Author Topic: Sagittarius A*  (Read 8649 times)

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Offline TimFoxTopic starter

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Sagittarius A*
« on: May 12, 2022, 07:51:13 pm »
This is not totally off-topic, since there is some interesting microwave stuff in the paper, especially in section 3.
I post this link, to a very well-written paper (without YouTube handwaving or animations) about the recent announcement of imaging a super-massive black hole that appears to be the center of our galaxy.
https://iopscience.iop.org/article/10.3847/2041-8213/ac6674#artAbst
Those only interested in the history should peruse the nice introduction section that discusses theoretical and experimental discoveries along the way.
 

Online vad

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Re: Sagittarius A*
« Reply #1 on: May 12, 2022, 08:04:48 pm »
Veritasium posted video few hours ago: https://youtu.be/Q1bSDnuIPbo
 

Offline TimFoxTopic starter

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Re: Sagittarius A*
« Reply #2 on: May 12, 2022, 08:43:08 pm »
It's a huge collaborative project, with a list of participants and funding acknowledgements to match.
Note that Xilenx got a specific acknowledgement for donating FPGAs.
 

Offline aetherist

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Re: Sagittarius A*
« Reply #3 on: May 12, 2022, 09:45:49 pm »
I suspect that the image is more a circular argument (ie based on dogma) rather than a true image.
If it is a true-ish image, then i suspect that that kind of image can be made by a black-ish hole rather than the silly Einsteinian mafia singularity.
Me myself i dont believe in singularity blackholes.
My version of aether theory says that blackholes are impossible, but that black-ish say brown holes exist.
My brown hole (not meant to be funny) might show as an image with a black center koz the central part would be very dim rather than black.
And of course in creating their blackhole image they would always make the center black, even if it aint, koz we all know that it must be so.
 

Offline aetherist

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Re: Sagittarius A*
« Reply #4 on: May 12, 2022, 10:01:19 pm »
I subscribe to the Sky Scholar youtube. Pierre Marie Robitaille is my hero. So is Stephen Crothers.
Here are some of their youtubes.













 

Offline TimFoxTopic starter

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Re: Sagittarius A*
« Reply #5 on: May 12, 2022, 10:10:03 pm »
I did not think you would see anything in which you don't believe.
 

Offline eugene

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Re: Sagittarius A*
« Reply #6 on: May 12, 2022, 10:14:40 pm »
In any case, thanks for not posting a link to a YT video. Ain't nobody got time to watch YT all day!
90% of quoted statistics are fictional
 

Offline TimFoxTopic starter

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Re: Sagittarius A*
« Reply #7 on: May 12, 2022, 10:23:02 pm »
The paper was peer-reviewed.
If anyone have just cause or impediment to this paper, let him cite on which page the error lies.
 

Offline raptor1956

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Re: Sagittarius A*
« Reply #8 on: May 12, 2022, 10:42:40 pm »
The image is the work of many instruments scattered around the globe and the way in which they are combined is amazing.  The amount of data and the amount of data processing is at another level.

Why am I not surprised aetherist is a "Sky Scholar" fanboy.


Brian
 
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Offline aetherist

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Re: Sagittarius A*
« Reply #9 on: May 12, 2022, 10:53:14 pm »
https://www.space.com/webb-flaring-milky-way-black-hole
JamesWebb probly wont be able to make a good image. But at least its image will be a true image, not a math rorscharch wankfest.
https://en.wikipedia.org/wiki/Rorschach_testre-creation .
 

Offline TimFoxTopic starter

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Re: Sagittarius A*
« Reply #10 on: May 12, 2022, 10:57:56 pm »
https://www.space.com/webb-flaring-milky-way-black-hole
JamesWebb probly wont be able to make a good image. But at least its image will be a true image, not a math rorscharch wankfest.
https://en.wikipedia.org/wiki/Rorschach_testre-creation .

Have you ever worked in or used modern imaging methods, such as x-ray computed axial tomography or magnetic resonance imaging?
All that work, all those personnel, all that money, and no one in a position to know blew the whistle on a fraudulent icky result, despite the risk of personal insults.
« Last Edit: May 12, 2022, 11:07:41 pm by TimFox »
 

Offline aetherist

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Re: Sagittarius A*
« Reply #11 on: May 12, 2022, 11:31:14 pm »
https://www.space.com/webb-flaring-milky-way-black-holeJamesWebb probly wont be able to make a good image. But at least its image will be a true image, not a math rorscharch wankfest.
https://en.wikipedia.org/wiki/Rorschach_testre-creation .
Have you ever worked in or used modern imaging methods, such as x-ray computed axial tomography or magnetic resonance imaging?
All that work, all those personnel, all that money, and no one in a position to know blew the whistle on a fraudulent icky result, despite the risk of personal insults.
Watch the Robitaille youtubes, he is an expert on imaging.
 
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Offline dietert1

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Re: Sagittarius A*
« Reply #12 on: May 13, 2022, 12:38:51 am »
Maybe somebody should explain how astronomers identified this object as the center of our galaxy. I just saw a zoom video that starts with a view of the milky way and ends up with that image of the black hole (similar to ESO/​Gravity Consortium/​L. Calçada/​N. Risinger https://www.eso.org/public/videos/eso1835c/). Amazing!

