The Universal Rotation-Curve Shape
Every galaxy normalized, with the median trend of each group
Thin lines: 134 individual SPARC galaxies (Lelli, McGaugh & Schombert 2016), each real rotation curve plotted point by point in normalized axes V/Vflat vs R/Rdisk. Thick lines: the running median of each group, computed from those same real curves — a summary of the data, not a model fit. Colours: A bulgeless disks, B bulged disks, C gas-rich dwarfs.
What the median curves reveal
Once each galaxy is expressed in its own units, the individual scatter collapses into a clear ordering of the three groups — and a shared destination:
- Bulged disks (red) reach the plateau almost immediately and slightly overshoot near the centre — the central bulge adds velocity at small radius.
- Bulgeless disks (green) rise over about two disk scale lengths, then flatten.
- Gas-rich dwarfs (blue) rise the most slowly — their mass is spread out and gas-dominated — and reach the plateau last.
The ordering is exactly what the mass distribution predicts: the more centrally concentrated the visible mass (bulge → disk → diffuse gas), the faster the curve rises. But the endpoint is identical for all: a flat plateau that the visible matter alone cannot sustain.
The rise differs by group, the plateau is universal. This single normalized shape — rising according to the visible mass concentration, then refusing to fall — is what any theory of galactic dynamics must reproduce from the visible components alone. It is the precise benchmark for the BeeTheory campaign: not one number per galaxy, but the full shape, group by group.
BeeTheory.com — Universal rotation-curve shape · Data: Lelli, McGaugh & Schombert 2016 · Initial generation: 21 May 2026 with Claude.ai · © Technoplane S.A.S. 2026