Does the gas in galaxy clusters flow like honey?

Does the gas in galaxy clusters flow like honey?
This image represents a deep dataset of the Coma galaxy cluster obtained by NASA's Chandra X-ray Observatory. Researchers have used these data to study how the hot gas in the cluster behaves. One intriguing and important aspect to study is how much viscosity, or "stickiness," the hot gas demonstrates in these cosmic giants. Credit: X-ray: NASA/CXC/Univ. of Chicago, I. Zhuravleva et al, Optical: SDSS

We have seen intricate patterns that milk makes in coffee and much smoother ones that honey makes when stirred with a spoon. Which of these cases best describes the behavior of the hot gas in galaxy clusters? By answering this question, a new study using NASA's Chandra X-ray Observatory has deepened our understanding of galaxy clusters, the largest structures in the Universe held together by gravity.

Galaxy clusters are comprised of three main components: individual , multimillion-degree gas that fills the space between the galaxies, and dark matter, a mysterious form of matter that is spread throughout a cluster and accounts for about 80 percent of the mass of the cluster.

A team of astronomers used a set of long Chandra observations, totaling about two weeks of observing, of the Coma galaxy cluster to probe gas properties on spatial scales comparable with a typical distance that travel between collisions with each other. This measurement helped them to learn about the viscosity—the technical term for the resistance to the motion of gas lumps with respect to each other—of the hot gas in Coma.

"Our finding suggests that gas viscosity in Coma is much lower than expected," said Irina Zhuravleva of the University of Chicago, who led the study. "This means that turbulence can easily develop in the hot gas in on small scales, analogous to swirling motions in a coffee mug."

The hot gas in Coma glows in X-ray light observed by Chandra. The gas is known to contain about six times more mass than all of the combined galaxies in the cluster. Despite its abundance, the density of the hot gas in Coma, which radio observations have shown is permeated by a weak magnetic field, is so low that the particles do not interact with each other very often. Such a low-density, hot gas cannot be studied in a laboratory on Earth, and so scientists must rely on cosmic laboratories such as the one provided by the intergalactic gas in Coma.

"We used Chandra to probe whether the density of the gas is smooth on the smallest scales we can detect," said Eugene Churazov, a co-author from the Max Planck Institute for Astrophysics in Garching and the Space Research Institute in Moscow. "We found that it is not, suggesting that turbulence is present even on these relatively small scales and the viscosity is low."

To reach these conclusions, the team concentrated on a region away from the center of the Coma Cluster where the density of the hot gas is even lower than it is in the center. Here, the particles have to travel longer distances—about 100,000 light-years on average—to interact with another particle. This distance is large enough to be probed with Chandra.

"Perhaps one of the most surprising aspects is that we were able to study physics on scales relevant to interactions between atomic particles in an object that's 320 million light-years away," said co-author Alexander Schekochihin of the University of Oxford in the United Kingdom. "Such observations open a great opportunity to use galaxy clusters as laboratories to study fundamental properties of hot gas."

Why is the viscosity of Coma's hot gas so low? One explanation is the presence of small-scale irregularities in the cluster's magnetic field. These irregularities can deflect particles in the hot gas, which is composed of electrically charged particles, mostly electrons, and protons. These deflections reduce the distance a particle can move freely and, by extension, the gas viscosity.

Knowledge of the viscosity of gas in a galaxy cluster and how easily turbulence develops helps scientists understand the effects of important phenomena such as collisions and mergers with other galaxy clusters, and galaxy groups. Turbulence generated by these powerful events can act as a source of heat, preventing the hot gas in clusters from cooling to form billions of new stars.

The researchers chose the Coma cluster for this study because it has the best combination of physical properties required. The average distance between particle collisions is higher for gas with hotter temperatures and lower densities. Coma is hotter than other brightest nearby galaxy clusters and has relatively low density, unlike cool and dense cores of other bright galaxy clusters including Perseus and Virgo. This gives astronomers a chance to use the Coma cluster as a laboratory for studying plasma physics.

