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Detached object

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Types of distant minor planets

Detached objects are nonclassical trans-Neptunian objects (TNOs) with a perihelion too far away from Neptune to be significantly influenced by it, and so appear to be “detached” from the solar system.[1][2] They have also been referred to as extended scattered disc objects (E-SDO),[3] Distant Detached Objects (DDO)[4] or Scattered-Extended in the formal classification by Deep Ecliptic Survey.[5] A total of nine such bodies have been securely identified.[6][a]

Orbits

Detached objects generally have highly elliptical, very large orbits with semi-major axes of up to a few hundred AU. Such orbits cannot have been created by gravitational scattering by the gas giants (in particular, Neptune). Instead, a number of explanations have been put forward, including an encounter with a passing star[7] or a distant, planet-sized object.[4] 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.[5]

Classification

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). Detached objects generally have a perihelion distance greater than 40 astronomical units (AU). However, there are no clear boundaries between the scattered and detached regions, since both can coexist as TNOs in an intermediate region with perihelion distance between 37 and 40 AU.[6]

The discovery of 90377 Sedna together with a few other objects such as 2000 CR105 and 2004 XR190 (also known as "Buffy") 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.[8] This line of thinking suggests that a lack of gravitational interaction with the outer planets disqualifies a trans-neptunian object from scattered disc membership, which would create an outer edge somewhere between Sedna and more conventional SDOs like Eris.

Notes

  1. ^ The nine are: (48639) 1995 TL8, (82075) 2000 YW134, 90377 Sedna, 2000 CR105, 2003 FZ129, 2003 QK91, 2003 UY291, 2004 XR190 and (145480) 2005 TB190.

References

  1. ^ P. S. Lykawka; T. Mukai (2008). "An Outer Planet Beyond Pluto and the Origin of the Trans-Neptunian Belt Architecture". Astronomical Journal. 135: 1161. doi:10.1088/0004-6256/135/4/1161. arXiv:0712.2198.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  2. ^ D.Jewitt, A.Delsanti The Solar System Beyond The Planets in Solar System Update : Topical and Timely Reviews in Solar System Sciences , Springer-Praxis Ed., ISBN 3-540-26056-0 (2006) Preprint of the article (pdf)
  3. ^ Evidence for an Extended Scattered Disk?
  4. ^ a b Rodney S. Gomes (2006). "A distant planetary-mass solar companion may have produced distant detached objects". Icarus. 184 (2). Elsevier: 589–601. doi:10.1016/j.icarus.2006.05.026. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help) Cite error: The named reference "Gomez 2006" was defined multiple times with different content (see the help page).
  5. ^ a b J. L. Elliot, S. D. Kern, K. B. Clancy, A. A. S. Gulbis, R. L. Millis, M. W. Buie, L. H. Wasserman, E. I. Chiang, A. B. Jordan, D. E. Trilling, and K. J. Meech The Deep Ecliptic Survey: A Search for Kuiper Belt Objects and Centaurs. II. Dynamical Classification, the Kuiper Belt Plane, and the Core Population. The Astronomical Journal, 129 (2006), pp. preprint. Cite error: The named reference "DES_Elliot2006" was defined multiple times with different content (see the help page).
  6. ^ a b Lykawka, Patryk Sofia & Mukai, Tadashi. (2007). Dynamical classification of trans-neptunian objects: Probing their origin, evolution, and interrelation. Icarus Volume 189, Issue 1, July , Pages 213-232. doi:10.1016/j.icarus.2007.01.001.
  7. ^ Morbidelli, Alessandro (2004). "Scenarios for the Origin of the Orbits of the Trans-Neptunian Objects 2000 CR105 and 2003 VB12". The Astronomical Journal. 128 (5): 2564–2576. doi:10.1086/424617. Retrieved 2008-07-02. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help); Unknown parameter |month= ignored (help)
  8. ^ Brown, Michael E. "Sedna (The coldest most distant place known in the solar system; possibly the first object in the long-hypothesized Oort cloud)". California Institute of Technology, Department of Geological Sciences. Retrieved 2008-07-02.
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