Ker Than for National Geographic News / October 15, 2009

Stevie Wonder may have been on to something when he sang about a ribbon in the sky

In a discovery that took astronomers by surprise, the first full-sky map of the solar system's edge—more than 9 billion miles (15 billion kilometers) away—has revealed a bright "ribbon" of atoms called ENAs.

The solar system is surrounded by a protective "bubble" called the heliosphere.

The narrow ribbon snakes along this bubble's inner wall between Voyager 1 and 2, twin spacecraft that have been exploring the solar system's boundary since 2004 and 2007, respectively. (Related: "Voyager Probes Send Surprises From Solar System's Edge.")

Voyager data, taken from specific regions within the boundary zone, had offered no hint that the ribbon existed. But from its orbit around Earth, NASA's Interstellar Boundary Explorer, or IBEX, spacecraft was able to give researchers a wider view.

IBEX team member Eric Christian, of NASA's Goddard Space Flight Center, compared the Voyager spacecraft to weather stations on Earth.

"Can you imagine trying to determine the weather of the entire Earth from two weather stations? You can't do it," Christian told reporters at a press conference this afternoon.

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