Future direct measurements of velocities of gas motions with the X-ray Imaging and Spectroscopy Mission (XRISM), a collaborative mission between the Japanese Exploration Agency and NASA, will provide more details on dynamics, allowing us to make robust studies of many nearby galaxy clusters. XRISM is expected to launch in the early 2020s.

A paper describing this result appeared in the June 17th issue of the journal Nature Astronomy.


Explore further

Clues to the growth of the colossus in Coma

More information: I. Zhuravleva et al. Suppressed effective viscosity in the bulk intergalactic plasma, Nature Astronomy (2019). DOI: 10.1038/s41550-019-0794-z , https://arxiv.org/abs/1906.06346
Journal information: Nature Astronomy

Citation: Does the gas in galaxy clusters flow like honey? (2019, June 18) retrieved 21 October 2019 from https://phys.org/news/2019-06-gas-galaxy-clusters-honey.html
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Jun 18, 2019
LOL They had to spoil the article's main premise by invoking the "mysterious dark matter" that has yet to be found, qualified and quantified as a REALITY of the Cosmos. Until that happens, "dark matter" is but a figment of the imaginings of those who wish it to be real.

Why is the viscosity of Coma's hot gas so low? One explanation is the presence of small-scale irregularities in the cluster's magnetic field. These irregularities can deflect particles in the hot gas, which is composed of electrically charged particles, mostly electrons, and protons. These deflections reduce the distance a particle can move freely and, by extension, the gas viscosity.

Knowledge of the viscosity of gas in a galaxy cluster and how easily turbulence develops helps scientists understand the effects of important phenomena such as collisions and mergers with other galaxy clusters, and galaxy groups. Turbulence generated by these powerful events can act as a source of heat, preventing the hot gas in


Jun 18, 2019
In other words, the plasma doesn't behave as expected if the electric currents aren't accounted for. This shouldn't come as a surprise, any other scientific endeavor would also likely be erroneous if only half the picture was accounted for.

Jun 18, 2019
@cantdrive85.

Mate, at last some mainstream plasma physicists are brave enough to start admitting things like:
In numerical simulations, one often cuts through these unknowns by MODELING these plasmas as HYDRODYNAMIC fluids, EVEN THOUGH LOCAL NON-HYDRODYNAMIC FEATURES OBSERVED IN CLUSTERS CONTRADICT THIS ASSUMPTION.


In any case, it still amazes me that they STILL call deep space plasma "hot gas" instead of just plasma. Maybe it should be made compulsory for writers/researchers in this field to start calling a spade a 'spade'...and not keep calling it a 'shovel', hey? :)
Also, they need to understand that, in deep space plasmas at least, the 'particle interactions' are much LONGER RANGE than 'direct collisions' would imply; because the constituent electrons, protons, heavier ions, magnetised dust grains can create FEEDBACK to ambient magnetic forces/fields, and so complicate/strengthen/cancel local fields so as to manifest long-range 'en masse' order/flows etc. :)

Jun 18, 2019
In other words, the plasma doesn't behave as expected if the electric currents aren't accounted for. This shouldn't come as a surprise, any other scientific endeavor would also likely be erroneous if only half the picture was accounted for.


What currents? You are obsessed, you loon.

Jun 18, 2019
LOL They had to spoil the article's main premise by invoking the "mysterious dark matter" that has yet to be found, qualified and quantified as a REALITY of the Cosmos. Until that happens, "dark matter" is but a figment of the imaginings of those who wish it to be real.


And what the hell would you know, you clueless oik?


Jun 18, 2019
Hey, @Castro!... give the nastiness a rest, willya? :)

Jun 18, 2019
Hey, @Castro!... give the nastiness a rest, willya? :)


When the scientifically illiterate loons stop posting utter crap on subjects they know nothing about, then I will be happy to be nice to them. Until then, I will treat these idiots with the contempt they deserve.

