I Black hole image: What are those "lobes"? [M87 10April2019]

EN2

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Lobes
Did anyone hear an explanation of the appearance of the lobes visible in the published image? I only caught part of the Q&A.

(Visible most prominently at at eleven o'clock and four o'clock positions, and to lesser degree at three and nine)

Do these type of observations generate "lense flare"?

Since they winnowed down so much data to generate this picture I have to presume it is valid observed data, as any 'noise effects'(e.g.) would have been filtered out prior to publication.

So what are those photons?
- Is it just a wider area of the disc (from a recent large meal perhaps?)
- Part of some other jets as yet not understood?
- And why this particular orientation /symmetry?

Have a look and see what you think
Thanks
 

davenn

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Do these type of observations generate "lense flare"?
041019_LG-EV-MT_EHT_feat.jpg



You do realise that it is not a photograph ? So lens flare isn't an issue

This is an image generated from the data collected by radio telescopes
Those brightest areas from around 3 o'clock to around 9 o'clock, aka the lower half
are where the radio signal is the strongest. It is radio signal output from the accretion disk that surrounds the black hole.

Those fainter areas at 11 and 4 o'clock are quite possibly hints of jets of material coming out of the accretion disk. M87 has been well known for its huge jet of material that is visible at optical and radio wavelengths for many years ......

241650


The EHT observations use a technique called very-long-baseline interferometry (VLBI) which synchronises telescope facilities around the world and exploits the rotation of our planet to form one huge, Earth-size telescope observing at a wavelength of 1.3 mm. VLBI allows the EHT to achieve an angular resolution of 20 micro-arcseconds — enough to read a newspaper in New York from a sidewalk café in Paris [6].
The telescopes contributing to this result were ALMA, APEX, the IRAM 30-meter telescope, the James Clerk Maxwell Telescope, the Large Millimeter Telescope Alfonso Serrano, the Submillimeter Array, the Submillimeter Telescope, and the South Pole Telescope [7]. Petabytes of raw data from the telescopes were combined by highly specialised supercomputers hosted by the Max Planck Institute for Radio Astronomy and MIT Haystack Observatory.
1.3 mm wavelength equals a frequency of ~ 230 GHz, very short wave microwave radio signal,
but still much longer than Infra Red radiation


Dave
 
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It looks like a highly smoothed version of an originally very sparse sample, or low resolution image to me. Do you think that the smooth/rounded, oversized, blob like shape of the lobes is mostly a processing artifact?
 

EN2

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View attachment 241649


You do realise that it is not a photograph ? So lens flare isn't an issue

This is an image generated from the data collected by radio telescopes
Those brightest areas from around 3 o'clock to around 9 o'clock, aka the lower half
are where the radio signal is the strongest. It is radio signal output from the accretion disk that surrounds the black hole.

Those fainter areas at 11 and 4 o'clock are quite possibly hints of jets of material coming out of the accretion disk. M87 has been well known for its huge jet of material that is visible at optical and radio wavelengths for many years ......

View attachment 241650



1.3 mm wavelength equals a frequency of ~ 230 GHz, very short wave microwave radio signal,
but still much longer than Infra Red radiation


Dave
Hi. I should have made my question more clear.
The “lobes” I’m referring to (for lack of a better term) are quite faint but not ‘zero data’.
The lobes at four and eleven o’clock are actually the brighter lobes (you referred to them as “those fainter areas”). The ones at three and nine are the smaller and dimmer lobes.
The lobes I’m referring to are not that bright ring nor the brightest sections of that ring. They are quite faint but definitely visible in the published image. (incidentally that main ring in the image isn’t the accretion disk, nor the event horizon, just in case anyone didn’t catch that fact)

The main plasma jets are at a wide enough angle that they wouldn’t be expected to interfere with this data. (Plus I don’t think they would be visible in this view with the techniques used...)

So back to those lobes... interesting in intensity, location, and how to explain... maybe a preview glimpse of a future meal!?

