Detached object#Orbits

Detached objects have perihelia much larger than Neptune's aphelion. They often have highly elliptical, very large orbits with semi-major axes of up to a few hundred astronomical units (AU, the radius of Earth's orbit). Such orbits cannot have been created by gravitational scattering by the giant planets, not even Neptune. Instead, a number of explanations have been put forward, including an encounter with a passing star{{cite journal |journal=The Astronomical Journal |issue=5 |volume=128 |pages=2564–2576 |date=November 2004 |title=Scenarios for the Origin of the Orbits of the Trans-Neptunian Objects {{mp|2000 CR|105}} and {{mp|2003 VB|12}} |first1=Alessandro |last1=Morbidelli |doi=10.1086/424617 |last2=Levison |first2=Harold F. |bibcode=2004AJ....128.2564M |arxiv=astro-ph/0403358|s2cid=119486916 }} or a distant planet-sized object, or Neptune migration (which may once have had a much more eccentric orbit, from which it could have tugged the objects to their current orbit){{cite journal |doi=10.1006/icar.2002.6860 |title=Evidence for an extended scattered disk |arxiv=astro-ph/0103435 |bibcode=2002Icar..157..269G |volume=157 |issue=2|journal=Icarus |pages=269–279 |year=2002 |last1=Gladman |first1=B. |last2=Holman |first2=M. |last3=Grav |first3=T. |last4=Kavelaars |first4=J. |last5=Nicholson |first5=P. |last6=Aksnes |first6=K. |last7=Petit |first7=J.-M.|s2cid=16465390 }}{{cite web |url=http://www.grantchronicles.com/12thplanetmk.htm |title=Mankind's Explanation: 12th Planet}}{{cite web |url=https://www.sciencenews.org/article/comets-odd-orbit-hints-hidden-planet?mode=magazine&context=293 |title=A comet's odd orbit hints at hidden planet |date=4 April 2001 }}{{cite web |url=http://www.spaceref.com/news/viewnews.html?id=309 |title=Is There a Large Planet Orbiting Beyond Neptune? }}{{Dead link|date=January 2024 |bot=InternetArchiveBot |fix-attempted=yes }}{{cite web |url=https://www.science.org/content/article/signs-hidden-planet |title=Signs of a Hidden Planet?}}

or ejected rogue planets (present in the early Solar System that were ejected).{{cite journal |doi=10.1086/505214 |title=Production of the Extended Scattered Disk by Rogue Planets|bibcode = 2006ApJ...643L.135G |volume=643 |issue=2 |journal=The Astrophysical Journal |pages=L135–L138 |citeseerx=10.1.1.386.5256 |year=2006 |last1=Gladman |first1=Brett |last2=Chan |first2=Collin |s2cid=2453782 }}{{cite web |url=http://www.findplanetnine.com/2016/01/the-long-and-winding-history-of-planet-x.html |title=The long and winding history of Planet X |access-date=2016-02-09 |archive-date=2016-02-15 |archive-url=https://web.archive.org/web/20160215164442/http://www.findplanetnine.com/2016/01/the-long-and-winding-history-of-planet-x.html |url-status=dead }}{{Cite journal |last1=Huang |first1=Yukun |last2=Gladman |first2=Brett |last3=Beaudoin |first3=Matthew |last4=Zhang |first4=Kevin |date=October 2022 |title=A Rogue Planet Helps to Populate the Distant Kuiper Belt |journal=The Astrophysical Journal Letters |language=en |volume=938 |issue=2 |pages=L23 |doi=10.3847/2041-8213/ac9480 |doi-access=free |arxiv=2209.09399 |bibcode=2022ApJ...938L..23H |issn=2041-8205}}

The classification suggested by the Deep Ecliptic Survey team introduces a formal distinction between scattered-near objects (which could be scattered by Neptune) and scattered-extended objects (e.g. 90377 Sedna) using a Tisserand's parameter value of 3.

The Planet Nine hypothesis suggests that the orbits of several detached objects can be explained by the gravitational influence of a large, unobserved planet between 200 AU and 1200 AU from the Sun and/or the influence of Neptune.{{cite journal |title=Evidence for a distant giant planet in the Solar system |first1=Konstantin |last1=Batygin |first2=Michael E. |last2=Brown |date=20 January 2016 |journal=The Astronomical Journal |volume=151 |number=2 |page=22 |doi=10.3847/0004-6256/151/2/22 |arxiv=1601.05438 |bibcode = 2016AJ....151...22B|s2cid=2701020 |doi-access=free }}

