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Voyager Enters Final Frontier Of Solar System
ljk4-1
post Jun 1 2006, 03:35 PM
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PHYSICS NEWS UPDATE

The American Institute of Physics Bulletin of Physics News

Number 778 May 26, 2006 by Phillip F. Schewe, Ben Stein,
and Davide Castelvecchi www.aip.org/pnu

THE MISSHAPEN SOLAR SYSTEM. Having traveled far beyond the planets
in their 28.5-year journey, the two Voyager spacecraft are providing
new information on the heliosphere, the teardrop-shaped bubble that
separates the solar system from interstellar space. At this week's
Joint Assembly Meeting in Baltimore of the American Geophysical
Union (AGU) and several other geophysics-related societies, Ed Stone
of Caltech reported that the heliosphere is deformed, according to
Voyager observations, with the teardrop's rounded edge bulging at
the top (the northern hemisphere of the solar system) and squashed
at the bottom (the southern hemisphere). (See pictures and movies at
http://www.nasa.gov/vision/universe/solars...er_2006agu.html
) As Rob Decker of Johns Hopkins University Applied Physics
Laboratory explained, the asymmetry is due to a magnetic field from
interstellar space pushing on the southern hemisphere. The field is
about 1/100,000 the strength of Earth's field but its effects can be
felt for billions of miles, since it is acting over a large area on
the very dilute gas at the solar system's edge.

The interstellar field even squashes an important spherical zone
inside the heliosphere, called the termination shock. Analogous to
the circle that forms when water splatters on a sink, the
termination shock represents the boundary at which the rapidly
traveling solar wind (the stream of charged gas from the sun) slows
down abruptly and piles up. Voyager 2's measurements indicate that
the southern part of the termination sphere might be a billion miles
closer to the sun than the northern part. Moreover, forces from the
solar wind cause the termination shock to breathe in and out roughly
every dozen years. Voyager 1 has already ventured beyond the
termination shock, to the heliosheath, the region where solar wind
and interstellar gas mix. So in a way, the end of the solar system
is not clearly defined. Stone guesses it could be another 10 years
(3-4 billion miles) before the two spacecraft pass through the
heliopause (the very outermost boundary of the heliosphere) and
enter purely interstellar space. The spacecraft have about another
15 years of power left in them. (Session SH02 at meeting; see
http://www.agu.org/meetings/ja06/?content=search)



QUOTE (Analyst @ May 27 2006, 02:39 AM) *
Do you have a link to the press kit? Or a press kit etc. of any of the other encounters?

Analyst


There is the Voyager Neptune Travel Guide online:

http://ntrs.nasa.gov/archive/nasa/casi.ntr..._1990004096.pdf

Other online Voyager documents from NASA can be found here by
scrolling all the way down (the spacecraft are listed in alphabetical order):

http://www.geocities.com/bobandrepont/unmannedpdf.htm


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I see that such intercourse long continued would make one thoroughly prosaic, hard,
and coarse. But the longest intercourse with Nature, though in her rudest moods, does
not thus harden and make coarse. A hard, sensible man whom we liken to a rock is
indeed much harder than a rock. From hard, coarse, insensible men with whom I have
no sympathy, I go to commune with the rocks, whose hearts are comparatively soft."

- Henry David Thoreau, November 15, 1853

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ljk4-1
post Jun 9 2006, 02:59 AM
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Voyager Reports March 3, 2006 to March 24, 2006 Available

http://voyager.jpl.nasa.gov/mission/weekly-reports/index.htm


--------------------
"After having some business dealings with men, I am occasionally chagrined,
and feel as if I had done some wrong, and it is hard to forget the ugly circumstance.
I see that such intercourse long continued would make one thoroughly prosaic, hard,
and coarse. But the longest intercourse with Nature, though in her rudest moods, does
not thus harden and make coarse. A hard, sensible man whom we liken to a rock is
indeed much harder than a rock. From hard, coarse, insensible men with whom I have
no sympathy, I go to commune with the rocks, whose hearts are comparatively soft."

- Henry David Thoreau, November 15, 1853

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MCS
post Sep 23 2006, 09:40 AM
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There's a new story at science.nasa.gov about some of the things Voyager 1 has found within the heliosheath. Magnetic turbulence, a slower than expected solar wind, and unexpected anomalous cosmic ray intensities are the main things mentioned. I hope this helps make the case for continued funding.
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dilo
post Apr 17 2008, 04:45 PM
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This is not exactly a new: Voyager 2 entered the heliosheath on August 30, 2007.
http://voyager.jpl.nasa.gov/news/voyager_squashed.html
However, incredibly, I completely ignored the event on this page and only now I "discovered" it by looking to these eloquent plots:
http://web.mit.edu/space/www/voyager/voyag...plot_recent.gif
(in the past, I was looking more often to these data but in recent months I'm more and more busy mad.gif ).
Looking to this Forum section, it seems nobody noticed it... cannot believe anyone missed it like me! blink.gif

Addendum: based on Solar System Simulator, cross occurred at 83.7 AU from sun, about 10 AU closer than Voyager-1!