Also did anyone hear if there are more images than this one or any more from this dataset on the way? (I know they implied there will be more observations plus SagA*)

Thanks
 

EN2

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It looks like a highly smoothed version of an originally very sparse sample, or low resolution image to me. Do you think that the smooth/rounded, oversized, blob like shape of the lobes is mostly a processing artifact?
Hi Jarvis, please see my reply to Dave.

What I meant in my original message is that it seems unlikely that a science team of this pedigree, and with this sophisticated processing at their disposal, plus the scrutiny they surely knew the image would undergo, would leave processing artifacts or noise in the data that wasn’t actually part of the data observed/received from their observations...
No?

So then... what are they? And is the geometry just a fluke?

PS the Veritasium YouTube video on this subject (released 9april2019) offers an incredible explanation of the image.

Cheers
 

davenn

Science Advisor
Gold Member
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Hi. I should have made my question more clear.
The “lobes” I’m referring to (for lack of a better term) are quite faint but not ‘zero data’.
The lobes at four and eleven o’clock are actually the brighter lobes (you referred to them as “those fainter areas”). The ones at three and nine are the smaller and dimmer lobes.

yes, I saw those and also commented on them :smile:


(incidentally that main ring in the image isn’t the accretion disk, nor the event horizon, just in case anyone didn’t catch that fact)

Yes it is

The EHT image reveals the shadow of M87’s black hole on its accretion disk. Appearing as a fuzzy, asymmetrical ring, it unveils for the first time a dark abyss of one of the universe’s most mysterious objects.

I knew that it was when I first responded to you even before I looked it up
The EM emissions from the accretion disk are VERY strong and go right up into the X-ray wavelengths


Dave
 

EN2

6
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yes, I saw those and also commented on them :smile:





Yes it is




I knew that it was when I first responded to you even before I looked it up
The EM emissions from the accretion disk are VERY strong and go right up into the X-ray wavelengths


Dave
oh i understood that the ring in the image was the photon sphere, at approx 2.6 Schwarzschild radii:
--paste---
The edge of the shadow is due to the photon sphere - the radius at which light goes around in closed orbits. If a light ray coming in at an oblique angle just skims the photon sphere and then travels on to our telescopes, that is the closest 'impact parameter' possible, and it occurs at sqrt(27)/2*r_s
 

davenn

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If a light ray coming in at an oblique angle just skims the photon sphere and then travels on to our telescopes, that is the closest 'impact parameter' possible, and it occurs at sqrt(27)/2*r_s

Again, this image is not an optical photograph of a black hole. It is an image generated from data from a bunch of radio telescopes at ~ 230 GHz frequency (1.3mm wavelength) a very long way below visible light wavelengths. :smile:


Dave
 

EN2

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Again, this image is not an optical photograph of a black hole. It is an image generated from data from a bunch of radio telescopes at ~ 230 GHz frequency (1.3mm wavelength) a very long way below visible light wavelengths. :smile:


Dave
Hmmm.
R i g h t ...
And what do you suppose we call a packet of energy from those “very long way below visible light wavelengths”? A photon.
My paste alluded to photons. No one here thinks that we are using classical photography of visible wavelengths of photons to capture it.
I do hope you’re only misreading my intended query and not purposely trying to derail or distract from it. (And Yes, I see your emoticons after every reply/rebut.)

So back to the discussion... “Why those faintly visible lobes?”
And actually you know, one thing you’ve demonstrated, Dave, is that a public internet science forum is probably not the place to seek a coherent discussion. So, maybe just never mind. I’ll email the team.
 

davenn

Science Advisor
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Hmmm.
R i g h t ...
And what do you suppose we call a packet of energy from those “very long way below visible light wavelengths”? A photon.
My paste alluded to photons.

you don't need photons to describe this image .... classical physics works quite well
you are just trying to complicate the issue


No one here thinks that we are using classical photography of visible wavelengths of photons to capture it.
some do, including you with this comment ......

Do these type of observations generate "lense flare"?
I do hope you’re only misreading my intended query and not purposely trying to derail or distract from it. (And Yes, I see your emoticons after every reply/rebut.)

I'm trying to give you clear factual info, but I am not convinced that you are understanding it ?


