APOD: Plasma Jets from Radio Galaxy Hercules A (2012 Dec 05)

[APOD Robot]

Plasma Jets from Radio Galaxy Hercules A

Explanation: Why does this galaxy emit such spectacular jets? No one is sure, but it is likely related to an active supermassive black hole at its center. The galaxy at the image center, Hercules A, appears to be a relatively normal elliptical galaxy in visible light. When imaged in radio waves, however, tremendous plasma jets over one million light years long appear. Detailed analyses indicate that the central galaxy, also known as 3C 348, is actually over 1,000 times more massive than our Milky Way Galaxy, and the central black hole is nearly 1,000 times more massive than the black hole at our Milky Way's center. Pictured above is a visible light image obtained by the Earth-orbiting Hubble Space Telescope superposed with a radio image taken by the recently upgraded Very Large Array (VLA) of radio telescopes in New Mexico, USA. The physics that creates the jets remains a topic of research with a likely energy source being infalling matter swirling toward the central black hole.

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[bystander]

http://asterisk.apod.com/viewtopic.php?t=30285

[jjohnson]

For a lucid explanation of how particles can be driven to escape velocities in a wide scale of cosmic objects, from planet to stars, galaxies, quasars, etc., read the article titled "Acceleration of Outflow of Matter From Celestial Objects" by Rickard Lundin (Swedish Institute of Space Physics) and Stanislav Barabash (Institute of Physics of the Earth, Russian Academy of Sciences, Moscow), in Geophysics Monograph 156, Particle Acceleration in Astrophysical Plasmas: Geospace and Beyond, 2005, copyright American Geophysical Union, Washington D.C. Disclaimer: there is not a single reference to black holes, dark matter, or dark energy in the article. The authors use familiar plasma equations and useful images of familiar astronomical objects and phenomena and graphs to convey their conclusions, in much the same manner as astronomer Philipp Kronberg did in his paper, Measurement of the Current in a Kpc Jet, last year, using active galaxy 3C303 as his model, Astrophysics Jornal, Letters, v741 L15, Nov 2011.

[Horus]

Hi guys, is it me or do those jets look like they are turning counter clockwise? The jet on the left coming towards us and the right one travelling away.

[starsurfer]

Hi guys, is it me or do those jets look like they are turning counter clockwise? The jet on the left coming towards us and the right one travelling away.

No I think that is an illusion. If that was the case, the left jet would appear blueshifted and the right one redshifted and if that was the case, then that would definitely have been mentioned in the article. However, I might be wrong as I haven't read the related paper (assuming there is a corresponding paper).

Also I find it amazing thats astrophysical jets manifest themselves on such a large variety of scales, from little ones in YSO's and planetary nebulae to huge gigantic ones in galaxies like this one or the ones associated with Centaurus A!

[neufer]

Hi guys, is it me or do those jets look like they are turning counter clockwise?
The jet on the left coming towards us and the right one travelling away.

No I think that is an illusion. If that was the case, the left jet would appear blueshifted and the right one redshifted and if that was the case, then that would definitely have been mentioned in the article. However, I might be wrong as I haven't read the related paper (assuming there is a corresponding paper).

The radio jet structure is simply a monochrome black & white radio wave intensity map that is color coded magenta to distinguish it from the Hubble background.

Besides which, there are no spectral lines to blue-shift or red-shift since the continuous synchrotron radiation comes from "relativistic electrons spiraling through magnetic fields."

The source black hole could well be slowly precessing so as to cause the slow moving jet exit regions to have the sort of "water spray" slow turning features that Horus suggests (or it could be simply an illusion as starsurfer suggests).

[Spif]

Hi guys, is it me or do those jets look like they are turning counter clockwise? The jet on the left coming towards us and the right one travelling away.

No I think that is an illusion. If that was the case, the left jet would appear blueshifted and the right one redshifted and if that was the case, then that would definitely have been mentioned in the article.

As I recall, I think such jets are supposed to emit from the rotational poles of the black hole. Given that the jets are on a scale of about a million light years, that would imply that the black hole is very rotationally stable.

In any case, if the jets were "rotating", presumably Horus is asking if the emission source is rotating? There would be no red/blue shift in that case because the emitted particles would still be flying relatively linear trajectories. But then if I'm right about the jet emitting from the poles, the only force that I can think of that might alter the black hole's rotation axis would be a huge influx of digested matter that has a different predominant average angular momentum than the black hole. But given the size of such black holes and the slow rate at which they typically ingest matter, that seems unlikely on a timescale of 1M years.

-s

[gurky]

Why do the jests spread as if they were jetting into a fluid? Is the
matter density that high?

[BMAONE23]

Given the size of this structure, it would just fit between the Milky Way and Andromeda galaxies.

If this were the case, would the plasma jets have any affect either galaxy?

