3I/ATLAS shows perihelion burst and radial-only non-gravitational acceleration within the ecliptic corridor [OC]

The orbital fits come straight from JPL SBDB elements, and all analysis was done through a custom MCMC pipeline built in Python (NumPy, SciPy, pandas, matplotlib) with covariance propagation, BIC model comparison, and Monte Carlo resampling.

I reran the orbital fits with the same MCMC pipeline and priors used for 1I and 2I.
Data source: JPL SBDB orbital elements (solution updated 2025-11-05).
Weighting, covariance propagation, and observational window unchanged.
No manual tuning between runs. Geometry and component behavior for 3I remain consistent; the alignment is persistent, not numerical.

3I rolling NGA:
Radial component climbs gradually through perihelion, peaks near 3 × 10⁻⁷ au·d⁻², then holds a long shoulder and steady instead of impulsive.
Transverse tracks at roughly 40–50 % of the radial amplitude, slightly lagged.
Normal remains statistically consistent with zero (σ ≈ 2 × 10⁻⁸ au·d⁻²).
So the acceleration stays in-plane the whole way, no measurable out-of-plane term.
Everything about the shape reads as thermally driven, but the directional coherence is too clean to ignore.

Orientation metrics:
1I/ʻOumuamua — retrograde, i ≈ 57°, angular momentum flipped relative to the Solar System mean.
2I/Borisov — prograde, i ≈ 44°, comfortably random.
3I/ATLAS — i ≈ 2–3°, almost perfectly co-planar with the ecliptic and Jupiter’s Laplace plane (offset < 0.5°).
By isotropic odds (p ≈ 0.03), that’s a roughly 1-in-33 alignment; not impossible, just disconcertingly neat.

Model diagnostics:
Gravity-only solution rejected (ΔBIC ≈ +2 favoring NGA).
Impulsive-jet model slightly outperforms comet-law (ΔBIC ≈ +1.7 dex), suggesting a short-duration, directionally stable vent near perihelion provides the best fit.
10³ Monte Carlo draws under isotropic priors reproduce the same R:T hierarchy, confirming the in-plane bias isn’t a covariance artifact.

Interpretive context:
1I/ʻOumuamua — non-thermal, oblique acceleration with strong normal component; likely geometric or impulsive, not sunlight-driven.
2I/Borisov — classic thermal comet behavior; steady radial sublimation scaling with heliocentric distance.
3I/ATLAS — thermal onset with directional confinement; venting localized near the subsolar region, thrust locked to the orbital plane.

All the parameters still fit within cometary physics, but 3Is razor flat geometry and perfectly planar acceleration don’t sit right. It basically behaves like a comet on paper and something else in motion.

I’ll likely run change-point tomorrow to see if the slope breaks line up with perihelion or plane drift. I just want a second set of eyes on it before this disappears. The in-plane lock is there, and the more I check, the harder it is to sleep.