Knot in Mystery Ribbon at Solar System's Edge Unravels

Artist's impression of NASA's IBEX spacecraft exploring the edge of our solar system. CREDIT: NASA/GSFC

The unraveling of a knot in a mysterious energy ribbon shows that the edge of our solar system is a much more dynamic place than previously thought, according to new research.

NASA's Interstellar Boundary Explorer spacecraft has revealed quickly changing conditions near the heliosphere, a protective bubble that shields our solar system from powerful, damaging cosmic rays. The observations, which include the loosening of a knot in a strange energy ribbon, could help scientists better design long-range space missions, researchers said.

The findings result from a new set of "all-sky" maps IBEX has produced of our solar system's interaction with the galaxy. IBEX creates these maps by measuring and counting particles called energetic neutral atoms (ENA's), which are created in an area of our solar system known as the interstellar boundary region.

In this region, charged particles from the sun — the million-mile-per-hour solar wind — stream outward far beyond the orbits of the planets and collide with material between stars. These collisions cause the energetic neutral atoms to travel inward toward the sun at velocities ranging from 100,000 mph to more than 2.4 million mph.

A mysterious ribbon

The IBEX spacecraft was launched in October 2008. Its science objective was to discover the nature of the interactions between the solar wind and the interstellar medium at the edge of our solar system.

In October 2009, IBEX produced its first all-sky map, which revealed a mysterious bright ribbon of ENA's zipping toward the sun from the edge of the solar system.

This discovery surprised scientists, because previous theoretical models of the region had not predicted anything like it.

This new second set of all-sky maps, which was compiled based on six months of observations, shows a bright knot in this ribbon appearing to unravel. This result demonstrates that the area around the heliosphere, which helps shield the solar system from highly energetic cosmic rays, can change very quickly, scientists said.

"Our discovery of changes over six months in the IBEX ribbon and other neutral atoms propagating in from the edge of our solar system show that the interaction of our sun and the galaxy is amazingly dynamic," David McComas, IBEX principal investigator at the Southwest Research Institute in San Antonio, said in a statement. "These variations are taking place on remarkably short timescales."

The new findings were published this week in the Journal of Geophysical Research - Space Physics.

A shrinking protective bubble

The new IBEX data are consistent with other recent studies, which also highlight how quickly things can change in our cosmic neighborhood. The heliosphere has been shrinking recently, research shows, likely because the solar wind — which inflates it like a bubble — has been weakening.

This change is not a trivial concern, according to researchers.

"As the heliosphere shrinks, it actually turns out it's a less good shield," McComas said in a teleconference with reporters today (Sept. 30). "More of these galactic cosmic rays can find their way in."

Getting a better handle on these patterns could help space agencies map out future manned missions, researchers said. It may be wise, for example, to plan deep-space trips to coincide with when the heliosphere is big and robust, so it can shield astronauts from more cosmic rays.

Learning more about how our heliosphere waxes and wanes could also inform our search for life on other planets, researchers said. A strong protective shield could be key to the establishment and evolution of alien life.

"We'll be able to predict in a better way the habitable zones of extrasolar planets," study researcher Merav Opher, of George Mason University, said in the teleconference.

• Images: Sun Storms
• Video: NASA's IBEX: Exploring the Solar System's Edge
• Mysterious Ribbon at the Edge of Solar System Explained