Interstellar dust and the sun

Nov 12, 2012
Interstellar Dust and the Sun
An artist’s concept of the heliosphere (seen in blue, including a shocked region). The Earth is at 1 AU, and the two Voyager spacecraft are seen beyond 100 AU (the Cassini spacecraft at Saturn is also shown). A new study investigates what happens to interstellar dust that encounters the solar system and the Sun's heliosphere. Credit: NASA and JHU/APL

(Phys.org)—The space between stars is not empty. It contains copious but diffuse amounts of gas and dust; in fact about 5-10% of the total mass of our Milky Way galaxy is in interstellar gas. About 1% of the mass of this interstellar material, quite a lot in astronomical terms, is in the form of tiny dust grains made predominantly of silicates (sand too is made of silicates), though some grains are also composed of carbon and other elements. Dust grains are important. They block visible light while emitting infrared light, and thus help determine what astronomers can see while controlling much of the energy balance in the interstellar medium (ISM) by virtue of the absorption and subsequent re-emission at longer wavelengths of light from stars. Dust is also essential to the chemistry that takes place in the ISM because it provides gas molecules with a surface on which to react with other molecules. Not least, dust contains a large fraction of many important elements in the universe like silicon, carbon, and iron. Moreover, astronomers think that at some stage in the evolution of new stars the dust around them will coagulate into large clumps—the first step towards forming planets.

CfA astronomer Jonathan Slavin and a team of six other astronomers wondered what happens to interstellar dust when it wanders into the solar system and gets close enough to the Sun to fall under the influence of its radiation, winds, and gravity. They note that the Sun (and its planets) is moving through a low density cloud of partially ionized gas. This motion, together with the wind of particles that the Sun emits, produces a bow-shaped region called the heliosphere, the bow-shaped end of which is about 100 AU from the Sun (one AU is the average distance of the Earth from the Sun).

Writing in the latest issues of the , the scientists report on the results of their theoretical models of the behavior of interstellar dust grains as the Sun moves through space. They build on in-situ observations of the heliosphere taken when the Voyager 1 and Voyager 2 spacecraft on their outward journey encountered the edges of the heliosphere, results that constrain its size and shape. Assuming typical grains made of olivine silicates, the team finds that the small grains (less than the wavelength of ultraviolet light) stay far away from the Sun, that gravity helps the large grains collect near the Sun, but that intermediate-sized grains - about the size of the wavelength of optical light - can actually pile up in diffuse structures at the edges of the heliosphere. The new results, besides providing important new information on dust grains in the solar system, suggest that radiation from these intermediate-sized grain structures could contaminate the images of the sky used to measure the cosmic backgrounds.

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Squirrel
3.7 / 5 (3) Nov 12, 2012
The 5-10% of the total mass of our Milky Way galaxy that is interstellar gas also makes the existence of near light speed travel between stars unlikely--even if getting near that velocity was possible, the energy released when hitting such particles makes such travel either unsafe or requiring protection that makes it impractical.
antialias_physorg
3.7 / 5 (3) Nov 12, 2012
Depends on how you travel. If you go with something like an Alcubierre drive then the stuff would possibly not be a problem to you ...

... but to anyone at your destination:
http://www.univer...ownside/
cantdrive85
1.3 / 5 (14) Nov 12, 2012
For a scientific description of the heliosphere rather than an "artist's concept", read this press release.
http://electric-c...2012.pdf
Here is a video for the reading challenged;
http://www.thunde...-ceases/
If the above is correct, and we consider these tidbits, it may help explain what is happening on the larger scale EM field created by the Sun and how we should expect cosmic rays and interstellar dust to the interact with the Sun's EM field and how the Sun's particles and energy behaves with the interstellar medium.
http://phys.org/n...eve.html http://phys.org/n...071.html

The advantage of a plasma model is that what we find in small scales is to be expected in large scales as well.

Tuxford
1 / 5 (8) Nov 12, 2012
Depends on how you travel.


Indeed. If you were to carry your own etheric frame along with you, you could exceed light speed, not suffer time effects, and not have to worry about colliding with anything, as you slip between the static etheric frame.
rubberman
4.3 / 5 (6) Nov 12, 2012
"Moreover, astronomers think that at some stage in the evolution of new stars the dust around them will coagulate into large clumps—the first step towards forming planets."

Starts with the electro magnetic force, transitions to gravity once the mass is sufficient to initiate formation of an accretion disk.


http://phys.org/n...rth.html
Infinion
1 / 5 (3) Nov 13, 2012
For a scientific description of the heliosphere rather than an "artist's concept", read this press release.
http://electric-c...2012.pdf

The advantage of a plasma model is that what we find in small scales is to be expected in large scales as well.



tried going to those links but they were broken..
Torbjorn_Larsson_OM
5 / 5 (2) Nov 13, 2012
Nice result, article and image (which for once don't depict the rejected "tailed" heliosphere model)!

@ antialias: No signal of any kind can go faster than the speed limit of the universe. If it did, physics would collapse.

Alcubierres makes that explicit, since they depend on having their inner volume created above that speed already. So they don't provide such volumes.