[Chris Peterson]

Besides which, there are no spectral lines to blue-shift or red-shift since the continuous synchrotron radiation comes from "relativistic electrons spiraling through magnetic fields."

There are no spectral lines, but the synchrotron radiation from any source does have a specific structure, and can therefore be compared to a diametric jet using Doppler measurements. This is one method of inferring jet velocity when both jets are visible (although at somewhat low resolution).

[Chris Peterson]

Why do the jests spread as if they were jetting into a fluid? Is the
matter density that high?

I think it's just diffusion. The particle density is high enough that there are fluid dynamic effects (that is, the particles interact with each other and slow down, at which point the lateral velocity components become apparent).

[neufer]

Why do the jests [sic] spread as if they were jetting into a fluid?

Is the matter density that high?

Jesting aside, the matter density is sufficiently high and it is constantly getting higher as more jet spews into it.

<<Intergalactic space is the physical space between galaxies. The huge spaces between galaxy clusters are called the voids. Present estimates put the average energy density of the Universe at the equivalent of 5.9 protons per cubic meter, including dark energy, dark matter, and ordinary, baryonic matter, or atoms. The atoms account for only 4.6% of the total energy density, or a density of one proton per four cubic meters (~4 milligrams of hydrogen per square meter per million light years) . The density of the universe, however, is clearly not uniform; it ranges from relatively high density in galaxies—including very high density in structures within galaxies, such as planets, stars, and black holes—to conditions in vast voids that have much lower density, at least in terms of visible matter.

Surrounding and stretching between galaxies, there is a rarefied plasma that is organized in a cosmic filamentary structure. This material is called the intergalactic medium (IGM). The density of the IGM is 5-200 times the average density of the Universe (i.e., a density of up to about one gram of hydrogen per square meter per million light years). It consists mostly of ionized hydrogen; i.e. a plasma consisting of equal numbers of electrons and protons. As gas falls into the intergalactic medium from the voids, it heats up to temperatures of 10⁵ K to 10⁷ K, which is high enough so that collisions between atoms have enough energy to cause the bound electrons to escape from the hydrogen nuclei; this is why the IGM is ionized. At these temperatures, it is called the warm–hot intergalactic medium (WHIM). (Although the gas is very hot by terrestrial standards, 10⁵ K is often called "warm" in astrophysics.) Computer simulations and observations indicate that up to half of the atomic matter in the universe might exist in this warm-hot, rarefied state. When gas falls from the filamentary structures of the WHIM into the galaxy clusters at the intersections of the cosmic filaments, it can heat up even more, reaching temperatures of 10⁸ K and above in the so-called intracluster medium.>>

[Spif]

Why do the jests spread as if they were jetting into a fluid? Is the
matter density that high?

Yes, essentially. There is medium of gas around the galaxy that the jets are pressing into.

The jets are sparse but they have very high velocity. The medium that the jets are flowing into must be comparable in density such that, on a distance scale of a million light years, a given jet particle is likely to experience at least one collision and scatter (emitting light when it does). Through this mechanism the jets push back the extra-galactic medium over the years and you get the turbulent flow patterns that you see. There might be some magnetodynamic factors in there too, I'm not sure, but I think the classical fluid flow explanation is probably largely valid.

-s

[dprovan]

I'm trying to get a sense of the scale of these structures, but my head hurts imagining how big they are. Are some or all of those other galaxies in the picture in the foreground?

[moconnor]

[I am not a scientist.]

I know it hasn't been proven, but I personally think that life exists in thousands, if not millions, of different places in the universe.

With that much energy being expelled from the center of that galaxy (Hercules A), but only in two directions, could life exist on a planet surrounding one of the stars in that galaxy, if it wasn't in the path of those jets? Could they exist, without being affected in any way? How would they be affected by those jets?

It must make for spectacular sunsets!

Marty

[Chris Peterson]

I'm trying to get a sense of the scale of these structures, but my head hurts imagining how big they are. Are some or all of those other galaxies in the picture in the foreground?

I think all the other galaxies seen here are well behind 3C 348.

[Chris Peterson]

With that much energy being expelled from the center of that galaxy (Hercules A), but only in two directions, could life exist on a planet surrounding one of the stars in that galaxy, if it wasn't in the path of those jets? Could they exist, without being affected in any way? How would they be affected by those jets?

I think the local effects are fairly small, except directly in the jets, and even then, close to the galaxy.

It must make for spectacular sunsets!

The jets aren't visible at all optically. So the sunsets would only be spectacular if those witnessing them could see in radio.

[neufer]

Click to play embedded YouTube video.

It must make for spectacular sunsets!

The jets aren't visible at all optically. So the sunsets would only be spectacular if those witnessing them could see in radio.

[Spif]

How would they be affected by those jets?

It must make for spectacular sunsets!

