Hotspots in an active galactic nucleus

Hotspots in an active galactic nucleus
An image taken at radio wavelengths of the dramatic jets of charged particles being ejected from the nucleus of the galaxy Cygnus-A. Newly obtained radio images were able to resolve hotspots in the jets at the places where they impact the surrounding medium. The conventional thinking is that the bulk of the radiation in such hotspots is produced by shocks, but the new results found that some other processes, perhaps absorption, must be involved. Credit: NRAO/AU

The nucleus of a so-called "active" galaxy contains a massive black hole that is vigorously accreting material. As a result, the nucleus often ejects bipolar jets of rapidly moving charged particles that radiate brightly at many wavelengths, in particular radio wavelengths. Active galaxies display a range of dramatically different properties, and the ones that are bright in the radio can beam as much as one trillion solar luminosities of radiation into space at those wavelengths.

The intense emission arises from the hot environment of the black hole because electrons, moving at close to the speed of light in an environment of , radiate in the radio. The directed particle jets eventually collide with the ambient medium and convert much of their bulk energy of motion into shocks. The points of termination in the jet flow are seen as very hot spots, bright and compact structures. The hotspots can reverse the flow the jets back towards the black hole, and thereby generate additional turbulence and random motions. The characteristic temperature of a hot spot (or more accurately, the spectral dependence of the brightness versus wavelength) reveals the nature of the physical processes at work. Most known active radio galaxies have hotspots whose spectral dependence conforms well with the idea of termination shocks and reverse flows, but some very luminous radio galaxies do not conform.

The radio galaxy Cygnus A is the nearest and most powerful example of a double radio galaxy and as such is an archetype of this class. It is also one of the first objects discovered whose hotspots did not seem to conform with the conventional picture, and for decades astronomers have debated the possible reasons. The limited ability of long wavelength (low frequency) radio telescopes to resolve the small sizes of the hotspots was one complicating factor. CfA astronomers Reinout van Weeren and Gianni Bernardi (now at SKA South Africa) were part of a large team who used the Low Frequency Array ("LOFAR") radio telescope to obtain high spatial resolution images of the hotspots in Cygnus A. Their results provide the first direct evidence that the spectral shape difference previously inferred is real. The scientists are presenting a detailed analysis in a separate paper, but in this paper the basic results indicate that some other process besides shock activity must be involved; the team suggests absorption of the radiation by intervening local material could be part of the final picture.


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More information: J. P. McKean et al. LOFAR imaging of Cygnus A – direct detection of a turnover in the hotspot radio spectra, Monthly Notices of the Royal Astronomical Society (2016). DOI: 10.1093/mnras/stw2105
Citation: Hotspots in an active galactic nucleus (2016, October 24) retrieved 19 October 2019 from https://phys.org/news/2016-10-hotspots-galactic-nucleus.html
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
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Oct 24, 2016
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Oct 24, 2016
There is also no mention of the matter in the abstract, and although pay walled, I'd put money on it that it is referred to as a gas in the paper. It's just another piece of evidence showing the complete disregard and ignorance of the plasma physics involved.

Oct 24, 2016
So where is the source of matter for those jets, if not from the source itself??

Notice the early formation of two daughter galaxies at the end of the jets, each with their own core stars forming. This is one mechanism for how galactic clusters can form.

Or, carry on as astronomers, with eyes wide shut.

http://phys.org/n...tml#nRlv

This black hole is some 2.5 billion times the mass of the Sun, and around a thousand times more massive than the black hole at the centre of our Milky Way galaxy.

The jets stretch for around 1.5 million light-years – roughly 15 times the size of the Milky Way.


Oct 24, 2016
Note that the word plasma does not once appear in this article
@hannes/reeve
note that this is an *article* and it is also based upon a study that is seeking specific information, which you either can't read or failed to look at, mr "researcher"
The low-frequency radio spectra of the hotspots within powerful radio galaxies can provide valuable information about the physical processes operating at the site of the jet termination. These processes are responsible for the dissipation of jet kinetic energy, particle acceleration, and magnetic-field generation. Here, we report new observations of the powerful radio galaxy Cygnus A using the Low Frequency Array (LOFAR)
more to the point: so f*cking what?

the study isn't pseudoscience like the eu crap is

Oct 24, 2016
@chlamydia-drive
It's just another piece of evidence showing the complete disregard and ignorance of the plasma physics involved
repeating a lie doesn't make it more true unless you believe in conspiracies or delusions that don't exist....

Oh wait:
Secret mind control programs such as MK-ULTRA fostered by "intelligence agencies"or the use of patsies by those same agencies to provoke societal and political changes for our elitist masters. The false flag is a favorite tactic of the current control paradigm. From controlled economic turmoil to wars fomented for profit, very little "just happens".
http://phys.org/n...ris.html

never mind... i forgot who you were
lie away! - it's your only means to ignore the evidence

for those who *can* read: http://www.pppl.gov/

proof you're full of crap, cd

Oct 24, 2016
This is one of the longest observable features in the universe, so how does it stay together?


I'll take a stab at it me. I am not a scientist so I could be wrong, and I don't mind being corrected as long as it makes sense and is not just some gobbledygook. So here I go,,,

Maybe it stays together because mass, inertia, momentum and the lack of stuffs to get in its way all works together, eh?

