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The solar system—the sun and all its planets—is surrounded by a protective magnetic bubble-like boundary called the heliosphere, which acts as a frontline against incoming cosmic rays and interstellar clouds. The science team had been using IBEX to construct the first-ever all-sky map of the interactions occurring at the edge of the solar system when they came across this puzzling ribbon that appears across much of the heliosphere.

While the ribbon doesn’t give off any light, for some unknown reason it emits copious amounts of particles, called energetic neutral atoms, towards the Sun—much more than the surrounding areas do. IBEX can pick up these emissions billions of miles away from Earth orbit, and use them to map the ribbon’s structure.

More than a dozen theories have been put forth to try and explain why mathematical models of the ribbon structure just didn’t quite match what astronomers were seeing (ie. ribbon is actually thicker than it should be according to theory). But now the IBEX science team thinks they have come up with an explanation that begins to explain their observations.

The new theory suggests that this ribbon sits in a particular location at the heliosphere where the solar wind from the Sun crosses the galactic magnetic field. The outward-bound neutral hydrogen atoms that make up this solar wind bounce off the boundary and form gyrating charged ions that create waves in the magnetic field.

The resulting particles stream back inward and form the ribbon of energized neutral atoms.

“This is a perfect example of the scientific process,” said David McComas, co-author on the study and the team leader for the IBEX mission, in a statement.

“We observe something completely new and unexpected with IBEX, develop various hypotheses to explain the observations, and then develop mathematical models to try to validate the hypotheses.”