@ cantdrive: The artist is on the money, see Wikipedias article on the basic science of this.

And there is no "plasma model", since there is no quantified prediction. You know this is how it works: you _look_ at the world. No lookie, only kookie.

Take your anti-science to the crackpot sites were it belongs. This is a science site.

@ Infinion: Don't bother, PU/EC is beyond science denialism, it is beyond anti-science crackpottery: they have made it a religion. Even cold fusion crackpots have some predictions (which they fail). These guys? Nada.
antialias_physorg
5 / 5 (2) Nov 13, 2012
No signal of any kind can go faster than the speed limit of the universe. If it did, physics would collapse.

The way I read it no part in the Alcubierre drive scheme moves faster than light - so there's no problem with physics/causality there. (And whether causality is a fundamental of physics or just an emergent property of stuff being confined to sub light speeds isn't, clear, anyhow)

We do know that (apparent) relative motions faster than c are possible due to inflation when objects cross the observability horizon (i.e. when expansion between them is faster than light can traverse it). So we do know that causal links can be broken (though not contradicted)*.

*under the assumption that information transmission is limited to c . Which seems to be a very solid assumption given current state of observations.
antialias_physorg
5 / 5 (1) Nov 13, 2012
The postulate that the exotic matter required would need to move at trans light speeds is a bit of a poser. But then again the whole idea of exotic matter and negative energies on that kind of scale is alredy a bit iffy. There may be ways around that.

Point being: I'm not at all convinced that an Alcubierre drive is possible. But given the various ideas floating around for interstellar travel in appreciable time and without the 'hazards' problem of interstellar dust (and generally blue-shifted cosmic radiation) at high speeds it's the one which has at least some solid/serious theoretical effort behind it.
cantdrive85
2 / 5 (8) Nov 13, 2012
cantdrive85
1.8 / 5 (10) Nov 13, 2012
@ cantdrive: The artist is on the money, see Wikipedias article on the basic science of this.

And there is no "plasma model", since there is no quantified prediction. You know this is how it works: you _look_ at the world. No lookie, only kookie.


No plasma model? Hannes Alfven spent much his life developing the PC model. And unlike the standard model, which leads to unexpected, mysterious, and enigmatic observations, PC's predicted models fit the observations.

I'm familiar with the standard model's POV (parroted by Wiki), but in all the explanations of the Sun's magnetic field there is not one mention of the electric currents or electric field that MUST accompany said magnetic field. With such a fundamental omission, the likelihood that the standard model is accurate is null.
barakn
5 / 5 (1) Nov 13, 2012
Thank goodness you fixed the links, especially to
http://electric-c...2012.pdf and
http://www.thunde...-ceases/
GSwift7
2.3 / 5 (4) Nov 15, 2012
The advantage of a plasma model is that what we find in small scales is to be expected in large scales as well


You were okay until you said that it is expected in large scales as well.

The very existence of the bow shock shows you that the sun's influence does not extend beyond that point. Magnetic fields fall off at the cube of distance. Gravity falls off at the square of distance. At interstellar distances, EM fields do not have the range to be influencial.

No plasma model? Hannes Alfven spent much his life developing the PC model


He abandonded the EM model later in his life, as evidence began to show that it could not be correct.
cantdrive85
1 / 5 (5) Nov 15, 2012
@Not to swift-
This from A. Peratt's site;
"But perhaps the most important characteristic of electromagnetism is that it obeys the longest-range force law in the universe. When two or more non-plasma bodies interact gravitationally, their force law varies inversely as the square of the distance between them; 1/4 the pull if they are 2 arbitrary measurement units apart, 1/9 the pull for a distance of 3 units apart, 1/16 the pull for 4 units apart, and so on. When plasmas, say streams of charged particles, interact electromagnetically, their force law varies inversely as the distance between them, 1/2 the pull if they are 2 arbitrary measurement units apart, 1/3 the pull for a distance of 3 units apart, 1/4 the pull for 4 units apart, and so on. So at 4 arbitrary distance units apart, the electromagnetic force is 4 times greater than that of gravitation, relatively speaking, and at 100 units, apart, the electromagnetic force is 100 times that of gravitation."

Sorry, you're wrong again.
cantdrive85
1.6 / 5 (7) Nov 15, 2012
He abandonded the EM model later in his life, as evidence began to show that it could not be correct.


What a completely spurious claim, an outright lie in fact.

http://plasmauniv...ven.html
Q-Star
2.7 / 5 (7) Nov 15, 2012
So at 4 arbitrary distance units apart, the electromagnetic force is 4 times greater than that of gravitation,,,,

Sorry, you're wrong again.


Actually he's not, but you are. Electromagnetic forces are governed by an inverse square law, just as gravity is. Unless you want to do away with Couloumb and Maxwell along with Einstein.

Peratt may not be your best source to quote. Especially since he's getting the fundamentals so wrong.
cantdrive85
1.5 / 5 (8) Nov 15, 2012
His example of the EM force of electric currents is correct, as is the inverse square law concerning non current applications is correct. The significance of using the plasma current analogy he mentioned is that 99.99% of the Universe is in a plasma state, which is subject to the longest distance force laws (EM) known to science.

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