Knot In The Ribbon At The Edge Of The Solar System Unties

One of the clear features visible in the IBEX maps is an apparent knot in the ribbon. Scientists were anxious to see how this structure would change with time. 

The second map showed that the knot in the ribbon somehow spread out. It is as if the knot in the knot was literally untangled over only six months.

This visualisation shows a close-up of the ribbon (green and red) superimposed on the stars and constellations in the nighttime sky. The animation begins by looking toward the nose of the heliosphere and then pans up and left to reveal the knot.

The twisted structure superimposed on the map is an artist's conception of the tangled up ribbon. The animation then shows this structure untangling as we fade into the second map of the heliosphere. Credit: IBEX ScienceTeam/Goddard Scientific Visualization Studio/ESA

Researchers believe the ribbon, first revealed in maps produced by NASA's Interstellar Boundary Explorer (IBEX) spacecraft, forms in response to interactions between interstellar space and the heliosphere, the protective bubble in which the Earth and other planets reside. Sensitive neutral atom detectors aboard IBEX produce global maps of this region every six months.

Analyses of the first map, released last fall, suggest the ribbon is somehow ordered by the direction of the local interstellar magnetic field outside the heliosphere, influencing the structure of the heliosphere more than researchers had previously believed.

The knot feature seen in the northern portion of the ribbon in the first map stood apart from the rest of the ribbon as the brightest feature at higher energies.

While the second map, released publicly with the just-published paper, shows the large-scale structure of the ribbon to be generally stable within the six-month period, changes are also apparent. The polar regions of the ribbon display lower emissions and the knot diminishes by as much as a third and appears to "untie" as it spreads out to both lower and higher latitudes.

"What we're seeing is the knot pull apart as it spreads across a region of the ribbon," says Dr. David J. McComas, IBEX principal investigator and an assistant vice president at Southwest Research Institute in San Antonio.

"To this day the science team can't agree on exactly what causes the knot or the ribbon, but by comparing different sky maps we find the surprising result that the region is changing over relatively short time periods. Now we have to figure out why."

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