Lineweaver et al. 2004: metallicity and supernova sterilisation combine to define an annular zone 7–9 kpc from galactic centre — but where does Omega Centauri (r ≈ 6 kpc) sit?
GHZ Parameters
Metallicity gradient and SN rate from Lineweaver 2004. Adjust threshold, rate scale, and time window.
GHZ peak radius
—
kpc from centre
P_hab at OC (r=6)
—
relative probability
P_hab at Sun (r=8)
—
relative probability
OC in GHZ?
—
relative to Sun P_hab
P_hab(r) vs galactocentric radius — 1 to 15 kpc
P_hab(r) = P_metal × P_survive
P_metal(r)
P_survive(r)
OC r=6 kpc
Sun r=8 kpc
Physics
The Galactic Habitable Zone combines two factors. Metallicity: stellar systems need sufficient heavy elements to form rocky planets. The metallicity gradient [Fe/H](r) = −0.07(r−8) is approximately linear; P_metal uses a logistic function peaked where [Fe/H] exceeds the threshold. Supernova sterilisation: high-energy events at the galactic centre suppress complex life. The SN rate Γ_SN(r) = Γ₀·exp(−r/3.5) falls off exponentially; P_survive(r) = exp(−Γ_SN(r)·0.1) is the probability of surviving a 0.1 Gyr sterilisation window. P_hab(r) = P_metal(r) × P_survive(r).
Omega Centauri orbits at r ≈ 6 kpc, inside the Sun's orbit at r ≈ 8 kpc. The GHZ peak in Lineweaver et al. 2004 is centred near 7–9 kpc. Whether OC falls inside the GHZ depends sensitively on the metallicity threshold and SN rate assumed — this tool makes that dependence explicit.
Limitations
The linear metallicity gradient is an approximation. SN rate models are uncertain by factors of a few. The sterilisation cross-section (0.1 Gyr window) is a simplification. The model does not account for galactic secular evolution, spiral arm passages, or the Milky Way's specific star formation history. It is a first-order illustration of competing effects.
Citation
Lineweaver, C. H., Fenner, Y., & Gibson, B. K. (2004). "The Galactic Habitable Zone and the Age Distribution of Complex Life in the Milky Way." Science, 303(5654), 59–62. DOI: 10.1126/science.1092322.
v1.0 — 2026-06-02