{{TNO}}

Detached objects are one of four distinct dynamical classes of TNO; the other three classes are classical Kuiper-belt objects, resonant objects, and scattered-disc objects (SDO).{{Cite book |last1=Gladman |first1=B. |url=https://ui.adsabs.harvard.edu/abs/2008ssbn.book...43G |title=Nomenclature in the Outer Solar System |last2=Marsden |first2=B. G. |last3=Vanlaerhoven |first3=C. |date=2008-01-01|bibcode=2008ssbn.book...43G }} Sednoids also belong to detached objects. Detached objects generally have a perihelion distance greater than 40 AU, deterring strong interactions with Neptune, which has an approximately circular orbit about 30 AU from the Sun. The boundary between the scattered and detached regions can be defined using an analytical resonance overlap criterion.{{Cite journal |last1=Batygin |first1=Konstantin |last2=Mardling |first2=Rosemary A. |last3=Nesvorný |first3=David |date=2021-10-01 |title=The Stability Boundary of the Distant Scattered Disk |journal=The Astrophysical Journal |volume=920 |issue=2 |pages=148 |doi=10.3847/1538-4357/ac19a4 |doi-access=free |arxiv=2111.00305 |bibcode=2021ApJ...920..148B |issn=0004-637X}}{{Cite journal |last1=Hadden |first1=Sam |last2=Tremaine |first2=Scott |date=2023-11-09 |title=Scattered disc dynamics: the mapping approach |url=https://academic.oup.com/mnras/article/527/2/3054/7408612 |journal=Monthly Notices of the Royal Astronomical Society |language=en |volume=527 |issue=2 |pages=3054–3075 |doi=10.1093/mnras/stad3478 |issn=0035-8711|doi-access=free }}

The discovery of 90377 Sedna in 2003, together with a few other objects discovered around that time such as {{mpl|(148209) 2000 CR|105}} and {{mpl|(612911) 2004 XR|190}}, has motivated discussion of a category of distant objects that may also be inner Oort cloud objects or (more likely) transitional objects between the scattered disc and the inner Oort cloud.

Although Sedna is officially considered a scattered-disc object by the MPC, its discoverer Michael E. Brown has suggested that because its perihelion distance of 76 AU is too distant to be affected by the gravitational attraction of the outer planets it should be considered an inner-Oort-cloud object rather than a member of the scattered disc.{{cite web |title=Sedna (The coldest most distant place known in the solar system; possibly the first object in the long-hypothesized Oort cloud) |last=Brown |first=Michael E. |author-link=Michael E. Brown |publisher=California Institute of Technology, Department of Geological Sciences |url=http://www.gps.caltech.edu/~mbrown/sedna/ |access-date=2008-07-02 |df=dmy-all}} This classification of Sedna as a detached object is accepted in recent publications.{{cite book |author1-link=David Jewitt |first1=D. |last1=Jewitt |first2=A. |last2=Moro-Martın |first3=P. |last3=Lacerda |contribution=The Kuiper belt and other debris disks |title=Astrophysics in the Next Decade |publisher=Springer Verlag |year=2009 |url=http://www.ifa.hawaii.edu/faculty/jewitt/papers/2008/JML08.pdf }}

This line of thinking suggests that the lack of a significant gravitational interaction with the outer planets creates an extended–outer group starting somewhere between Sedna (perihelion 76 AU) and more conventional SDOs like {{mpl-|15874|1996 TL|66}} (perihelion 35 AU), which is listed as a scattered–near object by the Deep Ecliptic Survey.{{cite web |author=Buie, Marc W. |author-link=Marc W. Buie |date=2007-12-28 |title=Orbit fit and astrometric record for 15874 |publisher=SwRI |department=Space Science Department |url=http://www.boulder.swri.edu/~buie/kbo/astrom/15874.html |access-date=2011-11-12 |df=dmy-all}}

One of the problems with defining this extended category is that weak resonances may exist and would be difficult to prove due to chaotic planetary perturbations and the current lack of knowledge of the orbits of these distant objects. They have orbital periods of more than 300 years and most have only been observed over a short observation arc of a couple years. Due to their great distance and slow movement against background stars, it may be decades before most of these distant orbits are determined well enough to confidently confirm or rule out a resonance. Further improvement in the orbit and potential resonance of these objects will help to understand the migration of the giant planets and the formation of the Solar System. For example, simulations by Emel'yanenko and Kiseleva in 2007 show that many distant objects could be in resonance with Neptune. They show a 10% likelihood that 2000 CR₁₀₅ is in a 20:1 resonance, a 38% likelihood that 2003 QK₉₁ is in a 10:3 resonance, and an 84% likelihood that {{mpl|(82075) 2000 YW|134}} is in an 8:3 resonance.{{cite journal |last=Emel'yanenko |first=V.V. |title=Resonant motion of trans-Neptunian objects in high-eccentricity orbits |journal=Astronomy Letters |volume=34 |issue=4 |pages=271–279 |year=2008 |bibcode=2008AstL...34..271E |doi=10.1134/S1063773708040075|s2cid=122634598 }}(subscription required) The likely dwarf planet {{mpl|(145480) 2005 TB|190}} appears to have less than a 1% likelihood of being in a 4:1 resonance.

