Most of our universe's mass lies unseen as an invisible agent known as dark matter, and while the nature of dark matter has puzzled scientists for decades, a new study says that's it's all really quite simple: it's made up of particles with a donut-shaped electromagnetic field.

"There are a great many different theories about the nature of dark matter. What I like about this theory is its simplicity, uniqueness and the fact that it can be tested," said professor Robert Scherrer, one of the study authors from Vanderbilt University.

Dark matter, the theory asserts, is made up of particles known as Majorana fermions. These fermions have long been hypothesized, but never proven. Scherrer and post-doctoral fellow Chiu Man Ho arrived at a simple way to test for the basic building blocks after realizing that the fermions should exhibit a unique, donut-shaped form of electromagnetism known as an anapole. Previous observations showed that dark matter cannot carry an electrical charge, but an anapole electromagnetic field is possible.

"Most models for dark matter assume that it interacts through exotic forces that we do not encounter in everyday life. Anapole dark matter makes use of ordinary electromagnetism that you learned about in school - the same force that makes magnets stick to your refrigerator or makes a balloon rubbed on your hair stick to the ceiling," said Scherrer.

"Further, the model makes very specific predictions about the rate at which it should show up in the vast dark matter detectors that are buried underground all over the world. These predictions show that soon the existence of anapole dark matter should either be discovered or ruled out by these experiments."

Particles with anapole fields do not react when stationary, meaning dark matter was much more prolific in the universe's early days. Because dark matter moves much slower today, detecting it has been difficult, until now - at least that's what the Vanderbilt scientists hope.

Dark matter is believed to make up 85 percent of the mass in the universe, and was first hypothesized back 1932.

You can read the full published study in the journal Physics Letters B.