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dilo
post Apr 17 2008, 09:11 PM
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Further infos: As you know, contrary to his brother, Voyager 2 has a working Plasma Science instrument that can directly measure the velocity, density and temperature of the solar wind.
I downloaded hourly data from this plasma science page. Following plots shows trend of measured proton speed, thermal speed (temperature) and density (second plot is a temporal enlargement covering the transition (window is 0.1 years or 36.5 days large):
Attached Image
Attached Image

As mentioned in the article, Voyager-2 had at least five shock crossings over a couple of days; perhaps they are the density peaks visible in second plot. QUESTION: why there is a so large hiatus (11 days) in the data immediately after this event??? Too strange for a coincidence!
They also found a much lower temperature beyond the shock than was predicted; anyway, based on following scatter plots (referred to data in the narrow temporal window of second plot above) there is a good correlation (almost inverse-square) between these twoparameters:
Attached Image


Any comment is welcomed!


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scalbers
post Apr 17 2008, 09:31 PM
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I saw a nice talk that Ed Stone gave on this topic three days ago. It will be interesting to follow along for a decade or so to see what the magnetic field looks like when Voyager gets completely into the interstellar medium.


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brellis
post Jul 2 2008, 08:18 PM
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(edit: of course this is old news to UMSF thread readers!)

The solar system is 'dented' as reported in this CNN Article.

I'm curious about how they refer to 'north' and 'south', and whether the motion of the Sun through the Milky Way impacts the escape velocities of the Voyagers.

(2nd edit: I thought I had asked the velocity question somewhere before, and found that dmuller provided insight in this post over in the New Horizons thread.

thank you dmuller!)
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Paolo
post Jul 27 2008, 02:12 PM
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In the latest issue of Astronomy & Astrophysics
Imaging the heliosheath using HSTOF energetic neutral atoms and Voyager 1 ion data


--------------------
I'm one of the most durable and fervent advocates of space exploration, but my take is that we could do it robotically at far less cost and far greater quantity and quality of results.

James Van Allen
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Fran Ontanaya
post Sep 24 2008, 06:48 AM
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You may want to look at Voyager 2 wind speed data:

http://web.mit.edu/afs/athena/org/s/space/...yager_data.html

There was a nice spike last month, from ~225 km/s to ~325 km/s, the fastest speed since it crossed the termination shock.


--------------------
"I can easily see still in my mind’s-eye the beautiful clusters of these berries as they appeared to me..., when I came upon an undiscovered bed of them... – the rich clusters drooping in the shade there and bluing all the ground" -- Thoreau
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Guest_PhilCo126_*
post Oct 27 2008, 07:07 PM
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Guests






http://www.nature.com/nature/videoarchive/voyager/
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Paolo
post Nov 1 2008, 04:15 PM
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The latest issue of Astronomy & Astrophystics (v491 n1) has some articles about heliospheric science, including results from Voyager, Ulysses, Cassini, Nozomi etc.


--------------------
I'm one of the most durable and fervent advocates of space exploration, but my take is that we could do it robotically at far less cost and far greater quantity and quality of results.

James Van Allen
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dilo
post Nov 1 2008, 09:14 PM
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Grazie, Paolo. Very interesting!


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Guest_Enceladus75_*
post Nov 3 2008, 06:07 PM
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Guests






I'm curious to know what science instruments are still functional on each Voyager. I'm aware that the cameras are now permanently turned off Voyager 2 has some more capability at measuring fields and particles over Voyager 1, but what instruments are actually still operational?

And for how long are they expected to remain operational?
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Fran Ontanaya
post Nov 3 2008, 06:25 PM
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About lifetime:

http://voyager.jpl.nasa.gov/spacecraft/spacecraftlife.html



--------------------
"I can easily see still in my mind’s-eye the beautiful clusters of these berries as they appeared to me..., when I came upon an undiscovered bed of them... – the rich clusters drooping in the shade there and bluing all the ground" -- Thoreau
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dilo
post Nov 3 2008, 06:41 PM
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and about instruments (from wikipedia):
As of the present date, the Voyager 2 and Voyager 1 scan platforms, including all of the platform instruments, have been powered down. The ultraviolet spectrometer (UVS) on Voyager 1 was active until 2003, when it too was deactivated. Gyro operations will end in 2010 for Voyager 2 and 2011 for Voyager 1. Gyro operations are used to rotate the probe 360 degrees six times a year to measure the magnetic field of the spacecraft, which is then subtracted from the magnetometer science data.


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