Observational Bias and the Clustering of Distant Eccentric Kuiper Belt Objects
Open accessAbstract
The hypothesis that a massive Planet Nine exists in the outer solar system on a distant eccentric orbit was inspired by observations showing that the objects with the most distant eccentric orbits in the Kuiper Belt have orbits that are physically aligned, that is, they are clustered in longitude of perihelion and have similar orbital planes. Questions have remained, however, about the effects of observational bias on these observations, particularly on the longitudes of perihelion. Specifically, distant eccentric Kuiper Belt objects (KBOs) tend to be faint and only observable near their perihelia, suggesting that the longitudes of perihelion of the known distant objects could be strongly biased by the limited number of locations in the sky where deep surveys have been carried out. We have developed a method to rigorously estimate the bias in longitude of perihelion for Kuiper Belt observations. We find that the probability that the 10 known KBOs with semimajor axis beyond 230 au are drawn from a population with uniform longitude of perihelion is 1.2%. Combined with the observation that the orbital poles of these objects are also clustered, the overall probability of detecting these two independent clusterings in a randomly distributed sample is 0.025%. While observational bias is clearly present in these observations, it is unlikely to explain the observed alignment of the distant eccentric KBOs.
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Brown (2017) constructed individual bias functions for each distant KBO using the entire catalog of KBO discoveries; the probability distribution function of longitude of perihelion for each distant object shows considerable bias, particularly against the galactic plane, but no overall preference for a single direction.
“Brown (2017) addresses the issue of observational bias in $ by using the entire catalog of KBO discoveries to construct individual bias functions for each of the distant KBOs. The probability distribution function of $ for each distant object indeed shows considerable bias, particularly against the galactic plane, but no overall preference for a single direction is found.”
From The planet nine hypothesis (2019) · cites this paper as Brown (2017)
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Experimental — accuracy not yet measuredThe lack of an explicit calculation of the bias in pole position in Brown (2017) remains a key impediment to a full treatment of the effect of observational biases on the observed clustering of distant objects.
“The lack of an explicit calculation of the bias in pole position in Brown (2017) remains a key impediment to a full treatment of the effect of observational biases on the observed clustering of distant objects.”
From Orbital Clustering in the Distant Solar System (2019) · cites this paper as Brown 2017
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Cites
Evidence for a Distant Giant Planet in the Solar System
Batygin, K., & Brown, M. E. (2016) · The Astronomical Journal · doi:10.3847/0004-6256/151/2/22 · Cited by 432 · see citing works
Self-citationThe Inclination Distribution of the Kuiper Belt
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Self-citationA Sedna-like body with a perihelion of 80 astronomical units
Trujillo, C. A., & Sheppard, S. S. (2014) · Nature · doi:10.1038/nature13156 · Cited by 303 · see citing works
Observational constraints on the orbit and location of Planet Nine in the outer solar system
Brown, M. E., & Batygin, K. (2016) · The Astrophysical Journal Letters · doi:10.3847/2041-8205/824/2/l23 · Cited by 112 · cited 3× · see citing works
“Consider 2013 RF98, the most eccentric of the objects originally identified by BB16, as the parent object of 3 a uniform population.”
BackgroundInfluentialSelf-citationNew Extreme Trans-Neptunian Objects: Toward a Super-Earth in the Outer Solar System
Sheppard, S. S., & Trujillo, C. (2016) · The Astronomical Journal · doi:10.3847/1538-3881/152/6/221 · Cited by 92 · see citing works
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OSSOS. V. Diffusion in the Orbit of a High-perihelion Distant Solar System Object
Bannister, M. T., Shankman, C., Volk, K., Chen, Y.-T., Kaib, N., Gladman, B., Jakubik, M., Kavelaars, J. J., Fraser, W. C., Schwamb, M. E., et al. (2017) · The Astronomical Journal · doi:10.3847/1538-3881/aa6db5 · Cited by 48 · see citing works
Consequences of a Distant Massive Planet on the Large Semimajor Axis Trans-Neptunian Objects
Shankman, C., Kavelaars, J. J., Lawler, S. M., Gladman, B. J., & Bannister, M. T. (2017) · The Astronomical Journal · doi:10.3847/1538-3881/153/2/63 · Cited by 42 · see citing works
OBSERVATIONAL SIGNATURES OF A MASSIVE DISTANT PLANET ON THE SCATTERING DISK
Lawler, S. M., Shankman, C., Kaib, N., Bannister, M. T., Gladman, B., & Kavelaars, J. J. (2017) · The Astronomical Journal · doi:10.3847/1538-3881/153/1/33 · Cited by 39 · see citing works
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Self-citationBatygin, K., Adams, F. C., Brown, M. E., & Becker, J. C. (2019) · Physics Reports · doi:10.1016/j.physrep.2019.01.009 · Cited by 181 · see citing works
“Brown (2017) addresses the issue of observational bias in$ by using the entire catalog of KBO discoveries to construct individual bias functions for each of the distant KBOs.”
