Constraints on the location of a possible 9th planet derived from the Cassini data
Open accessAbstract
To explain the unusual distribution of Kuiper belt objects, several authors have advocated the existence of a super-Earth planet in the outer solar system. It has recently been proposed that a 10 M⊕ object with an orbit of 700 AU semi major axis and 0.6 eccentricity can explain the observed distribution of Kuiper belt objects around Sedna. Here we use the INPOP planetary ephemerides model as a sensor for testing for an additional body in the solar system. We test the possibility of adding the proposed planet without increasing the residuals of the planetary ephemerides, fitted over the whole INPOP planetary data sample. We demonstrate that the presence of such an object is not compatible with the most sensitive data set, the Cassini radio ranging data, if its true anomaly is in the intervals [−130°: −100° ] or [−65°:85° ]. Moreover, we find that the addition of this object can reduce the Cassini residuals, with a most probable position given by a true anomaly v = 117.8°+11°-10° .
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Most of the Planet Nine parameter space, in particular the best fit case, has already been ruled out by Fienga et al. [19].
“although most of them, in particular the 'best fit case', have already been ruled out by Fienga et al. [19].”
From Has Kronos Devoured Planet Nine and Its Epigones? (2026) · cites this paper as [19]
Section 4 (Results; page unavailable) identifies two forbidden true-anomaly intervals, totaling 180° of the 360° orbit tested—not most of it. It places the strongest reduction in Cassini residuals at 117.8°, and Section 6 (Conclusions; page unavailable) calls that the most probable position rather than ruling it out. The paper does not identify a separate configuration called the “best fit case.” (LLM, conf=0.88)
Checked by a reasoning model — may be wrong.
Experimental — accuracy not yet measuredA hypothetical planet with mass m = 10 Earth masses would produce perturbations to Saturn's orbit detectable via Cassini telemetry if it were currently closer to the Sun than about r ≲ 370 AU.
“For example, a hypothetical planet with mass m = 10 M would produce perturbations to Saturn's orbit that would be detectable via telemetry of the Cassini spacecraft, if it were currently closer to the Sun than about r ≲ 370 AU (Fienga et al., 2016).”
From The planet nine hypothesis (2019) · cites this paper as Fienga et al., 2016
The Introduction identifies the tested planet as 10 Earth masses, and the Results (§4; page unavailable) find that Cassini ranging data exclude it at specified true anomalies. The paper does not give a 370 AU detection threshold: its exclusions depend on position along the particular orbit tested, so the claim overgeneralizes them into a distance-only rule. (LLM, conf=0.84)
Experimental — accuracy not yet measuredFienga et al. (2016) perform full fits to the locations of all planets and nearly 300 asteroids with and without a 10 M_e Planet Nine at various positions along an orbit with a=700 au and e=0.6.
“Fienga et al. (2016)perform full fits to the locations of all planets and nearly 300 asteroids observed from ancient times to the present with and without a 10 M e Planet Nine at various positions along an orbit with = a 700 au 9 and e 9 = 0.6, consistent with the nominal orbit suggested in Batygin & Brown (2016).”
From Observational constraints on the orbit and location of Planet Nine in the outer solar system (2016) · cites this paper as Fienga et al. (2016)
Sections 2 and 3.2 describe global fits of planetary orbits with and without a 10-Earth-mass Planet Nine at positions sampled around its proposed orbit; the Abstract gives a = 700 AU and e = 0.6. Section 3.1 says the model takes up to 298 asteroids into account, but it does not say the authors fitted those asteroids’ locations. The fits described in Section 3.2 are of planetary-orbit parameters. (LLM, conf=0.87)
Experimental — accuracy not yet measuredPlanet Nine near perihelion would cause such a large effect on the Earth-Saturn distance that the Fienga et al. (2016) analysis and an extension by Holman & Payne (2016) can rule out any of the Planet Nine solutions near perihelion over the range of R.A. > 255° and R.A. < 2°.
“At its the nearest possible locations, in particular, Planet Nine would cause such a large effect on the Earth-Saturn distance that the Fienga et al. (2016) analysis and an extension by Holman & Payne (2016) (which assumes the same residuals) can rule out any of the Planet Nine solutions near perihelion over the range of R.A. of R.A. > 255 9 , R.A. < 2 9 deg.”