Jun 18, 2019
In any case, it still amazes me that they STILL call deep space plasma "hot gas" instead of just plasma. Maybe it should be made compulsory for writers/researchers in this field to start calling a spade a 'spade'...and not keep calling it a 'shovel', hey? :)


Learn to read. What is the title of the paper? 'Suppressed effective viscosity in the bulk intergalactic **plasma**.' What are the first few lines of the abstract?

Transport properties, such as viscosity and thermal conduction, of the hot intergalactic **plasma** in clusters of galaxies are largely unknown. Whereas for laboratory **plasmas** these characteristics are derived from the gas density and temperature, such recipes can be fundamentally different for the intergalactic **plasma** owing to a low rate of particle collisions and a weak magnetic field. In numerical simulations, these unknowns can often be avoided by modelling these **plasmas**......


Jun 18, 2019
@Castrogiovanni.
In any case, it still amazes me that they STILL call deep space plasma "hot gas" instead of just plasma. Maybe it should be made compulsory for writers/researchers in this field to start calling a spade a 'spade'...and not keep calling it a 'shovel', hey? :)
Learn to read. What is the title of the paper? 'Suppressed effective viscosity in the bulk intergalactic **plasma**.'...
Please know that I was referring to the article writer/quoted researchers usage of the old/misleading "hot gas" term at all; and I now point out examples of such usage above in case you missed them:

One researcher was quoted as saying...
"This means that turbulence can easily develop in the *hot gas* in galaxy clusters on small scales, analogous to swirling motions in a coffee mug."


And the writer said:
The *hot gas* in Coma glows in X-ray light observed by Chandra.
Hence my specific point that writers/researchers STILL use such old/misleading terminology. Ok? :)

Jun 18, 2019
And the writer said:
The *hot gas* in Coma glows in X-ray light observed by Chandra.
Hence my specific point that writers/researchers STILL use such old/misleading terminology. Ok? :)


And what have I said about relying on press releases? The author could be a biology grad. Read the papers.

Jun 18, 2019
@Castrogiovanni.
And the writer said:
The *hot gas* in Coma glows in X-ray light observed by Chandra.
Hence my specific point that writers/researchers STILL use such old/misleading terminology. Ok? :)
And what have I said about relying on press releases? The author could be a biology grad. Read the papers.
I already did read the paper. It wasn't the paper per se I was commenting on. It was the writer/researcher still using old/misleading terminology, as I specifically pointed to above...,because BOTH the writer AND the quoted researcher who was one of the AUTHORS ion that paper used the old/misleading "hot gas" instead of just saying "plasma" when reporting/conveying their results to NON-scientists and even between themselves. That was my point: the misleading usage leads to all sorts of unnecessary cross-purpose exchanges/confusions even between astrophysics/astronomy student; and also hampers common understanding during/from discussions such as here. Ok? :)

Jun 18, 2019
here are a lot of cosmic structures - cavities with tenuous, high temperature gas. The nomenclature of these cavities is not finally established yet, but in general there are cavities with a characteristic size of 10 pc – bubbles, about 100 pc – superbubbles, and extended up to 1 kpc or more – supershells. There are a lot of global outflows in our and other star-forming galaxies that percolate galactic disk and are streaming away in galactic halo. These are so called chimneys, fountains, winds and high velocity clouds. All of these structures have an enigmatic nature. In this paper we offer the mechanism which explains their nature in the uniform manner that is based on our original elaston model of the space.
https://www.acade...nd_Winds

Jun 18, 2019
I already did read the paper. It wasn't the paper per se I was commenting on. It was the writer/researcher still using old/misleading terminology, as I specifically pointed to above...,because BOTH the writer AND the quoted researcher who was one of the AUTHORS ion that paper used the old/misleading "hot gas" instead of just saying "plasma" when reporting/conveying their results to NON-scientists and even between themselves. That was my point: the misleading usage leads to all sorts of unnecessary cross-purpose exchanges/confusions even between astrophysics/astronomy student; and also hampers common understanding during/from discussions such as here. Ok? :)


So you have access to Nature Astronomy? Or did you pay the $8.99 to read it?
And we don't know what the author said. Only as it was (para)phrased by the reporter, who may be dumbing down the author's words for a wider audience, who might think plasma is something to do with blood.