Yes, I think it is entirely plausible for life to exist around that galaxy since the jets are so focused.

Keep in mind that that image is a manipulated composite of both visual and radio data. The jet emissions are in radio light so normal eyeballs as we think of them could not see the jets.

Radio astronomers in that galaxy are probably fairly annoyed by that damned black hole as the jets probably wash out huge sectors of the sky in certain frequencies.

[hawkeye]

Gents, While I look at all the APODS without much real understanding, one thing that I was wondering about when looking at the Jets from galaxy Hercules A was, wouldn't these black holes reach a density so crushing that they would explode like a miniature big bang or before that, like a nebula? I know we don't know much about black holes and perhaps this falls into that category. Thanks

[Strangerbarry]

Re: "I know it hasn't been proven, but I personally think that life exists in thousands, if not millions, of different places in the universe."

Scientists often talk about life evolving on other worlds based on educated assumptions about the types of conditions that might support it. This seems to suggest that life might reasonably be expected to arise anywhere where conditions are ideal, as if life itself were a universal weed. Aside from my own personal belief that this view does a great disservice to the tremendous beauty and complexity of life (and no I am not a creationist), the fact is we have no information and can derive no statistical inference about the probability that life might arise from non-living material (abiogenesis) under any set of conditions, ideal or otherwise, based on our sample of size of one (the Earth).

Consider then a couple of scenarios about the probability of successful abiogenesis and what the universe might look like under those scenarios. Current estimates of the number of stars in an "average" galaxy are somewhere between 50 and 500 billion (let's call this number X). If the probability that life might arise in orbit around any given star is much greater than 1 in X then we might reasonably expect there to be many living worlds in most galaxies - of course even then those worlds would likely be on the order of 1 in a million or even 1 in billion stars so finding those worlds even if they exist in your own galaxy would be your classic needle in a haystack scenario at best. But consider the scenario where the probability that life might arise in orbit around any given star is much less than 1 in X - and given that we know nothing of the probabilty of abiogenesis, who can say this is an unreasonable scenario to contemplate - under that scenario most GALAXIES would be entirely devoid of life - and life - where it exists - would be isolated worlds spread out among a small minority of galaxies. Now with roughly 100 billion galaxies in the observable universe, even if only 1 in 1000 galaxies had only one world supporting life in it (which would mean that 1 in 1,000,000 might have two), that would still allow for 100 million worlds supporting life. But you can imgaine that with only 1 in 1000 galaxies supporting any kind of life (which could be nothing more complex than bacteria for all we would know), it would not be reasonable to expect that we would ever find any evidence of this life, let alone find it or contact it. I'm not unsympathetic to the view that life may exist widely throughout the universe, but I believe that we will never find it, we will always be alone.

[Roland]

Anyone know ratio of energy emitted by the jets with respect to the energy emitted by the rest of the galaxy?

[Strangerbarry]

Can anyone tell me why it appears that these jets are diffusing from their initially narrow jet into giant balls where the plasma appears to be meeting some kind of drag and slowing down ? It looks like what you'd expect to see if you were releasing steam from a valve under pressure into a large space - an initially tight high speed jet diffusing and cooling into a large space. This isn't some kind of cosmic Joule Thomson effect is it ?

[Chris Peterson]

Gents, While I look at all the APODS without much real understanding, one thing that I was wondering about when looking at the Jets from galaxy Hercules A was, wouldn't these black holes reach a density so crushing that they would explode like a miniature big bang or before that, like a nebula? I know we don't know much about black holes and perhaps this falls into that category. Thanks

The density a black hole can mean different things. It is possible that the center of a black hole consists of a singularity; if so, the density there is infinite, regardless of the mass of the black hole. More generally, the density of a black hole is its mass divided by the volume within its Schwarzschild radius- a value that decreases as the mass increases. The density of the black hole in 3C 348 is less than one... it would float in a big tub of water.

[Spif]

Gents, While I look at all the APODS without much real understanding, one thing that I was wondering about when looking at the Jets from galaxy Hercules A was, wouldn't these black holes reach a density so crushing that they would explode like a miniature big bang or before that, like a nebula? I know we don't know much about black holes and perhaps this falls into that category. Thanks

Yeah, we humans are still working on the physics that describes the universe on those scales. The realm of what matter becomes after it gets crushed down to something smaller than protons or even quarks is pretty much just philosophy right now. (Quark stars are have been posited, and I seem to recall someone claiming that they think they found one, but if they exist, I believe they would still be puffier than their own Schwarzchild radius.)

String theory, if it were to evolve into a viable and reasonably complete form, could perhaps address that new state of matter. For example, imagine if some base state of strings were the next most fundamental state of a particle below protons/quarks, then perhaps a black hole is just caused by a ball of degenerate strings? We just don't know right now and so I don't think we can predict much about what limits black holes have ... yet.

-s