Probe to Examine Our Space in Space

Oct. 13, 2008 -- As the solar system carts around our little section of the Milky Way galaxy, it disturbs the relative calm and cold fabric of intergalactic space. Not much is known about this boundary, except that the meeting is far from sedate -- something akin to a boat slamming through water at 50,000 mph.

So far, only the Voyager probes have crossed into the boundary zone, some eight to nine billion miles from Earth, with surprising results. On Sunday, NASA plans to launch a spacecraft that for the first time will be able to map the zone -- without having to go there.

The spacecraft is known as the Interstellar Boundary Explorer, or IBEX. It works by detecting particles that were stripped of electric charges in the outer regions of the heliosphere, the solar wind-filled bubble that delineates our solar system from intergalactic space.

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The particles are called energetic neutral atoms and they were discovered accidentally about 20 years ago during a mission that studied the Earth's magnetosphere and the solar wind. Instruments on the satellites to measure what should have been low background levels of energetic particles sometimes detected extra counts.

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"It wasn't random," IBEX lead scientist David McComas, with the Texas-based Southwest Research Institute, told Discovery News. "There were extra counts when the detector was pointing at Earth and when there were geomagnetic storms."

Scientists learned that these energetic neutral atoms were being generated from inside the magnetosphere and realized a similar process would occur from the solar system's magnetic bubble as well.

The neutral atoms are created when a neutral atom from interstellar space passes a positively-charged particle from the sun. When this happens, an electron can jump from one to the other, making the charged atom neutral.

The next challenge was to figure out how to put a spacecraft far enough away from Earth's magnetic field so it could find the atoms transformed by the solar system's passage through intergalactic space.

"It was this concept of having a new measuring system that created a way to look at things at a distance," McComas said. "It's amazing and interesting to see in science when a new capability arises how quickly it's grabbed onto and people realize 'Wow, we can really do something with this.'"