoar''' ([[Astronomy:Minor-planet designation|minor-planet designation]] '''50000 Quaoar''') is a ringed [[Astronomy:Dwarf planet|dwarf planet]] in the [[Astronomy:Kuiper belt|Kuiper belt]], a region of icy [[Astronomy:Planetesimal|planetesimal]]s beyond [[Astronomy:Neptune|Neptune]]. A non-resonant object ([[Astronomy:Classical Kuiper belt object|cubewano]]), it measures approximately {{cvt|1086|km}} in diameter, about the size of Saturn's moon Dione or half the size of [[Astronomy:Pluto|Pluto]]. The object was discovered by American astronomers [[Biography:Chad Trujillo|Chad Trujillo]] and [[Biography:Michael E. Brown|Michael Brown]] at the [[Organization:Palomar Observatory|Palomar Observatory]] on 4 June 2002. Signs of water ice on the surface of Quaoar have been found, which suggests that cryovolcanism may be occurring on Quaoar. A small amount of [[Chemistry:Methane|methane]] is present on its surface, which can only be retained by the largest Kuiper belt objects.

Quaoar has one known moon, Weywot, which was discovered by Brown in February 2007.<ref name="IAUC8812"/> Both objects were named after mythological figures from the Native American Tongva people in Southern California. Quaoar is the Tongva creator deity and Weywot is his son. In 2023, astronomers announced the discovery of two [[Astronomy:Ring system|rings]] orbiting Quaoar outside its [[Physics:Roche limit|Roche limit]], which defies theoretical expectations that these rings should not be stable.<ref name="Pereira2023"/>

== History ==
=== Discovery ===
[[File:P48 1994 Jean Large.jpg|thumb|left|Quaoar was discovered using the Samuel Oschin telescope at Palomar Observatory]]
[[File:Quaoar discovery animation.gif|thumb|left|Animation of three discovery images taken over a period of 4.5 hours, showing the slow movement of Quaoar (indicated by the arrow)<ref name="precovery"/>]]
Quaoar was discovered on 4 June 2002 by American astronomers [[Biography:Chad Trujillo|Chad Trujillo]] and [[Biography:Michael E. Brown|Michael Brown]] at the [[Organization:Palomar Observatory|Palomar Observatory]] in the Palomar Mountain Range in San Diego County, California.<ref name="MPC-object"/> The discovery formed part of the Caltech Wide Area Sky Survey, which was designed to search for the brightest [[Astronomy:Kuiper belt|Kuiper belt]] objects using the Palomar Observatory's 1.22-meter [[Astronomy:Samuel Oschin telescope|Samuel Oschin telescope]].<ref name="Trujillo2003"/> Quaoar was first identified in images by Trujillo on 5 June 2002, when he noticed a dim, 18.6-[[Astronomy:Apparent magnitude|magnitude]] object slowly moving among the stars of the [[Astronomy:Constellation|constellation]] [[Astronomy:Ophiuchus|Ophiuchus]].<ref name="FAQ-Quaoar"/><ref name="MPEC-2002-T34"/> Quaoar appeared relatively bright for a distant object, suggesting that it could have a size comparable to the diameter of the [[Astronomy:Dwarf planet|dwarf planet]] [[Astronomy:Pluto|Pluto]].<ref name="nasascience"/>

To ascertain Quaoar's orbit, Brown and Trujillo initiated a search for archival [[Astronomy:Precovery|precovery]] images. They obtained several precovery images taken by the [[Organization:Near-Earth Asteroid Tracking|Near-Earth Asteroid Tracking]] survey from various observatories in 1996 and 2000–2002.<ref name="precovery"/> In particular, they had also found two archival [[Physics:Photographic plate|photographic plate]]s taken by astronomer [[Biography:Charles T. Kowal|Charles T. Kowal]] in May 1983,<ref name="MPEC-2002-T34"/> who at the time was searching for the hypothesized [[Astronomy:Planet X|Planet X]] at the Palomar Observatory.<ref name="caltech"/><ref name="NYT-20021008"/> From these precovery images, Brown and Trujillo were able to calculate Quaoar's orbit and distance. Additional precovery images of Quaoar have been later identified, with the earliest known found by Edward Rhoads on a photographic plate imaged on 25 May 1954 from the Palomar Observatory Sky Survey.<ref name="MPC-object"/><ref name="jpldata"/>

Before announcing the discovery of Quaoar, Brown had planned to conduct follow-up observations using the [[Astronomy:Hubble Space Telescope|Hubble Space Telescope]] to measure Quaoar's size.<ref name="hubblesite"/> He had also planned to announce the discovery as soon as possible and found it necessary to keep the discovery information confidential during the follow-up observations.<ref name="plutokiller"/> Rather than submitting his Hubble proposal under peer review, Brown submitted his proposal directly to one of Hubble's operators, who promptly allocated time to Brown.<ref name="plutokiller"/><ref name="HST-9678"/> While setting up the observing algorithm for Hubble, Brown had also planned to use one of the Keck telescopes in [[Earth:Mauna Kea|Mauna Kea]], Hawaii, as a part of a study on cryovolcanism on the [[Astronomy:Moons of Uranus|moons]] of [[Astronomy:Uranus|Uranus]].<ref name="plutokiller"/> This provided him additional time for follow-up observations and took advantage of the whole observing session in July to analyze Quaoar's [[Spectrum|spectrum]] and characterize its surface composition.<ref name="Schaller2007"/><ref name="plutokiller"/>

The discovery of Quaoar was formally announced by the [[Organization:Minor Planet Center|Minor Planet Center]] in a [[Organization:Minor Planet Center#Publications|Minor Planet Electronic Circular]] on 7 October 2002.<ref name="MPEC-2002-T34"/> It was given the [[Astronomy:Provisional designation|provisional designation]] {{mp|2002 LM|60}}, indicating that its discovery took place during the first half of June 2002.<ref name="MPEC-2002-T34"/><ref name="Nomenclature"/> Quaoar was the 1,512th object discovered in the first half of June, as indicated by the preceding letter and numbers in its provisional designation.{{efn|In the convention for minor planet provisional designations, the first letter represents the half-month of the year of discovery while the second letter and numbers indicate the order of discovery within that half-month. In the case for {{mp|2002 LM|60}}, the first letter 'L' corresponds to the first half-month of June 2002 while the preceding letter 'M' indicates that it is the 12th object discovered on the 61st cycle of discoveries (with 60 cycles completed). Each completed cycle consists of 25 letters representing discoveries, hence 12 + (60 completed cycles × 25 letters) {{=}} 1,512.<ref name="Nomenclature"/>}} On that same day, Trujillo and Brown reported their scientific results from observations of Quaoar at the 34th annual meeting of the American Astronomical Society's [[Organization:Division for Planetary Sciences|Division for Planetary Sciences]] in Birmingham, Alabama. They announced Quaoar was the largest Kuiper belt object found yet, surpassing previous record holders [[Astronomy:20000 Varuna|20000 Varuna]] and {{mpl|2002 AW|197}}.<ref name="Trujillo2003"/><ref name="hubblesite"/> Quaoar's discovery has been cited by Brown as having contributed to the [[Astronomy:IAU definition of planet|reclassification of Pluto]] as a dwarf planet.<ref name="plutokiller"/> Since then, Brown has contributed to the discovery of larger trans-Neptunian objects, including [[Astronomy:Haumea|Haumea]], {{dp|Eris}}, [[Astronomy:Makemake|Makemake]] and {{dp|Gonggong}}.

=== Name and symbol ===
Upon Quaoar's discovery, it was initially given the temporary nickname "Object X" as a reference to [[Astronomy:Planet X|Planet X]], due to its potentially large size and unknown nature.<ref name="plutokiller"/> At the time, Quaoar's size was uncertain, and its high brightness led the discovery team to speculate that it may be a possible tenth planet. After measuring Quaoar's size with the Hubble Space Telescope in July, the team began considering names for the object, particularly those from local Native American mythologies.<ref name="plutokiller"/> Following the [[Organization:International Astronomical Union|International Astronomical Union]]'s (IAU) [[Astronomy:Planetary nomenclature|naming convention]] for [[Astronomy:Minor planet|minor planet]]s, non-resonant Kuiper belt objects are to be named after [[Religion:Creator deity|creation deities]].<ref name="Nomenclature"/> The team settled on the name ''Kwawar'', the creator god of the Tongva people indigenous to the Los Angeles Basin, where Brown's institute, the [[Organization:California Institute of Technology|California Institute of Technology]], was located.<ref name="caltech"/>

According to Brown, the name "Quaoar" is pronounced with three syllables, and Trujillo's website on Quaoar gives a three-syllable pronunciation, {{IPAc-en|ˈ|k|w|ɑː|.|oʊ|(|w|)|ɑːr}}, as an approximation of the Tongva pronunciation {{IPA-azc|ˈkʷaʔuwar|}}.<ref name="FAQ-Quaoar"/> The name can be also pronounced as two syllables, {{IPAc-en|ˈ|k|w|ɑː|w|ɑːr}}, reflecting the usual English spelling and pronunciation of the deity Kwawar.<ref name="hubblesite"/><ref name="Street2008"/><ref>NASA/JHUAPL/SwRI (2016) [https://solarsystem.nasa.gov/resources/400/quaoar/ Quaoar] {{Webarchive|url=https://web.archive.org/web/20230318090111/https://solarsystem.nasa.gov/resources/400/quaoar/ |date=18 March 2023 }}</ref>

In Tongva mythology, Kwawar is the genderless<ref name="Street2008"/> creation force of the universe, singing and dancing deities into existence.<ref name="Schmadel2006"/> He first sings and dances to create Weywot (Sky Father), then they together sing Chehooit (Earth Mother) and Tamit (Grandfather Sun) into existence. As they did this, the creation force became more complex as each new deity joined the singing and dancing. Eventually, after reducing chaos to order, they created the seven great giants that upheld the world,<ref name="FAQ-Quaoar"/><ref name="hubblesite"/> then the animals and finally the first man and woman, Tobohar and Pahavit.<ref name="FAQ-Quaoar"/>

