EHT M87* shadow

Event Horizon Telescope shadow of M87* — DCT inherits Schwarzschild geometry.

Prediction	GR Schwarzschild shadow diameter \(\theta_{\rm sh}\) for \(M = 6.5 \times 10^9 M_\odot\)
Measured	\(\theta_{\rm sh} = 42 \pm 3\,\mu\)as (EHT Paper VI, 2019)
Residual	0.77σ
Status	PASS
Source paper	DCT-PPN-01

Mechanism

The no-scalar-hair theorem (DCT-SBD-01) locks \(P = 1\) at the horizon, so the photon sphere and shadow geometry inherit the GR Schwarzschild values exactly. Predicted shadow diameter matches EHT Paper VI at \(0.77\sigma\).

Derivation

Horizon-locked \(P = 1\) implies the photon-sphere radius \(r_{\rm ph} = 3GM/c^2\) and shadow diameter \(\theta_{\rm sh} = 6\sqrt{3}\,GM/(c^2 D)\) for distance \(D = 16.8\) Mpc, \(M = 6.5 \times 10^9 M_\odot\); the DCT prediction sits within \(0.77\sigma\) of the EHT measurement.

Python verification

The verification script for this observable is ligo_gravitational_wave_analysis.py. Run it with python3 ligo_gravitational_wave_analysis.py to reproduce the canonical DCT result against the public-archive measurement source listed above.

Methodology

Domain	Solar-system / strong-gravity (GR)
Input data source	See "References" below for the canonical public-archive citation. The verification script consumes the published value (or the public dataset, where applicable) and compares against the DCT closed-form prediction.
Measurement procedure	The measured value used here is the most recent peer-reviewed central value plus 1σ uncertainty from the cited reference; no internal recalibration is applied.
Acceptance threshold	HIT: residual within 1σ of measurement. SOFT: directional agreement, residual within bracketing range. OPEN: untested or unresolved.
Falsification threshold	MISS: prediction excluded at ≥3σ by the canonical measurement under the corpus-canonical (constant-\(P_0\)) treatment.
Current status	See the verdict pill in the prediction table above.

Cross-references

Related observables in the same domain: eht-sgr-a.

Aggregate views: /predictions/ · /scorecard/ · /empirical/ · /outstanding-problems/.

Audit notes

Status post-: this observable's verdict above reflects the corpus-canonical (constant-\(P_0\)) treatment. Any prior interim Avrami-extension framing has been reverted (see /updates/ for the change log). The cluster-paper deep-link above (DCT-PPN-01) is the canonical source of the derivation chain.

References

EHT M87* Paper VI
Source paper: DCT-PPN-01

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