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Voyager 1 Finds Unexpected Wrinkles At the Edge Of the Solar System 164

Posted by timothy
from the damn-thetans-are-playing-with-us dept.
Voyager 1 has been close to the boundary of the solar system for quite a while; we've mentioned that the edge is near a few times before, including an evidently premature report in 2010 that Voyager had reached a distance so far from the sun that it could no longer detect solar winds and another in 2011 that it had reached an "outer shell" of solar influence. It turns out that the boundaries of the solar system are fuzzier than once anticipated; the L.A. Times is reporting that "Toward the end of July 2012, Voyager 1's instruments reported that solar winds had suddenly dropped by half, while the strength of the magnetic field almost doubled, according to the studies. Those values then switched back and forth five times before they became fixed on Aug. 25. Since then, solar winds have all but disappeared, but the direction of the magnetic field has barely budged." Also at Wired, which notes "That's hard to explain because the galaxy's magnetic field is thought to be inclined 60 degrees from the sun's field. No one is entirely sure what's going on. ... [It's] almost as if Voyager thought it was going outside but instead found itself standing in the foyer of the sun's home with an open door that allows wind to blow in from the galaxy."
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Voyager 1 Finds Unexpected Wrinkles At the Edge Of the Solar System

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  • Re: XKCD (Score:5, Interesting)

    by tysonedwards (969693) on Sunday June 30, 2013 @09:02AM (#44147093)
    The only thing that is shocking to me is the belief amidst the cited astrophysicists that once passing the heliosheath that there would be "uniform, high intensity cosmic radiation" as opposed to "non-uniform directional radiation". Our solar system is a very tiny dot versus a ginormous amalgamation of radiation sources at the center of our galaxy. It seems HIGHLY intuitive that the center of our galaxy would be a single, highly directional radiation source that would dwarf the very distant radiation sources.
  • Not too surprising (Score:5, Interesting)

    by Mr Z (6791) on Sunday June 30, 2013 @09:13AM (#44147131) Homepage Journal

    Someone else (who I think I saw here on Slashdot the last time Voyager was mentioned) had a great analogy for what we're likely seeing. I can't take credit for this at all, but I think it makes a lot of sense.

    Suppose we're a small probe, making our way off an island, down the beach, and into the ocean. All we have is a wind-speed detector, and a water detector. As we near the water, waves start lapping over us. When they do, our wind-speed detector says "no wind", and our water detector says "we're wet." Have we entered the ocean yet? The answer is "not quite, but we're really darn close."

    It doesn't seem surprising to me at all that the boundary neither perfectly uniform, nor stationary in time. I think we'll be in this transition band for a while.

  • Re:XKCD (Score:5, Interesting)

    by hcs_$reboot (1536101) on Sunday June 30, 2013 @09:35AM (#44147263)
    Funny drawing. But it seems the problem here is the interpretation of the Voyager's data. Not the probes that still do a magnificent job. I've always been fascinated how the Voyagers did/do a great job since 1977. Starting by providing really amazing pictures of our "external planets", following a smart path (that could have been even more awesome [wikipedia.org] if budget wouldn't have been reduced) now they're still able to work and communicate successfully with Earth, from a 120+ AU distance, thanks to a 1977 technology.
  • by TapeCutter (624760) on Sunday June 30, 2013 @10:42AM (#44147555) Journal
    You are not separate from the universe, you're part of it. One of many entities that allows the universe to observe and talk to itself. - Sagan (paraphrased).
  • Re: XKCD (Score:5, Interesting)

    by Anonymous Coward on Sunday June 30, 2013 @11:31AM (#44147799)

    Our solar system is a very tiny dot versus a ginormous amalgamation of radiation sources at the center of our galaxy.

    Actually, by analysis of cyclotron emissions, there are plenty of far more local galactic cosmic ray sources. The problem with something like Sagitarrius A* or something else near the center of the galaxy, is that is very far way for the energy scales being measured. Because cosmic rays are charged particles and there is a background magnetic field in the galaxy, such particles could not make a straight line from the center of the galaxy to here and instead would be trapped and susceptible to interaction with things in between. Even when you get into the TeV range of particles (the ones voyager was looking at was 2 MeV to 600 MeV), the gyroradius is on the order of dozens of AU.