Upon their investigation of names from Tongva mythology, Brown and Trujillo realized that there were contemporary members of the Tongva people, whom they contacted for permission to use the name.<ref name="plutokiller"/> They consulted tribal historian Marc Acuña, who confirmed that the name ''Kwawar'' would indeed be an appropriate name for the newly discovered object.<ref name="FAQ-Quaoar"/><ref name="Street2008"/> However, the Tongva preferred the spelling ''Qua-o-ar'', which Brown and Trujillo adopted, though with the hyphens omitted.<ref name="plutokiller"/> The name and discovery of Quaoar were publicly announced in October, though Brown had not sought approval of the name by the IAU's Committee on Small Body Nomenclature (CSBN).<ref name="plutokiller"/> Indeed, Quaoar's name was announced before the official numbering of the object, which [[Biography:Brian G. Marsden|Brian Marsden]]—the head of the Minor Planet Center—remarked in 2004 to be a violation of the protocol.<ref name="plutokiller"/><ref name="MPEC-2004-S73"/> Despite this, the name was approved by the CSBN, and the naming citation, along with Quaoar's official numbering, was published in a [[Astronomy:Minor Planet Circular|Minor Planet Circular]] on 20 November 2002.<ref name="MPC47066"/>

Quaoar was given the [[Astronomy:Minor planet number|minor planet number]] 50000, which was not by coincidence but to commemorate its large size, being that it was found in the search for a Pluto-sized object in the Kuiper belt.<ref name="MPC47066"/> The large Kuiper belt object 20000 Varuna was similarly numbered for a similar occasion.<ref name="MPC41805"/> However, subsequent even larger discoveries such as 136199 Eris were simply numbered according to the order in which their orbits were confirmed.<ref name="Nomenclature"/>

Planetary symbols are no longer much used in astronomy, so Quaoar never received a symbol in the astronomical literature. A symbol {{angbr|[[File:Quaoar symbol (fixed width).svg|16px|🝾]]}}, used mostly among astrologers,<ref name=miller>{{cite web|url=https://www.unicode.org/L2/L2021/21224-dwarf-planet-syms.pdf|title=Unicode request for dwarf-planet symbols|last=Miller|first=Kirk|date=26 October 2021|website=unicode.org|access-date=29 January 2022|archive-date=23 March 2022|archive-url=https://web.archive.org/web/20220323174107/https://www.unicode.org/L2/L2021/21224-dwarf-planet-syms.pdf|url-status=live}}</ref> is included in [[Unicode]] as U+1F77E.<ref>{{Cite web |url=https://www.unicode.org/alloc/Pipeline.html |title=Proposed New Characters: The Pipeline |access-date=29 January 2022 |archive-date=29 January 2022 |archive-url=https://web.archive.org/web/20220129110620/https://www.unicode.org/alloc/Pipeline.html |url-status=live }}</ref> The symbol was designed by Denis Moskowitz, a software engineer in Massachusetts; it combines the letter Q (for 'Quaoar') with a canoe, and is stylized to recall angular Tongva rock art.<ref name=anderson>{{cite web |url=http://blog.unicode.org/2022/05/out-of-this-world-new-astronomy-symbols.html |title=Out of this World: New Astronomy Symbols Approved for the Unicode Standard |last=Anderson |first=Deborah |date=4 May 2022 |website=unicode.org |publisher=The Unicode Consortium |access-date=6 August 2022 |archive-date=6 August 2022 |archive-url=https://web.archive.org/web/20220806075352/http://blog.unicode.org/2022/05/out-of-this-world-new-astronomy-symbols.html |url-status=live }}</ref>

== Orbit and classification ==
[[File:TheKuiperBelt Orbits Quaoar.svg|thumb|upright=1.5|[[Astronomy:Ecliptic|Ecliptic]] view of Quaoar's orbit (blue) compared to Pluto (red) and Neptune (white). The approximate perihelion (''q'') and aphelion (''Q'') dates are marked for their respective orbits.]]
[[File:Cubewanos.png|thumb|upright=1|Polar view of Quaoar's orbit (yellow) along with various other large Kuiper belt objects]]
Quaoar orbits the [[Astronomy:Sun|Sun]] at an average distance of {{convert|43.7|AU|e9km e9mi|lk=in|sp=us|abbr=unit}}, taking 288.8 years to complete one full orbit around the Sun. With an [[Astronomy:Orbital eccentricity|orbital eccentricity]] of 0.04, Quaoar follows a nearly circular orbit, only slightly varying in distance from 42&nbsp;AU at perihelion to 45&nbsp;AU at aphelion.<ref name="jpldata"/> At such distances, light from the Sun takes more than 5 hours to reach Quaoar.<ref name="FAQ-Quaoar"/> Quaoar has last passed aphelion in late 1932 and is currently approaching the Sun at a rate of 0.035&nbsp;AU per year, or about {{convert|170|m/s|mph|sp=us}}.<ref name="HORIZONS"/> Quaoar will reach perihelion around February 2075.<ref name="perihelion"/>

Because Quaoar has a nearly circular orbit, it does not approach close to [[Astronomy:Neptune|Neptune]] such that its orbit can become significantly [[Astronomy:Perturbation|perturbed]] under the gravitational influence of Neptune.<ref name="Buie"/> Quaoar's [[Astronomy:Minimum orbit intersection distance|minimum orbit intersection distance]] from Neptune is only 12.3&nbsp;AU—it does not approach Neptune within this distance over the course of its orbit, as it is not in a mean-motion orbital resonance with Neptune.<ref name="MPC-object"/><ref name="Buie"/> Simulations by the [[Astronomy:Deep Ecliptic Survey|Deep Ecliptic Survey]] show that the perihelion and aphelion distances of Quaoar's orbit do not change significantly over the next 10 million years; Quaoar's orbit appears to be stable over the long term.<ref name="Buie"/>

Quaoar is generally classified as a trans-Neptunian object or [[Astronomy:Distant minor planet|distant minor planet]] by the Minor Planet Center since it orbits in the outer Solar System beyond Neptune.<ref name="MPC-object"/><ref name="jpldata"/> Since Quaoar is not in a mean-motion resonance with Neptune, it is also classified as a [[Astronomy:Classical Kuiper belt object|classical Kuiper belt object]] (cubewano) by the Minor Planet Center and Deep Ecliptic Survey.<ref name="Buie"/><ref name="MPEC-2008-O05"/> Quaoar's orbit is moderately inclined to the [[Astronomy:Ecliptic|ecliptic]] plane by 8 degrees, relatively high when compared to the inclinations of Kuiper belt objects within the dynamically cold population.<ref name="plutokiller"/><ref name="Delsanti2006"/> Because Quaoar's [[Astronomy:Orbital inclination|orbital inclination]] is greater than 4 degrees, it is part of the dynamically hot population of high-inclination classical Kuiper belt objects.<ref name="Delsanti2006"/> The high inclinations of hot classical Kuiper belt objects such as Quaoar are thought to have resulted from gravitational scattering by Neptune during its outward [[Astronomy:Planetary migration|migration]] in the early Solar System.<ref name="Levison2008"/>

== Physical characteristics ==
[[File:Artist impression of Quaoar and its ring ESA24681885.jpeg|thumb|upright=2.5|Artist's impression of Quaoar with its ring and its moon Weywot]]

Quaoar's [[Earth:Albedo|albedo]] or reflectivity could be as low as 0.1, similar to {{dp|Varuna}}'s albedo of 0.127.<ref name="TNOsCool9"/> This may indicate that fresh ice has disappeared from Quaoar's surface.<ref name="Fraser2010"/> The surface is moderately red, meaning that Quaoar is relatively more reflective in the red and near-infrared spectrum than in the blue.<ref name="Jewitt2004"/> The Kuiper belt objects Varuna and {{dp|Ixion}} are also moderately red in the spectral class. Larger Kuiper belt objects are often much brighter because they are covered in more fresh ice and have a higher albedo, and thus they present a neutral color.<ref name="Brown2008"/> A 2006 model of internal heating via [[Physics:Radioactive decay|radioactive decay]] suggested that Quaoar may not be capable of sustaining an internal ocean of liquid water at the mantle–core boundary.<ref name="Hussman2006"/>

The presence of methane and other [[Earth:Volatile (astrogeology)|volatiles]] on Quaoar's surface suggest that it may support a tenuous [[Astronomy:Atmosphere|atmosphere]] produced from the [[Sublimation (phase transition)|sublimation]] of volatiles.<ref name="Fraser2013b"/> With a measured mean temperature of ~ {{cvt|44|K|C}}, the upper limit of Quaoar's [[Physics:Atmospheric pressure|atmospheric pressure]] is expected to be in the range of a few microbars.<ref name="Fraser2013b"/> Due to Quaoar's small size and mass, the possibility of Quaoar having an atmosphere of [[Chemistry:Nitrogen|nitrogen]] and [[Chemistry:Carbon monoxide|carbon monoxide]] has been ruled out, since the gases would escape from Quaoar.<ref name="Fraser2013b"/> The possibility of a methane atmosphere, with the upper limit being less than 1 microbar,<ref name="Braga-Ribas2013"/><ref name="Fraser2013b"/> was considered until 2013, when Quaoar occulted a 15.8-magnitude star and revealed no sign of a substantial atmosphere, placing an upper limit to at least 20 nanobars, under the assumption that Quaoar's mean temperature is {{cvt|42|K|C}} and that its atmosphere consists of mostly methane.<ref name="Braga-Ribas2013"/><ref name="Fraser2013b"/> The upper limit of atmosphere pressure was tightened to 10 nanobars after another stellar occultation in 2019.<ref name="Arimatsu2019"/>

=== Mass and density ===
Because Quaoar is a [[Astronomy:Minor-planet moon|binary]] object, the mass of the system can be calculated from the orbit of the secondary. Quaoar's estimated density of around {{val|2.2|u=g/cm3}} and estimated size of {{cvt|1110|km}} suggests that it is a [[Astronomy:Dwarf planet|dwarf planet]]. American astronomer [[Biography:Michael E. Brown|Michael Brown]] estimates that rocky bodies around {{cvt|900|km}} in diameter relax into [[Astronomy:Hydrostatic equilibrium|hydrostatic equilibrium]], and that icy bodies relax into hydrostatic equilibrium somewhere between {{cvt|200|km}} and {{cvt|400|km}}.<ref name="Brown-DP"/> With an estimated mass greater than {{val|1.6|e=21|u=kg}}, Quaoar has the mass and diameter "usually" required for being in hydrostatic equilibrium according to the [[Astronomy:IAU definition of planet#Draft proposal|2006 IAU draft definition of a planet]] (5{{e|20}} kg, 800&nbsp;km),<ref name="IAU0601"/> and Brown states that Quaoar "must be" a [[Astronomy:Dwarf planet|dwarf planet]].<ref name="Brown-dplist"/> Light-curve-amplitude analysis shows only small deviations, suggesting that Quaoar is indeed a spheroid with small albedo spots and hence a dwarf planet.<ref name="Tancredi2008"/> The IAU itself has called Quaoar a dwarf planet in a 2022–2023 annual report.<ref>{{cite web |url=https://www.iau.org/static/science/scientific_bodies/divisions/f/division-f-annual-report-2022-2023.pdf |title=Report of Division F “Planetary Systems and Astrobiology”: Annual Report 2022-23 |last= |first= |date=2022–2023 |website= |publisher=International Astronomical Union |access-date=8 December 2023 |quote= |archive-date=8 December 2023 |archive-url=https://web.archive.org/web/20231208112824/https://www.iau.org/static/science/scientific_bodies/divisions/f/division-f-annual-report-2022-2023.pdf |url-status=live }}</ref>

