Editing Kuiper belt (section)

== Exploration ==
{{Main|New Horizons}}
[[File:KBO 2014 MU69 HST.jpg|thumb|upright|The KBO [[486958 Arrokoth]] (green circles), the selected target for the ''New Horizons'' Kuiper belt object mission]]
On 19 January 2006, the first spacecraft to explore the Kuiper belt, ''[[New Horizons]]'', was launched, which flew by [[Pluto]] on 14 July 2015. Beyond the Pluto flyby, the mission's goal was to locate and investigate other, farther objects in the Kuiper belt.<ref>{{cite web |url=http://discoverynewfrontiers.nasa.gov/missions/missions_nh.cfml |title=New Frontiers Program: New Horizons Science Objectives |work=NASA – New Frontiers Program |access-date=15 April 2015 |url-status=dead |archive-url=https://web.archive.org/web/20150415224640/http://discoverynewfrontiers.nasa.gov/missions/missions_nh.cfml |archive-date=15 April 2015  }}</ref>

[[File:2014 MU69 orbit.jpg|thumb|left|upright=1|Diagram showing the location of 486958 Arrokoth and trajectory for rendezvous]]
[[File:Ultima_Thule_New_Horizons_CA06_vertical.png|thumb|upright|''New Horizons'' grayscale image of Arrokoth, its surface likely covered in organic compounds.<ref name="NASA-20190516">{{cite web|url=https://www.nasa.gov/feature/nasa-s-new-horizons-team-publishes-first-kuiper-belt-flyby-science-results|title=NASA's New Horizons Team Publishes First Kuiper Belt Flyby Science Results|publisher=NASA|date=16 May 2019|access-date=16 May 2019|archive-date=16 December 2019|archive-url=https://web.archive.org/web/20191216073527/https://www.nasa.gov/feature/nasa-s-new-horizons-team-publishes-first-kuiper-belt-flyby-science-results/|url-status=live}}</ref> So far, it is the only KBO besides Pluto and its satellites to be visited by a spacecraft.]]

