Interaction of Stars Hosting Planets with Sgr A* Black hole

Nazanin Davari; Rainer Spurzem; Roberto Capuzzo-Dolcetta

REVIEW 3 major objections 3 minor 15 references

Interaction of Stars Hosting Planets with Sgr A* Black hole

T0 review · 3 major / 3 minor · reviewed 2026-08-14 · deepseek-v4-flash

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Pith's one-line read Simulations of S-stars with planetary systems show that inner planets remain bound to their hosts during close encounters with Sgr A*, while outer planets are preferentially stripped.

desk verdict A modest but genuine first step: simulated multi-planet survival around S-stars, whose main trend is plausible but rests on a single realization per configuration. read the letter →

arxiv 1908.06298 v1 pith:ZVPRAQ4U submitted 2019-08-17 astro-ph.EP astro-ph.SR

Nazanin Davari , Roberto Capuzzo-Dolcetta , Rainer Spurzem This is my paper · ORCID

classification astro-ph.EPastro-ph.SR

keywords SgrA*S-starsplanetarysystemsN-bodysimulationpost-NewtoniandynamicsGalacticCenterplanetsurvivalorbitalstability

verification ladder T0 review T1 audit T2 compute T3 formal

The pith

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The reading

This paper asks whether planets can survive when their host stars make close passes by Sagittarius A*, the supermassive black hole at the center of the Milky Way. It runs N-body simulations of the 40 innermost S-stars, each given a miniature Solar System, with relativistic corrections in the equations of motion. The central result is that the innermost planets—Mercury, Venus, Earth, and Mars analogues—remain bound to their host stars far more often than the outer planets, and Mercury-like planets around late-type stars stay bound in 100% of the runs. If true, planetary systems can persist in the immediate neighborhood of a supermassive black hole, at least in their inner parts.

What carries the argument

The load-bearing mechanism is a regularized N-body integrator with post-Newtonian corrections up to order 2.5, which lets the simulation follow close encounters with the black hole without numerical singularities. The 40 S-stars are initialized on their observed orbits, and each host star is assigned a planetary system patterned on the Solar System: seven planets for late-type stars and the three outer planets for early-type stars. The planetary system is inclined relative to the stellar orbit by angles from 0 to 180 degrees, and the quantity that carries the argument is the fraction of planets still bound to their host stars at the end of the simulation.

What would settle it

A transit or radial-velocity survey sensitive to close-in planets around S-stars that finds none would undercut the premise that planetary systems are present, though it would not by itself disprove the dynamics. A direct numerical check is to rerun the same 40-star simulation with randomly sampled planetary mean anomalies and mutual inclinations; if the Mercury-type bound fraction drops well below the reported 100%, the result depends on the chosen initial conditions rather than on the encounter dynamics.

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Extended reading notes

Core claim

The paper claims that during close encounters with Sgr A*, the innermost planets of a solar-like system are preferentially retained. In its simulations, Mercury-type planets around late-type S-stars remain bound in every case, Venus- and Earth-type planets in 72.5% of cases, and Mars-type in 61.85%; for early-type stars, which start with only Jupiter, Saturn, and Uranus analogues, the bound fractions are 75.62%, 47.5%, and 35.31%, respectively. The paper also reports that some early-type stars escape the Galactic Center and that their planetary systems can be swapped to a nearby star during the encounter.

Load-bearing premise

The whole exercise assumes that the S-stars were born elsewhere, migrated to the Galactic Center, and kept their planetary systems during the trip; if S-stars arrived planet-free, the survival rates describe a hypothetical rather than an actual population.

