View source for Astronomy:(471325) 2011 KT19

{{DISPLAYTITLE:{{mp|471325|2011 KT|19}}}}
{{Infobox planet
| minorplanet = yes
| background = #C2E0FF
| name = {{mp|471325|2011 KT|19}}
| image = 
| image_size = 
| caption = 
| discovery_ref = <ref name="MPEC2011-L09" />
| discoverer = [[Astronomy:Mount Lemmon Survey|Mount Lemmon Srvy.]]<br />
  {{collapsible list |
* Ying-Tung Chen
* Hsing Wen Lin
* [[Biography:Matthew J. Holman|Matthew J. Holman]]
* Matthew J. Payne
* Wesley C. Fraser
* Pedro Lacerda
* Wing-Huen Ip
* Wen-Ping Chen
* Rolf-Peter Kudritzki
* [[Biography:Robert Jedicke|Robert Jedicke]]
* Richard J. Wainscoat
* John L. Tonry
* Eugene A. Magnier
* Christopher Waters
* Nick Kaiser
* Shiang-Yu Wang
* Matthew Lehner
  }}
| discovery_site = [[Astronomy:Mount Lemmon Observatory|Mount Lemmon Obs.]]
| discovered = 31 May 2011
| mpc_name = 
| pronounced = {{IPAc-en|'|n|iː|k|uː}}
| alt_names = Niku
| adjectives = 
| named_after = A Chinese adjective meaning "rebellious" <ref name="newscientist" />
| mp_category = [[Astronomy:Trans-Neptunian object|TNO]]<ref name="jplorbit" />{{·}}[[Astronomy:Centaur (small Solar System body)|centaur]]<ref name="johnstonsarchive-TNO-list" /><br />damocloid
| orbit_ref = <ref name="jplorbit" />
| epoch = [[Astronomy:Julian day|JD]] 2457600.5
| uncertainty = 2
| observation_arc = 1779 days (4.87 yr)
| aphelion = 47.427 AU
| perihelion = 23.7805 AU
| semimajor = 35.604 AU
| eccentricity = 0.33208
| period = 212.45 years
| avg_speed = 
| inclination = 110.1537[[Degree (angle)|°]]
| asc_node = 243.77772°
| arg_peri = 322.174°
| mean_anomaly = 29.487°
| tisserand = −1.552
| satellites = 
| physical_characteristics = 
| sidereal_day = 
| mean_diameter = 75–250 km<ref name="mpcorbit"/><br />161 km<ref name="johnstonsarchive-TNO-list" />
| albedo = 
| single_temperature = 
| spectral_type = 
| abs_magnitude = 7.2<ref name="mpcorbit">{{cite web |title=IAU Minor Planet Center - 2011 KT19 |url=https://www.minorplanetcenter.net/db_search/show_object?object_id=2011+KT19 |website=Minor Planet Center |publisher=IAU |access-date=12 August 2016}}</ref><ref name="jplorbit"/>
| magnitude = 22<ref name=AstDyS>{{cite web |title=AstDyS (471325) 2011KT19 Ephemerides |url=https://newton.spacedys.com/astdys/index.php?pc=1.1.3.0&n=2011KT19 |access-date=18 February 2017}}</ref>
}}

'''{{mp|471325|2011 KT|19}}''', nicknamed '''Niku''' ({{IPAc-en|n|iː|k|uː}}), is a [[Astronomy:Trans-Neptunian object|trans-Neptunian object]] whose orbit is tilted 110[[Degree (angle)|°]] with respect to the planets' [[Astronomy:Orbital plane|orbital plane]]. Thus, it has a nearly polar retrograde orbit around the [[Astronomy:Sun|Sun]].<ref name="newscientist">{{cite web |url=https://www.newscientist.com/article/2100700-mystery-object-in-weird-orbit-beyond-neptune-cannot-be-explained/ |archive-url=https://web.archive.org/web/20160811163627/https://www.newscientist.com/article/2100700-mystery-object-in-weird-orbit-beyond-neptune-cannot-be-explained/ |url-status=dead |archive-date=11 August 2016 |work=New Scientist |title=Mystery object in weird orbit beyond Neptune cannot be explained |date=10 August 2016 |access-date=11 August 2016}}</ref><ref name="arxiv5aug">{{cite journal |first1=Ying-Tung |last1=Chen |first2=Hsing Wen |last2=Lin |first3=Matthew J |last3=Holman |first4=Matthew J |last4=Payne |first5=Wesley C |last5=Fraser |first6=Pedro |last6=Lacerda |first7=Wing-Huen |last7=Ip |first8=Wen-Ping |last8=Chen |first9=Rolf-Peter |last9=Kudritzki |first10=Robert |last10=Jedicke |first11=Richard J |last11=Wainscoat |first12=John L |last12=Tonry |first13=Eugene A |last13=Magnier |first14=Christopher |last14=Waters |first15=Nick |last15=Kaiser |first16=Shiang-Yu |last16=Wang |first17=Matthew |last17=Lehner |arxiv=1608.01808 |title=Discovery of A New Retrograde Trans-Neptunian Object: Hint of A Common Orbital Plane for Low Semi-Major Axis, High Inclination TNOs and Centaurs |date=5 August 2016 |display-authors=4 |doi=10.3847/2041-8205/827/2/L24 |volume=827 |journal=The Astrophysical Journal |issue=2 |page=L24|bibcode = 2016ApJ...827L..24C |s2cid=4975180 |doi-access=free }}</ref><ref>{{Cite web |author1=Charles Q. Choi |date=2016-10-24 |title=What's Up with 'Niku'? Object's Weird Orbit Puzzles Scientists |url=https://www.space.com/34479-niku-weird-objects-orbit-puzzles-scientists.html |access-date=2022-12-21 |website=Space.com |language=en}}</ref><ref>{{Cite web |url=http://www.sciencefriday.com/segments/what-makes-the-solar-system-like-a-crime-scene/ |title=What Makes the Solar System Like a Crime Scene? - Science Friday |date=19 August 2016 |language=en-US |access-date=19 August 2016}}</ref>

