Unispiral: The One-Armed Spiral Shape in Astronomy

Unispiral is a term used in the context of spiral-shaped structures, such as spiral galaxies or spiral shells. It refers to a spiral shape that has only one arm, as opposed to a bispiral shape which has two arms.

In the case of spiral galaxies, unispiral galaxies are those that have a single arm of stars and gas that winds around the center of the galaxy. Bispiral galaxies, on the other hand, have two arms of stars and gas that wind around the center of the galaxy.

Unispiral shells are also found in various astronomical objects, such as planetary nebulae or supernova remnants. These shells are formed when a star expands and sheds its outer layers, creating a spiral shape with only one arm.

Overall, the term unispiral is used to describe any spiral structure that has only one arm, whether it's a galaxy, a shell, or another type of astronomical object.