BackgroundMethodSelf-citationLawler, S. M., Kavelaars, J. J., Alexandersen, M., Bannister, M. T., Gladman, B., Petit, J.-M., & Shankman, C. (2018) · Frontiers in Astronomy and Space Sciences · doi:10.3389/fspas.2018.00014 · Cited by 61 · see citing works
Brown, M. E., & Batygin, K. (2021) · The Astronomical Journal · doi:10.3847/1538-3881/ac2056 · Cited by 57 · see citing works
“In analyses of all available contemporary data and their biases, Brown (2017) and Brown & Batygin (2019, hereafter BB19) find only a 0.2% chance that the orbits of the distant Kuiper belt objects (KBOs) are consistent with a uniform distribution of objects.”
BackgroundInfluentialSelf-citationTesting the Isotropy of the Dark Energy Survey’s Extreme Trans-Neptunian Objects
Bernardinelli, P. H., Bernstein, G. M., Sako, M., Hamilton, S., Gerdes, D. W., Adams, F. C., Saunders, W. R., Aguena, M., Allam, S., Avila, S., et al. (2020) · The Planetary Science Journal · doi:10.3847/psj/ab9d80 · Cited by 39 · see citing works
Orbital Clustering in the Distant Solar System
Brown, M. E., & Batygin, K. (2019) · The Astronomical Journal · doi:10.3847/1538-3881/aaf051 · Cited by 36 · see citing works
“Given this simplistic initial assumption about observational biases and the importance of understanding this potential clustering, Brown (2017) developed a more rigorous method of estimating the longitude of perihelion bias by using the collection of all reported KBO discoveries to back out the…”
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Fienga, A., Di Ruscio, A., Bernus, L., Deram, P., Durante, D., Laskar, J., & Iess, L. (2020) · Astronomy & Astrophysics · doi:10.1051/0004-6361/202037919 · Cited by 32 · see citing works
Generation of Low-inclination, Neptune-crossing Trans-Neptunian Objects by Planet Nine
Batygin, K., Morbidelli, A., Brown, M. E., & Nesvorný, D. (2024) · The Astrophysical Journal Letters · doi:10.3847/2041-8213/ad3cd2 · Cited by 11 · see citing works
“…observability analysis of all available data indicates that, after accounting for observational biases, distant KBOs are jointly clustered in Runge-Lenz (eccentricity) and angular momentum vectors with a significance level of approximately 99.6% (Brown 2017; Brown & Batygin 2019, 2021).”
BackgroundInfluentialSelf-citationNo Evidence for Orbital Clustering in the Extreme Trans-Neptunian Objects
Napier, K. J., Gerdes, D. W., Lin 林, H. W. 省., Hamilton, S. J., Bernstein, G. M., Bernardinelli, P. H., Abbott, T. M. C., Aguena, M., Annis, J., Avila, S., et al. (2021) · The Planetary Science Journal · doi:10.3847/psj/abe53e · Cited by 1 · see citing works
- Authors
- Brown, M. E.
- Affiliations
- California Institute of Technology (US)
- Corresponding author
- Brown, Michael E.
- ORCID
- Brown, Michael E.
- Venue
- The Astronomical Journal
- Publisher
- American Astronomical Society
- Published
- 2017-07-21
- Volume
- 154
- Issue
- 2
- Pages
- 65
- ISSN
- 0004-6256 (ISSN-L)
- 1538-3881
- OpenAlex
- W2624730759
- Cited by
- 48
- References
- 9
- Citations by year
- 2025: 2 · 2024: 1 · 2023: 2 · 2022: 2 · 2021: 9 · 2020: 13 · 2019: 8 · 2018: 6 · 2017: 2 · 2016: 3
- FWCI
- 4.34
- Type
- journal article
- Language
- en
- Open access
- bronze
- doi.org
- Licence
- Locations
- The Astronomical Journal (publishedVersion)
- arXiv (Cornell University) (submittedVersion)
- CaltechAUTHORS (California Institute of Technology) (submittedVersion)
- arXiv (Cornell University)
- Topics
- Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Astro and Planetary Science
- Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Stellar, planetary, and galactic studies
- Physical Sciences › Engineering › Aerospace Engineering › Space Satellite Systems and Control
- Keywords
- Planet Nine, observational bias, Kuiper belt objects, orbital clustering, longitude of perihelion, eccentric orbits, outer solar system, deep sky survey, orbital alignment
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