Editorial extensions

If this is right

Planetary systems around S-stars, if present, should arrive at the Galactic Center heavily truncated: inner planets survive, outer planets are stripped.
The stripped outer planets become free-floating planets wandering in the Galactic Center region.
Early-type S-stars are expected to lose most or all of their planetary systems, and some may exchange planets with other stars during close encounters.
Observational searches for planets around S-stars should concentrate on close-in orbits, where the survival probability is highest.
The simulated bound fractions give a quantitative prior for interpreting future detections or non-detections of planets in the S-star cluster.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

The simulations do not include planet-planet scattering, stellar evolution, or the mechanism that originally placed planets around these stars; any of these could change the retention fractions, so the 100% Mercury survival should be read as a dynamical statement, not a formation statement.
A natural testable extension is to vary the planetary architecture, for example using hot Jupiters on eccentric orbits or multiple planets with mutual inclinations, and check whether inner-planet survival remains the robust pattern.
If the swap of planetary systems during encounters is common, the Galactic Center may be a place where planets change host stars, producing systems with no analog in the field.
The survival hierarchy inner > outer suggests that any planetary system discovered around an S-star is likely a compact, multi-planet system with its outermost planets missing.

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Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Desk Editor's Note

read the letter

Worth a look if you care about planetary survival near Sgr A*. This proceedings paper reports N-body simulations that assign Solar-System-like planetary systems to 40 S-stars, integrate for 4000 yr with post-Newtonian terms, and report bound fractions. That is new: prior work (Trani et al. 2016) treated single planets, not full systems. The qualitative result—inner planets survive better than outer giants—comes straight out of Table 2 and is physically reasonable: tighter orbits are harder to unbind in a tidal encounter. The use of actual S-star orbital elements from Gillessen et al. is a plus, and the ARGdfcode regularization gives confidence the close encounters are handled properly.

The soft spots are real but not fatal. First, the migration premise (S-stars carry planets into the GC) is stated without evidence. The paper is upfront that these are "putative" systems, so it is framed as a hypothetical scenario rather than a claim about actual detections. That is acceptable for a first exploration, though it limits the astrophysical interpretation.

Second, and more important: Table 2 presents one realization per inclination per star. The planetary orbits are initialized as near-circular, coplanar copies of the Solar System, with no randomization of phases, eccentricities, or mutual inclinations. Since the impulsive kick from a close Sgr A* passage depends on orbital phase, a single phase choice can systematically skew the bound fraction. The 61–100% inner versus 16–49% outer spread could be a property of the dynamics, or it could be an artifact of the chosen initial conditions. The paper needs an ensemble average over random phases and eccentricities before the central claim is solid. This is an internal robustness issue, not a question of the migration premise.

There are also no error bars, no convergence tests, and the masses of the S-stars are set to representative values (12 M☉, 1.5 M☉) rather than drawn from the measured distribution. For a conference proceedings, this is understandable, but it means the results should be treated as preliminary, as the authors themselves say. The citation pattern is fine—they engage the relevant S-star and planetary dynamics literature without padding.

Bottom line: a modest but real contribution, with a clear and testable claim that currently rests on a single-per-configuration numerical experiment. The paper deserves a serious referee if expanded into a full journal article with ensemble runs and sensitivity tests. I would bring it to the reading group only if someone is actively working on GC planetary dynamics; otherwise it's a maybe. I wouldn't cite it in my own work until the ensemble check is done. Recommendation: engage with it as a legitimate preliminary study, send it to peer review in a venue that allows short contributions, but ask for the ensemble robustness analysis before accepting.

Referee Report

3 major / 3 minor

Summary. The paper hypothesizes that the S-stars in the Galactic Center may host planetary systems and investigates their dynamical fate under repeated close encounters with Sgr A*. Using a regularized N-body code with post-Newtonian corrections to order 2.5 and the observed orbital elements of about 40 S-stars, the authors attach a solar-like planetary system to each star (7 planets for late-type stars, 3 outer planets for early-type stars) and vary the inclination of the planetary orbital plane relative to the stellar orbit from 0 to 180 degrees. They report preliminary bound fractions in Table 2, concluding that inner planets (Mercury through Mars) remain bound at higher rates than outer planets (Jupiter through Uranus) for late-type hosts, and that some early-type stars escape the Galactic Center with their planetary systems swapped by a nearby star. The paper is explicitly a preliminary proceedings contribution.