On 15 October 2014, it was revealed that ''Hubble'' had uncovered three potential targets, provisionally designated PT1 ("potential target 1"), PT2 and PT3 by the ''New Horizons'' team.<ref>{{cite web |title=NASA's Hubble Telescope Finds Potential Kuiper Belt Targets for New Horizons Pluto Mission |work=press release |publisher=Johns Hopkins [[Applied Physics Laboratory]] |date=15 October 2014 |access-date=16 October 2014 |archive-date=16 October 2014 |url=http://www.jhuapl.edu/newscenter/pressreleases/2014/141015_2.asp |archive-url=https://web.archive.org/web/20141016023345/http://www.jhuapl.edu/newscenter/pressreleases/2014/141015_2.asp}}</ref><ref>{{cite web |author=Buie, Marc |author-link=Marc W. Buie |title=New Horizons HST KBO Search Results: Status Report |url=http://www.stsci.edu/institute/stuc/oct-2014/New-Horizons.pdf |publisher=[[Space Telescope Science Institute]] |date=15 October 2014 |page=23 |access-date=29 August 2015 |archive-date=27 July 2015 |archive-url=https://wayback.archive-it.org/all/20150727213348/http://www.stsci.edu/institute/stuc/oct-2014/New-Horizons.pdf |url-status=dead }}</ref> The objects' diameters were estimated to be in the 30–55&nbsp;km range; too small to be seen by ground telescopes, at distances from the Sun of 43–44 AU, which would put the encounters in the 2018–2019 period.<ref name = "Lakdawalla2014">{{cite web |last=Lakdawalla |first=Emily |author-link=Emily Lakdawalla |title=Finally! New Horizons has a second target |work=Planetary Society blog |publisher=[[Planetary Society]] |date=15 October 2014 |access-date=15 October 2014 |archive-date=15 October 2014 |url=http://www.planetary.org/blogs/emily-lakdawalla/2014/10151024-finally-new-horizons-has-a-kbo.html |archive-url=https://web.archive.org/web/20141015230432/http://www.planetary.org/blogs/emily-lakdawalla/2014/10151024-finally-new-horizons-has-a-kbo.html |url-status=live}}</ref> The initial estimated probabilities that these objects were reachable within ''New Horizons''{{'}} fuel budget were 100%, 7%, and 97%, respectively.<ref name="Lakdawalla2014"/> All were members of the "cold" (low-[[orbital inclination|inclination]], low-[[orbital eccentricity|eccentricity]]) [[classical Kuiper belt]], and thus very different from Pluto. [[2014 MU69|PT1]] (given the temporary designation "1110113Y" on the HST web site<ref>{{cite web |title=Hubble to Proceed with Full Search for New Horizons Targets |work=HubbleSite news release |publisher=[[Space Telescope Science Institute]] |date=1 July 2014 |access-date=15 October 2014 |url=http://hubblesite.org/newscenter/archive/releases/2014/35/image/a/ |archive-date=12 May 2015 |archive-url=https://web.archive.org/web/20150512031618/http://hubblesite.org/newscenter/archive/releases/2014/35/image/a/ |url-status=live }}</ref>), the most favorably situated object, was magnitude 26.8, 30–45&nbsp;km in diameter, and was encountered in January 2019.<ref name="VOX-20150414">{{cite web |last=Stromberg |first=Joseph |title=NASA's New Horizons probe was visiting Pluto — and just sent back its first color photos |url=https://www.vox.com/2015/4/14/8412031/pluto-new-horizons |date=14 April 2015 |work=[[Vox (website)|Vox]] |access-date=14 April 2015 |archive-date=6 April 2020 |archive-url=https://web.archive.org/web/20200406132908/https://www.vox.com/2015/4/14/8412031/pluto-new-horizons |url-status=live }}</ref> Once sufficient orbital information was provided, the [[Minor Planet Center]] gave official designations to the three target KBOs: {{mpl|2014 MU|69}} (PT1), {{mpl|2014 OS|393}} (PT2), and {{mpl|2014 PN|70}} (PT3). By the fall of 2014, a possible fourth target, {{mpl|2014 MT|69}}, had been eliminated by follow-up observations. PT2 was out of the running before the Pluto flyby.<ref>{{cite web |author=Corey S. Powell |title=Alan Stern on Pluto's Wonders, New Horizons' Lost Twin, and That Whole "Dwarf Planet" Thing |url=http://blogs.discovermagazine.com/outthere/2015/03/29/alan-stern-on-plutos-wonders/ |magazine=[[Discover (magazine)|Discover]] |date=29 March 2015 |author-link=Corey S. Powell |access-date=29 August 2015 |archive-date=16 November 2019 |archive-url=https://web.archive.org/web/20191116104116/http://blogs.discovermagazine.com/outthere/2015/03/29/alan-stern-on-plutos-wonders/ |url-status=dead }}</ref><ref>{{cite journal |url=http://www.hou.usra.edu/meetings/lpsc2015/pdf/1301.pdf |title=Orbits and Accessibility of Potential New Horizons KBO Encounter Targets |issue=1832 |pages=1301 |date=2015 |journal=USRA-Houston |archive-url=https://web.archive.org/web/20160303182211/http://www.hou.usra.edu/meetings/lpsc2015/pdf/1301.pdf |archive-date=3 March 2016|bibcode=2015LPI....46.1301P |last1=Porter |first1=S. B. |last2=Parker |first2=A. H. |last3=Buie |first3=M. |last4=Spencer |first4=J. |last5=Weaver |first5=H. |last6=Stern |first6=S. A. |last7=Benecchi |first7=S. |last8=Zangari |first8=A. M. |last9=Verbiscer |first9=A. |last10=Gywn |first10=S. |last11=Petit |first11=J. -M. |last12=Sterner |first12=R. |last13=Borncamp |first13=D. |last14=Noll |first14=K. |last15=Kavelaars |first15=J. J. |last16=Tholen |first16=D. |last17=Singer |first17=K. N. |last18=Showalter |first18=M. |last19=Fuentes |first19=C. |last20=Bernstein |first20=G. |last21=Belton |first21=M. }}</ref>

