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Friday, May 11, 2012

The Edge of the Solar System is Different Than Previously Believed

Nasa's probes have seen the 'edge' of our solar system for the first time - and it's completely different from what scientists thought.

Our solar system is flying through space more slowly than we thought - and Nasa's IBEX - Interstellar Boundary Explorer - has found it doesn't have a 'bow shock', an area of gas or plasma that shields our solar system as it hurtles though space

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For about a quarter of a century, researchers believed that the heliosphere moved through the interstellar medium at a speed fast enough to form a bow shock.

IBEX data have shown that the heliosphere actually moves through the local interstellar cloud at about 52,000 miles per hour, roughly 7,000 miles per hour slower than previously thought -- slow enough to create more of a bow ‘wave’ than a shock.

‘While bow shocks certainly exist ahead of many other stars, we’re finding that our Sun’s interaction doesn’t reach the critical threshold to form a shock, so a wave is a more accurate depiction of what’s happening ahead of our heliosphere -- much like the wave made by the bow of a boat as it glides through the water,’ says McComas.

Another influence is the magnetic pressure in the interstellar medium. IBEX data, as well as earlier Voyager observations, show that the magnetic field is stronger in the interstellar medium requiring even faster speeds to produce a bow shock. Combined, both factors now point to the conclusion that a bow shock is highly unlikely.

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[Using the IBEX probe,] [r]esearchers found 74 oxygen atoms for every 20 neon atoms in the interstellar wind. In our own solar system, there are 111 oxygen atoms for every 20 neon atoms.

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'Our solar system is different than the space right outside it, suggesting two possibilities,' David McComas, IBEX principal investigator, at the Southwest Research Institute in San Antonio, said.

'Either the solar system evolved in a separate, more oxygen-rich part of the galaxy than where we currently reside, or a great deal of critical, life-giving oxygen lies trapped in interstellar dust grains or ices, unable to move freely throughout space.'

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