A river flows toward a whirlpool, but a dam with a notch blocks the way. Most water piles up before the dam, but some, gaining height, leaps over it and falls straight into the funnel. So it is with gas in a galaxy: it streams toward the center but hits a ring of stars and gas, like a dam. Usually, everything stops there, swirling into a dense vortex.

But in the three-dimensional model built by scientists, some gas behaves differently. It rises above the galaxy's plane by about a hundred parsecs (roughly 300 light-years) and flies over the ring. For this to happen, the gas must not only jump high but also lose some of its rotation. Then it falls inward, toward the very center — where the supermassive black hole sits.

This leap is not chaotic: the gas that reaches the center moves along a narrow corridor defined by the ring's thickness. Most of the gas still remains in the ring and gives birth to new stars there. But the fraction that jumps over is enough to feed the black hole and explain why disks around it are often tilted relative to the galaxy.