From Observational constraints on the orbit and location of Planet Nine in the outer solar system (2016) · cites this paper as Fienga et al. (2016)
Split into 2 atoms — 1 confirmed, 1 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.
Experimental — accuracy not yet measuredWith no Planet Nine, Fienga et al.'s best fit to the position of Saturn has Earth-Saturn distance residuals that roughly follow a sinusoid with a 12-year period and a full amplitude of ∼70 m.
“With no Planet Nine, their best fit to the position of Saturn has Earth-Saturn distance residuals that roughly follow a sinusoid with a 12-year period and a full amplitude of ∼70 m.”
From Observational constraints on the orbit and location of Planet Nine in the outer solar system (2016) · cites this paper as Fienga et al. (2016)
The Results section and Fig. 1 caption identify post-fit Cassini ranging residuals for the nominal INPOP ephemerides without Planet Nine. They do not describe those residuals as a 12-year sinusoid with a full amplitude of about 70 m; the reported 74.9 m is a standard deviation, not an amplitude. No page number is available in our copy. (LLM, conf=0.88)
Experimental — accuracy not yet measured
In a previous analysis, the present method did not provide constraints in contrast to those inferred by reprocessing the data record by including Planet Nine in the dynamical force models.
“Be that as it may, in a previous analysis [2] the present method did not provide constraints in contrast to those inferred by reprocessing the data record by including P9 in the dynamical force models [19].”
From Has Kronos Devoured Planet Nine and Its Epigones? (2026) · cites this paper as [19]
Fienga et al. (2016) calculations point to a small reduction in the residuals of the ranging data if the true anomaly of P9 is taken to be ν9 ≈ 118 deg.
“Moreover, the calculations of Fienga et al. (2016) point to a small reduction in the residuals of the ranging data if the true anomaly of P9 is taken to be 9 118 deg.”
From The planet nine hypothesis (2019) · cites this paper as Fienga et al. (2016)
The reanalysis by Folkner et al. (2016) suggests that gravitational determinations of Planet Nine's on-sky location are considerably less precise than advocated by Fienga et al. (2016) and Holman and Payne (2016a,b).
“The reanalysis of the ephemeris carried out by Folkner et al. (2016), however, highlights the sensitivity of Fienga et al.'s results to the specifics of the underlying dynamical model, suggesting that the gravitational determinations of Planet Nine's on-sky location are in reality considerably less precise than advocated by Fienga et al. (2016); Holman and Payne (2016a,b).”
From The planet nine hypothesis (2019) · cites this paper as Fienga et al. (2016)
Fienga et al. (2016) find that the strongest constraint on the existence of Planet Nine comes from the very precise measurements of the distance to Saturn as measured by the Cassini spacecraft over the past decade.
“They find that the strongest constraint on the existence of Planet Nine comes from the very precise measurements of the distance to Saturn as measured by the Cassini spacecraft over the past decade.”
From Observational constraints on the orbit and location of Planet Nine in the outer solar system (2016) · cites this paper as Fienga et al. (2016)
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- Authors
- Fienga, A., Laskar, J., Manche, H., & Gastineau, M.
- Affiliations
- Centre National de la Recherche Scientifique (FR)
- Venue
- Astronomy & Astrophysics
- Publisher
- EDP Sciences
- Published
- 2016-03
- Volume
- 587
- Issue
- L8
- Pages
- L8
- ISSN
- 0004-6361 (ISSN-L)
- 1432-0746
- OpenAlex
- W2283852246
- Cited by
- 76
- References
- 24
- Citations by year
- 2025: 3 · 2024: 2 · 2023: 5 · 2022: 1 · 2021: 2 · 2020: 10 · 2019: 8 · 2018: 7 · 2017: 14 · 2016: 24
- FWCI
- 8.19
- Type
- journal article
- Language
- en
- Open access
- bronze
- doi.org
- Locations
- Astronomy and Astrophysics (publishedVersion)
- arXiv (Cornell University) (submittedVersion)
- HAL (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 › Physics and Astronomy › Astronomy and Astrophysics › History and Developments in Astronomy
- Keywords
- ninth planet, Planet Nine, Sedna, orbital constraints, true anomaly, outer solar system
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