Planetary scientist [[Biography:Erik Ian Asphaug|Erik Asphaug]] has suggested that Quaoar may have collided with a much larger body, stripping the lower-density mantle from Quaoar, and leaving behind the denser core. He envisioned that Quaoar was originally covered by a mantle of ice that made it {{cvt|300|km}} to {{cvt|500|km}} bigger than its present size, and that it collided with another Kuiper belt object about twice its size—an object roughly the diameter of Pluto, or even approaching the size of [[Astronomy:Mars|Mars]].<ref name="Musser2009"/> This model was made assuming Quaoar actually had a density of 4.2&nbsp;g/cm<sup>3</sup>, but more recent estimates have given it a more Pluto-like density of only 2&nbsp;g/cm<sup>3</sup>, with no further need for the collision theory.<ref name="Braga-Ribas2013"/>

=== Size ===
{{TNO imagemap}}
{| class="wikitable floatleft" style="text-align: center; font-size: 0.9em; margin-right: 12px;"
|+ Size estimates for Quaoar
!Year!!Diameter (km)!!Method!!Refs
|-
|2004
|{{val|1260|190|fmt=commas}}
|imaging
|<ref name="Brown2004"/>
|-
|2007
|{{val|844|207|190}}
|thermal
|<ref name="Stansberry2008"/>
|-
|2010
|{{val|890|70}}
|thermal/imaging
|<ref name="Fraser2010"/>
|-
|2013
|{{val|1074|138|fmt=commas}}
|thermal
|<ref name="TNOsCool8"/>
|-
|2013
|{{val|1110|5|fmt=commas}}
|occultation
|<ref name="Braga-Ribas2013"/>
|-
|2023
|{{val|1086|4|fmt=commas}}
|occultation
|<ref name="Pereira2023"/>
|}
[[File:Quaoar, Earth & Moon size comparison.png|thumb|upright=1.5|right|Quaoar compared to the [[Astronomy:Earth|Earth]] and the Moon]]
[[File:Quaoar hubble.jpg|thumb|upright|right|Hubble photo used to measure size of Quaoar]]

Quaoar is thought to be an oblate spheroid around {{cvt|1110|km}} in diameter, being slightly flattened in shape.<ref name="Braga-Ribas2013"/><ref name="Arimatsu2019"/> The estimates come from observations of stellar occultations by Quaoar, in which it passes in front of a star, in 2013 and 2019.<ref name="Braga-Ribas2013"/><ref name="Arimatsu2019"/> Given that Quaoar has an estimated oblateness of {{val|0.0897|0.006}} and a measured equatorial diameter of {{val|1138|+48|-34|u=km|fmt=commas}}, Quaoar is believed to be in hydrostatic equilibrium, being described as a [[Astronomy:Maclaurin spheroid|Maclaurin spheroid]].<ref name="Braga-Ribas2013"/> Quaoar is about as large and massive as (if somewhat smaller than) Pluto's moon [[Astronomy:Charon (moon)|Charon]].{{efn|name=mass|Charon's mass is {{val|1.586|0.015|e=21|u=kg}}<ref name="Stern2018"/> while Quaoar's mass is {{val|1.4|0.1|e=21|u=kg}}.<ref name="TNOsCool8"/> Both values are approximately similar, though Charon is slightly more massive. In a similar case, Charon's diameter is {{val|1212|1|u=km|fmt=commas}} while Quaoar's diameter is {{val|1110|5|u=km|fmt=commas}}, being slightly smaller than Charon.}} Quaoar is roughly half the size of Pluto.<ref name="plutokiller"/>

Quaoar was the first [[Astronomy:Trans-Neptunian object|trans-Neptunian object]] to be measured ''directly'' from [[Astronomy:Hubble Space Telescope|Hubble Space Telescope]] images, using a method comparing images with the Hubble [[Physics:Point spread function|point spread function]] (PSF).<ref name="Brown2004"/> In 2004, Quaoar was estimated to have a diameter of {{cvt|1260|km}} with an uncertainty of {{cvt|190|km}}, using Hubble's measurements.<ref name="Brown2004"/><ref name="Braga-Ribas2011"/> Given its distance Quaoar is on the limit of Hubble's resolution of 40 milliarcseconds and its image is consequently "smeared" on a few adjacent pixels.<ref name="Brown2004"/> By comparing carefully this image with the images of stars in the background and using a sophisticated model of Hubble optics (PSF), Brown and Trujillo were able to find the best-fit disk size that would give a similar blurred image.<ref name="Brown2004"/> This method was also applied by the same authors to measure the size of the dwarf planet Eris.<ref name="Stansberry2008"/>

At the time of its discovery in 2002, Quaoar was the largest object found in the [[Astronomy:Solar System|Solar System]] since the discovery of [[Astronomy:Pluto|Pluto]].<ref name="plutokiller"/> Quaoar's size was subsequently revised downward and was later superseded in size as larger objects ({{dp|Eris}}, {{dp|Haumea}}, {{dp|Makemake}} and {{dp|Gonggong}}) were discovered. The uncorrected 2004 Hubble estimates only marginally agree with the 2007 [[Physics:Infrared|infrared]] measurements by the [[Astronomy:Spitzer Space Telescope|Spitzer Space Telescope]] that suggest a higher [[Earth:Albedo|albedo]] (0.19) and consequently a smaller diameter ({{val|844.4|+206.7|-189.6|u=km}}).<ref name="Stansberry2008"/> Adopting a Uranian satellite [[Astronomy:Limb darkening|limb darkening]] profile suggests that the 2004 Hubble size estimate for Quaoar was approximately 40 percent too large, and that a more proper estimate would be about 900&nbsp;km.<ref name="Fraser2010"/> In 2010, Quaoar was estimated to be about {{val|890|u=km}} in diameter, using a weighted average of Spitzer and corrected Hubble estimates.<ref name="Fraser2010"/> In observations of the object's shadow as it occulted an unnamed 16th-magnitude star on 4 May 2011, Quaoar was estimated to be {{cvt|1170|km}} in diameter.<ref name="Braga-Ribas2011"/> Measurements from the [[Astronomy:Herschel Space Observatory|Herschel Space Observatory]] in 2013 suggested that Quaoar has a diameter of {{cvt|1070|km}}.<ref name="TNOsCool8"/> In that same year, Quaoar occulted a 15.8-magnitude star, with multiple positive detections yielding a mean diameter of {{val|1110|5|fmt=commas|u=km}}, consistent with the Herschel estimate.<ref name="Braga-Ribas2013"/> Another occultation by Quaoar in June 2019 yielded a similar chord length of {{val|1121|1.2|fmt=commas|u=km}}.<ref name="Arimatsu2019"/>

=== Rotation and shape ===
Rotational [[Astronomy:Light curve|light curve]]s of Quaoar observed on March through June 2003 gave two possible rotation periods: 8.64 hours for a single-peaked light curve by a [[Spheroid|spheroid]]al body, or 17.68 hours for a double-peaked light curve by an elongated [[Ellipsoid|ellipsoid]]al body.<ref name="Ortiz2003"/><ref name="Fraser2013a"/> The discovery of Quaoar's two rings in 2023 showed that its true rotation period should most likely be 17.68 hours in order to explain the rings' locations in stable spin-orbit resonances.<ref name="Morgado2023"/><ref name="Pereira2023"/> This in turn implies Quaoar should be somewhat elongated to induce such a resonance.<ref name="Morgado2023"/> Various occultation measurements of Quaoar's dimensions show that its diameter slightly varies at different epochs, further supporting the possibility of a triaxial ellipsoid shape for Quaoar.<ref name="Pereira2023"/>

=== Composition and cryovolcanism ===
In 2004, signs of [[Earth:Crystal|crystal]]line water [[Earth:Ice|ice]] were found on Quaoar, indicating that the temperature rose to at least {{cvt|110|K|C}} sometime in the last ten million years.<ref name="Jewitt2004"/> Speculation began as to what could have caused Quaoar to heat up from its natural temperature of {{cvt|55|K|C}}. Some have theorized that a barrage of mini-meteors may have raised the temperature, but the most discussed theory speculates that cryovolcanism may be occurring, spurred by the decay of [[Physics:Radioactive|radioactive]] elements within Quaoar's core.<ref name="Jewitt2004"/> Crystalline water ice was also found on {{dp|Haumea}} in 2006, but it is present in larger quantities and is thought to have originated from an impact.<ref name="Trujillo2007"/> 

More precise observations of Quaoar's near infrared spectrum in 2007 indicated the presence of small quantities (5%) of solid [[Chemistry:Methane|methane]] and [[Chemistry:Ethane|ethane]]. Given its [[Physics:Boiling point|boiling point]] of {{cvt|112|K|C}}, methane is a volatile ice at average surface temperatures of Quaoar, unlike water ice or ethane. Both models and observations suggest that only a few larger bodies ([[Astronomy:Pluto|Pluto]], {{dp|Eris}} and {{dp|Makemake}}) can retain the volatile ices whereas the dominant population of small [[Astronomy:Trans-Neptunian object|trans-Neptunian object]]s lost them. Quaoar, with only small amounts of methane, appears to be in an intermediary category.<ref name="Schaller2007"/> 