    This problem means that except at the highest of energies for extra-galactic cosmic rays, the direction of cosmic rays are scrambled and not pointing back to their source. The distribution of galactic cosmic rays has more to do with the magnetic field structure in the near by neighborhood. Additionally, in this case here, it has a lot to do with the interaction of high energy particles and shock waves in plasma, which is still a big, active area of research. This would determine how much is emitted or blocked by the heliosheath, but would also still depend on the structure of the area which is quite turbulent. An understanding of the interaction between the solar wind, very local sources like other near by stars and previous novas in the area is what this will come down to, and very little to do with the center of the galaxy.

  • by rusty0101 (565565) on Sunday June 30, 2013 @11:32AM (#44147805) Homepage Journal

    I"m trying to remember if we're going faster than our sun at the moment, or slower. Ah, well, not finding a ready reference, however a couple of back of the envelope calculations should work. The planet is in an elliptical orbit around the sun, dictated by gravity, and with no appreciable forces of acceleration affecting the planet that are not also affecting the path of the sun. (Yes that can happen, consider the possibility that the orbit of the earth passes through one of the jets of a supernova, where the jet does not directly interact with the sun. However we'd probably notice something like that, or cease to notice anything else.) Neither do we appear to be generating a field or having any reaction sources that act as a drive. I'm not suggesting that we won't ever find such, but I do not expect that we will, as I think that if the planet were doing this, or affected by such, that again, we would be able to detect it, and the best information I'm aware of doesn't indicate that we have detected such a phenomena.

    In this orbit, we vary from leading the sun in it's orbit of the galaxy by approximately one AU, to trailing the sun by approximately the same distance, over the period of a year. An AU is approximately 150 billion meters, so we're looking at an orbit approximately 300 billion meters from trail, to lead. At trail and lead points in the orbit, the speed of the planet around the galaxy matches that of the sun, so the points of interest are where the orbit crosses the plane perpendicular to the orbit of the sun intersecting the line between the sun and the galactic center. These two points are inflection points in the change in apparent acceleration due to gravity where as we are moving ahead of the sun our acceleration starts decreasing, and as we move to trailing the sun our acceleration is increasing.

    Now you can apply some trig to get the numbers, but it's just as easy to work out the various speeds by noting that in 6 months, the planet earth travels 300 billion meters relative to the earth, and starts with a relative velocity of zero. At 3600 seconds per hour, 24 hours per day, and 182.5 days per half year, that means that we have 15,768,000 seconds to work with. 300,000,000,000 meters divided by 15,768,000 seconds means that we on average travel 19,025.875, call it 19,026 meters per second over that half a year. To start at zero, and end at zero, that means that at the inflection points, were traveling som 38,051 meters per second faster, or slower than the sun. Call it 38 kps. (approximate) The speed of light is some 300,000 kps, so our change in velocity is just over 1/10000'th of the speed of light for that half of the orbit, or twice that 1/5000th of the speed of light for the entire orbit.

    Consider the estimated distance out from the center of the galaxy that we are at, and the fact that in the presumed lifespan of the sun, just over 4.5 billion years, calculations show that the sun has made some 12 orbits of the galaxy, (i.e. approximately 300 million years per orbit) and it's trivial to show that you really don't need to 'compensate' for the orbital speed of the sun around the galactic center.

    To add to the interest, I'll leave it as an exercise of the reader to discover what the change in velocity for Mercury, and Jupiter (starting point, mercury has an orbit of approx .4 au, and a period of approx 88 days, while Jupiter has an orbit of just over 5 au, and a period of 4331 days, or just under 12 years.) Which you should see that having an orbit closer to the sun results in having a _lower_ change in velocity relative to the sun, not a higher. i.e. to put a solar probe into an orbit closer to the sun, you actually need to slow down the orbital velocity of the probe, not increase it's speed. You do Accelerate the probe, however that acceleration is 'negative' with respect to it's existing orbital speed about the sun.

  • by HiThere (15173) <`charleshixsn' `at' `earthlink.net'> on Sunday June 30, 2013 @12:24PM (#44148083)

    You left out the Deists, who believe that God created the universe and left it to evolve. (IIRC they never actually said that God created life, and they didn't talk about evolution, but then they were prominent before Darwin.)

    OTOH, I'm not sure how many Diests are around anymore.

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