Out at the edge of the solar system, surprises for Voyager 1 (+video)

Voyager 1 seems to have hit the doldrums as it approaches the edge of the sun's sphere of influence. Still, says a lead scientist, 'We all have the sense that something big is imminent.'

By Pete Spotts,?Staff writer / September 6, 2012

Thirty-five years after leaving Earth, Voyager 1 is reaching for the stars. Sooner or later, the workhorse spacecraft will bid adieu to the solar system and enter a new realm of space ? the first time a man-made object will have escaped to the other side.

NASA/AP

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The closer Voyager 1 gets to interstellar space 35 years after leaving Earth, the more surprises it is springing on mission scientists as they repeat a question familiar to any parent who has taken a child on a long road trip: Are we there yet?

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A look behind the scenes at Voyager 1 operations on the ground.

Features that, according to theory, Voyager should be detecting by now if it's close to the boundary between the sun's sphere of influence and interstellar space haven't appeared, according to a new study appearing in Thursday's issue of the journal Nature.

But subsequent data taken over the past few months and yet to be published also show activity no theorist predicted and could hint at the beginning of Voyager's breakout.

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"We all have the sense that something big is imminent," says Stamatios Krimigis, a researcher at the Johns Hopkins University's Applied Physics Laboratory in Laurel, Md., and the lead scientist on one of Voyager's still-operating instruments.

But, he adds, "If I were a theorist I would feel pretty humble right about now."

Expecting the unexpected is the bread and butter of exploration, and the edge of the solar system is as good an illustration of that as any place NASA has sent a spacecraft.

Launched in 1977, Voyager 1 and Voyager 2 have long since finished their revolutionary tour of the outer planets. Voyager 1 flew by Saturn in 1980, then headed for interstellar space. Voyager 2 left Neptune in 1989 on a similar mission, but in a different direction. At 11.3 billion miles from Earth, Voyager 1 has traveled the farthest.

The hope is that one or both craft will have crossed the boundary between a bubble the sun's solar wind sets up around the solar system and the galactic wind before 2025. The solar wind is a constant stream of charged particles the sun hurls into space in all directions at a million miles an hour. The 2025 deadline is set by the crafts' plutonium power supplies. That's the year the power sources no longer will provide enough energy to run the instruments needed to study the solar and galactic winds and the processes in the transition zone between them.

Inside the bubble "the wind is from the sun, and outside the wind is from the explosion of supernovae five, 10, and 15 million years ago," said Ed Stone, the mission's project scientist and former director of NASA's Jet Propulsion Laboratory in Pasadena, Calif., during a panel discussion of the twin crafts' mission Tuesday.

The challenge in knowing how big the sun's bubble is stems from the fact "that we haven't gotten outside yet," Dr. Stone says. One experiment Voyager 1 ran allowed researchers to estimate that the boundary between the bubble and interstellar space ? the heliopause ? fell somewhere between 117 and 177 astronomical units (AU), or 117 to 177 times the distance from the sun to Earth.

Source: http://rss.csmonitor.com/~r/feeds/science/~3/Oqc1dpjnuPY/Out-at-the-edge-of-the-solar-system-surprises-for-Voyager-1-video

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