Mike Brown—who made the Planet Nine hypothesis—makes an observation that "all of the known distant objects which are pulled even a little bit away from the Kuiper seem to be clustered under the influence of this hypothetical planet (specifically, objects with semimajor axis > 100 AU and perihelion > 42 AU)".{{cite web |url=http://www.findplanetnine.com/2016/02/why-i-believe-in-planet-nine.html |author=Mike Brown |title=Why I believe in Planet Nine |author-link=Michael E. Brown}}

Carlos de la Fuente Marcos and Ralph de la Fuente Marcos have calculated that some of the statistically significant commensurabilities are compatible with the Planet Nine hypothesis; in particular, a number of objects{{efn|60 minor planets with a semi-major axis greater than 150 AU and perihelion greater than 30 AU are known.{{cite web |url=http://minorplanetcenter.net/db_search/show_by_properties?perihelion_distance_min=30&semimajor_axis_min=150 |title=Minor Planets with semi-major axis greater than 150 AU and perihelion greater than 30 AU}}}} which are called extreme trans-Neptunian object (ETNOs){{cite journal |author1=C. de la Fuente Marcos |author2=R. de la Fuente Marcos |title=Extreme trans-Neptunian objects and the Kozai mechanism: Signalling the presence of trans-Plutonian planets |journal=Monthly Notices of the Royal Astronomical Society |volume=443 |issue=1 |pages=L59–L63 |arxiv=1406.0715 |bibcode=2014MNRAS.443L..59D |doi=10.1093/mnrasl/slu084 |date=September 1, 2014 |doi-access=free |s2cid=118622180 |df=dmy-all}} may be trapped in the 5:3 and 3:1 mean-motion resonances with a putative Planet Nine with a semimajor axis ~700 AU.{{cite journal |doi=10.1093/mnrasl/slw077|title=Commensurabilities between ETNOs: a Monte Carlo survey |arxiv=1604.05881 |bibcode=2016MNRAS.460L..64D |first1=Carlos |last1=de la Fuente Marcos |first2=Raúl |last2=de la Fuente Marcos |journal=Monthly Notices of the Royal Astronomical Society: Letters |volume=460 |issue=1 |pages=L64–L68 |date=21 July 2016|doi-access=free |s2cid=119110892 }}

{{See also|Sednoid|Extreme trans-Neptunian object}}

{{Update|date=October 2023|demospace=section|type=section}}

This is a list of known objects by discovery date that could not be easily scattered by Neptune's current orbit and therefore are likely to be detached objects, but that lie inside the perihelion gap of ≈50–75 AU that defines the sednoids.{{cite web|date=10 September 2013 |title=How many dwarf planets are there in the outer solar system? (updates daily) |publisher=California Institute of Technology |author=Michael E. Brown |url=http://www.gps.caltech.edu/~mbrown/dps.html |access-date=2013-05-27 |quote=Diameter: 242km |url-status=dead |archive-url=https://web.archive.org/web/20111018154917/http://www.gps.caltech.edu/~mbrown/dps.html |archive-date=2011-10-18 |df=dmy-all |author-link=Michael E. Brown }}{{cite web |url=http://minorplanetcenter.net/db_search/show_by_properties?perihelion_distance_min=40&aphelion_distance_min=60&perihelion_distance_max=55 |title=objects with perihelia between 40–55 AU and aphelion more than 60 AU}}{{cite web |url=http://minorplanetcenter.net/db_search/show_by_properties?perihelion_distance_min=40&aphelion_distance_min=100&perihelion_distance_max=55 |title=objects with perihelia between 40–55 AU and aphelion more than 100 AU}}{{cite web |url=http://minorplanetcenter.net/db_search/show_by_properties?perihelion_distance_min=40&semimajor_axis_min=50&perihelion_distance_max=55 |title=objects with perihelia between 40–55 AU and semi-major axis more than 50 AU}}{{cite web |url=http://minorplanetcenter.net/db_search/show_by_properties?perihelion_distance_min=40&eccentricity_min=0.5&perihelion_distance_max=55 |title=objects with perihelia between 40–55 AU and eccentricity more than 0.5}}{{cite web |url=http://minorplanetcenter.net/db_search/show_by_properties?perihelion_distance_min=37&eccentricity_min=0.5&perihelion_distance_max=40 |title=objects with perihelia between 37–40 AU and eccentricity more than 0.5}}

Objects listed below have a perihelion of more than 40 AU, and a semi-major axis of more than 47.7 AU (the 1:2 resonance with Neptune, and the approximate outer limit of the Kuiper Belt):{{cite web |title=MPC list of q > 40 and a > 47.7 |url=http://minorplanetcenter.net/db_search/show_by_properties?perihelion_distance_min=40&semimajor_axis_min=47.7 |publisher=Minor Planet Center |access-date=7 May 2018}}

The following objects can also be generally thought to be detached objects, although with slightly lower perihelion distances of 38–40 AU.

• Classical Kuiper belt object
• List of Solar System objects by greatest aphelion
• List of trans-Neptunian objects
• Extreme trans-Neptunian object
• Planets beyond Neptune

{{notelist|1}}

{{reflist|25em|refs=

{{cite web

|title = List of Known Trans-Neptunian Objects

|publisher = Johnston's Archive

|date = 7 October 2018

|url = http://www.johnstonsarchive.net/astro/tnoslist.html

|access-date = 23 October 2018}}

}}

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Category:Oort cloud

Category:Solar System