In Star Trek, an astral eddy is a subspace disruption anomaly. The phenomenon was first encountered in 2373. A Vostigye science station, in the Delta Quadrant, was torn apart by an astral eddy with the temperature gradient of nine million kelvins. Eddies collapsing back to the interfold layer also trapped a probe and the shuttlecraft Cochrane, while it was gathering plasma particles with bussard collectors from the wake of an eddy. (VOY: "Real Life"). An erupting eddy is shaped like a ring emanating from a whirlpool center. Within the ring there are massive discharges of plasmatic energy. The center however is totally calm. Matter inside the anomaly is exchanged between space and subspace. Astral eddies form inside interfold layers, between space and subspace. A sufficiently large eddy periodically erupts into normal space via a subspace rupture. The eddy forms, expands, moves, dissipates and collapses back into the interfold layer. Due to the fact that an eddy is highly charged with plasma, it leaves behind an unusual wake of plasma particles that emanate from subspace. This wake produces dangerous levels of radiation. A human traveling in the wake on a class 2 shuttle can temporarily be protected from the effects with hyronalin and lectrazine.

Astral eddies disable starship propulsion and navigation. They cause turbulence in the levels that transporters cannot be used to beam anything to or from the anomaly. An erupting eddy also produces graviton waves that impact objects further away. Phasers may be able to disperse an eddy when it erupts into normal space.

There is no such phenomena termed as astral eddies in real astrophysics. However, the images used to illustrate astral eddies in Star Trek very clearly indicate a phenomena similar to a black hole. Contemporary models proposed to describe the flow into a black hole from the turbulent flow of matter in initially circular orbits about the black hole do illustrate the possibility of eddy formations. The shear between fluid elements at slightly different orbital radii causes turbulent eddies to be formed. These eddies determine the dissipation rate of kinetic energy into thermal energy. For approximately circular orbits, the magnitude of the gravitational potential energy is always equal to twice the kinetic energy; the destruction of the latter resulting in a reduction in the orbital radius and hence the potential energy. In this model, the turbulent eddy rotation period is presumed to be determined by the gradient in the gravity acceleration, leading to an eddy period proportional to the orbital period. If the flow speeds are supersonic but not relativistic, then the turbulent eddy size is set by the product of the eddy rotation period and the speed of sound. At a certain smaller radius, the orbital speeds and hence the dissipation rate are so great that the speeds become relativistic and the molecular speed tends toward its limit. Then the effective eddy size is controlled by the product of the eddy rotation period and the speed of light. Using these estimates for the important eddy size, the dissipation rate, temperature, density and sinking speed as a function of the orbital radius and the rate of mass flow into the black hole are derived.