Oct 24, 2016
Good guess, Uncle Paedo.
Common sense 1 - EU 0

Why is it not surprising you would consider such a moronic guess as common sense and some sort of "win" against asking questions...
And yes, Uncle Paedo's guess is moronic and contrary to known gas physics.

Oct 24, 2016
As opposed to Uncle Paedo's guess, there is an explanation that predicts the "mysterious" aspects of these phenomena that relies on actual physics that agree with the observation.

http://www.plasma...PS-I.pdf

Oct 25, 2016
This comment has been removed by a moderator.

Oct 25, 2016
And yes, Uncle Ira's guess is ...contrary to known gas physics
@chlamydia-drive
point:
IF
his argument is contrary to known gas physics
AND
you say you can argue from an evidenciary point
THEN
why aren't you actually linking reputable physics or peer reviewed journal studies to validate your claim?

that would be the only way that anyone can argue against a point with anything like a scientific or evidenciary answer, so why did you link a pseudoscience site?

was it because you can't actually find any reputable evidence?

or is it because you know you're full of sh*t?

@chlamydia reeve/hannes
you are no better, and given that you've claimed to be a researcher, why is it that you can't actually provide evidence that isn't subjective?

where is your study links?
where is the science?
where is the references and studies that can be checked, validated and are based on known physics laws out of real labs like PPPL.gov?

spread your cult message elsewhere

Oct 25, 2016
Hi all. :)

If I may make a friendly suggestion: check out all the recent mainstream studies/efforts being applied to 'preventing excursions' in the plasma streams in Fusion Power systems. They know that plasma flows are inherently unstable and will at stages 'implode' (think Z-pinch) and then 'explode' (think mutual repulsion) due to various electron-ion waves and shocks across the plasmic streamflows. This is one of those situations when neither gravity nor Newtonian inertial motion etc can prevent such 'sudden and extremely energetic excursions'. Hence the likely reality is that some of the plasma jet material is being dispersed sideways along the jet path, and some is being entrained by Z-pinch like 'nodal' resonances along the path until the jet energy/mass content 'rarifies' to ambient intergalactic medium densities to form the 'lobes' observed. Resist simplistic/naive interpretations of observations which are more complex than you may realize. Cheers all. :)

Oct 25, 2016
PS: And then there is the overall galactic magnetic field torus pattern whose 'axis' provides a path of least resistance (least action) all the way out until the magnetic field pattern is itself too weak to 'contain' the plasma flow within a stable pathway along the erstwhile axial pathway. Again, there's a lot going on, and no simplistic analysis/interpretation will represent the whole messy reality physics therein. Good luck all. :)

Oct 25, 2016
For the jets to be so long and straight a good 'memory' is required, something that allows the flowing material to maintain a uniform direction for a very long time,
Well I just don't think memory is a good scientifical word for this, conservation is better, eh?

a million years or more, which would be the travel time of some of the jets if the matter flowed at the speed of light."
That is where the mass, inertia and momentum come in, especially at relativistic speeds, millions of years might sound like a long time to you, but but them things might "remembering" (conserving) their momentum for 10's of millions of years.

Like I say, if I am wrong with my thinking, that is okay, it just means I am making a mistake. But gobbledygook and double-talk about "memory" and "speed of light" and "millions of years" don't really set me straight. I am thinking that this Verckuurt-Skippy might be a crankpot.

Oct 25, 2016
Newton's first law does the trick.*
*This blog, Uncle Paedo.

Phails1 again shouting from the rooftops; "I am moron, hear me roar."
Such a notion that the paedophile Uncle Skippy is correct flies in the face of observation of the magnetic fields which are present. And yes, it is the million + light years long electric discharge which is creating the magnetic fields.

Oct 25, 2016
@cd,
And yes, it is the million + light years long electric discharge which is creating the magnetic fields.


Says who? Point us to the research, please. Not crankery; not mythology based book sales websites - some actual science. Or is this another one of Wal's Velikovskian 'Thunderbolts of the Gods' fantasies?
When are you lot actually going to start doing some science, instead of just jumping on every thread pretending that you actually have a clue what you're talking about?
Let's see the research; the mechanism; the EMF (what is it, what keeps it going?). Presumably the electric geniuses have thought this through and published it, yes?


Oct 25, 2016
The paper was already linked jonesdumb, and yes published years ago.

Oct 25, 2016
The paper was already linked...
@cd
no, it wasn't
the only link you've provided was to a PSEUDOSCIENCE phishing site with known overt religious cult presentations on science

therefore you've not linked source material from a reputable peer-reviewed site or journal that can validate your claim...

you've simply said "i believe in [x] and so does peratt - see this opinion link to a known pseudoscience site?"

you might as well link the catholic church website, or perhaps the moonies because there aint no difference between yall


Oct 26, 2016
Sarcasm is powerless
@Phys
when dealing with the level of delusion of conspiracist ideation combined with the cult-like fanaticism of a religious order, all forms of humour are powerless

if you utilise it, it is evidence supporting their claim
if you don't, it is evidence of conspiracy

.

just keep posting evidence so that the average reader (who typically isn't familiar with science or it's protocols) will get the message that cd and the rest of the cult is pushing pseudoscience

remember the target audience and post accordingly
PEACE

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