While the object has not received a formal name, it received the moniker "Niku" (逆骨), meaning "rebellious" in the [[Social:Chinese language|Chinese language]], by its discoverers.<ref>{{cite web |last1=Grossman |first1=David |title=Meet Niku, the Weird Object Beyond Neptune That Nobody Can Figure Out |url=https://www.popularmechanics.com/space/deep-space/a22293/niku-weird-object-beyond-neptune/ |website=Popular Mechanics |access-date=21 December 2021 |date=11 August 2016}}</ref><ref>{{cite news |last1=Choi |first1=Charles Q. |title=What's Up with 'Niku'? Object's Weird Orbit Puzzles Scientists |url=https://www.space.com/34479-niku-weird-objects-orbit-puzzles-scientists.html |access-date=21 December 2021 |work=Space.com |date=24 October 2016 |language=en}}</ref>

==Details==
{{mp|471325|2011 KT|19}} was discovered by the [[Astronomy:Mount Lemmon Survey|Mount Lemmon Survey]] on 31 May 2011. Its rediscovery was announced in August 2016 by a team of astronomers using the [[Astronomy:Pan-STARRS|Pan-STARRS]] telescope. It was soon linked with a supposed prograde [[Astronomy:Centaur (minor planet)|centaur]] ({{mp|2011 KT|19}}; inclination = 38° and semi-major axis = 28 AU) that had been lost due to a short [[Astronomy:Observation arc|observation arc]].<ref name="MPEC2011-L09"/><ref name=arxiv5aug/> {{mp|2011 KT|19}} is in a 7:9 resonance with Neptune. Currently it is the only object with a nearly polar orbit that is in resonance with a planet.<ref name="Morais_Namouni_2017">{{cite journal |last1=Morais |first1=M. H. M. |last2=Nomouni |first2=F. |title=First transneptunian object in polar resonance with Neptune |date=2017 |arxiv=1708.00346 |doi=10.1093/mnrasl/slx125 |journal=Monthly Notices of the Royal Astronomical Society |volume=472 |issue=1 |pages=L1–L4 |department=Letters |bibcode=2017MNRAS.472L...1M }}</ref> Notably, it is part of a group of objects that orbit the Sun in a highly inclined orbit; the reasons for this unusual orbit are unknown as of August 2016.<ref name=engadget>{{cite web |first=Andrew |last=Dalton |url=https://www.engadget.com/2016/08/10/beyond-neptune-niku-discovery/ |title=There's something weird going on beyond Neptune |work=Engadget |publisher=AOL |date=10 August 2016 |access-date=11 August 2016}}</ref>

The orbital characteristics of {{mp|2011 KT|19}} have been compared to those of {{mpl|2008 KV|42}} (Drac). The orbits of {{mp|2011 KT|19}}, {{mp|2008 KV|42}}, {{mpl|2002 XU|93}}, {{mpl|2010 WG|9}}, {{mpl|2007 BP|102}}, {{mpl|2011 MM|4}}, appear to occupy a common plane, with three in prograde and three in retrograde orbits. The probability of this alignment occurring by chance is 0.016%. These orbits should leave a common plane in a few million years because the precession of prograde and retrograde orbits are in opposite directions. Simulations including the hypothetical [[Astronomy:Planet Nine|Planet Nine]] did not maintain a common orbital plane and the plane does not coincide with  the plane of the predicted high-inclination large semi-major axis objects of that model. Other simulations with a few Earth-mass dwarf planet on a high-inclination orbit also failed to reproduce the alignment.<ref name=arxiv5aug/>

{| style="width: 550px;"
|-
|[[File:2011 KT19 orbit views.png|550px]]
|-
|The orbit of {{mp|2011 KT|19}} in relation to [[Astronomy:Pluto|Pluto]] and the planets of the [[Astronomy:Solar System|Solar System]]
|-
|[[File:Niku and Drac.gif|Niku and Drac|550px]]
|-
|The orbit of Niku (purple), is shown with another steep retrograde TNO, Drac (yellow), and the other planets. Pluto's orbit is in red.
|}

== References ==
{{reflist|refs=

<ref name="jplorbit">{{cite web |title=JPL Small-Body Database (2011 KT19) |url=https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2011KT19 |website=JPL |publisher=[[Organization:NASA|NASA]] |access-date=12 August 2016}}</ref>

<ref name="MPEC2011-L09">{{cite web |title=MPEC 2011-L09 : 2011 KT19 |publisher=IAU Minor Planet Center |date=2 June 2011 |url=https://www.minorplanetcenter.net/iau/mpec/K11/K11L09.html}} (K11K19T; E-assumed due to short arc)</ref>

<ref name="johnstonsarchive-TNO-list">{{cite web
  |title      = List of Known Trans-Neptunian Objects
  |work       = Johnston's Archive
  |date       = 18 August 2020
  |last       = Johnston |first= Wm. Robert
  |url        = http://www.johnstonsarchive.net/astro/tnoslist.html
  |accessdate = 18 July 2021}}</ref>

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

== External links ==
* {{JPL small body|id=471325}}

{{Minor planets navigator | |number=471325 |PageName={{mp|471325|2011 KT|19}} | }}
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[[Category:Trans-Neptunian objects]]

{{Sourceattribution|(471325) 2011 KT19}}