voyager 1
July 24, 2014

Has Voyager 1 Actually Reached Interstellar Space?

redOrbit Staff & Wire Reports - Your Universe Online

Nearly two years ago, NASA scientists first announced that the Voyager 1 spacecraft had departed the heliosphere and passed into interstellar space – but new research suggests the historic proclamation might have been somewhat premature.

Even though there have been multiple observations supporting the Voyager mission team’s claims, including data collected from a new “tsunami wave” generated by the sun earlier this month, some scientists argue that the probe is still within the magnetic bubble surrounding the sun and planets and has not yet made its way to the space between the stars.

Now, Voyager team scientists George Gloeckler and Len Fisk have devised a test which they claim could help definitely prove whether or not the spacecraft has crossed the threshold. Their test, which will be detailed in a future edition of Geophysical Research Letters, proposes using Voyager 1 observations to find out exactly what its current location is.

According to Gloeckler and Fisk, within the next two years, the probe will cross the current sheet (the surface inside the heliosphere where the polarity of the sun’s magnetic field changes from positive to negative). They go on to predict that the spacecraft will detect the magnetic field reversal, which would prove that it is still in the heliosphere.

However, if that reversal does not occur during the next year or two as expected, the study authors said that it will confirm that Voyager 1 has already passed into interstellar space, as previously reported on the basis of the “interstellar music” given off by electron waves in the ionized gas (plasma) as the probe traveled through this region.

Gloeckler, a professor in atmospheric, oceanic and space sciences at the University of Michigan in Ann Arbor and lead author of the study, said in a statement Wednesday that the debate over Voyager 1’s whereabouts would have to be “resolved by measurements.” He added that, if his theory is proven correct, it would be “the highlight of my life. There is nothing more gratifying than when you have a vision or an idea and you make a prediction and it comes true.”

In response to the forthcoming paper, Voyager project scientist Ed Stone from the California Institute of Technology said in a NASA statement that 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.”

Stone said that other models, which he and his colleagues used to conclude the probe had entered interstellar space, predict the interstellar wind outside of the heliosphere is actually 40 times denser than the solar wind on the inside. Careful analysis of the spacecraft’s observational data revealed that the plasma density was 40 times higher, leading to the conclusion that Voyager 1 had departed the solar bubble in late August 2012.

However, as Elizabeth Landau of NASA’s Jet Propulsion Laboratory (JPL) in Pasadena pointed out, the new paper “argues that solar wind inside the heliosphere can be compressed to the point that the solar wind density inside is just as high as interstellar space outside. Therefore, Voyager 1 could still be inside.”