NASA's Voyager 1, built to last just five years to probe Earth's planetary neighbors, has reached the solar system's final frontier and may have surfed into interstellar space, more than 26 years after its launch.
Whether or not it has escaped the sun's sphere of influence -- known to astronomers as the heliosphere -- Voyager 1 has exceeded all expectations and on Wednesday was more than 8 billion miles from Earth, or 90 times the distance between Earth and the sun.
The Earth-sun distance, 93 million miles, is a convenient measure for astronomers and is known as one astronomical unit or AU. Voyager 1 is the only human-made object known to have traveled 90 AU.
At this point, scientists are loath to predict when Voyager 1 will give up the ghost, because it is still sending data.
"We do have enough electrical power, if nothing breaks on the spacecraft, we can continue till 2020," Edward Stone, a Voyager project scientists based at the California Institute of Technology, said at a briefing at NASA headquarters.
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