Scientists in Germany have created a simple but powerful experiment that uses a swirling water tornado in a tank to mimic how planets form in space.
Built with easy-to-find parts like aquarium pumps and plastic cylinders, the experiment is a low-cost way to study the mysterious process of planet formation inside spinning discs of gas and dust around young stars.
In space, these swirling discs — called accretion discs — surround stars and contain gas mixed with tiny grains of dust.
Over time, the dust clumps together and grows into larger bodies that can eventually become planets.
Because these discs are so far away and incredibly complex, researchers usually rely on computer simulations to study them.
However, simulations can’t always capture every detail or run long enough to show how everything plays out. That’s where this new hands-on experiment can help.
The setup is surprisingly simple. It involves two clear plastic cylinders, one smaller and placed inside a larger one.
Water is pumped into the tank using an aquarium device, entering through two side nozzles that spin the water in opposite directions.
This spinning flow creates a vortex — like a small tornado — that reaches from the bottom of the tank to the top.
At the bottom, a central hole allows water to drain out, mimicking how gas spirals toward a star in a real accretion disc. The resulting tornado has the same kind of pull and rotation seen in space.
To study how particles move in the vortex, the team dropped tiny plastic beads into the water. These beads float near the surface and follow the swirling currents. High-speed cameras captured their motion, and a computer program tracked their paths.
Interestingly, the motion of these beads followed two of Kepler’s laws of planetary motion — rules first developed in the 1600s to describe how planets move around the Sun.
The beads moved faster near the centre, just like planets orbiting close to a star, and their orbits fit the pattern where larger circles take more time to complete. While the orbits weren’t perfect ellipses, the overall behaviour was very similar to what happens in space.
Researchers were especially excited that the fluid dynamics — the way the water flowed — closely matched what is expected in real planet-forming discs. That means this simple water tornado could help scientists better understand how dust and gas interact and how they come together to build planets.
This current version is just a prototype, but the team plans to improve it by scaling it up and changing the shape of the tank to reduce turbulence. A larger and smoother setup would allow more accurate experiments that could offer deeper insights into the earliest stages of planet formation.
“We’re thrilled with how well this works,” said Mario Flock from the Max Planck Institute for Astronomy. “With a few tweaks, this experiment could become a valuable tool to explore the secrets of how planets are born.”
