Voyager 2 Shows Solar System Is "Dented"

Selikoff writes "NASA's Voyager 2 spacecraft has found that our solar system is not round but is 'dented' by the local interstellar magnetic field, space experts said on Monday. The data were gathered by the craft on its 30-year journey when it crossed into a region called the 'termination shock.' The data showed that the southern hemisphere of the solar system's heliosphere is being pushed in. Voyager 2 is the second spacecraft to enter this region of the solar system, behind Voyager 1, which reached the northern region of the heliosheath in December 2004."

Re:I don't get it

[MichaelSmith]

how does the spacecraft survive in those temperatures?

The density is very low. The body of the spacecraft might get hit by individual molecules which have that temperature, but what are a few thousand molecules going to do to it?

Re:I don't get it

[Anonymous Coward]

Probably simple physics ... remember, the density of the gas in space is very low (almost non existant); this implies that there are very few particles hitting the craft at that temperature. Meaning that the craft only needs to have roughly 10000 times the density of space to operate at a "normal" temperature. Given the craft is made out of solid things like metal, that shouldn't be too hard...

Re:Shape?

[entrigant]

See: http://en.wikipedia.org/wiki/Heliosphere [wikipedia.org]

Basically the suns solar winds push back interstellar matter. This can have a shape.

Re:Is this any better than conjecture?

[andphi]

Actually, they seem to base their conclusion on the fact that Voyager 1 and Voyager 2 don't seem to have entered the termination shock at the same distance from the earth.

FTA:

"Voyager 2 entered the termination shock almost 1 billion miles closer within the southern hemisphere of the heliosphere of the solar system than Voyager 1 previously had," said Voyager Project scientist Edward Stone of the California Institute of Technology.

Re:Is this any better than conjecture?

[MikeyVB]

Actually, they seem to base their conclusion on the fact that Voyager 1 and Voyager 2 don't seem to have entered the termination shock at the same distance from the earth.

Actually, they seem to base their conclusion not only on that fact, but also because they had theorized that it might be that way from computer models that predicted when Voyager 1 and Voyager 2 reached the termination. So far Voyager 1 (actually, not sure on V1) and Voyager 2 reached the termination shock around where they thought they would according to the model that the Solar System is asymmetrical as described in TFA. (This [www.cbc.ca]arcicle briefly mentions the computer model)

Re:Halp!

[Gabrill]

Right hand rule. Fist your right hand, and the fingers indicate direction of spin. The thumb indicates North. Most of the Milky Way galaxy follows this rule, in conjunction with Earth (excepting Uranus, not a team player).

Re:Its not really hostile

[coinreturn]

Cold is generally good for equipment, but not too much of course.

Actually, the "cold" of space doesn't help at all. Because the density of particles is so low, spacecraft can't cool down by convection. Cooling spacecraft (eg shedding internally generated heat) is a big problem. Also, the main "harsh" ingredient of space is radiation. The technology used in spacecraft is usually way behind commercial technology because it also has to be "rad-hardened."

Re:I just find it amazin

[Technopaladin]

I ANAAP but Earth is 8 Light minutes from the sun...so I would suspect we are talking an hour or so.

Re:Shape?

[Anonymous Coward]

This is the common method of viewing what termination shock is on earth: go to a sink and turn it on, as you will see in the basin, when the water hits, its ejected out on all sides. On the outskirts of the basin, where the water is forced by gravity back down, the water will become regular, non-moving, etc. This is the interstellar medium, the ambient pressure from outside our solar system is pushing against the solar wind (the water thats rushing away from its impact location) creating a location thats called termination shock. This location, as you can clearly see, is moving, always fluctuating. It changes its shape in response to the outside pressure (which here on earth, is caused by gravity wanting to pull the water down in the basin). You can probably easily see how a object could pass this boundary several times, especially when you realize that our solar system is much, much bigger then this example. A dented shock boundary could occur when, for whatever reason, the rushing water is being pushed back sooner. Perhaps there is more pressure on that side, or, in the case of space, you have some magnetic influences acting against the solar wind. Granted there could be other reasons, but the smart minds of today say its probably magnetic influences.

Almost 12 light-hours, actually

[yeremein]

This article [newscientist.com] says it's 84 AU out, which is a little more than 11.6 light-hours [google.com].

isn't much

[Quadraginta]

Matter is unbelievably thin out there. Roughly 1 atom every 10 cubic centimeters. By contrast the best vacuums we can produce on Earth (around a trillionth of an atmosphere) contain 250 million atoms in every 10 cubic centimeters.

It doesn't damage the spacecraft because, as anyone who has put out a candle flame with his fingers can tell you, it's not temperature that is dangerous but heat. Things with very little heat to transfer -- in this case, some unbelievably tiny amount of matter -- but at very high temperature, are harmless.

An analogous situation exists with respect to electricity: it isn't voltage per se that is dangerous to you but rather charge. Things that are at very high voltages (e.g. the static charge you built up when you scuff your shoes on a dry winter day) can be quite harmless if the amount of charge that can be transferred is very small, e.g. just a little spark.

The confusion exists in part because usually things at high temperature (or high voltage) have plenty of heat (or charge) to transfer, and then they are more dangerous than equivalent reservoirs at lower temperature (or voltage), because they transfer the lethal dose of heat (or charge) much faster.

Re:human defined?

[AeroIllini]

Except those approximations of pi are expressed in (usually) base-10 notation, which is a human-created construction.

Asking if there is something that exists that is not defined by humans is a tricky question. All of these things "exist", but all the tools we have for sensing them and measuring them are largely based on human-defined systems of measurements. We can't talk about these things without resorting to standards of measurement, which are wholly arbitrary and based on human experience.

So, yes, there are lots of things that exist that are not human defined. However, once we name it or measure it or look at it or smell it or hear it or touch it, we are ascribing human-created standards to it so we can describe it to other people. It is these standards of measurement which are defined by humans, not the things themselves.

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