In 2022, near-infrared (0.7–5 &mu;m) [[Physics:Spectroscopy|spectroscopic]] observations by the [[Astronomy:James Webb Space Telescope|James Webb Space Telescope]] (JWST) revealed the presence of significant amounts of [[Chemistry:Ethane|ethane]] ice (C<sub>2</sub>H<sub>6</sub>) on the surface of Quaoar. The JWST spectra also contain evidence of presence of small amounts of [[Chemistry:Methane|methane]] (CH<sub>4</sub>) and [[Chemistry:Carbon dioxide|carbon dioxide]] (CO<sub>2</sub>) ices as well as complex organics. Other possible chemical compounds include [[Chemistry:Hydrogen cyanide|hydrogen cyanide]] (HCN) and [[Chemistry:Carbon monoxide|carbon monoxide]] (CO).<ref name="Emery2024"/>

== Ring–moon system ==
=== Satellite ===
Quaoar has one known moon, Weywot (full designation ''(50000) Quaoar I Weywot''), discovered in 2006 and named after the sky god Weywot, son of Quaoar.<ref name="IAUC8812"/><ref name=Search>[http://www.searchmagazine.org/Archives/Back%20Issues/July-August%202008/full-heavenly-bodies.html "Heavenly Bodies and the People of the Earth"] {{Webarchive|url=https://archive.today/20090105205052/http://www.searchmagazine.org/Archives/Back%20Issues/July-August%202008/full-heavenly-bodies.html |date=5 January 2009 }}, Nick Street, ''Search Magazine,'' July/August 2008</ref> It orbits Quaoar at distance of about 13,300&nbsp;km and is thought to be approximately {{cvt|170|km}} in diameter.<ref name="JOA2020-1"/>

=== Discovery of rings===
[[File:Quaoar rings 2022-08-09 occultation chord.png|thumb|upright=2|[[Astronomy:Light curve|Light curve]] graph of a star's brightness as seen by the Gemini North Observatory during the 9 August 2022 occultation by Quaoar and its two rings. The asymmetry of the outer Q1R ring's opacity is apparent from its differing brightness dips before and after the occultation by Quaoar at the center.]]
Besides accurately determining sizes and shapes, stellar occultation campaigns were planned on a long-term basis to search for rings and/or atmospheres around small bodies of the outer solar system. These campaigns agglomerated efforts of various teams in France, Spain and Brazil and were conducted under the umbrella of the European Research Council project ''Lucky Star''.<ref name="Morgado2023"/> The discovery of Quaoar's first known ring, Q1R, involved various instruments used during stellar occultations observed between 2018 and 2021: the robotic ATOM telescope of the [[Astronomy:High Energy Stereoscopic System|High Energy Stereoscopic System]] (HESS) in Namibia, the 10.4-m [[Astronomy:Gran Telescopio Canarias|Gran Telescopio Canarias]] (La Palma Island, Spain); the ESA [[Astronomy:CHEOPS|CHEOPS]] space telescope, and several stations run by citizen astronomers in Australia where a report of a Neptune-like ring originated and a dense arc in Q1R was first observed.<ref name="Morgado2023"/><ref name="ESA-20230208"/><ref name="S&T-20230507"/> Taken together, these observations reveal the presence of a partly dense, mostly tenuous and uniquely distant ring around Quaoar, a discovery announced in February 2023.<ref name="Morgado2023"/><ref name="ESA-20230208"/>

In April 2023, astronomers of the ''Lucky Star'' project published the discovery of another ring of Quaoar, Q2R.<ref name="Pereira2023"/> The Q2R ring was detected by the highly-sensitive 8.2-m Gemini North and the 4.0-m Canada-France-Hawaii Telescope in Mauna Kea, Hawaii, during an observing campaign to confirm Quaoar's Q1R ring in a stellar occultation on 9 August 2022.<ref name="Pereira2023"/> Quaoar is the third minor planet known and confirmed to have a [[Astronomy:Ring system|ring system]], after [[Astronomy:10199 Chariklo|10199 Chariklo]] and 136108 Haumea.<ref name="Morgado2023"/>{{efn|[[Astronomy:2060 Chiron|2060 Chiron]] is also thought to have rings, but the evidence is tentative.}}

=== Ring properties ===
{{multiple image
 |direction = vertical
 |align = right
 |total_width = 300
 |header = Orbit diagrams of the Quaoar–Weywot system
 |image1 = Quaoar-Weywot orbit diagram projected.png |caption1 = Viewed from Earth
 |image2 = Quaoar-Weywot orbit diagram top.png |caption2 = Viewed top-down over Quaoar's north pole
}}

Quaoar possesses two narrow rings, provisionally named Q1R and Q2R by order of discovery, which are confined at radial distances where their orbital periods are integer ratios of Quaoar's rotational period. That is, the rings of Quaoar are in spin-orbit resonances.<ref name="Pereira2023"/>

{| class="wikitable"
|+ Ring–moon system data<ref name="Pereira2023"/>
|- 
|colspan=4 align=center|'''Rings'''
|-
! Ring<br />designation
! Radius<br />(km)
! Width<br />(km)
! [[Physics:Optical depth|Optical depth]]<br />(τ)
|-
! Q2R
| {{val|2520|20}}
| 10
| ≈0.004
|-
! Q1R
| {{val|4057|6}}
| 5–300
| 0.004–0.7
|- 
|colspan=4 align=center|'''Moon'''
|-
! Name
! Semi-major axis<br />(km)
! Diameter<br />(km)
! Period<br />(days)
|-
! Weywot
| {{val|13289|189}}
| 170
| {{val|12.4311|0.0015}}
|}

The outer ring, Q1R, orbits Quaoar at a distance of {{cvt|4057 ± 6|km|mi|0}}, over seven times the radius of Quaoar and more than double the theoretical maximum distance of the [[Physics:Roche limit|Roche limit]].<ref name="Pereira2023"/> The Q1R ring is not uniform and is strongly irregular around its circumference, being more opaque (and denser) where it is narrow and less opaque where it is broader.<ref name="Morgado2023" /> The Q1R ring's radial width ranges from {{cvt|5|to|300|km|mi|sigfig=1}} while its [[Physics:Optical depth|optical depth]] ranges from 0.004 to 0.7.<ref name="Pereira2023"/> The irregular width of the Q1R ring resembles [[Astronomy:Saturn|Saturn]]'s frequently-[[Astronomy:Perturbation|perturbed]] F ring or [[Astronomy:Neptune|Neptune]]'s [[Astronomy:Rings of Neptune|ring arc]]s, which may imply the presence of small, kilometer-sized [[Astronomy:Moonlet|moonlet]]s embedded within the Q1R ring and gravitationally perturbing the material. The Q1R ring likely consists of icy particles that [[Physics:Elastic collision|elastically collide]] with each other without accreting into a larger mass.<ref name="Morgado2023" />

Q1R is located in between the 6:1 mean-motion orbital resonance with Quaoar's moon Weywot at {{cvt|4021 ± 57|km|mi|0}} and Quaoar's 1:3 spin-orbit resonance at {{cvt|4197 ± 58|km|mi|0}}. The Q1R ring's coincidental location at these resonances implies they play a key role in maintaining the ring without having it accrete into a single moon.<ref name="Morgado2023"/> In particular, the confinement of rings to the 1:3 spin-orbit resonance may be common among ringed small Solar System bodies, as it has been previously seen in Chariklo and Haumea.<ref name="Morgado2023"/>

The inner ring, Q2R, orbits Quaoar at a distance of {{cvt|2520 ± 20|km|mi|0}}, about four and a half times Quaoar's radius and also outside Quaoar's Roche limit.<ref name="Pereira2023"/> The Q2R ring's location coincides with Quaoar's 5:7 spin-orbit resonance at {{cvt|2525 ± 58|km|mi|0}}. Compared to Q1R, the Q2R ring appears relatively uniform with a radial width of {{cvt|10|km|mi}}. With an optical depth of 0.004, the Q2R ring is very tenuous and its opacity is comparable to the least dense part of the Q1R ring.<ref name="Pereira2023"/>

== Exploration ==
[[File:Quaoar_animation_dark_crsub_circle.gif|thumb|Quaoar from ''New Horizons'' viewed at a distance of 14 AU]]

It has been calculated that a flyby mission to Quaoar using a Jupiter gravity assist would take 13.6 years, for launch dates of 25 December 2026, 22 November 2027, 22 December 2028, 22 January 2030 and 20 December 2040. Quaoar would be 41 to 43 AU from the Sun when the spacecraft arrived.<ref name="McGranaghan2011"/> In July 2016, the [[Astronomy:Long Range Reconnaissance Imager|Long Range Reconnaissance Imager]] (LORRI) aboard the ''[[Astronomy:New Horizons|New Horizons]]'' spacecraft took a sequence of four images of Quaoar from a distance of about 14&nbsp;AU.<ref name="NH-Quaoar"/> ''[[Engineering:Interstellar Probe (spacecraft)|Interstellar Probe]]'', a concept by Pontus Brandt and his colleagues at Johns Hopkins [[Organization:Applied Physics Laboratory|Applied Physics Laboratory]] would potentially fly by Quaoar in the 2030s before continuing to the [[Astronomy:Interstellar medium|interstellar medium]], and the first of [[Organization:China National Space Administration|China National Space Administration]]'s proposed ''Shensuo'' probe designed to explore the heliosphere has it considered as a potential flyby target.<ref name="AGU334466"/><ref name="AGU394448"/><ref name="SpaceNews">{{cite news |last1=Jones |first1=Andrew |title=China to launch a pair of spacecraft towards the edge of the solar system |url=https://spacenews.com/china-to-launch-a-pair-of-spacecraft-towards-the-edge-of-the-solar-system/ |access-date=29 April 2021 |work=SpaceNews |publisher=SpaceNews |date=16 April 2021 |archive-date=29 September 2021 |archive-url=https://web.archive.org/web/20210929080320/https://spacenews.com/china-to-launch-a-pair-of-spacecraft-towards-the-edge-of-the-solar-system/ |url-status=live }}</ref> Quaoar has been chosen as a flyby target for missions like these particularly for its [[Earth:Atmospheric escape|escaping methane atmosphere]] and possible cryovolcanism, as well as its close proximity to the [[Astronomy:Heliosphere|heliospheric nose]].<ref name="AGU334466"/>
{{clear|left}}

== Notes ==
{{notelist}}

== References ==
{{Reflist|30em|refs=

<ref name="jpldata">{{cite web
 |type         = 2019-08-31 last obs.
 |title        = JPL Small-Body Database Browser: 50000 Quaoar (2002 LM60)
 |url          = https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2050000
 |publisher    = [[Organization:Jet Propulsion Laboratory|Jet Propulsion Laboratory]]
 |date         = 24 September 2019
 |access-date  = 20 February 2020
 |archive-date = 9 April 2020
 |archive-url  = https://web.archive.org/web/20200409035545/https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2050000
 |url-status   = live
}}</ref>

