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Voyager 1 Returns Surprising Data about an Unexplored Region of Deep Space

The views expressed are those of the author and are not necessarily those of Scientific American.


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Voyager 1

Credit: NASA

About the Voyager 1 spacecraft, this much is clear: the NASA probe has traveled farther than any other. Voyager 1 is now more than 18.5 billion kilometers from the sun—almost 125 times the distance between Earth and the sun. The spacecraft, one of two Voyagers launched by NASA in 1977, is truly in unexplored territory—so much so that defining its current whereabouts poses a bit of a challenge.

Someday soon, it is expected, Voyager 1 will become the first spacecraft to exit the heliosphere—the bubble of solar plasma encasing the sun and planets—and enter the interstellar medium. Right now, however, Voyager appears to be crossing through one of several puzzling new regions of the heliosphere that mission planners had not anticipated.

In a trio of studies published online June 27 in Science, Voyager scientists describe the latest heliospheric wrinkle discovered by the probe en route to interstellar space. Voyager 1, they report, appears to have crossed last August into what is now being called the “heliosheath depletion region.” The researchers described some characteristics of the new region in a December 2012 teleconference with reporters, but the new studies go into far more detail about Voyager 1’s environs.

Voyager 1 instruments

Credit: NASA

One major change signaling that Voyager had entered new territory was a sudden decrease in the number of particles from the sun hitting the spacecraft’s Low Energy Charged Particle (LECP) instrument. On August 25, those solar particles dropped to less than one-thousandth their prior levels. Simultaneously, cosmic rays emanating from sources elsewhere in the galaxy began striking the LECP at a rate nearly 10 percent above the previous clip.

A second particle detector known as the Voyager Cosmic Ray Subsystem noted a similar change: charged atomic nuclei from the sun disappeared as nuclei from outside the solar system surged.

Such changes might seem a clear marker that Voyager 1 has completed its ultimate mission by breaking free of the sun’s plasma cocoon and reporting back from the unexplored realm of interstellar space. But crucial measurements from a third Voyager instrument contradict that conclusion.

The heliopause—the boundary between the local heliosphere and the interstellar medium beyond—is a boundary not only of particles but of magnetic fields as well. And although the magnetometer on Voyager 1 did register an increase in magnetic field strength as the spacecraft crossed over into the new realm, the direction of the magnetic field did not change. So either Voyager 1 has measured the interstellar magnetic field and found that it somehow perfectly aligns with the solar system (a possibility that the Voyager researchers consider “highly improbable”) or, more likely, the spacecraft remains within the sun’s magnetic domain.

Taken together, the evidence suggests that the heliosheath depletion region now being explored by Voyager is a new kind of solar system environment, one where the sun’s influence wanes and interstellar particles can enter more easily. And although the new region appears not to qualify as interstellar, the researchers report, it “may form part of the interface between solar plasma and the galaxy.”

So godspeed, Voyager. May you soon reach interstellar space—a place humankind has never before accessed. And may we know it when you see it.

About the Author: John Matson is an associate editor at Scientific American focusing on space, physics and mathematics. Follow on Twitter @jmtsn.

The views expressed are those of the author and are not necessarily those of Scientific American.





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  1. 1. Argyle9 3:19 pm 06/27/2013

    Awesome article and news, in such a clearly-explained manner for scientific ‘laypersons’ such as myself (which I consider myself, since I only took two Astronomy classes in college). The journey and data of the Voyager vessels is just as exciting to me as any other NASA field of endeavor. (off-topic: thank you, Mr. Matson, for A) making good use of your spell/grammar-checker, and/or B) knowing good grammar and how to spell in the first place…I see more & more examples of poor English in written news lately, so your well-written contribution is a welcome change)

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  2. 2. veronica_tg 5:57 pm 06/27/2013

    “So godspeed, Voyager’, what is that all about. Does anyone think in the slightest that any God has had anything to do with the Voyager? Wow, what a dumb thing to say.

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  3. 3. mleenheer 6:35 pm 06/27/2013

    Yes, veronica_tg, someone does think that. More than one person, I suspect. No need to be rude.

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  4. 4. yancyeaton 6:36 pm 06/27/2013

    It’s pretty incredible to think that that piece of technology was made in the 70′s and is still chugging along. I wonder how long until we lose contact with it?

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  5. 5. DaniEder 6:37 pm 06/27/2013

    Something to note is while Voyager may pass the limits of the heliosphere – the region which the Solar wind and magnetic field permeates, it is still far from the limits of the Solar System in terms of objects orbiting the Sun.

    If you examine this table from the IAU Minor Planet Center, and sort on the column “Q” (maximum distance from the Sun)

    http://www.minorplanetcenter.net/iau/lists/t_centaurs.html

    you will find 60 objects whose orbits reach farther from the Sun than Voyager is now (125 AU). The farthest of these reaches 19 times Voyager’s distance.