Significance. If the central claim holds, this is a first estimate of the survival probability of putative planetary systems around S-stars, with direct relevance to the possibility of planets in the Galactic Center. The strengths of the work are that the simulations use a well-tested regularized N-body code with PN corrections, adopt observed S-star orbits as initial conditions, and contain no parameter fitted to the survival fractions—the bound rates emerge from the assumed initial conditions. However, the result is conditional on a speculative planetary architecture and on the migration premise, and the reported rates lack ensemble statistics and sensitivity tests. The paper therefore constitutes an interesting preliminary finding rather than a fully established result.

major comments (3)

[Section 3, Table 2] The central claim that inner planets remain bound at higher rates (61–100% vs 16–49%) rests on a single realization per star per inclination: each of the ~40 S-stars is seeded with an identical copy of the Solar System with fixed orbital phases, eccentricities, and mutual inclinations, and the inclination of the planetary plane is the only varied parameter. Because the tidal perturbation from Sgr A* depends on planetary phase at pericenter, the reported dichotomy could be an artifact of the chosen initial phases rather than a generic dynamical property. Please rerun the simulations for an ensemble of random mean anomalies and small eccentricities for each star and inclination, and report mean bound fractions with standard deviations or confidence intervals. Without such averaging, the numbers in Table 2 overstate the precision (e.g., '61.85%' from a small sample) and the qualitative conclusion is not yet robust.
[Section 2] The simulated planetary systems are all exact solar twins, with planet masses, semi-major axes, and eccentricities fixed to Solar System values, and for early-type stars an ad-hoc choice to include only Jupiter, Saturn, and Uranus ('Since it is less likely that massive early-type stars could harbor planets so close'). This architecture directly determines the columns of Table 2. The paper should test sensitivity to plausible alternative architectures (e.g., different planet multiplicities, semi-major axis distributions, or an extra ice-giant belt) and to the uncertain stellar masses (8–14 M⊙ and 0.5–2 M⊙) before claiming a general result for S-star planetary systems.
[Abstract and Section 1] The premise that S-stars 'probably still keep their planetary systems throughout their voyage' is asserted without support. Given that the preferred migration scenario is binary disruption (Hills 1988), the retained companion may be ejected with a kick that could strip or destabilize its planets; the simulations instead start with the planets already in place around their host on the observed S-star orbits. Please either add a justification or test of planetary survival during the migration event, or explicitly reframe the conclusion as applying to a hypothetical population of stars that arrived with their planetary systems intact. This also affects the physical interpretation of the bound fractions in Table 2.

minor comments (3)

[Section 3] The sentence 'Our simulations shows that the innermost planets i.e, Mercury, Venus, Earth and Mars...' contains a subject-verb agreement error ('simulations shows') and a punctuation error ('i.e,' should be 'i.e.,').
[Table 2 caption] The caption states 'the inclinations in the range of 0° − 90°' while the text (Section 2) says the inclination is varied over 0° − 180°; clarify whether Table 2 is a subset of the runs and why the 90°–180° results are omitted.
[Figure 2] Figure 2 is described only by the caption; the text should state what each plotted curve represents and how the statement 'six out of seven planets remain bound to the star S89' is inferred from the plotted orbital elements. The current description is too vague for the reader to verify the result.

Circularity Check

0 steps flagged · score 0.0 of 10

No significant circularity: the simulated bound fractions are genuine outputs of N-body integrations, not fits to themselves.

full rationale

The paper's central claim is the survival fraction of planets around S-stars, reported in Table 2. These fractions are computed by direct N-body simulation using ARGdfcode from assumed initial conditions: each S-star is assigned a copy of the Solar System with specified masses, eccentricities, and semi-major axes, and the planetary inclinations are varied from 0 to 180 degrees. No parameter is fitted to make Mercury survive more often, and the simulation outcomes are not fed back into the initial conditions. The use of ARGdfcode (Arca-Sedda & Capuzzo-Dolcetta 2019) is a tool citation: the paper does not rely on that code's results as evidence for the astrophysical claim. The premise that S-stars migrated from elsewhere and may carry planetary systems is an assumption stated in the abstract and introduction, but an assumption is not a circular step because the survival fractions do not presuppose the conclusion that inner planets are more likely to remain bound. There is no equation in which the output is defined in terms of itself, no fitted parameter renamed as a prediction, and no uniqueness argument imported from the authors' prior work. The stronger statement that the inner-planet survival advantage is a robust physical property would benefit from an ensemble of randomized planetary phases and eccentricities, but that is a robustness concern, not circularity.