<ref name="MPC-object">{{cite web
 |title        = 50000 Quaoar (2002 LM60)
 |publisher    = International Astronomical Union
 |work         = Minor Planet Center
 |url          = https://www.minorplanetcenter.net/db_search/show_object?object_id=50000
 |access-date  = 30 November 2017
 |archive-date = 1 December 2017
 |archive-url  = https://web.archive.org/web/20171201032222/http://www.minorplanetcenter.net/db_search/show_object?object_id=50000
 |url-status   = live
}}</ref>

<ref name="lcdb">{{cite web
 |title       = LCDB Data for (50000) Quaoar
 |work       = Asteroid Lightcurve Database
 |url       = http://www.minorplanet.info/PHP/generateOneAsteroidInfo.php?AstInfo=50000%7CQuaoar
 |access-date       = 30 November 2017
 |archive-date       = 3 October 2020
 |archive-url       = https://web.archive.org/web/20201003200841/http://www.minorplanet.info/PHP/generateOneAsteroidInfo.php?AstInfo=50000%7CQuaoar
 |url-status       = live
 }}</ref>

<!--<ref name="johnston-list">{{cite web
 |title       = List of Known Trans-Neptunian Objects
 |url         = http://www.johnstonsarchive.net/astro/tnoslist.html
 |work        = Johnston's Archive
 |last        = Johnston |first = W. R.
 |date        = 27 December 2019
 |access-date = 21 January 2020}}</ref>-->

<ref name="Buie">{{cite web
 |title        = Orbit Fit and Astrometric record for 50000
 |url          = http://www.boulder.swri.edu/~buie/kbo/astrom/50000.html
 |last         = Buie
 |first        = M. W.
 |publisher    = Southwest Research Institute
 |access-date  = 27 February 2018
 |archive-date = 29 January 2020
 |archive-url  = https://web.archive.org/web/20200129011518/https://www.boulder.swri.edu/~buie/kbo/astrom/50000.html
 |url-status   = live
}}</ref>

<ref name="HORIZONS">{{cite web
 |type         = (Select Ephemeris Type: Observer, Observer Location: @sun, and Time Span: Start=1932-01-01, Step=1 d)
 |title        = Horizon Online Ephemeris System for 50000 Quaoar (2002 LM60)
 |url          = http://ssd.jpl.nasa.gov/horizons.cgi?find_body=1&body_group=sb&sstr=50000
 |publisher    = Jet Propulsion Laboratory
 |access-date  = 24 January 2020
 |archive-date = 9 April 2020
 |archive-url  = https://web.archive.org/web/20200409035556/https://ssd.jpl.nasa.gov/horizons.cgi?find_body=1&body_group=sb&sstr=50000
 |url-status   = live
}}</ref>

<ref name="Nomenclature">{{cite web
 |title        = How Are Minor Planets Named?
 |url          = https://minorplanetcenter.net/iau/info/HowNamed.html
 |publisher    = International Astronomical Union
 |work         = Minor Planet Center
 |access-date  = 5 January 2017
 |archive-date = 25 January 2021
 |archive-url  = https://web.archive.org/web/20210125062316/https://minorplanetcenter.net//iau/info/HowNamed.html
 |url-status   = live
}}</ref>

<ref name="Brown-dplist">{{cite web
 |title        = How many dwarf planets are there in the outer solar system?
 |url          = http://web.gps.caltech.edu/~mbrown/dps.html
 |first        = Michael E.
 |last         = Brown
 |publisher    = California Institute of Technology
 |access-date  = 27 February 2018
 |archive-date = 18 October 2018
 |archive-url  = https://web.archive.org/web/20181018043029/http://web.gps.caltech.edu/~mbrown/dps.html
 |url-status   = live
}}</ref>

<ref name="Brown-DP">{{cite web
 |title        = The Dwarf Planets
 |url          = http://web.gps.caltech.edu/~mbrown/dwarfplanets/
 |first        = Michael E.
 |last         = Brown
 |publisher    = California Institute of Technology
 |access-date  = 27 February 2018
 |archive-date = 29 January 2008
 |archive-url  = https://web.archive.org/web/20080129195021/http://web.gps.caltech.edu/~mbrown/dwarfplanets/
 |url-status   = live
}}</ref>

<ref name="HST-9678">{{cite journal
 |title        = Direct Measurement of the Size of the Largest Kuiper Belt Object
 |url          = https://www.stsci.edu/hst/phase2-public/9678.prop
 |first        = Michael E.
 |last         = Brown
 |pages        = 9678
 |journal      = Mikulski Archive for Space Telescopes
 |publisher    = Space Telescope Science Institute
 |date         = 18 June 2002
 |access-date  = 8 January 2020
 |bibcode      = 2002hst..prop.9678B
 |archive-date = 3 October 2020
 |archive-url  = https://web.archive.org/web/20201003145607/https://www.stsci.edu/hst/phase2-public/9678.prop
 |url-status   = dead
}}</ref>

<ref name="MPEC-2002-T34">{{cite web
 |title        = MPEC 2002-T34 : 2002 LM60
 |url          = https://www.minorplanetcenter.net/mpec/K02/K02T34.html
 |last         = Marsden
 |first        = Brian G.
 |work         = Minor Planet Electronic Circular
 |publisher    = Minor Planet Center
 |date         = 7 October 2002
 |access-date  = 8 January 2020
 |archive-date = 7 February 2019
 |archive-url  = https://web.archive.org/web/20190207015217/https://www.minorplanetcenter.net/mpec/K02/K02T34.html
 |url-status   = live
}}</ref>

<ref name="FAQ-Quaoar">{{cite web
 |title        = Frequently Asked Questions About Quaoar
 |url          = http://www.chadtrujillo.com/quaoar/
 |first        = Chad |last = Trujillo
 |publisher    = Northern Arizona University
 |website      = physics.nau.edu
 |access-date  = 30 November 2017
 |url-status   = live
 |archive-url  = https://web.archive.org/web/20070211094355/http://www.chadtrujillo.com/quaoar/
 |archive-date = 11 February 2007}}</ref>

<ref name="precovery">{{cite web
 |title        = Quaoar Precoveries
 |url          = http://www.gps.caltech.edu/~chad/quaoar/precovery.html
 |first        = Chad |last = Trujillo
 |website      = www.chadtrujillo.com
 |access-date  = 30 November 2017
 |url-status   = dead
 |archive-url  = https://web.archive.org/web/20021206194727/http://www.gps.caltech.edu/~chad/quaoar/precovery.html
 |archive-date = 6 December 2002}}</ref>

<ref name="hubblesite">{{cite web
 |title        = Hubble Spots an Icy World Far Beyond Pluto
 |url          = http://hubblesite.org/newscenter/archive/releases/2002/17/text/
 |work         = HubbleSite
 |publisher    = Space Telescope Science Institute
 |date         = 7 October 2002
 |url-status   = dead
 |archive-url  = https://web.archive.org/web/20070802014217/http://hubblesite.org/newscenter/archive/releases/2002/17/text/
 |archive-date = 2 August 2007}}</ref>

<ref name="caltech">{{cite web
 |title        = Caltech scientists find largest object in solar system since Pluto's discovery
 |url          = https://www.caltech.edu/about/news/caltech-scientists-find-largest-object-solar-system-plutos-discovery-618
 |first        = Elisabeth
 |last         = Nadin
 |work         = Caltech Matters
 |publisher    = California Institute of Technology
 |date         = 7 October 2002
 |access-date  = 8 January 2020
 |archive-date = 6 May 2020
 |archive-url  = https://web.archive.org/web/20200506160521/https://www.caltech.edu/about/news/caltech-scientists-find-largest-object-solar-system-plutos-discovery-618
 |url-status   = live
}}</ref>

<ref name="nasascience">{{cite web
 |title        = A Cold New World
 |url          = https://science.nasa.gov/science-news/science-at-nasa/2002/07oct_newworld
 |work         = NASA Science
 |publisher    = NASA
 |date         = 7 October 2002
 |access-date  = 8 January 2020
 |archive-date = 20 December 2019
 |archive-url  = https://web.archive.org/web/20191220043605/https://science.nasa.gov/science-news/science-at-nasa/2002/07oct_newworld
 |url-status   = live
}}</ref>

<ref name="NYT-20021008">{{cite news
 |title        = Telescopes Find a Miniplanet At the Solar System's Edge
 |url          = https://www.nytimes.com/2002/10/08/science/telescopes-find-a-miniplanet-at-the-solar-system-s-edge.html?searchResultPosition=3
 |first        = John Noble
 |last         = Wilford
 |work         = The New York Times
 |date         = 8 October 2002
 |access-date  = 8 January 2020
 |archive-date = 13 July 2020
 |archive-url  = https://web.archive.org/web/20200713105752/https://www.nytimes.com/2002/10/08/science/telescopes-find-a-miniplanet-at-the-solar-system-s-edge.html?searchResultPosition=3
 |url-status   = live
}}</ref>

<ref name="MPC41805">{{cite web
 |title        = M.P.C. 41805
 |url          = http://www.minorplanetcenter.org/iau/ECS/MPCArchive/2001/MPC_20010109.pdf
 |publisher    = International Astronomical Union
 |work         = Minor Planet Center
 |date         = 9 January 2001
 |access-date  = 15 March 2019
 |archive-date = 6 March 2012
 |archive-url  = https://web.archive.org/web/20120306024843/http://www.minorplanetcenter.org/iau/ECS/MPCArchive/2001/MPC_20010109.pdf
 |url-status   = live
}}</ref>
<!-- citation for Varuna's special numbering -->

<ref name="MPC47066">{{cite web
 |title        = M.P.C. 47066
 |url          = https://minorplanetcenter.net/iau/ECS/MPCArchive/2002/MPC_20021120.pdf
 |publisher    = International Astronomical Union
 |work         = Minor Planet Center
 |date         = 20 November 2002
 |access-date  = 4 December 2019
 |archive-date = 20 September 2021
 |archive-url  = https://web.archive.org/web/20210920103457/https://minorplanetcenter.net//iau/ECS/MPCArchive/2002/MPC_20021120.pdf
 |url-status   = live
}}</ref>
<!-- numbering of Quaoar -->

