Voyager spacecraft might not have reached interstellar space

Jul 23, 2014
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. Credit: Southwest Research Institute

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.

But, in the nearly two years since that historic announcement, and despite subsequent observations backing it up, uncertainty about whether Voyager 1 really crossed the threshold continues. There are some scientists who say that the spacecraft is still within the heliosphere – the region of space dominated by the Sun and its wind of energetic particles – and has not yet reached the space between the stars.

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 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.

"This controversy will continue until it is resolved by measurements," Gloeckler said.

This artist’s concept shows the Voyager 1 spacecraft entering the space between stars. The Voyager mission team announced in 2012 that the Voyager 1 spacecraft had passed into interstellar space, but some scientists say it is still within the heliosphere – the region of space domininated by the Sun and its wind of energetic particles. In a new study, two Voyager team scientists are proposing a test that they say could prove once and for all of Voyager 1 has crossed the boundary. Credit: NASA/JPL-Caltech

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 in a 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."

Alan Cummings, a senior research scientist at California Institute of Technology in Pasadena and a co-investigator on the Voyager mission, believes Voyager 1 has most likely crossed into interstellar space, but he said there is a possibility that Gloeckler and Fisk are right and the spacecraft is still in the heliosphere. He said that if Voyager 1 experiences a current sheet crossing like the one being proposed in the new study, it could also mean that the heliosphere is expanding and crossed the again.

"If the magnetic field had cooperated, I don't think we'd be having this discussion," Cummings said. "This is a puzzle. It is very reasonable to explore alternate explanations. We don't understand everything that happened out there."

Stephen Fuselier, director of the space science department at the Southwest Research Institute in San Antonio, Texas, who is not involved with the research and is not on the Voyager 1 team, said the scientists have come up with a good test to prove once and for all if Voyager 1 has crossed into interstellar space. However, he does not agree with the assumption that the paper is making about the how fast the solar wind is moving. But, he said there is no way to measure this flow velocity, and if Gloeckler and Fisk's assumptions are correct, the model makes sense and Voyager 1 could still be inside the heliosphere.

"I applaud them for coming out with a bold prediction," said Fuselier, who works on the Interstellar Boundary Explorer mission that is examining the boundary between the and the . "If they are right, they are heroes. If they are wrong, though, it is important for the community to understand why … If they are wrong, then that must mean that one or more of their assumptions is incorrect, and we as a community have to understand which it is."

Fuselier, who believes Voyager 1 has entered interstellar space, said he will reserve judgment on whether Gloecker and Fisk are correct until 2016. He said there is a sizeable fraction of the space community that is skeptical that Voyager 1 has entered interstellar space, but the new proposed test could help end that debate. Another good test will come when Voyager 2 crosses into in the coming years, Fuselier and Cummings said.

"If you go back 10 years and talk to the Voyager people, they would have told you 10 years ago that what they would see upon exiting the is very, very different from what they are seeing now," Fuselier said. "We are just loaded down with surprises and this might be one of them."

Explore further: Sun sends more 'tsunami waves' to Voyager 1

More information: Geophysical Research Letters DOI: 10.1002/2014GL060781

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User comments : 24

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RichTheEngineer
1.6 / 5 (13) Jul 23, 2014
Maybe we should send some of these scientists out there to check for themselves.
xstos
2.3 / 5 (3) Jul 23, 2014
Spool up the FTLs. Set condition one throughout the ship.
tothal
4.8 / 5 (5) Jul 23, 2014
Shouldn't we leave Solar system first before we speak about interstellar space? I mean there are 80,000 more years to pass thru Oort cloud which is part of the Solar system.
Dr_toad
Jul 23, 2014
This comment has been removed by a moderator.
cantdrive85
1 / 5 (17) Jul 23, 2014
in the nearly two years since that historic announcement, and despite subsequent observations backing it up,


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.


Here is a guy who doesn't want to believe he is wrong, his entire career and much of which he has taught is in danger of being trivialized. Pride is a bastard.

There are some whose models are being confirmed by the data, some don't require the magnetic field direction to change. If the sun is a stellar z-pinch within a galactic Birkeland current then what they are observing fits quite nicely.

http://electric-c...xies.pdf

http://electric-c...2012.pdf

It's ironic they still include the diagram of the heliosphere at the top of the article being that the model has been completely falsified by the observations.
cantdrive85
1 / 5 (15) Jul 23, 2014
Shouldn't we leave Solar system first before we speak about interstellar space? I mean there are 80,000 more years to pass thru Oort cloud which is part of the Solar system.


That is hypothetical, the Oort cloud has yet to be directly observed.
InterestedAmateur
4.8 / 5 (13) Jul 23, 2014
Here is a guy who doesn't want to believe he is wrong, his entire career and much of which he has taught is in danger of being trivialized. Pride is a bastard.


I'm sure he'll treat your opinion with the respect it deserves, I certainly have....
Dr_toad
Jul 23, 2014
This comment has been removed by a moderator.
Shootist
2.1 / 5 (14) Jul 23, 2014
By you? Maybe you see only as far as the end of your nose on a good day, baboso.

Your tiresome and automatic denial of anything here is evidence that you "live by faith, not by reason".

Fox News is trying to reform their image, I'm told. Maybe you can get a clue?


Down voted for the senseless foxnews remark.
Dr_toad
Jul 23, 2014
This comment has been removed by a moderator.
bluehigh
1.6 / 5 (14) Jul 24, 2014
.. that you "live by faith, not by reason".
- Toad.