Jun 18, 2019
ps @ Castro.

Anyhow, you haven't said anything about that other item I mentioned/quoted in my post to @cantdrive; ie, re the relevant researcher acknowledging the non-hydrodynamic nature of the plasma being confirmed by observation; and how past 'modelling' based on such hydrodynamic "assumptions" did not reflect the reality? :)

Jun 18, 2019
@Castrogiovanni.
I already did read the paper.

So you have access to Nature Astronomy?
Didn't need it. I read the arxiv linked paper:

https://arxiv.org...6346.pdf


Jun 18, 2019
ps @ Castro.

Anyhow, you haven't said anything about that other item I mentioned/quoted in my post to @cantdrive; ie, re the relevant researcher acknowledging the non-hydrodynamic nature of the plasma being confirmed by observation; and how past 'modelling' based on such hydrodynamic "assumptions" did not reflect the reality? :)


Why would I need to say anything? Non-MHD models have been used for decades in all sorts of scenarios.

Jun 18, 2019
@Castrogiovanni.
ps @ Castro.

Anyhow, you haven't said anything about that other item I mentioned/quoted in my post to @cantdrive; ie, re the relevant researcher acknowledging the non-hydrodynamic nature of the plasma being confirmed by observation; and how past 'modelling' based on such hydrodynamic "assumptions" did not reflect the reality? :)
Why would I need to say anything? Non-MHD models have been used for decades in all sorts of scenarios.
My comment was in longstanding context of past arguments between you and @cantdrive. He insisted that simulations/interpretations of data/observations were NOT allowing for the NON-hydrodynamic nature of astrophysical plasma features/phenomena. You ridiculed him for pointing out that therefore the hydrodynamics-dependent assumptions/interpretations by astrophysicists could not reflect the actual space plasma reality. Now this paper points out the same thing @cantdrive did. Hence why I asked if you had any comment on that. :)

Jun 18, 2019
In other words, the plasma doesn't behave as expected if the electric currents aren't accounted for. This shouldn't come as a surprise, any other scientific endeavor would also likely be erroneous if only half the picture was accounted for.


What currents? You are obsessed, you loon.


"In order to understand the phenomena in a certain plasma region, it is necessary to map not only the magnetic but also the electric field and the electric currents." Hannes Alfven, Nobel Laureate

It's about physics and doing it right. Then there are folks such as yourself who are A-OK with half-assing it and inventing faerie dust.

Jun 18, 2019
@Castrogiovanni.
ps @ Castro.

Anyhow, you haven't said anything about that other item I mentioned/quoted in my post to @cantdrive; ie, re the relevant researcher acknowledging the non-hydrodynamic nature of the plasma being confirmed by observation; and how past 'modelling' based on such hydrodynamic "assumptions" did not reflect the reality? :)
Why would I need to say anything? Non-MHD models have been used for decades in all sorts of scenarios.
My comment was in longstanding context of past arguments between you and @cantdrive. He insisted that simulations/interpretations of data/observations were NOT allowing for the NON-hydrodynamic nature of astrophysical plasma features/phenomena. You ridiculed him for pointing out that therefore the hydrodynamics-dependent assumptions/interpretations by astrophysicists could not reflect the actual space plasma reality. Now this paper points out the same thing @cantdrive did.


In the words of da schnied, I WIN!

Jun 18, 2019
In other words, the plasma doesn't behave as expected if the electric currents aren't accounted for. This shouldn't come as a surprise, any other scientific endeavor would also likely be erroneous if only half the picture was accounted for.


What currents? You are obsessed, you loon.


