11 Jun 2011

At the edge of the solar system, it's choppy

2:00 pm on 11 June 2011

NASA says new data sent back to Earth by the two Voyager spacecraft shows the edge of the solar system resembles a turbulent ocean and is much less smooth than believed.

It says the new data calls into question existing theories about the region.

NASA's Voyager probes, which were launched in 1977, are now approaching the very edge of our sun's influence, more than 14 billion kilometres from Earth; and they are still returning data.

That information, the BBC reports, has allowed scientists to build a better picture of what conditions are like in the zone where matter blown out from the sun pushes up against interstellar space.

This process is sculpting the wind into discrete bubbles tens of millions of kilometres wide.

Eugene Parker of the University of Chicago says computer modelling based on the Voyager insights suggests the edge of our solar system is a froth of activity, like "an agitated jacuzzi".

Insight into cosmic rays

Researchers say this has implications for our understanding of cosmic rays - the storm of high-energy particles that are accelerated in Earth's direction by exploded stars, black holes and other exotic locations in the galaxy.

The observation is of interest not just to physicists but also to astronauts, who must protect themselves from the damaging health effects of cosmic rays, and to spacecraft engineers who have to "harden" the electronic circuitry in satellites against the impact of high-energy particles.

Researchers confess to being surprised; they thought the outskirts of our solar neighbourhood would be more sedate - that the sun's field lines would simply turn around and reconnect with the sun.