Yet you choose to support a belief in luck or chance as scientific explanations. Hypocrite.
ROBTHEGOB
5 / 5 (4) Jul 24, 2014
"The Kirk Unit is defective. I will effect repairs........"
alfie_null
4.7 / 5 (15) Jul 24, 2014
Here is a guy who doesn't want to believe he is wrong . . . Pride is a bastard.

Coming from a guy who has tirelessly pushed his own electric universe crankology on the unwilling attention of the rest of the world - now that's irony. Particularly as he goes on to plug his crank science yet again. Dare we guess at cantdrive's motives - what's going on inside that squirmy little mind of his?
JohnGee
4 / 5 (12) Jul 24, 2014
.. that you "live by faith, not by reason".
- Toad.

Yet you choose to support a belief in luck or chance as scientific explanations. Hypocrite.


You're the hypocrite that claims to be Christian and issues death threats to strangers for disagreeing with you.
bluehigh
1.6 / 5 (13) Jul 24, 2014
You Mr Gee are a twisted psychotic punk. It would be my pleasure to throw you to the lions or nail you to a cross to slowly die in agony, as God loving Christians might do, when faced with dissent. Nothing hypocritical there. An eye for an eye. In the meanwhile, you might focus on the remarkable achievement of the Voyager spacecraft, rather than worry about your impending death, you insignificant flea.
Dr_toad
Jul 24, 2014
This comment has been removed by a moderator.
Scroofinator
1.7 / 5 (6) Jul 24, 2014
it could also mean that the heliosphere is expanding and crossed the spacecraft again.


Umm, ya, did we really think that it was a static bubble around the solar system? Voyager is right on the edge, but the heliosphere's boundaries are in constant flux due to the Sun's ever changing (and not very well understood) magnetic field. Voyager would be out, then in, then out again, and I think this is why nobody really knows.

Like waves on the surface of water, only on the outer edges of our heliospheric "bubble".
Scroofinator
1 / 5 (4) Jul 24, 2014
What's the point of the 1 star Thermo? Did I say something wrong, or just something that the standard model didn't predict thus the typical downvote?
rockwolf1000
5 / 5 (8) Jul 24, 2014
What's the point of the 1 star Thermo? Did I say something wrong, or just something that the standard model didn't predict thus the typical downvote?


My guess: Using this "waves on the surface of water" will generally get you 1 star votes no matter what you're trying to say.

You can thank Zephir for that.
thermodynamics
5 / 5 (7) Jul 24, 2014
What's the point of the 1 star Thermo? Did I say something wrong, or just something that the standard model didn't predict thus the typical downvote?


As Rockwolf said, there are specific things I think are worth a 1. Going to "water waves" is one of them and denigrating the standard model without a reason is another. We know the standard model is lacking, but not in describing the interaction of standard particles and the known forces. Since there is no evidence that what we are seeing at the edge of the heliosphere is outside the standard model and space is not water - you get a 1.
Captain Stumpy
5 / 5 (8) Jul 24, 2014
It would be my pleasure to throw you to the lions or nail you to a cross to slowly die in agony, as God loving Christians might do, when faced with dissent. Nothing hypocritical there
@highblue
so much for your god of love, eh?
what happened to thou shalt not commit murder? or are you going to quote old testament to us? maybe you think JC had it all wrong when he talked about the two most important commandments? in light of YOUR OWN BELIEF, per the words of YOUR SAVIOR, you are definitely a hypocrite and a cowardly liar... but that is just YOUR religion talking... here you are even worse, because you present NO scientific basis for your argument.

When you start demonstrating the ability to function with empirical evidence and not quote the bible or threaten someone, you might be able to THEN have a conversation worth having... until then, you are a fanatic, and no better than any terrorist, regardless of religion.

STICK TO THE SCIENCE
bluehigh
1 / 5 (5) Jul 24, 2014
because you present NO scientific basis for your argument.


Which argument, CS? Have you been drinking too much again?

Scroofinator
1 / 5 (1) Jul 24, 2014
Lol, nice guess rockwolf.

Going to "water waves" is one of them and denigrating the standard model without a reason is another. We know the standard model is lacking, but not in describing the interaction of standard particles and the known forces.


First, your telling me that the combined forces of solar wind and the magnetic field are static? Second, water waves is a valid analogy for 2d, but it is inaccurate in for 3d. My apologies for pushing the Zephir button.

It would be illogical to assume that the outer shell of the heliosphere would remain constant. The forces that create it are far from it.
jsdarkdestruction
5 / 5 (9) Jul 24, 2014
"You Mr Gee are a twisted psychotic punk."
"It would be my pleasure to throw you to the lions or nail you to a cross to slowly die in agony,"
Who is the twisted psychotic one here?
bluehigh
1.8 / 5 (8) Jul 24, 2014
Whatever. I'll choose not to take your bait JS so as to avoid escalating this disagreement. We are polluting these comments with personal attacks. To quote CS - stick to the science.
Jason_
3.7 / 5 (3) Jul 25, 2014
Interstellar Space to Voyager: "Are you in yet?"
JohnGee
5 / 5 (1) Jul 25, 2014
Nice attempt at backpedaling bluehigh.
Bob Osaka
not rated yet Jul 28, 2014
The graphic has a bow shock which is an out-dated model, it's thought to be a gentle bow wave which is still strange because of the Parker spiral. August 25, 2012 at 113au and now at <122au Voyager indeed passed through the heliopause and on into interstellar space. If there is a polarity change, it will be interesting but, no one will really know what it means. It is a robust little probe however, malfunctions are possible. Don't count on it though, they don't make them like they used to.