<ref name="Trujillo2003">{{cite journal
 |first1       = C. A.
 |last1        = Trujillo
 |first2       = M. E.
 |last2        = Brown
 |date         = June 2003
 |title        = The Caltech Wide Area Sky Survey
 |url          = http://web.gps.caltech.edu/~mbrown/papers/ps/wide.pdf
 |journal      = Earth, Moon, and Planets
 |volume       = 92
 |issue        = 1
 |pages        = L13–L16
 |doi          = 10.1023/B:MOON.0000031929.19729.a1
 |bibcode      = 2003EM&P...92...99T
 |s2cid        = 189905639
 |access-date  = 9 January 2020
 |archive-date = 3 October 2020
 |archive-url  = https://web.archive.org/web/20201003115156/http://web.gps.caltech.edu/~mbrown/papers/ps/wide.pdf
 |url-status   = live
}}</ref>

<ref name="Ortiz2003">{{cite journal
 |first1       = J. L.
 |last1        = Ortiz
 |first2       = P. J.
 |last2        = Gutiérrez
 |first3       = V.
 |last3        = Casanova
 |first4       = V. R.
 |last4        = Teixeira
 |date         = October 2003
 |title        = Rotational brightness variations in Trans-Neptunian Object 50000 Quaoar
 |url          = https://www.aanda.org/articles/aa/pdf/2003/38/aafg143.pdf
 |journal      = Astronomy & Astrophysics
 |volume       = 409
 |issue        = 2
 |pages        = L13–L16
 |doi          = 10.1051/0004-6361:20031253
 |bibcode      = 2003A&A...409L..13O
 |doi-access   = free
 |access-date  = 3 December 2019
 |archive-date = 12 May 2021
 |archive-url  = https://web.archive.org/web/20210512042020/https://www.aanda.org/articles/aa/pdf/2003/38/aafg143.pdf
 |url-status   = live
}}</ref>

<ref name="Brown2004">{{cite journal
 |first1       = Michael E.
 |last1        = Brown
 |first2       = Chadwick A.
 |last2        = Trujillo
 |date         = April 2004
 |title        = Direct Measurement of the Size of the Large Kuiper Belt Object (50000) Quaoar
 |url          = http://web.gps.caltech.edu/~mbrown/papers/ps/qu.pdf
 |journal      = The Astronomical Journal
 |volume       = 127
 |issue        = 4
 |pages        = 2413–2417
 |doi          = 10.1086/382513
 |bibcode      = 2004AJ....127.2413B
 |s2cid        = 1877283
 |access-date  = 27 February 2018
 |archive-date = 7 January 2018
 |archive-url  = https://web.archive.org/web/20180107175824/http://web.gps.caltech.edu/~mbrown/papers/ps/qu.pdf
 |url-status   = live
}}</ref>

<ref name="MPEC-2004-S73">{{cite web
 |title        = MPEC 2004-S73 : Editorial Notice
 |url          = https://minorplanetcenter.net/mpec/K04/K04S73.html
 |last         = Marsden
 |first        = Brian G.
 |work         = Minor Planet Electronic Circular
 |publisher    = Minor Planet Center
 |date         = 28 September 2004
 |access-date  = 8 January 2020
 |archive-date = 8 May 2020
 |archive-url  = https://web.archive.org/web/20200508090811/https://minorplanetcenter.net//mpec/K04/K04S73.html
 |url-status   = live
}}</ref>

<ref name="Jewitt2004">{{cite journal
 |first1       = David C.
 |last1        = Jewitt
 |first2       = Jane
 |last2        = Luu
 |title        = Crystalline water ice on the Kuiper belt object (50000) Quaoar
 |url          = http://www2.ess.ucla.edu/~jewitt/papers/2004/JL2004.pdf
 |date         = December 2004
 |journal      = Nature
 |volume       = 432
 |issue        = 7018
 |pages        = 731–733
 |doi          = 10.1038/nature03111
 |bibcode      = 2004Natur.432..731J
 |pmid         = 15592406
 |s2cid        = 4334385
 |access-date  = 14 April 2013
 |archive-date = 9 August 2017
 |archive-url  = https://web.archive.org/web/20170809002738/http://www2.ess.ucla.edu/~jewitt/papers/2004/JL2004.pdf
 |url-status   = live
}}</ref>

<ref name="Delsanti2006">{{cite book
 |first1        = Audrey |last1 = Delsanti
 |first2        = David |last2 = Jewitt
 |title         = Solar System Update
 |year          = 2006
 |publisher     = Springer
 |editor1-first = P. |editor1-last = Blonde
 |editor2-first = J. |editor2-last = Mason
 |chapter       = The Solar System Beyond The Planets
 |chapter-url   = http://www2.ess.ucla.edu/~jewitt/papers/2006/DJ06.pdf
 |pages         = 267–293
 |doi           = 10.1007/3-540-37683-6_11
 |bibcode       = 2006ssu..book..267D
 |isbn          = 3-540-26056-0
 |archive-url   = https://web.archive.org/web/20070925203400/http://www.ifa.hawaii.edu/faculty/jewitt/papers/2006/DJ06.pdf
 |archive-date  = 25 September 2007}}</ref>

<ref name="Schmadel2006">{{cite book
 |title        = Dictionary of Minor Planet Names – (50000) Quaoar, Addendum to Fifth Edition: 2003–2005
 |chapter-url  = https://books.google.com/books?id=aeAg1X7afOoC&q=%2850000%29+Quaoar&pg=PA1339
 |first        = Lutz D.
 |last         = Schmadel
 |publisher    = Springer Berlin Heidelberg
 |chapter      = (50000) Quaoar
 |page         = 1197
 |date         = 2006
 |isbn         = 978-3-540-00238-3
 |doi          = 10.1007/978-3-540-29925-7
 |url          = https://cds.cern.ch/record/1339660
 |access-date  = 7 December 2019
 |archive-date = 2 February 2020
 |archive-url  = https://web.archive.org/web/20200202044928/https://cds.cern.ch/record/1339660
 |url-status   = live
}}</ref>

<ref name="IAU0601">{{cite press release
 |title        = The IAU draft definition of "planet" and "plutons"
 |url          = https://www.iau.org/news/pressreleases/detail/iau0601/
 |publisher    = International Astronomical Union
 |date         = August 2006
 |access-date  = 27 February 2018
 |archive-date = 15 July 2009
 |archive-url  = https://web.archive.org/web/20090715110915/http://www.iau.org/public_press/news/release/iau0601/
 |url-status   = live
}}</ref>

<ref name="Hussman2006">{{cite journal
 |first1  = Hauke |last1 = Hussmann
 |first2  = Frank |last2 = Sohl
 |first3  = Tilman |last3 = Spohn
 |date    = November 2006
 |title   = Subsurface oceans and deep interiors of medium-sized outer planet satellites and large trans-neptunian objects
 |journal = Icarus
 |volume  = 185
 |issue   = 1
 |pages   = 258–273
 |doi     = 10.1016/j.icarus.2006.06.005
 |bibcode = 2006Icar..185..258H}}</ref>

<ref name="Trujillo2007">{{cite journal
 |first1  = Chadwick A. |last1 = Truijillo
 |first2  = Michael E. |last2 = Brown
 |first3  = Kristina M. |last3 = Barkume
 |first4  = Emily L. |last4 = Schaller
 |first5  = David L. |last5 = Rabinowitz
 |date    = February 2007
 |title   = The Surface of 2003<sub>EL61</sub> in the Near Infrared
 |journal = The Astrophysical Journal
 |volume  = 655
 |issue   = 2
 |pages   = 1172–1178
 |doi     = 10.1086/509861
 |arxiv   = astro-ph/0601618
 |bibcode = 2007ApJ...655.1172T|s2cid = 118938812
 }}</ref>

<ref name="Tegler2007">{{cite web
 |title        = Kuiper Belt Object Magnitudes and Surface Colors
 |url          = http://www.physics.nau.edu/~tegler/research/survey.htm
 |first        = Stephen C. |last = Tegler
 |publisher    = Northern Arizona University
 |date         = 1 February 2007
 |access-date  = 27 February 2018
 |archive-url  = https://web.archive.org/web/20060901063349/http://www.physics.nau.edu/~tegler/research/survey.htm
 |archive-date = 1 September 2006
 |url-status   = dead}}</ref>

<ref name="IAUC8812">{{cite periodical
 |title        = Satellites of 2003 AZ_84, (50000), (55637), and (90482)
 |number       = 8812
 |url          = http://www.cbat.eps.harvard.edu/iauc/08800/08812.html#Item1
 |editor-first = Daniel W. E. |editor-last = Green
 |periodical   = International Astronomical Union Circular
 |publisher    = International Astronomical Union
 |date         = 22 February 2007
 |bibcode      = 2007IAUC.8812....1B
 |issn         = 0081-0304
 |archive-url  = https://web.archive.org/web/20110719205520/http://www.cbat.eps.harvard.edu/iauc/08800/08812.html
 |archive-date = 19 July 2011
 |url-status   = live}}</ref>

<ref name="Schaller2007">{{cite journal
 |title   = Detection of Methane on Kuiper Belt Object (50000) Quaoar
 |first1  = E. L. |last1 = Schaller
 |first2  = M. E. |last2 = Brown
 |date    = November 2007
 |journal = The Astrophysical Journal
 |volume  = 670
 |issue   = 1
 |pages   = L49–L51
 |doi     = 10.1086/524140
 |arxiv   = 0710.3591
 |bibcode = 2007ApJ...670L..49S|s2cid = 18587369 }}</ref>

<!-- Distant objects list -->
<ref name="MPEC-2008-O05">{{cite web
 |title        = MPEC 2008-O05 : Distant Minor Planets (2008 Aug. 2.0 TT)
 |url          = https://minorplanetcenter.net/mpec/K08/K08O05.html
 |last         = Marsden
 |first        = Brian G.
 |work         = Minor Planet Electronic Circular
 |publisher    = Minor Planet Center
 |date         = 17 July 2008
 |access-date  = 27 February 2018
 |archive-date = 2 October 2018
 |archive-url  = https://web.archive.org/web/20181002121454/https://minorplanetcenter.net/mpec/K08/K08O05.html
 |url-status   = live
}}</ref>

