Most accounts claim that thanks to dark matter, stars orbit at the same speed regardless of distance from the galactic center. They don't say whether this is li

Most accounts claim that thanks to dark matter, stars orbit at the same speed regardless of distance from the galactic center. They don't say whether this is linear or angular velocity, but even if we assume it's linear velocity, how can it be that the sun (which is half way out) orbits every 0.25 Gyr and stars at the rim orbit every 1 Gyr?