Glimpses of Solar Systems edge
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Posted 16 October 2009 - 06:49 AM
The first results from Nasa's Interstellar Boundary Explorer (Ibex) spacecraft have shown unexpected features at our Solar System's edge. Ibex was launched nearly one year ago to map the heliosphere, the region of space defined by the extent of our Sun's solar wind.
Ibex's first glimpses show that the heliosphere is not shaped as many astronomers have believed. A series of papers in the journal Science outlines the results. 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.
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