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J/AJ/154/62        Orbital parameters of Kuiper Belt objects       (Volk+, 2017)

The curiously warped mean plane of the Kuiper Belt. Volk K., Malhotra R. <Astron. J., 154, 62-62 (2017)> =2017AJ....154...62V (SIMBAD/NED BibCode)
ADC_Keywords: Solar system ; Minor planets Keywords: celestial mechanics - Kuiper belt: general Abstract: We measured the mean plane of the Kuiper Belt as a function of semimajor axis. For the classical Kuiper Belt as a whole (the nonresonant objects in the semimajor axis range 42-48au), we find a mean plane of inclination im=1.8°-0.4°+0.7° and longitude of ascending node Ωm=77°-14°+18° (in the J2000 ecliptic-equinox coordinate system), in accord with theoretical expectations of the secular effects of the known planets. With finer semimajor axis bins, we detect a statistically significant warp in the mean plane near semimajor axes 40-42au. Linear secular theory predicts a warp near this location due to the ν18 nodal secular resonance; however, the measured mean plane for the 40.3-42au semimajor axis bin (just outside the ν18) is inclined ∼13° to the predicted plane, a nearly 3σ discrepancy. For the more distant Kuiper Belt objects of semimajor axes in the range 50-80au, the expected mean plane is close to the invariable plane of the solar system, but the measured mean plane deviates greatly from this: it has inclination im=9.1°-3.8°+6.6° and longitude of ascending node Ωm=227°-44°+18°. We estimate this deviation from the expected mean plane to be statistically significant at the ∼97%-99% confidence level. We discuss several possible explanations for this deviation, including the possibility that a relatively close-in (a≲100au), unseen, small planetary-mass object in the outer solar system is responsible for the warping. Description: Our starting point is the list of minor planets in the outer solar system cataloged in the database of the Minor Planet Center ( and as of 2016 October 20. The complete listing of our sample, including best-fit orbital parameters and sky locations, is provided in Table1. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 108 906 List objects used to calculate mean planes
See also: B/astorb : Orbits of Minor Planets (Bowell+ 2014) : Minor Planet Center Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 7 A7 --- MPC Minor Planet Center designation (1) 9- 19 E11.5 AU a [36.3/149.85] Best-fit barycentric semi-major axis (2) 21- 29 E9.3 AU e_a [0.0005/4.14] The 1-σ uncertainty in a (da) (3) 31- 41 E11.5 --- e [0.0018/0.76] Best-fit eccentricity (2) 43- 53 E11.5 rad i [0.0018/0.88] Best-fit inclination (2) 55- 65 E11.5 rad Omega [0.0022/6.28] Best-fit longitude of ascending node (Ω) (2) 67- 77 E11.5 rad omega [0.0014/6.27] Best-fit argument of perihelion (ω) (2) 79- 84 F6.3 rad lambda [-3.14/3.14] Ecliptic longitude (λ) (2) 86- 91 F6.3 rad beta [-0.844/0.805] Ecliptic latitude (β) (2) 93- 98 F6.3 AU Dist [31.544/96.255] Heliocentric distance (rh) 100-108 F9.1 d Epoch Epoch of the orbit fit and sky position (in Julian Date)
Note (1): The MPC designations are given in their packed format (see Note (2): The orbital elements are the best-fit barycentric elements from a Bernstein & Khushalani (2000AJ....120.3323B) orbit fit to the astrometry available for each object from the Minor Planet Center (MPC). All elements are referenced to the J2000 ecliptic coordinate system. Note (3): Taken from the orbit-fit covariance matrix.
History: From electronic version of the journal
(End) Prepared by [AAS]; Sylvain Guehenneux [CDS] 07-Nov-2017
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