When superfluid physics creates the illusion of alien civilizations

Sometimes astronomy goes nuts in many different ways at once. On rotating neutron stars (pictured), it gets particularly wild, because superfluids are involved. The result? Stars covered in highly regular triangular patterns — as if somebody built them that way.

Superfluids are liquids that have zero viscosity. Like superconductors, most superfluids need to be cooled to within spitting distance of absolute zero to show any effect. Unlike superconductors, they don't need electricity to do things that seem to make no sense. Most liquids have some internal friction - a resistance to change. A superfluid doesn't. Without any friction pulling at it, it can use the weak attraction between atoms to climb the walls of its container and flow out of it. It can also drip through molecule-sized cracks in a regular dish. The most common superfluid we know of is cooled helium, but superfluids made of fermions - the subatomic particles that make up atoms - are present under less controlled conditions. They slosh around the surface of neutron stars.

And they slosh a lot, since neutron stars are moving. Many neutron stars rotate. It's hard to predict the behavior of superfluids under the best of conditions, but researchers recently came up with a model that indicates that superfluids get even stranger when spun fast enough. Most people have spun a cup of coffee or water and seen a vortex form in the middle. Neutron stars spin somewhere between one and a thousand times per second. As they spin, the superfluids create their own vortex. Then they create more.


The faster the star spins, the more vortices open up in the superfluid on the surface of the star. They don't do so randomly - they form in triangular patterns. When the patterns get large enough, they form latticework on the surface of the star. Someone approaching (and compensating for the spin) would see the surface of the star pitted in a regular pattern. Someone looking at a more slow-moving star would see huge triangles made up of regularly-spaced holes floating on the star's surface. They would look like large, stable, geometric structures - seemingly too regular to be natural. Sometimes, it seems, the laws of physics themselves are trying to fool us into thinking we've found aliens.

Image of Vortices in Liquid Helium: NASA. Image of rotating neutron star: Chandra X-Ray Observatory

Via Scientific American and University of Washington.