    Because of the nature of elliptical orbits, most of this class of objects spend most of their time at the outer end of their trip around the Sun, where we currently cannot find them (they are too dim for today’s telescopes). Thus for the 60 we see now, there are likely a few thousand more we have not found yet. It will be centuries before Voyager passes the last of these coldest and darkest Solar System members.

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  6. 6. nicholasjh1 6:42 pm 06/27/2013

    I wonder how this will inform physics.

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  7. 7. popseal 7:16 pm 06/27/2013

    While I take space exploration very seriously, I can’t help but think the name for this new region of the solar system sounds like the next title for the TV’s cartoonish “Big Bang Theory”.

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  8. 8. CurrentOutlook 7:49 pm 06/27/2013

    @2. veronica_tg

    “Wow, what a dumb thing to say.”

    LOL! As you are apparently unfamiliar with that common term, you should have looked it up in a dictionary before showing your ignorance.

    http://dictionary.reference.com/browse/godspeed?s=t

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  9. 9. Xopher425 11:29 pm 06/27/2013

    Or maybe scientists have misjudged the strength of the magnetic field in calculations . . . .Or maybe they’re trying to find a finite definition to something that is malleable and indistinct.

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  10. 10. SigmaEyes 12:14 am 06/28/2013

    Wouldn’t it be neat if Voyager could tell when it lost radio contact, and had enough remaining fuel to turn, and return to Earth orbit? People love that spacecraft.

    And wouldn’t it be worth while if one of NASA’s unmanned projects created a new series of crafts (Voyager like) that could travel much faster (although, I imagine the faster one would fly, the more likely that a small particle of dust could do catastrophic impact damage). Each member of the series would go in different directions.

    I wonder how long it takes for the data Voyager transmits to be received on Earth by NASA.

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  11. 11. emeraldfenix 12:42 am 06/28/2013

    @ veronica_tg

    Another note about “God”. The author (or editor) specifically spelled the word without a capital letter, thus indicating that God (in whom I believe, without being a Christian) is not involved in the well-wishing.

    @ all

    I think that it may be time for humankind to put together another “Voyager” (echoing SigmaEyes) with current technology, power sources, and orbital engineering intellect that will be able to gather more data, travel faster, and enter true extra-solar space prior to the original. I am 43 and would love to read about true extra-solar data from something created by humans before I die.

    My 2 cents.

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  12. 12. Bionate 1:28 am 06/28/2013

    Yes but would not it be fun if it just suddenly stopped and it turns out that we are viewing the universe through a very large protective bubble! I know I am being silly but it would still be fun.

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  13. 13. BillR 9:06 am 06/28/2013

    “And although the magnetometer on Voyager 1 did register an increase in magnetic field strength as the spacecraft crossed over into the new realm, the direction of the magnetic field did not change.”

    Perhaps the solar magnetic field is being compressed by the galactic magnetic field and intensifying the field strength. That could indicate that the “skin of the bubble” has been reached and breakout is imminent.

    Of course, that also assumes that the strength of the galactic magnetic field is strong enough to counter the solar magnetic field at that distance. I suspect that the galactic magnetic field is also distorted by all of the different stellar magnetic fields imbedded in it so it may not be perfectly uniform in strength or direction either.

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  14. 14. edprochak 9:11 am 06/28/2013

    Sending more voyagers with better sensors and communications would be great. However, sending such devices faster will take a LARGE technology increase. Why?

    Because the Voyager missions used gravity assists from the outer planets to get up the speed to escape. Those planets were roughly aligned in 1976. The next time such an alignment will happen is 2157. So don’t expect another Voyager like mission to go faster any time soon.

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  15. 15. rloldershaw 11:09 am 06/28/2013

    A natural model for the morphology of the boundary between the heliosphere and interstellar space would be a fractal model featuring complex and multi-scaled inter-fingering of the two distinct domains.

    Fractal boundaries are commonly observed in natural phenomena like the mixing of different fluids.

    Such a model might help in understanding the complexity and variability of the observed phenomena.

    Robert L. Oldershaw

    http://www3.amherst.edu/~rloldershaw

    Discrete Scale Relativity/Fractal Cosmology

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  16. 16. jh443 2:10 pm 06/28/2013

    I strongly suspect the author was making reference to a much earlier use of the word “godspeed” by a NASA official – as when John Glenn became the first American to orbit the Earth and was wished “Godspeed, John Glenn” – the Voyager is also performing a feat for the first time and is being wished godspeed.

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  17. 17. Quinn the Eskimo 1:15 am 06/29/2013

    If we are looking at the universe through an inflated “bubble” would not a fast moving project and vehicle penetrate it? If our bubble were to burst, we might leak out. I imagine there would be hell to pay.

