What is really amazing is that the probe still operates after over 3 decades, which is a testament to the design team. It’s a SNAP to keep powered up though. – Anthony
Artist concept of Voyager near interstellar space. Image credit: NASA/JPL
From NASA JPL: (h/t to Dr. Leif Svalgaard)
PASADENA, Calif. – The 33-year odyssey of NASA’s Voyager 1 spacecraft has reached a distant point at the edge of our solar system where there is no outward motion of solar wind.
Now hurtling toward interstellar space some 17.4 billion kilometers (10.8 billion miles) from the sun, Voyager 1 has crossed into an area where the velocity of the hot ionized gas, or plasma, emanating directly outward from the sun has slowed to zero. Scientists suspect the solar wind has been turned sideways by the pressure from the interstellar wind in the region between stars.
The event is a major milestone in Voyager 1’s passage through the heliosheath, the turbulent outer shell of the sun’s sphere of influence, and the spacecraft’s upcoming departure from our solar system.
“The solar wind has turned the corner,” said Ed Stone, Voyager project scientist based at the California Institute of Technology in Pasadena, Calif. “Voyager 1 is getting close to interstellar space.”
Our sun gives off a stream of charged particles that form a bubble known as the heliosphere around our solar system. The solar wind travels at supersonic speed until it crosses a shockwave called the termination shock. At this point, the solar wind dramatically slows down and heats up in the heliosheath.
Launched on Sept. 5, 1977, Voyager 1 crossed the termination shock in December 2004 into the heliosheath. Scientists have used data from Voyager 1’s Low-Energy Charged Particle Instrument to deduce the solar wind’s velocity. When the speed of the charged particles hitting the outward face of Voyager 1 matched the spacecraft’s speed, researchers knew that the net outward speed of the solar wind was zero. This occurred in June, when Voyager 1 was about 17 billion kilometers (10.6 billion miles) from the sun.
Because the velocities can fluctuate, scientists watched four more monthly readings before they were convinced the solar wind’s outward speed actually had slowed to zero. Analysis of the data shows the velocity of the solar wind has steadily slowed at a rate of about 20 kilometers per second each year (45,000 mph each year) since August 2007, when the solar wind was speeding outward at about 60 kilometers per second (130,000 mph). The outward speed has remained at zero since June.
The results were presented today at the American Geophysical Union meeting in San Francisco.
“When I realized that we were getting solid zeroes, I was amazed,” said Rob Decker, a Voyager Low-Energy Charged Particle Instrument co-investigator and senior staff scientist at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md. “Here was Voyager, a spacecraft that has been a workhorse for 33 years, showing us something completely new again.”
Scientists believe Voyager 1 has not crossed the heliosheath into interstellar space. Crossing into interstellar space would mean a sudden drop in the density of hot particles and an increase in the density of cold particles. Scientists are putting the data into their models of the heliosphere’s structure and should be able to better estimate when Voyager 1 will reach interstellar space. Researchers currently estimate Voyager 1 will cross that frontier in about four years.
“In science, there is nothing like a reality check to shake things up, and Voyager 1 provided that with hard facts,” said Tom Krimigis, principal investigator on the Low-Energy Charged Particle Instrument, who is based at the Applied Physics Laboratory and the Academy of Athens, Greece. “Once again, we face the predicament of redoing our models.”
A sister spacecraft, Voyager 2, was launched in Aug. 20, 1977 and has reached a position 14.2 billion kilometers (8.8 billion miles) from the sun. Both spacecraft have been traveling along different trajectories and at different speeds. Voyager 1 is traveling faster, at a speed of about 17 kilometers per second (38,000 mph), compared to Voyager 2’s velocity of 15 kilometers per second (35,000 mph). In the next few years, scientists expect Voyager 2 to encounter the same kind of phenomenon as Voyager 1.
The Voyagers were built by NASA’s Jet Propulsion Laboratory in Pasadena, Calif., which continues to operate both spacecraft. For more information about the Voyager spacecraft, visit: http://www.nasa.gov/voyager . JPL is a division of the California Institute of Technology in Pasadena.
Leif Svalgaard says:
December 14, 2010 at 7:07 pm
..at Voyager 2 have been relatively steady since about 2009.4, in contrast to the large quasi-recurrent variations observed from 2007.66 (termination shock) to 2009.4. The low-energy ion energy spectrum at Voyager 2 is slightly harder than that at Voyager 1. The Voyager 2 spectrum averaged over 2007.66-2009.4 shows a rollover, with the spectral index changing from -1.3 to -1.5. After about 2009.4 at Voyager 2, the lower energy ion channels show large anisotropies consistent with the observed direction of heliosheath plasma flow, but not with its speed.
~
Thanks Leif..Hope AGU was some fun for you and that you learned something new. (lol)
Anyway, period of time for the above stats was during some of the lowest solar winds speeds, fields etc. of the space age. The heliosphere was still in shrinking mode. Frisch is suggesting that the shrinking is due to pressure changes of the VLISM. (very local interstellar medium) . If in I remember correctly .. one interstellar flow from Oph. and one interstellar flow from sco. cen. But none the less two interstellar flows are seen in the nearby VLISM. One of these flows faster and producing more pressure. I believe one of those flows was 28 km/sec. And since there is a hemispheric huge dent in the southern solar heliosphere, my thoughts are maybe this is the reason for that.
Vuks, they say that the flow of interstellar He is 26 km/s through the heliosphere. Was doing some scouting on the “He gravitational focusing cone.” Jupiter in its orbit hits the cone including the most dense portion of the cone on the backside of the sun.
Thanks Carla.
Would appreciate the link, if you got one.