"In order to understand the phenomena in a certain plasma region, it is necessary to map not only the magnetic but also the electric field and the electric currents." Hannes Alfven, Nobel Laureate

It's about physics and doing it right. Then there are folks such as yourself who are A-OK with half-assing it and inventing faerie dust.


What currents? Where is any such thing mentioned in the paper? Stop making crap up, you loon.

Jun 18, 2019
My comment was in longstanding context of past arguments between you and @cantdrive. He insisted that simulations/interpretations of data/observations were NOT allowing for the NON-hydrodynamic nature of astrophysical plasma features/phenomena. You ridiculed him for pointing out that therefore the hydrodynamics-dependent assumptions/interpretations by astrophysicists could not reflect the actual space plasma reality. Now this paper points out the same thing @cantdrive did. Hence why I asked if you had any comment on that. :)


Which is total and utter bullshit, you idiot. Stop commenting on things you do not understand. i.e. science. I have said, you idiot, that MHD is appropriate where it is appropriate. That is, at length scales and timescales where the magnetic Reynolds number dictates that the magnetic field can be treated as frozen-in to the plasma. Such as the solar wind. I have never said anything about modeling intergalactic plasmas, you dickhead. Learn the subject, idiot

Jun 18, 2019
In the words of da schnied, I WIN!


Nope. You are still a total ignoramus wrt plasma physics. Your cult possesses no plasma physicists. None of them have contributed anything to plasma physics, due to not understanding it. Stick to mythology, and Earth orbiting Saturn.

Jun 18, 2019
In other words, the plasma doesn't behave as expected if the electric currents aren't accounted for. This shouldn't come as a surprise, any other scientific endeavor would also likely be erroneous if only half the picture was accounted for.

There's a whole lot more than electric fields to account for...

Jun 18, 2019
From the paper.

In contrast to the expectations for a Coulomb-collision-dominated plasma, the effective Reynolds number appears to be large.


Is a field more or less likely to be frozen into a plasma when there is a high magnetic Reynold's number? So, what is that sentence telling us? Hint;

If Rm is large then convection dominates, and the magnetic field is frozen into the plasma. Else if Rm is small then diffusion dominates. In the solar system, and in astrophysics generally, Rm is very large, e.g., 10^8 in a solar flare, and 10^11 in the solar system and planetary magnetospheres. We shall see that Rm is not large everywhere; thin boundary layers form where Rm ∼ 1 and ideal MHD breaks down. As in most branches of physics, these boundary layers mediate the global dynamics by controlling the rate of transport of mass, momentum, and energy through the system.


Take a guess.

http://www.sp.ph....ster.pdf

Jun 18, 2019
We shall see that Rm is not large everywhere; thin boundary layers form where Rm ∼ 1 and ideal MHD breaks down. As in most branches of physics, these boundary layers mediate the global dynamics by controlling the rate of transport of mass, momentum, and energy through the system.

IOW, double layers and circuitry. And these aspects are certainly not accounted for in the standard guesswork, they know it yet still continue do half-assed physics.

Jun 19, 2019
In other words, the plasma doesn't behave as expected if the electric currents aren't accounted for. This shouldn't come as a surprise, any other scientific endeavor would also likely be erroneous if only half the picture was accounted for.

There's a whole lot more than electric fields to account for...

Electric currents/fields and the magnetic fields they create are primary, the rest that happens are the effects.

Jun 19, 2019
Nothing to do with the subject material, but if you want to see how badly written some science articles can be written feast your eyes on this. LMAO
https://in.mashab...ack-hole

Jun 19, 2019
I have said, you idiot, that MHD is appropriate where it is appropriate. That is, at length scales and timescales where the magnetic Reynolds number dictates that the magnetic field can be treated as frozen-in to the plasma.

You have made many pseudoscientific claims, it's what you do. And the frozen-in condition is pure pseudoscience, to which you still seem proud to promote.