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  18. 18. barrycr 12:11 pm 06/29/2013

    I recall reading a number of years ago that Voyager’s path was not lining up with what was expected/predicted according to gravitational theory (i.e., small but measurably significant variation). Do any readers know anything about this (true, false, or if true speculations why) and care to comment?

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  19. 19. Dr. Strangelove 9:22 pm 06/30/2013

    At 125 AU, Voyager 1 is still far from the edge of the solar system. The Oort cloud is 20,000 AU away. That’s the “edge” of the sun’s gravitational field. Our current spacecrafts are too slow to reach interstellar space within human lifetime.

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  20. 20. David Cummings 8:42 am 07/2/2013

    Even though the gravity of the sun reaches farther than 125 AU, I still think it’s possible that Voyager 1 can now be considered to be in “interstellar space”. What are the limits to gravitational force? Isn’t the gravity of the sun measurable (at least in theory) from Alpha Centauri? If so, does that make Alpha Centauri part of our solar system? And does that mean a journey to Alpha Centauri would never pass through “interstellar space”?

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  21. 21. David Cummings 9:23 am 07/2/2013

    “The interstellar medium begins where the interplanetary medium of the Solar System ends. The solar wind slows to subsonic velocities at the termination shock, 90—100 astronomical units from the Sun. In the region beyond the termination shock, called the heliosheath, interstellar matter interacts with the solar wind. Voyager 1, the farthest human-made object from the Earth, crossed the termination shock December 16, 2004 and may soon enter interstellar space, providing the first direct probe of conditions in the ISM…”

    –Wikipedia

    In my opinion, the latest data from Voyager does not render this Wikipedia discussion of the ISM obsolete.

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  22. 22. Dr. Strangelove 9:50 pm 07/2/2013

    Isn’t the gravity of the sun measurable (at least in theory) from Alpha Centauri? Yes

    If so, does that make Alpha Centauri part of our solar system? No

    And does that mean a journey to Alpha Centauri would never pass through “interstellar space”? No. Alpha Centauri is farther than Oort cloud.

    Oort cloud is part of our solar system because it is composed of small objects orbiting the sun. It is a region in space where sun’s gravity still dominates.

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  23. 23. David Cummings 8:29 am 07/3/2013

    My point is that you don’t have to get past every single orbiting object to be out in the Interstellar Medium (ISM), which is where — in my opinion and the opinion of many — Voyager now is.

    As for the Oort Cloud, this is from wikipedia:

    The Oort cloud /ˈɔrt/[1] (named after Jan Oort), or Öpik–Oort cloud,[2] is a hypothesized spherical cloud of predominantly icy planetesimals that may lie roughly 50,000 AU, or nearly a light-year, from the Sun.[3] This places the cloud at nearly a quarter of the distance to Proxima Centauri, the nearest star to the Sun.

    It is HYPOTHESIZED.
    It MAY LIE roughly 50,000 AU from the Sun.

    I’m not saying there is no Oort Cloud, I’m saying that if there is, it is way out in the ISM. Voyager, on the other hand, is at the boundary of the ISM.

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  24. 24. carbonunit1 8:12 pm 07/3/2013

    wow,fantastic,this is where mankinds ingenuity and energys should be directed,not in war and destruction,can voyager transmit pictures from so far away?

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  25. 25. Postman1 11:16 pm 07/3/2013

    Quinn the Eskimo :) +10

    carbonunit1 – Pictures of what? The sun would look like any other star, the Earth would be invisible, and there is nothing else anywhere nearby.

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  26. 26. Dr. Strangelove 11:28 pm 07/3/2013

    If you don’t believe in the Oort cloud, that’s ok. But it is widely accepted by the scientific community. No direct observation because it’s too far away. Celestial mechanics predict Halley’s comet and Sedna originated in the Oort cloud.

    BTW interstellar medium is not a boundary of the solar system because the latter is inside an interstellar cloud 60-light year across.

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  27. 27. karl 6:57 pm 07/4/2013

    I like the idea of a Voyager remake, as long as they don’t make a sixth ship, or name that one Janeway (trek stuff, don’t mind)
    Seriously, you could use Ion engines, bigger computers and breeder nuclear reactors of some sort to have much better performance, even if the new voyagers won’t outrun good old V’ger 1.
    even if they don’t have a “grand tour” alignment as they did in 1976, the science you could win just by shooting them in other directions would be worthless (is the heliopause symetrical?, how accurate is that what Voyager 1 measuring holding? remember that ugly face on mars, or the death star orbiting saturn (mimas), which are artifacts due to the resolution of instruments back then, and the toothache they have become.

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  28. 28. Dr. Strangelove 8:11 pm 07/5/2013

    To put it on scale, if Alpha Centauri is Hawaii and earth is Long Beach, California. Voyager 1 is one nautical mile from the beach. And it is claiming it is already in international sea because it is sailing on the water of the Pacific Ocean.

    Link to this

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