Assumptions & free parameters 2 free parameters · 5 assumptions · 0 invented entities

The central result depends on several stated assumptions: the migration scenario, solar-like planetary architectures, and published orbital parameters. These are reasonable for a preliminary study but are not independently verified, and the fixed stellar masses in the preliminary runs are chosen by hand.

free parameters (2)

early_type_star_mass_preliminary = 12 M_sun
Set by hand in the preliminary runs, chosen from the literature range 8-14 M_sun. Not fitted to data, but affects the dynamics and survival rates.
late_type_star_mass_preliminary = 1.5 M_sun
Set by hand in the preliminary runs, chosen from the literature range 0.5-2 M_sun. Not fitted to data, but affects the dynamics and survival rates.

assumptions (5)

domain assumption S-stars migrated from elsewhere and still carry their planetary systems.
Central motivation of the paper, stated in the Abstract and Section 1. If false, the simulated scenario does not correspond to real S-stars.
domain assumption Planetary systems initially resemble the Solar System in mass, eccentricity, and semi-major axis.
Section 2: 'We assign planetary systems to each of the stars in S-star cluster similar to our Solar planetary system in mass, eccentricity and semi-major axis.' This assumption shapes all results.
domain assumption Orbital parameters of the 40 S-stars from Gillessen et al. (2009, 2017) are reliable initial conditions.
Section 2 uses these published data as initial conditions. Any errors or selection effects in those data propagate into the simulation.
domain assumption Post-Newtonian corrections to order 2.5 are sufficient to model close encounters with Sgr A*.
Section 2 states that PN terms up to order 2.5 are included. No convergence tests or comparisons with higher-order terms are shown.
domain assumption Mass estimates for early-type stars can be extrapolated by magnitude to stars not directly measured by Habibi et al. (2017).
Section 2: 'We use their evaluation to estimate the mass of other early-type stars which have a similar magnitude.' This extrapolation is uncertain.

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Cite this review

Pith. "Pith review of Interaction of Stars Hosting Planets with Sgr A* Black hole." pith.science (2026). https://pith.science/paper/ZVPRAQ4U

@misc{pith2026190806298,
  author       = {Pith},
  title        = {Pith review of: Interaction of Stars Hosting Planets with Sgr A* Black hole},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/ZVPRAQ4U}},
  note         = {Machine review of arXiv:1908.06298}
}

read the original abstract

We present some preliminary results of our ongoing project about planetary systems around S-stars in the vicinity of Sgr A* black hole. Since S-stars might have migrated in the Galactic Centre (GC) from elsewhere, they probably still keep their planetary systems throughout their voyage. In this work, we study the destiny of their putative planetary systems after close interaction with the central black hole of our galaxy.

Figures

Figures reproduced from arXiv: 1908.06298 by the authors.

**Figure 1.** Comparison of trajectories of the S-stars projected onto the plane of the sky due to Gillessen et al. (2009) (top) with their orbits due to our simulation including PN terms up to order 2.5 (bottom). The scale of the both figures is the same in arcsecond. so far to investigate the dynamics and stability of planetary systems in star clusters (e.g., Spurzem et al. 2009; Cai et al. 2017). Following the migration scenar… view at source ↗

**Figure 2.** The stability of orbital elements versus time for ”S89” planetary system. The black line shows the eccentricity of the host star ”S89” [PITH_FULL_IMAGE:figures/full_fig_p004_2.png] view at source ↗

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Reference graph

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Pith tools

Reviewed August 14, 2026 · model on record in the stance chip above.

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