Jun 19, 2019
We shall see that Rm is not large everywhere; thin boundary layers form where Rm ∼ 1 and ideal MHD breaks down. As in most branches of physics, these boundary layers mediate the global dynamics by controlling the rate of transport of mass, momentum, and energy through the system.

IOW, double layers and circuitry. And these aspects are certainly not accounted for in the standard guesswork, they know it yet still continue do half-assed physics.


@cantthink well you should be an expert on half assed physics.

Jun 19, 2019
You have made many pseudoscientific claims, it's what you do. And the frozen-in condition is pure pseudoscience, to which you still seem proud to promote.


Nope, it is not me making those claims. It is the whole of the plasma physics community. High Reynold's number = plasma can be treated as frozen-in. Go read about it thicko.

Jun 19, 2019
We shall see that Rm is not large everywhere; thin boundary layers form where Rm ∼ 1 and ideal MHD breaks down. As in most branches of physics, these boundary layers mediate the global dynamics by controlling the rate of transport of mass, momentum, and energy through the system.

IOW, double layers and circuitry. And these aspects are certainly not accounted for in the standard guesswork, they know it yet still continue do half-assed physics.


Wrong. In the magnetosphere leading to magnetic reconnection, which requires the breakdown of the frozen-in condition. As observed.

Jun 19, 2019
@Castrogiovanni.
...MHD is appropriate where it is appropriate..... I have never said anything about modeling intergalactic plasmas,...
Please calm yourself, @Castro. You miss the salient point due to your personal animosity/frustrations which should have no part in rational polite science discourse. Ok?

The salient point (as highlighted by above researcher/observations) is that usual modelling ASSUMED things NOW SEEN to be CONTRADICTED by observations. Hence ANY previous modelling assumptions for interpreting ANY plasma phenomena in 'free space' (ie not physically contained) contexts should be revisited.

This is the SALIENT point you keep missing while knee-jerking to bile-and-bias reaction. Please calm down long enough to consider...

Classical Hydrodynamic equations/assumptions were 'modified' into Magneto-Hydrodynamic equations ASSUMED to be 'ok'...BUT above clearly admits that SIMPLISTIC 'modification' is NOT enough. It's COMPLEX; due to Magnetic FEEDBACKS etc. :)

Jun 19, 2019
@Castrogiovanni.
...MHD is appropriate where it is appropriate..... I have never said anything about modeling intergalactic plasmas,...
Please calm yourself, @Castro. You miss the salient point due to your personal animosity/frustrations which should have no part in rational polite science discourse. Ok?

The salient point (as highlighted by above researcher/observations) is that usual modelling ASSUMED things NOW SEEN to be CONTRADICTED by observations. Hence ANY previous modelling assumptions for interpreting ANY plasma phenomena in 'free space' (ie not physically contained) contexts should be revisited.

This is the SALIENT point you keep missing while knee-jerking to bile-and-bias reaction. Please calm down long enough to consider.:)
says RealityCheck

You may as well have been talking to a wall, RC. You should know by now that jonesy hates anything that brings changes to his beloved "status quo" that would require learning new science that throws out the old.

Jun 20, 2019
We shall see that Rm is not large everywhere; thin boundary layers form where Rm ∼ 1 and ideal MHD breaks down. As in most branches of physics, these boundary layers mediate the global dynamics by controlling the rate of transport of mass, momentum, and energy through the system.

IOW, double layers and circuitry. And these aspects are certainly not accounted for in the standard guesswork, they know it yet still continue do half-assed physics.


@cantthink well you should be an expert on half assed physics.

I am, I used to think the standard guesswork was correct and studied it thoroughly.

Jun 23, 2019
IOW, double layers and circuitry. And these aspects are certainly not accounted for in the standard guesswork, they know it yet still continue do half-assed physics.


@cantthink well you should be an expert on half assed physics.


Rather, he is an expert on erroneous "guesswork" - actually a belief system since he is no longer interested in the subject matter of known physics as described in the article.

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