On 26 August 2015, the first target, {{mp|2014 MU|69}} (nicknamed "Ultima Thule" and later named [[486958 Arrokoth]]), was chosen. Course adjustment took place in late October and early November 2015, leading to a flyby in January 2019.<ref>{{cite web |last=McKinnon |first=Mika |url=http://space.gizmodo.com/new-horizons-locks-onto-next-target-lets-explore-the-k-1727298103 |title=New Horizons Locks Onto Next Target: Let's Explore the Kuiper Belt! |work=Earth & Space |date=28 August 2015 |url-status=live |archive-url=https://web.archive.org/web/20151231190843/http://space.gizmodo.com/new-horizons-locks-onto-next-target-lets-explore-the-k-1727298103 |archive-date=31 December 2015}}</ref> On 1 July 2016, NASA approved additional funding for ''New Horizons'' to visit the object.<ref>{{cite web|title=New Horizons Receives Mission Extension to Kuiper Belt, Dawn to Remain at Ceres|url=https://www.nasa.gov/feature/new-horizons-receives-mission-extension-to-kuiper-belt-dawn-to-remain-at-ceres|date=1 July 2016|author=Dwayne Brown / Laurie Cantillo|publisher=NASA|access-date=15 May 2017|archive-date=20 August 2016|archive-url=https://web.archive.org/web/20160820075642/http://www.nasa.gov/feature/new-horizons-receives-mission-extension-to-kuiper-belt-dawn-to-remain-at-ceres/|url-status=live}}</ref>

On 2 December 2015, ''New Horizons'' detected what was then called {{mpl|1994 JR|1}} (later named ''15810 Arawn'') from {{convert|170|e6mi|e6km|order=flip}} away.<ref>[http://www.spacedaily.com/reports/New_Horizons_catches_a_wandering_Kuiper_Belt_Object_not_far_off_999.html New Horizons' catches a wandering Kuiper Belt Object not far off] {{Webarchive|url=https://web.archive.org/web/20211126230455/http://www.spacedaily.com/reports/New_Horizons_catches_a_wandering_Kuiper_Belt_Object_not_far_off_999.html |date=26 November 2021 }} spacedaily.com Laurel MD (SPX). 7 December 2015.</ref>

On 1 January 2019, ''New Horizons'' successfully flew by Arrokoth, returning data showing Arrokoth to be a [[Contact binary (small Solar System body)|contact binary]] 32&nbsp;km long by 16&nbsp;km wide.<ref name="NYT-20190210">{{cite news |last=Corum |first=Jonathan |title=New Horizons Glimpses the Flattened Shape of Ultima Thule – NASA's New Horizons spacecraft flew past the most distant object ever visited: a tiny fragment of the early solar system known as 2014 MU69 and nicknamed Ultima Thule. – Interactive |url=https://www.nytimes.com/interactive/2018/12/31/science/new-horizons-ultima-thule-flyby.html |date=10 February 2019 |work=[[The New York Times]] |access-date=11 February 2019 |archive-date=24 December 2021 |archive-url=https://web.archive.org/web/20211224050632/https://www.nytimes.com/interactive/2018/12/31/science/new-horizons-ultima-thule-flyby.html |url-status=live }}</ref> The [[Ralph (New Horizons)|Ralph]] instrument aboard ''New Horizons'' confirmed Arrokoth's red color. Data from the fly-by will continue to be downloaded over the next 20 months.

