CoChat
Sign Up
Cited by 60Stellar, planetary, and galactic studiesAstro and Planetary ScienceAstrophysics and Star Formation Studies

INTERACTION CROSS SECTIONS AND SURVIVAL RATES FOR PROPOSED SOLAR SYSTEM MEMBER PLANET NINE

Open access
Li, Gongjie, Adams, Fred C.·2016·The Astrophysical Journal Letters
DOI 10.3847/2041-8205/823/1/l3
Open this paper in CoChat — free accountOpen PDF

Abstract

Motivated by the report of a possible new planetary member of the solar system, this work calculates cross sections for interactions between passing stars and this proposed Planet Nine. Evidence for the new planet is provided by the orbital alignment of Kuiper belt objects, and other solar system properties, which suggest a Neptune-mass object on an eccentric orbit with a semimajor axis a 9 ≈ 400–1500 au. With such a wide orbit, Planet Nine has a large interaction cross section and is susceptible to disruption by passing stars. Using a large ensemble of numerical simulations (several million) and Monte Carlo sampling, we calculate the cross sections for different classes of orbit-altering events: (A) scattering the planet into its proposed orbit from a smaller orbit, (B) ejecting it from the solar system from its current orbit, (C) capturing the planet from another system, and (D) capturing a free-floating planet. Results are presented for a range of orbital elements with planetary mass m 9 = 10 M ⊕. Removing Planet Nine from the solar system is the most likely outcome. Specifically, we obtain ejection cross sections σ int ∼ 5 × 10 6 au 2 (5 × 10 4 au 2) for environments corresponding to the birth cluster (field). With these cross sections, Planet Nine is likely to be ejected if the Sun resides within its birth cluster longer than Δ t ≳ 100 Myr. The probability of ejecting Planet Nine due to passing field stars is ≲3% over the age of the Sun. Probabilities for producing the inferred Planet Nine orbit are low (≲5%).

The claims and statistics of this paper haven’t been checked yet.

Run the check — free, no account needed. It reads the open-access text and checks the sources it cites.

A few free checks a day · papers already verified open instantly · results are public

Integrity signals

Registry

Crossref · 10.3847/2041-8205/823/1/l3

Cites

37 of 37 references verified0 citation errors · 0 not checkable

Statistics

Claims the paper makes

The claims and statistics of this paper haven’t been checked yet.

Run the check — free, no account needed. It reads the open-access text and checks the sources it cites.

A few free checks a day · papers already verified open instantly · results are public

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

  • For conditions expected in the solar birth cluster, the probability for successful capture of Planet Nine is of order a few percent, both for freely floating planets and for planets captured from other planetary systems.

    “For the conditions expected in the solar birth cluster, the probability for successful capture is of order a few percent, both for freely floating planets (Li and Adams, 2016), and for planets captured from other planetary systems (Mustill et al., 2016).”

    From The planet nine hypothesis (2019) · cites this paper as Li and Adams, 2016

    Li and Adams (2016) is cited for capture of freely floating planets, not capture from other planetary systems, which the sentence cites to Mustill et al. In §3, the paper gives a successful-capture probability of about 0.2% for freely floating planets; its §4 conclusion says successful capture through either channel is at most 1%, rather than a few percent. (LLM, conf=0.88)

    Checked by a reasoning model — may be wrong.

    Experimental — accuracy not yet measured

  • Limits from the solar birth cluster are much more restrictive, so that surviving planets must have semi-major axes a < 1000 AU.

    “The corresponding limits from the solar birth cluster are much more restrictive, so that surviving planets must have semi-major axes a &lt; 1000 AU(Li and Adams 2016; see also section 7 for more detail).”

    From The planet nine hypothesis (2019) · cites this paper as Li and Adams 2016

    Section 3 (page not specified) finds ejection optical depths of order unity in the solar birth cluster for the 400–1000 AU orbits studied, versus 0.003–0.03 in the field. This supports the claim that the birth cluster imposes a much stronger survival constraint, but the paper does not establish a strict requirement that every surviving planet have a semimajor axis below 1000 AU. (LLM, conf=0.88)

    Experimental — accuracy not yet measured

  • For interactions in a cluster with velocity dispersion vc = 1 km/s and a planet with aphelion 640 AU, Li and Adams (2016) derive an ejection cross-section of σint ≈ 2.5×10^6 AU^2.

    “For interactions in a cluster with velocity dispersion of vc = 1 km / s, and a planet with an aphelion distance of 640 AU (comparable to our best-fit P9 orbital solution obtained in section 5), Li and Adams (2016) derive an ejection cross-section of int 2 : 5 10 6 AU 2 .”

    From The planet nine hypothesis (2019) · cites this paper as Li and Adams (2016)

  • The work of Li & Adams (2016) has shown that P9-type orbits have a negligible probability of being stripped away by passing stars within the field.

    “the work ofLi & Adams (2016) have shown that P9type orbits have a negligible probability of being stripped away by passing stars within the field.”

    From Generation of Low-inclination, Neptune-crossing Trans-Neptunian Objects by Planet Nine (2024) · cites this paper as Li & Adams (2016)

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

The self-check needs the paper’s full text.

Cites

Flagged first, then by citations

Research works printed but not linked: 1

  1. Binney, J., & Tremaine, S. 2008, Galactic Dynamics (Princeton, NJ: Princeton Univ. Press)

Cited by

Sorted by citations

Related

Authors
Li, G., & Adams, F. C.
Affiliations
  • Harvard University (US)
  • University of Michigan (US)
ORCID
Venue
The Astrophysical Journal Letters
Publisher
American Astronomical Society
Published
2016-05-12
Volume
823
Issue
1
Pages
L3
ISSN
  • 2041-8205 (ISSN-L)
  • 2041-8213
DOI
10.3847/2041-8205/823/1/l3
OpenAlex
W2291602825
Cited by
60
References
37
Citations by year
2026: 2 · 2025: 2 · 2024: 2 · 2023: 7 · 2022: 6 · 2021: 1 · 2020: 7 · 2019: 6 · 2018: 8 · 2017: 7 · 2016: 12
FWCI
5.26
Type
journal article
Language
en
Open access
Licence
Locations
  • The Astrophysical Journal Letters (publishedVersion)
  • arXiv (Cornell University) (submittedVersion)
  • arXiv (Cornell University)
Topics
  • Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Stellar, planetary, and galactic studies
  • Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Astro and Planetary Science
  • Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Astrophysics and Star Formation Studies
Keywords
Planet Nine, interaction cross sections, survival rate, planetary ejection, wide-orbit planets, free-floating planets

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

What counts as a claim ›How we measure confidence ›How we check this ›

Are you an author, or do you see a problem with this page? Request a review