Mission finds bright ribbon at solar system border

This is the kind of surprising discovery that makes science so fun and rewarding.

WASHINGTON (Reuters) - A bright ribbon of hydrogen atoms marks the edge of the solar system, where the Sun's wind meets emissions from the rest of the galaxy, researchers reported on Thursday.

They used telescopes aboard the orbiting Interstellar Boundary Explorer spacecraft or IBEX to look toward the heliopause, which is the boundary where solar wind meets galactic wind at the edge of the solar system beyond Pluto.

Researchers combined images from IBEX with data from the Cassini spacecraft, which is near Saturn, and said it completely alters their ideas about what this border area looks like.

"The IBEX results are truly remarkable, with emissions not resembling any of the current theories or models of this never-before-seen region," David McComas of the Southwest Research Institute in San Antonio, Texas, who led the research, said in a statement. …

Glimpses of Solar System's edge

…Our Solar System is whipping around the centre of the galaxy. Just like a hand held out of a moving car, the Solar System feels a "wind" of particles from the region between our star and its nearest neighbours.

At the same time, the solar wind - a constant stream of fast-moving particles in all directions - blows outwards from the Sun.

The boundary at which the incoming and outgoing particles are at equivalent pressures, known as the heliopause, defines the heliosphere - the "bubble" in space generated by our own Sun's exhalations.

The true extent and shape of the heliosphere has been a subject of debate for more than half a century. Until now, the best clues came from the two Voyager spacecraft, which are believed to have passed through the heliopause at two different distances.

Through a process known as "charge exchange" at the heliosphere's edge, fast-moving neutral or uncharged particles are created, and it is these energetic neutral atoms or ENAs that the Ibex spacecraft aims to measure.

It orbits the Earth in a vast ellipse, gathering incoming ENAs flying back from the heliopause at a range of speeds.

What a number of researchers have found is that the flow of the ENAs is uneven, with a significantly higher flow in a "ribbon" across the sky. …

Mission finds bright ribbon at solar system border

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