No follow-up missions for ''New Horizons'' are planned, though at least two concepts for missions that would return to orbit or land on Pluto have been studied.<ref>{{Cite news|url=https://www.nasa.gov/directorates/spacetech/niac/2017_Phase_I_Phase_II/Fusion_Enabled_Pluto_Orbiter_and_Lander|title=Fusion-Enabled Pluto Orbiter and Lander|last=Hall|first=Loura|date=2017-04-05|work=NASA|access-date=2018-07-13|archive-date=21 April 2017|archive-url=https://web.archive.org/web/20170421033505/https://www.nasa.gov/directorates/spacetech/niac/2017_Phase_I_Phase_II/Fusion_Enabled_Pluto_Orbiter_and_Lander/|url-status=live}}</ref><ref>{{Cite web|url=https://www.eurekalert.org/pub_releases/2017-09/gac-gac092117.php|title=Global Aerospace Corporation to present Pluto lander concept to NASA|website=EurekAlert!|access-date=2018-07-13|archive-date=21 January 2019|archive-url=https://web.archive.org/web/20190121154920/https://www.eurekalert.org/pub_releases/2017-09/gac-gac092117.php|url-status=live}}</ref> Beyond Pluto, there exist many large KBOs that cannot be visited with ''New Horizons'', such as the dwarf planets [[Makemake]] and [[Haumea]]. New missions would be tasked to explore and study these objects in detail. [[Thales Alenia Space]] has studied the logistics of an orbiter mission to Haumea,<ref>{{Cite journal|date=2011-03-01|title=A preliminary assessment of an orbiter in the Haumean system: How quickly can a planetary orbiter reach such a distant target?|journal=Acta Astronautica|volume=68|issue=5–6|pages=622–628|doi=10.1016/j.actaastro.2010.04.011|issn=0094-5765|bibcode=2011AcAau..68..622P|last1=Poncy|first1=Joel|last2=Fontdecaba Baig|first2=Jordi|last3=Feresin|first3=Fred|last4=Martinot|first4=Vincent}}</ref> a high priority scientific target due to its status as the parent body of a collisional family that includes several other TNOs, as well as Haumea's ring and two moons. The lead author, Joel Poncy, has advocated for new technology that would allow spacecraft to reach and orbit KBOs in 10–20 years or less.<ref>{{Cite web|url=https://www.centauri-dreams.org/2009/07/15/haumea-technique-and-rationale/|title=Haumea: Technique and Rationale|website=www.centauri-dreams.org|access-date=2018-07-13|archive-date=13 July 2018|archive-url=https://web.archive.org/web/20180713143305/https://www.centauri-dreams.org/2009/07/15/haumea-technique-and-rationale/|url-status=live}}</ref> ''New Horizons'' Principal Investigator Alan Stern has informally suggested missions that would flyby the planets Uranus or Neptune before visiting new KBO targets,<ref>{{Cite news|url=https://www.space.com/40453-chasing-new-horizons-alan-stern-interview.html|title=New Horizons' Dramatic Journey to Pluto Revealed in New Book|work=Space.com|access-date=2018-07-13|archive-date=13 July 2018|archive-url=https://web.archive.org/web/20180713133732/https://www.space.com/40453-chasing-new-horizons-alan-stern-interview.html|url-status=live}}</ref> thus furthering the exploration of the Kuiper belt while also visiting these [[ice giant]] planets for the first time since the ''[[Voyager 2]]'' flybys in the 1980s.

===Design studies and concept missions===
[[50000 Quaoar|Quaoar]] has been considered as a flyby target for a probe tasked with exploring the [[interstellar medium]], as it currently lies near the [[Heliosphere|heliospheric]] nose; Pontus Brandt at [[Johns Hopkins University|Johns Hopkins]] [[Applied Physics Laboratory]] and his colleagues have studied a probe that would flyby Quaoar in the 2030s before continuing to the interstellar medium through the heliospheric nose.<ref name="exploration">{{Citation|last=TVIW|title=22. Humanity's First Explicit Step in Reaching Another Star: The Interstellar Probe Mission|date=2017-11-04|url=https://www.youtube.com/watch?v=Ailuk9ou0YI| archive-url=https://ghostarchive.org/varchive/youtube/20211030/Ailuk9ou0YI| archive-date=2021-10-30|access-date=2018-07-24}}{{cbignore}}</ref><ref>{{Cite news|url=https://agu.confex.com/agu/2018tess/meetingapp.cgi/Paper/334466|title=Triennial Earth Sun-Summit|access-date=2018-07-24|archive-date=3 August 2020|archive-url=https://web.archive.org/web/20200803050843/https://agu.confex.com/agu/2018tess/meetingapp.cgi/Paper/334466|url-status=live}}</ref> Among their interests in Quaoar include its likely disappearing methane atmosphere and [[Cryovolcano|cryovolcanism]].<ref name="exploration"/> The mission studied by Brandt and his colleagues would launch using [[Space Launch System|SLS]] and achieve 30&nbsp;km/s using a Jupiter flyby. Alternatively, for an orbiter mission, a study published in 2012 concluded that [[28978 Ixion|Ixion]] and [[38628 Huya|Huya]] are among the most feasible targets.<ref>{{Cite conference|last1=Gleaves|first1=Ashley|last2=Allen|first2=Randall|last3=Tupis|first3=Adam|last4=Quigley|first4=John|last5=Moon|first5=Adam|last6=Roe|first6=Eric|last7=Spencer|first7=David|last8=Youst|first8=Nicholas|last9=Lyne|first9=James|date=2012-08-13|title=A Survey of Mission Opportunities to Trans-Neptunian Objects – Part II, Orbital Capture|conference=AIAA/AAS Astrodynamics Specialist Conference, Minneapolis, Minnesota|location=Reston, Virginia|publisher=American Institute of Aeronautics and Astronautics|doi=10.2514/6.2012-5066|isbn=9781624101823|s2cid=118995590}}</ref> For instance, the authors calculated that an orbiter mission could reach Ixion after 17 years cruise time if launched in 2039.