So back to the discussion... “Why those faintly visible lobes?”

I still suspect that as I stated way back in the thread, that they are related to jets coming out .... this is something seen with a number of active cored galaxies and the fact that 2 of them are around 180 deg apart would support that possibility


Dave
 
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Hi Jarvis, please see my reply to Dave.

What I meant in my original message is that it seems unlikely that a science team of this pedigree, and with this sophisticated processing at their disposal, plus the scrutiny they surely knew the image would undergo, would leave processing artifacts or noise in the data that wasn’t actually part of the data observed/received from their observations...
No?

So then... what are they? And is the geometry just a fluke?

PS the Veritasium YouTube video on this subject (released 9april2019) offers an incredible explanation of the image.

Cheers
The data that we are able to gather is often low resolution, sparse, or noisy. So data scientists commonly estimate/infer what it should look like, smooth it out, and filter out noise. In doing this, they do add something that wasn't there in the raw data, and by doing so, with some level of uncertainty, are able to produce something that is more realistic.

For example, an image like the one in question could have been produced from raw data that looks like this (where the positions of each point have some uncertainty)

241665


or something like this, but with some added low level noise in the black background.

241667


Please don't take these examples too seriously, I'm just pointing out that some of what you are seeing may not be what it seems if you don't know how the final image was produced. I'm curious about it actually myself.
 
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davenn

Science Advisor
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The data that we are able to gather is often low resolution, sparse, or noisy. So data scientists commonly estimate/infer what it should look like, smooth it out, and filter out noise. In doing this, they do add something that wasn't there in the raw data, and by doing so, with some level of uncertainty, are able to produce something that is more realistic.

For example, an image like the one in question could have been produced from raw data that looks like this (where the positions of each point have some uncertainty)

but in the case of the presented image, the resolution was very good.....

The EHT observations use a technique called very-long-baseline interferometry (VLBI) which synchronises telescope facilities around the world and exploits the rotation of our planet to form one huge, Earth-size telescope observing at a wavelength of 1.3 mm. VLBI allows the EHT to achieve an angular resolution of 20 micro-arcseconds — enough to read a newspaper in New York from a sidewalk café in Paris [6].
To put it mildly, this is outstanding !
 
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A lot of people are complaining about confusion about false color, but a lot of people are also confused with the idea that it is a direct, but perhaps enhanced image, when it more of an estimation from limited data. What we can make out of any specific features is not clear to me still. My assumption is that the ring shape, and asymmetry of the brightness on the ring are most likely confident estimations, but beyond that I'm not sure. It seems like the process of estimating an image from the data while maintaining an acceptable level of bias was a highly non-trivial task.

Edit: Here are some of the papers about techniques used

Interferometric Imaging Directly with Closure Phases and Closure Amplitudes

The Size, Shape, and Scattering of Sagittarius A* at 86 GHz: First VLBI with ALMA

Reconstructing Video from Interferometric Measurements of Time-Varying Sources
 
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Zeke137

Gold Member
14
13
Do you know if a paper has been published on the algorithms for estimating the image? A lot of people are complaining about confusion about false color, but a lot of people are also confused with the idea that it is a direct, but perhaps enhanced image, when in fact it is an estimation from very limited data
You might like to start with a couple of the papers released by the EHT team at the same time as they made public this now famous image:

https://iopscience.iop.org/article/10.3847/2041-8213/ab0c57/meta entitled "First M87 Event Horizon Telescope Results. III. Data Processing and Calibration"

and

https://iopscience.iop.org/article/10.3847/2041-8213/ab0e85/meta entitled "First M87 Event Horizon Telescope Results. IV. Imaging the Central Supermassive Black Hole"

These give details of the calibration, data-reduction amd image-processing schemes used by the EHT team.
 
jarvis323 said:
My assumption is that the ring shape, and asymmetry of the brightness on the ring are most likely confident estimations...
The variations of the ring's brightness are due to multiple gravitational lensing of the radio waves that depends on the combined rotational velocity of the black hole with the orbital velocities of the accretion disk.
 

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