Has Voyager 1 REALLY passed into interstellar space? Claims Nasa jumped the gun with announcement
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It has becoming a running joke within the astronomy community - every few months, a new claim is made that Nasa's voyager craft has passed into interstellar space.
Earlier this month, Nasa claimed that it has effectively ended the debate, saying the craft had finally, definitely left the sun's reach.
However - a new study says that, in fact, that may not be the case - but researchers say they have finally developed a test that could end the debate once and for all.
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The Voyager 1 spacecraft
VOYAGER'S MISSION
It is 37 years since the twin Voyager 1 and 2 spacecraft were launched and the pair continue to explore where nothing from Earth has flown before.
Their primary mission was the exploration of Jupiter and Saturn.
After making a string of discoveries there -- such as active volcanoes on Jupiter's moon Io and intricacies of Saturn's rings -- the mission was extended.
Voyager 2 went on to explore Uranus and Neptune, and is still the only spacecraft to have visited those outer planets.
The current mission for both spacecraft, the Voyager Interstellar Mission, is to explore the outermost edge of the Sun's domain and beyond.
In 2012, the Voyager mission team announced that the Voyager 1 spacecraft had passed into interstellar space, traveling further from Earth than any other manmade object.
Now, two Voyager team scientists have developed a test that they say could prove once and for all if Voyager 1 has crossed the boundary.
The new test is outlined in a study accepted for publication in Geophysical Research Letters, a journal of the American Geophysical Union.
The scientists predict that, in the next two years, Voyager 1 will cross the current sheet – the sprawling surface within the heliosphere where the polarity of the sun's magnetic field changes from plus to minus.
The spacecraft will detect a reversal in the magnetic field, proving that it is still within the heliosphere.
But, if the magnetic field reversal doesn't happen in the next year or two as expected, that is confirmation that Voyager 1 has already passed into interstellar space.
'The proof is in the pudding,' said George Gloeckler, a professor in atmospheric, oceanic and space sciences at the University of Michigan in Ann Arbor and lead author of the new study.
Gloeckler has worked on the Voyager mission since 1972 and has been a vocal opponent of the view that Voyager 1 has entered interstellar space.
He said that, although the spacecraft has observed many of the signs indicating it may have reached interstellar space, like cosmic rays, Voyager 1 did not see a change in magnetic field that many were expecting.
WHAT IS THE HELIOSPHERE?
The heliosphere, in which the Sun and planets reside, is a large bubble inflated from the inside by the high-speed solar wind blowing out from the Sun.
Pressure from the solar wind, along with pressure from the surrounding interstellar medium, determines the size and shape of the heliosphere.
The heliosphere, in which the Sun and planets reside, is a large bubble inflated from the inside by the high-speed solar wind blowing out from the Sun. Pressure from the solar wind, along with pressure from the surrounding interstellar medium, determines the size and shape of the heliosphere. The supersonic flow of solar wind abruptly slows at the termination shock, the innermost boundary of the solar system. The edge of the solar system is the heliopause. The bow shock pushes ahead through the interstellar medium as the heliosphere plows through the galaxy.
The supersonic flow of solar wind abruptly slows at the termination shock, the innermost boundary of the solar system.
The edge of the solar system is the heliopause.
The bow shock pushes ahead through the interstellar medium as the heliosphere plows through the galaxy.
'This controversy will continue until it is resolved by measurements,' Gloeckler said.
If the new prediction is right, 'this will be the highlight of my life,' he said.
'There is nothing more gratifying than when you have a vision or an idea and you make a prediction and it comes true.'
The Voyager 1 and 2 spacecraft were launched in 1977 to study Jupiter and Saturn.
The mission has since been extended to explore the outermost limits of the Sun's influence and beyond. Voyager 2, which also flew by Uranus and Neptune, is on its way to interstellar space.
Gloeckler and co-author, Len Fisk, also a professor in atmospheric, oceanic and space sciences at the University of Michigan, are basing their new test on a model they developed and published earlier this year in The Astrophysical Journal.
The model assumes that the solar wind is slowing down and, as a result, that the solar wind can be compressed.
Based on this assumption, the study says Voyager 1 is moving faster than the outward flow of the solar wind and will encounter current sheets where the polarity of the magnetic field will reverse, proving that the spacecraft has not yet left the heliosphere.
The scientists predict this reversal will most likely happen during 2015, based on observations made by Voyager 1.
'If that happens, I think if anyone still believes Voyager 1 is in the interstellar medium, they will really have something to explain," Gloeckler said.
'It is a signature that can't be missed.'
Ed Stone of the California Institute of Technology in Pasadena and NASA's Voyager Project Scientist said 'It is the nature of the scientific process that alternative theories are developed in order to account for new observations.
'This paper differs from other models of the solar wind and the heliosphere and is among the new models that the Voyager team will be studying as more data are acquired by Voyager.'
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