Postcards from the edge

Message from a craft at the solar system's final frontier holds surprises.

By Ron Cowen, 11:42 AM July 2, 2008

There are no signs to announce the edge of the solar system, but when the venerable Voyager 2 spacecraft approached this final frontier last Aug. 31 it was in for quite a shock. So were the scientists who analyzed the data that the craft radioed back to Earth, along with related observations by NASA’s twin Earth-orbiting STEREO spacecraft.

The signals reveal that at a distance of 83.7 astronomical units (1 AU is the average Earth-sun separation), Voyager 2 had at least five encounters with a t...

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