Ribbon of Particles Seen at Galaxy's Edge

The first all-sky maps reveal an odd ribbon between our galactic home and interstellar space.

The bubble of gas enveloping Earth and the rest of the solar system has some seriously weird formations where it abuts interstellar space, a region expected to show only smooth uniformity.

"This is a shocking new result for us and one that is not entirely understood," said David McComas, the lead scientist on a NASA mission called IBEX to map the heliosphere, a region of space dominated by boil-off of the sun's corona into what is known as the solar wind.

The sun pumps out streams of ionized particles that blast out into space in all directions at about 1 million miles per hour, forming a protective bubble and defining edge to the solar system. But the rivers of gas face pressure -- and some unknown physics -- when and where they encounter charged particles and magnetic fields emanating from interstellar space.

The solar system is currently traveling through a rather wispy interstellar cloud in the Milky Way galaxy, which gives the heliosphere plenty of breathing room. But the outside world apparently has some sharp elbows.

In their first big-picture view of the heliosphere, scientists discovered a well-defined ribbon of neutrally charged particles, precisely tailored -- process unknown -- by magnetic fields in the interstellar sea.

"This ribbon is organized around this magnetic field," said Rosine Lallement, senior scientist at the French National Center for Scientific Research in Paris. "It is truly new physics."

The ribbon snakes right between two NASA Voyager spacecraft, which reached the boundary zone between the heliosphere and interstellar space in 2004 and 2007.

The Voyager twins were launched in 1977 to explore the outer planets of the solar system. They took different paths toward the edge of the solar system and continue to radio data back to Earth about their local environments.

"Voyager 1 and Voyager 2 are like weather stations, but can you imagine trying to determine the weather on the entire Earth from two weather stations?" said Eric Christian, IBEX deputy mission scientist at NASA's Goddard Space Flight Center in Greenbelt, Md.

"They were both out there making these local observation and had no idea that the main 'storm' so to speak was running right down between them," added McComas, a senior executive director with the San Antonio, Texas-based Southwest Research Institute.

From a long, looping orbit around Earth, IBEX -- an acronym for Interstellar Boundary Explorer -- scans the whole sky for electrically neutral atoms coming in from the very edge of the heliosphere roughly 10 billion miles away.

"Sometimes a particle can come close to another particle and steal an electron. They then go zipping off in whatever direction they were going and some of them go right back in toward us and go right into the aperture of the IBEX spacecraft," McComas said.

Scientists had expected slight variations in the numbers of these energetic neutral atoms across the heliosphere, but IBEX found concentrations of up to about 300 percent.

"It shows that what we thought we understood about this interaction is definitely not right," McComas said. "We kind of have to go back and start over."

The discovery, reported in this week's Science, was verified by secondary measurements made by the IBEX instruments and also by a similar instrument on the Saturn-orbiting Cassini spacecraft.

The IBEX team is beginning to piece together a second all-sky map and already has gotten hints that the ribbon is changing.

"It's really going to be fascinating to watch this feature potentially change over years," McComas said.fascinating

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