NASA's Voyager 1 Probe Has Left Solar System: Study

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NASA's Voyager 1 Probe Has Left Solar System: Study
By Tia Ghose | SPACE.com – 2 hrs 53 mins ago...

NASA's Voyager 1 spacecraft — the farthest-flung object created by human hands — has left the solar system forever, a new study suggests.

On Aug. 25, 2012, 35 years after the Voyager 1 mission launched, Earth's most distant spacecraft detected a sharp change in the intensity of fast-moving charged particles called cosmic rays, suggesting it had left the outermost reaches of the heliosphere marking the edge of the solar system.

"Within just a few days, the heliospheric intensity of trapped radiation decreased, and the cosmic ray intensity went up as you would expect if it exited the heliosphere," said Bill Webber, professor emeritus of astronomy at New Mexico State University in Las Cruces, in a statement.

Though Voyager 1 has apparently exited the sun's sphere of influence, the scientists still don't know for sure whether the probe has entered interstellar space or a mysterious in-between region beyond the solar system.

"It's outside the normal heliosphere, I would say that," Webber said. "We're in a new region. And everything we're measuring is different and exciting."



Webber and his colleagues noticed the dramatic cosmic ray signal drop when Voyager 1 was about 11 billion miles (17.7 billion kilometers) from the sun. Anomalous cosmic rays trapped in the heliosphere's outer reaches dropped to 1 percent of their previous level. Meanwhile, galactic cosmic rays, which come from outside the solar system, jumped to twice their previous levels, reaching their highest levels since the spacecraft launched, researchers said.

The findings have been accepted for publication in the journal Geophysical Research Letters.

Voyager 1 was actually the second of NASA's two Voyager spacecraft to launch on historic tours of the solar system. Voyager 2 blasted off on Aug. 20, 1977, with Voyager 1 following a few weeks later on Sept. 5 of that year.

Both spacecraft carry a gold-plated copper disc containing sounds and images of Earth. The golden record is about 12 inches (30 centimeters) across and attached to the hull of each Voyager probe. The records are engraved with a diagram that explains how to play them and where Earth can be found, just in case the Voyager probes are discovered by intelligent extraterrestrial lifeforms.

http://news.yahoo.com/nasas-voyager-1-probe-left-solar-system-study-164614640.html

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Why Voyager 1's Solar System Exit Is So Hard to Predict
By Mike Wall | SPACE.com – 20 hrs ago...


NASA's Voyager 1 probe is tantalizingly close to the edge of the solar system, but predicting when it will finally pop free into interstellar space is a challenging proposition, mission team members say.

Voyager 1 is plying new and exotic terrain at the limits of the sun's sphere of influence, and scientists simply don't know what to expect from these unexplored regions.

"We've never been there before," said Voyager project manager Suzanne Dodd of NASA's Jet Propulsion Laboratory in Pasadena, Calif. "That's what makes it very hard. It's not unlike the first explorers sailing across the Atlantic Ocean to the New World. They thought they might know what they would see, but they saw things that were quite a bit different."



Knocking on the door

Voyager 1 and its twin, Voyager 2, launched a few weeks apart in 1977 to study the giant planets Saturn, Jupiter, Uranus and Neptune. After completing this unprecedented "grand tour," the two probes kept flying, streaking through unexplored realms on their way to interstellar space. [Voyager: Humanity's Farthest Journey (Video)]

It looks like Voyager 1 will get there first. The probe is now more than 11.3 billion miles (18.2 billion kilometers) from Earth, making it the most far-flung manmade object in the universe.

Voyager 1 has also encountered strange new conditions in the outer layers of the heliosphere — the huge bubble of charged particles and magnetic fields surrounding the sun — suggesting that the probe may be about to leave the solar system forever.

Specifically, Voyager 1 has seen a spike in the levels of ultrafast cosmic rays that originate in interstellar space, along with a big drop in the number of lower-energy particles coming from the sun. But the probe has yet to measure a shift in magnetic field orientation, another phenomenon that mission scientists expect to observe outside the solar system.

"The particle data very clearly state that we're in a new region of the heliosphere," Dodd told SPACE.com. "But the Voyager spacecraft still senses the same magnetic field that we've always sensed — in the same direction. It's increasing slightly in strength, but basically it's the same as it's been for several years."



Making the call

If and when Voyager 1 tells its handlers that the magnetic field has flipped from the solar system's roughly east-west orientation to a north-south one, then humanity will probably have reached beyond its own backyard for the first time ever.

But forecasting when that historic moment will come is difficult, Dodd and other mission team members have stressed, because scientists don't know for sure how far the heliosphere extends, or what conditions are like in its extreme outer reaches.

Voyager mission chief scientist Ed Stone, a physicist at Caltech in Pasadena, has estimated that the probe won't pop free for another two years or so, though he stressed that this is just an educated guess.

"That's not science — that's just saying scaling sort of suggests that," Stone told SPACE.com this past December.

The Voyager team is prepared for the unexpected, as both spacecraft have delivered plenty of surprises in their 35-year space journeys.

"Every discovery that we've made has really been things that were not predicted before we got there," Dodd said. "So this is just a continuation of Voyager's travels of discovery."

But Stone, Dodd and the rest of the Voyager team are doubtless hoping Voyager 1's big moment comes before 2020. A declining power supply will force engineers to shut down the first science instrument that year, and all of them will probably stop working by 2025.

http://news.yahoo.com/why-voyager-1s-solar-system-exit-hard-predict-201234755.html