<ref name="Levison2008">{{cite journal
 |first1  = Harold F. |last1 = Levison
 |first2  = Alessandro |last2 = Morbidelli
 |first3  = Christa |last3 = Van Laerhoven
 |first4  = Rodney S. |last4 = Gomes
 |first5  = Kleomenis |last5 = Tsiganis
 |title   = Origin of the Structure of the Kuiper Belt during a Dynamical Instability in the Orbits of Uranus and Neptune
 |date    = July 2008
 |journal = Icarus
 |volume  = 196
 |issue   = 1
 |pages   = 258–273
 |doi     = 10.1016/j.icarus.2007.11.035
 |arxiv   = 0712.0553
 |bibcode = 2008Icar..196..258L|s2cid = 7035885
 }}</ref>

<ref name="Tancredi2008">{{cite conference
 |title        = Which are the dwarfs in the solar system?
 |url          = http://www.lpi.usra.edu/meetings/acm2008/pdf/8261.pdf
 |last1        = Tancredi
 |first1       = G.
 |last2        = Favre
 |first2       = S.
 |date         = July 2008
 |conference   = Asteroids, Comets, Meteors
 |publisher    = Lunar and Planetary Institute
 |issue        = 1405
 |id           = 8261
 |bibcode      = 2008LPICo1405.8261T
 |access-date  = 25 August 2011
 |archive-date = 3 June 2016
 |archive-url  = https://web.archive.org/web/20160603215320/http://www.lpi.usra.edu/meetings/acm2008/pdf/8261.pdf
 |url-status   = live
}}</ref>

<ref name="Street2008">{{cite magazine
 |title        = Heavenly Bodies and the People of the Earth
 |url          = http://www.searchmagazine.org/Archives/Back%20Issues/2008%20July-August/full-heavenly-bodies.html
 |last         = Street |first = Nick
 |magazine     = Search Magazine
 |publisher    = Heldref Publications
 |date         = August 2008
 |access-date  = 8 January 2020
 |url-status   = dead
 |archive-url  = https://web.archive.org/web/20090518012454/http://www.searchmagazine.org/Archives/Back%20Issues/2008%20July-August/full-heavenly-bodies.html
 |archive-date = 18 May 2009}}</ref>

<ref name="Stansberry2008">{{cite book
 |first1       = John
 |last1        = Stansberry
 |first2       = Will
 |last2        = Grundy
 |first3       = Mike
 |last3        = Brown
 |first4       = Dale
 |last4        = Cruikshank
 |first5       = John
 |last5        = Spencer
 |first6       = David
 |last6        = Trilling
 |first7       = Jean-Luc
 |last7        = Margot
 |date         = 2008
 |chapter      = Physical Properties of Kuiper Belt and Centaur Objects: Constraints from the Spitzer Space Telescope
 |chapter-url  = https://www.lpi.usra.edu/books/ssbn2008/7017.pdf
 |title        = The Solar System Beyond Neptune
 |pages        = 161–179
 |publisher    = University of Arizona Press
 |isbn         = 978-0-8165-2755-7
 |arxiv        = astro-ph/0702538
 |bibcode      = 2008ssbn.book..161S
 |access-date  = 4 December 2019
 |archive-date = 21 September 2020
 |archive-url  = https://web.archive.org/web/20200921004939/https://www.lpi.usra.edu/books/ssbn2008/7017.pdf
 |url-status   = live
}}</ref>
<!-- https://www.lpi.usra.edu/books/ssbn2008/download.html -->

<ref name="Brown2008">{{cite book
 |first        = Michael E.
 |last         = Brown
 |date         = 2008
 |chapter      = The Largest Kuiper Belt Objects
 |chapter-url  = http://web.gps.caltech.edu/~mbrown/out/kbbook/Chapters/Brown_Planetoids.pdf
 |title        = The Solar System Beyond Neptune
 |pages        = 335–344
 |publisher    = University of Arizona Press
 |isbn         = 978-0-8165-2755-7
 |bibcode      = 2008ssbn.book..335B
 |access-date  = 15 March 2019
 |archive-date = 27 March 2019
 |archive-url  = https://web.archive.org/web/20190327090458/http://web.gps.caltech.edu/~mbrown/out/kbbook/Chapters/Brown_Planetoids.pdf
 |url-status   = live
}}</ref>

<ref name="Musser2009">{{cite magazine
 |title        = What do we really know about the Kuiper Belt? Fifth dispatch from the annual planets meeting
 |url          = http://blogs.scientificamerican.com/observations/what-do-we-really-know-about-the-kuiper-belt-fifth-dispatch-from-the-annual-planets-meeting/
 |first        = George |last = Musser
 |magazine     = Scientific American
 |date         = 13 October 2009
 |archive-url  = https://web.archive.org/web/20091014222424/http://www.scientificamerican.com/blog/post.cfm?id=what-do-we-really-know-about-the-ku-2009-10-13
 |archive-date = 14 October 2009
 |url-status   = live}}</ref>

<ref name="Fraser2010">{{cite journal
 |first1  = Wesley C. |last1 = Fraser
 |first2  = Michael E. |last2 = Brown
 |date    = May 2010
 |title   = Quaoar: A Rock in the Kuiper Belt
 |journal = The Astrophysical Journal
 |volume  = 714
 |issue   = 2
 |pages   = 1547–1550
 |doi     = 10.1088/0004-637X/714/2/1547
 |arxiv   = 1003.5911
 |bibcode = 2010ApJ...714.1547F|s2cid = 17386407
 }}</ref>

<ref name="McGranaghan2011">{{cite journal
 |first1       = Ryan
 |last1        = McGranaghan
 |first2       = Brent
 |last2        = Sagan
 |first3       = Gemma
 |last3        = Dove
 |first4       = Aaron
 |last4        = Tullos
 |first5       = James E.
 |last5        = Lyne
 |first6       = Joshua P.
 |last6        = Emery
 |date         = September 2011
 |title        = A Survey of Mission Opportunities to Trans-Neptunian Objects
 |url          = https://www.researchgate.net/publication/258495993
 |journal      = Journal of the British Interplanetary Society
 |volume       = 64
 |pages        = 296–303
 |bibcode      = 2011JBIS...64..296M
 |access-date  = 5 December 2019
 |archive-date = 29 January 2020
 |archive-url  = https://web.archive.org/web/20200129011416/https://www.researchgate.net/publication/258495993
 |url-status   = live
}}</ref>

<ref name="Braga-Ribas2011">{{cite conference
 |display-authors = etal
 |first1          = F.
 |last1           = Braga-Ribas
 |first2          = B.
 |last2           = Sicardy
 |first3          = J. L.
 |last3           = Ortiz
 |first4          = E.
 |last4           = Jehin
 |first5          = J. I. B.
 |last5           = Camargo
 |first6          = M.
 |last6           = Assafin
 |date            = October 2011
 |title           = Stellar Occultations by TNOs: the January 08, 2011 by (208996) 2003 AZ84 and the May 04, 2011 by (50000) Quaoar
 |url             = http://meetingorganizer.copernicus.org/EPSC-DPS2011/EPSC-DPS2011-1060-1.pdf
 |conference      = EPSC-DPS Joint Meeting 2011
 |publisher       = European Planetary Science Congress
 |volume          = 6
 |access-date     = 17 January 2012
 |archive-date    = 17 April 2012
 |archive-url     = https://web.archive.org/web/20120417044313/http://meetingorganizer.copernicus.org/EPSC-DPS2011/EPSC-DPS2011-1060-1.pdf
 |url-status      = live
}}</ref>

<ref name="Fraser2013a">{{cite journal
 |first1    = Wesley C. |last1 = Fraser
 |first2    = Konstantin |last2 = Batygin
 |first3    = Michael E. |last3 = Brown
 |first4    = Antonin |last4 = Bouchez
 |date      = January 2013
 |title     = The mass, orbit, and tidal evolution of the Quaoar–Weywot system
 |journal   = Icarus
 |volume    = 222
 |issue     = 1
 |pages     = 357–363
 |doi       = 10.1016/j.icarus.2012.11.004
 |arxiv     = 1211.1016
 |bibcode   = 2013Icar..222..357F
 |citeseerx = 10.1.1.441.8949|s2cid = 17196395
 }}</ref>

<ref name="TNOsCool8">{{cite journal
 |display-authors = etal
 |first1          = S. |last1 = Fornasier
 |first2          = E. |last2 = Lellouch
 |first3          = T. |last3 = Müller
 |first4          = P. |last4 = Santos-Sanz
 |first5          = P. |last5 = Panuzzo
 |first6          = C. |last6 = Kiss
 |date            = July 2013
 |title           = TNOs are Cool: A survey of the trans-Neptunian region. VIII. Combined Herschel PACS and SPIRE observations of nine bright targets at 70–500 μm
 |journal         = Astronomy & Astrophysics
 |volume          = 555
 |issue           = A15
 |page            = 22
 |doi             = 10.1051/0004-6361/201321329
 |arxiv           = 1305.0449v2
 |bibcode         = 2013A&A...555A..15F|s2cid = 119261700 }}</ref>

<ref name="Braga-Ribas2013">{{cite journal
 |display-authors = etal
 |first1          = F.
 |last1           = Braga-Ribas
 |first2          = B.
 |last2           = Sicardy
 |first3          = J. L.
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 |first4          = E.
 |last4           = Lellouch
 |first5          = G.
 |last5           = Tancredi
 |first6          = J.
 |last6           = Lecacheux
 |date            = August 2013
 |title           = The Size, Shape, Albedo, Density, and Atmospheric Limit of Transneptunian Object (50000) Quaoar from Multi-chord Stellar Occultations
 |journal         = The Astrophysical Journal
 |volume          = 773
 |issue           = 1
 |page            = 13
 |doi             = 10.1088/0004-637X/773/1/26
 |bibcode         = 2013ApJ...773...26B
 |hdl             = 11336/1641
 |s2cid           = 53724395
 |url             = https://orbi.uliege.be/handle/2268/156970
 |hdl-access      = free
 |access-date     = 29 April 2021
 |archive-date    = 21 April 2022
 |archive-url     = https://web.archive.org/web/20220421180714/https://orbi.uliege.be/handle/2268/156970
 |url-status      = live
}}</ref>

