Gough Compressed-Spring Spiral Galaxy Model

Julian Gough 2024: early AGN jets act as a compressed spring, expanding the thin disc beyond the thick disc — five quantitative predictions tested against observations

Galaxy Parameters

Galaxy stellar mass sets disc radii, age contrast, metallicity gradient, and formation timescale

Galaxy stellar mass log₁₀(M/M☉)10.5

10⁸ M☉10¹⁰10¹²

Spring strength (model parameter)1.0

0.5 (weak)1.02.0 (strong)

R_thick (kpc)

—

thick disc radius

R_thin (kpc)

—

thin disc radius

Disc ratio R_thin/R_thick

—

predicted > 1 always

Formation timescale

—

Gyr (longer in dwarfs)

Thick disc age

10.0

Gyr (≈ universal)

Thin disc age

—

Gyr (younger)

[Fe/H] inner thin disc

—

more metal-rich

[Fe/H] outer thin disc

—

more metal-poor

Disc Cross-Section Diagram (edge-on view)

Thick disc (amber) embedded within the larger thin disc (teal). Scale bar in kpc.

Milky Way Prediction vs Observation

At M_gal = 10^10.5 M☉ (Milky Way) preset. Green = match, amber = marginal, red = mismatch.

Prediction	Model	Observed	Match?
R_thin > R_thick	—	R_thin ~ 14–17 kpc > R_thick ~ 5–7 kpc	—
Thin disc younger	—	Thin ~4 Gyr, Thick ~10 Gyr	—
Inner [Fe/H] enriched	—	~+0.1 to +0.2 dex	—
Outer thin disc metal-poor	—	~−0.3 to −0.5 dex	—
Formation time (Gyr)	—	~2–3 Gyr for MW disc	—

⚠ All model values are from Gough's speculative framework; they are calibrated to the MW and are not independent predictions. The key novel claim is the causal mechanism (compressed spring from AGN jets), not the numerical values themselves.

What the model predicts

Gough's "compressed-spring model" proposes that early supermassive black hole jets (the "Blowtorch" from his earlier work) inject magnetic pressure into the protogalactic disc, compressing it. When the jet switches off, the magnetically compressed material springs outward, forming a thin disc that is radially larger than the pre-existing thick disc. Five quantitative predictions follow:

1. R_thin > R_thick always. The thin disc must extend beyond the thick disc in any spiral galaxy, because the spring expansion pushes it outward. Confirmed by MW observations: R_thick ~ 5–7 kpc, R_thin ~ 14–17 kpc (ratio ≈ 2.5).

2. Thin disc stars are younger. They form after the spring releases, while thick disc stars formed earlier. Confirmed: MW thick disc ~10 Gyr, thin disc ~4–6 Gyr.

3. Inner thin disc more metal-rich than outer. Inside-out formation: the inner thin disc forms first from gas that has already been enriched by thick disc stellar evolution. Observed in the MW as a negative metallicity gradient.

4. Outer thin disc gas/stars are lower metallicity. The outer regions form later from less-enriched gas pushed outward by the spring. Consistent with MW observations and the pattern seen in Tsukui et al. 2025 at z > 4.

5. Low-mass galaxies take longer. The formation timescale T_form ∝ (M_gal)^(-0.3) — weaker self-gravity means the spring releases more slowly. Consistent with observations of extended star formation in dwarfs.

Epistemic note

This model is speculative and not peer-reviewed. It is published on Gough's Substack "The Egg and the Rock" (2024). The model builds on his Blowtorch Theory (also non-peer-reviewed) and on Tsukui et al. (2025, Nature Astronomy), which is peer-reviewed. The qualitative predictions match observations, but the model lacks a full quantitative derivation and has not been tested against a broad observational sample.

References

Gough, J. (2024). "A compressed-spring model of spiral galaxy formation." The Egg and the Rock. theeggandtherock.com Tsukui, T. et al. (2025). Nature Astronomy. (Thin disc / thick disc observations at high-z) Bland-Hawthorn, J. & Gerhard, O. (2016). ARA&A 54:529. DOI: 10.1146/annurev-astro-081915-023441 Minchev, I. et al. (2013). A&A 558:A9. DOI: 10.1051/0004-6361/201220189

v1.0 — 2026-06-02