You are, of course, right. That’s what happens when you do things from memory in old age. Had my units mixed and was thinking about the 3×10 to the 8th M/s and put that 3 in there instead of the 1 for the 186,000 miles per second. Have not figured out how to type exponentials on this computer so went with the English units. Mea Culpa, Mea Culpa, Mea Maxima Culpa.
@Puckster
‘The electronics 33 years ago were not hardened like they are today.’
I scrapped all your other text because the above bugs me. Are you absolutely positively insane!
Why do you think everything has gotten bloody cheaper? Back in the day they created stuff to last, because it was friggin expensive. Over the years, as is only proper, evolution, however, get to things to be much “thinner” because it saves money not because it makes stuff more “hardened” or last longer. What bone head company would want their stuff to last, today? Do you know that what made the network cards manufacturer go with life time warranty was such a simple thing as not wanting to reveal their design to nosy geeks trying to fix damaged, but otherwise very expansive, cards, and that is also why computer manufacturers in the 90’s already tried the sealed thin client approach. Hardware frakking suck today compared to how they were built before building to warranty length to save money became an issue for the buyer.
It is the same almost everywhere from building cars to houses, you don’t design nor build neither to last a hundred years today unless you can afford it or are very very special or some such, and space industry, today, can’t afford it, mostly because too few governments want to spend too big money on it.
Carla says:
December 16, 2010 at 5:30 am
I believe one of those flows was 28 km/sec.
It is the Sun that moves through the interstellar medium at ~26 km/s. When I drove to the AGU this morning, I drove through the fog at 50 mph. The fog does not move much.
vukcevic says:
December 16, 2010 at 1:02 pm
Thanks Carla.
Would appreciate the link, if you got one.
~
Two different articles Vuks, not sure which one you were referring.
I do think that it is interesting that the interstellar He neutrals flow through at 26 km/sec. One hand is saying, that sounds right and the other hand is making funny faces at me.
“”INTERSTELLAR NEUTRAL ATOMS AT 1 AU OBSERVED BY THE IMAGE/LENA IMAGER””
S. A. Fuselier1, A. G. Ghielmetti1, and P. Wurz2
published 2009 May 27
1. INTRODUCTION
..””Interstellar neutral helium has been observed in the inner
solar system directly (Witte et al. 2004) and through indirect
means, i.e., by pickup ion measurements (M¨obius et al. 1985;
Gloeckler & Geiss 1998) and EUV measurements (Vallerga
et al. 2004). The properties of these neutrals are reasonably
well understood. They appear as a relatively compact (∼few
degrees wide) source arriving from λ = 74. ◦ 5, β = −5. ◦ 5 (i.e.,
very near the apex direction) with a speed of approximately
26 km s−1 (14.5 eV), a temperature of ∼6300 K, and a density
of 1.5 × 10−2 cm−3 (M¨obius et al. 2004). These parameters
represent the unperturbed flow of neutrals into the heliosphere.
Interstellar neutral hydrogen with nearly the same speed (i.e.,
with an energy of a few eV) has been inferred from a variety of
measurements (e.g., Lallement et al. 1996; Gloeckler & Geiss
1998).”’
Or did you mean the Fritsch team on VLISM and CHISM and Flows and what not? Too many articles in the fire right now Vuks. Be back..
Leif Svalgaard says:
December 16, 2010 at 2:50 pm
Carla says:
December 16, 2010 at 5:30 am
I believe one of those flows was 28 km/sec.
It is the Sun that moves through the interstellar medium at ~26 km/s. When I drove to the AGU this morning, I drove through the fog at 50 mph. The fog does not move much
The Frisch team is suggesting that 2 km/sec difference would create a substantial differnce in the pressure gradient. Thats a 10 AU dent out there Doc.
So you couldn’t push the fog around, bummer driving like that.
Carla says:
December 16, 2010 at 5:51 pm
The Frisch team is suggesting that 2 km/sec difference would create a substantial differnce in the pressure gradient.
I don’t think they really mean that. Show us.
Leif Svalgaard says:
December 16, 2010 at 6:55 pm
Carla says:
December 16, 2010 at 5:51 pm
The Frisch team is suggesting that 2 km/sec difference would create a substantial differnce in the pressure gradient.
I don’t think they really mean that. Show us.
~
Well .. in context yes they did mean that.
And the article went on with the math comps on how they arrived at that conclusion. There has been several articles, as of late, from the Frisch team suggesting that the interstellar region is shaping the bubble and not the solar cycle. Maybe the solar cycle is the response to those interstellar changes . NO No can’t say that now.
I can show us, when my badly in need of a defrag brain finds it. lol That two different flow directions possibility would have been of some import, so should have that on paper. hmm
Vuks the relationship to the sudden stratospheric warming, the the polar vortex shear? May be related to the earth’s orbit out from the focusing cone. The description of the event is located in the last link. The event being, exiting the focusing cone. The exit not being the same as the entry. The time period and description is a bit more than coincidental.
Hypothesis: A perpendicular magnetic field to the pathway of the charged particles is deflecting those charged particles sideways.
Initially I was confused by the claims of the solar wind being zero, until I realized what confused me. The article says:
When the speed of the charged particles hitting the outward face of Voyager 1 matched the spacecraft’s speed, researchers knew that the net outward speed of the solar wind was zero
Note that this means the particles hitting the front or “outward facing” side of Voyager. It’s the side of the vehicle which is pointing away from the sun. So if the vehicle is moving at MPH relative to the sun, and Voyager tells us that particles are hitting its “windshield” at the same MPH, then it must be that those particles are not moving relative to the sun.