<ref name="TNOsCool9">{{cite journal
 |display-authors = etal
 |first1          = E.
 |last1           = Lellouch
 |first2          = P.
 |last2           = Santos-Sanz
 |first3          = P.
 |last3           = Lacerda
 |first4          = M.
 |last4           = Mommert
 |first5          = R.
 |last5           = Duffard
 |first6          = J. L.
 |last6           = Ortiz
 |date            = September 2013
 |title           = "TNOs are Cool": A survey of the trans-Neptunian region. IX. Thermal properties of Kuiper belt objects and Centaurs from combined Herschel and Spitzer observations
 |url             = http://www.aanda.org/articles/aa/pdf/2013/09/aa22047-13.pdf
 |journal         = Astronomy & Astrophysics
 |volume          = 557
 |issue           = A60
 |pages           = 19
 |doi             = 10.1051/0004-6361/201322047
 |bibcode         = 2013A&A...557A..60L
 |doi-access      = free
 |access-date     = 23 October 2019
 |archive-date    = 31 October 2019
 |archive-url     = https://web.archive.org/web/20191031112734/https://www.aanda.org/articles/aa/pdf/2013/09/aa22047-13.pdf
 |url-status      = live
}}</ref>

<ref name="plutokiller">{{cite book
 |title      = How I Killed Pluto and Why It Had It Coming
 |title-link = How I Killed Pluto and Why It Had It Coming
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 |pages      = [https://archive.org/details/howikilledplutow00mike/page/63 63–85]
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<ref name="Fraser2013b">{{cite journal
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 |first7  = J. J. |last7 = Kavelaars
 |date    = September 2013
 |title   = Limits on Quaoar's Atmosphere
 |journal = The Astrophysical Journal Letters
 |volume  = 774
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 |doi     = 10.1088/2041-8205/774/2/L18
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<ref name="Belskaya2015">{{cite journal
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 |bibcode = 2015Icar..250..482B}}</ref>

<ref name="NH-Quaoar">{{cite web
 |title        = New Horizons Spies a Kuiper Belt Companion
 |url          = http://pluto.jhuapl.edu/Multimedia/Science-Photos/image.php?gallery_id=2&image_id=459
 |website      = pluto.jhuapl.edu
 |publisher    = Johns Hopkins University Applied Physics Laboratory
 |date         = 31 August 2016
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 |archive-url  = https://web.archive.org/web/20171115201511/http://pluto.jhuapl.edu/Multimedia/Science-Photos/image.php?gallery_id=2&image_id=459
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<ref name="AGU334466">{{cite conference
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 |url             = https://www.hou.usra.edu/meetings/V2050/pdf/8173.pdf
 |conference      = Planetary Science Vision 2050 Workshop
 |publisher       = Lunar and Planetary Institute
 |id              = 8173
 |date            = February 2017
 |access-date     = 24 July 2018
 |bibcode         = 2017LPICo1989.8173B
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 |archive-url     = https://web.archive.org/web/20210313011632/https://www.hou.usra.edu/meetings/V2050/pdf/8173.pdf
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<ref name="Stern2018">{{cite journal
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 |date            = September 2018
 |title           = The Pluto System After New Horizons
 |journal         = Annual Review of Astronomy and Astrophysics
 |volume          = 56
 |pages           = 357–392
 |doi             = 10.1146/annurev-astro-081817-051935
 |arxiv           = 1712.05669
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<ref name="AGU394448">{{cite conference
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 |first4       = P. C.
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 |first5       = R. L.
 |last5        = McNutt
 |title        = Kuiper Belt Planet Geoscience from Interstellar Probe
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 |conference   = AGU Fall Meeting 2018
 |publisher    = American Geophysical Union
 |id           = SH32C-10
 |date         = December 2018
 |access-date  = 30 March 2019
 |bibcode      = 2018AGUFMSH32C..10R
 |archive-date = 3 October 2020
 |archive-url  = https://web.archive.org/web/20201003164445/https://agu.confex.com/agu/fm18/meetingapp.cgi/Paper/394448
 |url-status   = live
}}</ref>

<ref name="JOA2020-1">{{cite journal
 |title        = Beyond Jupiter – (50000) Quaoar
 |url          = http://iota-es.de/JOA/JOA2020_1.pdf
 |first        = M.
 |last         = Kretlow
 |date         = January 2020
 |journal      = Journal for Occultation Astronomy
 |volume       = 10
 |issue        = 1
 |pages        = 24–31
 |bibcode      = 2020JOA....10a..24K
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}}</ref>

<ref name="Grundy-orbits">{{cite web
 |title        = Quaoar and Weywot (50000 2002 LM60)
 |url          = http://www2.lowell.edu/users/grundy/tnbs/50000_2002_LM60_Quaoar.html
 |first        = Will
 |last         = Grundy
 |publisher    = Lowell Observatory
 |date         = 5 November 2019
 |access-date  = 2 December 2019
 |archive-date = 25 March 2019
 |archive-url  = https://web.archive.org/web/20190325013632/http://www2.lowell.edu/users/grundy/tnbs/50000_2002_LM60_Quaoar.html
 |url-status   = live
}}</ref>

<ref name="Arimatsu2019">{{cite journal
 |display-authors = etal
 |first1       = Ko |last1 = Arimatsu
 |first2       = Ryou |last2 = Ohsawa
 |first3       = George L. |last3 = Hashimoto
 |first4       = Seitaro |last4 = Urakawa
 |first5       = Jun |last5 = Takahashi
 |first6       = Miyako |last6 = Tozuka
 |title        = New constraint on the atmosphere of (50000) Quaoar from a stellar occultation
 |date         = December 2019
 |journal      = The Astronomical Journal
 |volume       = 158
 |issue        = 6
 |pages        = 7
 |arxiv        = 1910.09988
 |bibcode      = 2019AJ....158..236A|doi = 10.3847/1538-3881/ab5058 |s2cid = 204823847 |doi-access = free }}</ref>

<ref name="Morgado2023">{{Cite Q|Q116754015|display-authors=1}}</ref>

<ref name="ESA-20230208">{{cite news
 |title        = ESA's Cheops finds an unexpected ring around dwarf planet Quaoar
 |url          = https://www.esa.int/Science_Exploration/Space_Science/Cheops/ESA_s_Cheops_finds_an_unexpected_ring_around_dwarf_planet_Quaoar
 |publisher    = European Space Agency
 |date         = 8 February 2023
 |accessdate   = 21 April 2023
 |archive-date = 8 February 2023
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 |url-status   = live
}}</ref>

<ref name="Pereira2023">{{Cite Q|Q117802048|display-authors=1}}</ref>

<ref name="S&T-20230507">{{cite news
 |title        = Second Ring Around Quaoar Puzzles Astronomers
 |url          = https://skyandtelescope.org/astronomy-news/second-ring-around-quaoar-puzzles-astronomers/
 |first        = Jeff
 |last         = Hecht
 |work         = Sky & Telescope
 |date         = 7 May 2023
 |accessdate   = 7 May 2023
 |archive-date = 7 May 2023
 |archive-url  = https://web.archive.org/web/20230507123007/https://skyandtelescope.org/astronomy-news/second-ring-around-quaoar-puzzles-astronomers/
 |url-status   = live
}}</ref>

<ref name="Emery2024">{{cite journal |last1=Emery |first1=J. P. |last2=Wong |first2=I. |last3=Brunetto |first3=R. |last4=Cook |first4=J. C. |last5=Pinilla-Alonso |first5=N. |last6=Stansberry |first6=J. A. |last7=Holler |first7=B. J. |last8=Grundy |first8=W. M. |last9=Protopapa |first9=S. |last10=Souza-Feliciano |first10=A. C. |last11=Fernández-Valenzuela |first11=E. |last12=Lunine |first12=J. I. |last13=Hines |first13=D. C. |title=A Tale of 3 Dwarf Planets: Ices and Organics on Sedna, Gonggong, and Quaoar from JWST Spectroscopy |journal=Arxiv |date=2023 |doi=10.48550/arXiv.2309.15230}}</ref>

<ref name="Wolfram1">{{cite web
 |url         = https://www.wolframalpha.com/input/?i=ellipsoid+surface+area+semi-axis+lengths+569+569+518
 |title         = Ellipsoid surface area: 3.82769×10^6 km<sup>2</sup>
 |website         = [[Physics:WolframAlpha|WolframAlpha]]
 |access-date         = 8 January 2020
 |archive-date         = 3 October 2020
 |archive-url         = https://web.archive.org/web/20201003115148/https://www.wolframalpha.com/input/?i=ellipsoid+surface+area+semi-axis+lengths+569+569+518
 |url-status         = live
 }}</ref>

<ref name="coordstransform">{{cite web
 |title = Coordinate Transformation & Galactic Extinction Calculator
 |url = https://ned.ipac.caltech.edu/forms/calculator.html
 |work = NASA/IPAC Extragalactic Database
 |publisher = California Institute of Technology
 |accessdate = 11 February 2023
 |archive-date = 22 January 2023
 |archive-url = https://web.archive.org/web/20230122012016/http://ned.ipac.caltech.edu/forms/calculator.html
 |url-status = live
 }} Equatorial → Ecliptic, J2000 for equinox and epoch. NOTE: When inputting equatorial coordinates, specify the units in the format "54.14d" instead of "54.14".</ref>

}} <!-- end of reflist -->

== External links ==
{{commons|50000 Quaoar}}
* [http://www.chadtrujillo.com/quaoar/ Frequently Asked Questions About Quaoar] {{Webarchive|url=https://web.archive.org/web/20100808123854/http://www.chadtrujillo.com/quaoar/ |date=8 August 2010 }}
* [http://vimeo.com/8475837 Quaoar could have hit a bigger Pluto-sized body at high speeds] (Video Credit: Craig Agnor, E. Asphaug)
* [https://web.archive.org/web/20041227095227/https://www.nature.com/news/2004/041206/pf/041206-7_pf.html Chilly Quaoar had a warmer past] – Nature.com article
* [https://www.space.com/25817-quaoar.html Quaoar: Planetoid Beyond Pluto] – SPACE.com article by Elizabeth Howell
* [http://iota-es.de/JOA/JOA2020_1.pdf Beyond Jupiter – (50000) Quaoar]
* {{AstDys|50000}}
* {{JPL small body}}

{{Trans-Neptunian objects}}
{{Dwarf planets}}
{{Moons of dwarf planets}}
{{Small Solar System bodies}}
{{Solar System}}
{{New Horizons}}

{{DEFAULTSORT:Quaoar}}
[[Category:Classical Kuiper belt objects|050000]]
[[Category:Named minor planets]]
[[Category:Dwarf planets]]

{{Sourceattribution|50000 Quaoar}}