Regards, Dieter
 

Offline TimFoxTopic starter

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Re: Sagittarius A*
« Reply #13 on: May 13, 2022, 02:15:32 am »
The paper discusses the options between this object and M87* (an even more massive black hole) in detail.
 

Offline eugene

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Re: Sagittarius A*
« Reply #14 on: May 13, 2022, 03:37:03 pm »
https://www.space.com/webb-flaring-milky-way-black-hole
JamesWebb probly wont be able to make a good image. But at least its image will be a true image, not a math rorscharch wankfest.
https://en.wikipedia.org/wiki/Rorschach_testre-creation .

You can define "true image" any way that pleases you. Just be aware that other people might disagree. Do that often enough and others will stop paying attention to you.
90% of quoted statistics are fictional
 

Offline TimFoxTopic starter

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Re: Sagittarius A*
« Reply #15 on: May 13, 2022, 04:18:03 pm »
I posted this article reference as a good example of a serious paper describing an interesting result from a huge experimental effort.
I appreciate that IOP has put the Astrophysical Journal into the open (no paywall), so these papers are readily accessible.

This is an astrophysical paper:  it contains physics (specifically, results of General Relativity) and astronomy (specific description of an astronomical object). 
Unfortunately for me, the results are quoted in terms of astronomical measurement units (not SI), so I need to look into them before I can better understand the results. 
I remember a lecture (ca. 1976) by Edward Purcell, after he started work on interstellar dust: he said that his first task was to calculate the conversion factor between magnitudes/parsec and dB/light-year.

If you look at the full list of acknowledgements, you will see a very large worldwide group of institutions and funding sources, including countries such as China and Taiwan that differ politically.

Section 1 has a good background for the theoretical and experimental results that preceded the group effort (six locations from the South Pole to Spain and Arizona at the north, total of eight machines).

Section 2.1 discusses the properties of "Sgr A*" itself.

Section 3 discusses the observation systems, basically long-baseline interferometry at two bands around 227 and 229 GHz, and the data processing. 
Essentially, a metric shitload (modern technical term) of data was loaded onto hard drives, which were then transported to a central location for image reconstruction. 
Modern imaging systems, such as CT and MRI, also "reconstruct" the image from multiple measurements (e.g., "projections" for CT), and this is another mature field of mathematical physics or engineering.

In Section 7, the implications of these results for General Relativity and related theories are discussed. 
Note that the "Kerr metric" is the GR description for a black hole with angular momentum, which has interesting differences from the "Schwarzschild metric" fir a non-rotating object. 
Simply put, a rotating black hole has two event horizons. 

An earlier paper, cited in this one, describes the equipment in detail, in conjunction with the earlier measurements on M87*.
https://iopscience.iop.org/article/10.3847/2041-8213/ab0c96/pdf
 

Offline TimFoxTopic starter

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Re: Sagittarius A*
« Reply #16 on: May 13, 2022, 04:21:12 pm »
"not a math rorscharch wankfest" is a puerile insult, not lessened by your idiosyncratic spelling of "Rorschach".
« Last Edit: May 13, 2022, 04:26:42 pm by TimFox »
 
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Offline RoGeorge

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Re: Sagittarius A*
« Reply #17 on: May 13, 2022, 04:55:01 pm »
Please everybody don't feed the trolls, there is a forum feature in each one's own profile, to avoid anoyances:
https://www.eevblog.com/forum/profile/?area=lists;sa=ignore
 
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Offline aetherist

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Re: Sagittarius A*
« Reply #18 on: May 13, 2022, 08:46:10 pm »
The paper was peer-reviewed.
If anyone have just cause or impediment to this paper, let him cite on which page the error lies.
Here are the lies in the earlier BH image.
 

Offline aetherist

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Re: Sagittarius A*
« Reply #19 on: May 13, 2022, 09:11:35 pm »
"not a math rorscharch wankfest" is a puerile insult, not lessened by your idiosyncratic spelling of "Rorschach".

Rorscharch is where the subject is shown an inkblot & her brain converts the blot into an image.
The amazing image(s)  of the blackhole(s) were created from blots that were no larger than say 5 pixels.
A homicidal rapist paedophile might create an image from 5 pixels, & a Nobel Prize winning Einsteinian might too.
 

Offline TimFoxTopic starter

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Re: Sagittarius A*
« Reply #20 on: May 13, 2022, 09:20:40 pm »
No, that is "Rorschach".  I also know what "wank" means.
I'm not surprised to see a forged image on YouTube.
See section 5 of the paper I cited which discusses the reconstructed images.
By the way, you seem to agree with Einstein, who in 1939 also found black hole solutions to his GR equations disturbing, dare I say "icky"?
https://www.jstor.org/stable/1968902?seq=1#page_scan_tab_contents
 

Offline aetherist

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Re: Sagittarius A*
« Reply #21 on: May 13, 2022, 09:24:45 pm »
https://www.space.com/webb-flaring-milky-way-black-hole
JamesWebb probly wont be able to make a good image. But at least its image will be a true image, not a math rorscharch wankfest.
https://en.wikipedia.org/wiki/Rorschach_testre-creation .
You can define "true image" any way that pleases you. Just be aware that other people might disagree. Do that often enough and others will stop paying attention to you.
Cosmologists & JamesWebb & Co use artificial colour etc, that’s ok.
Creating a 100,000 pixel image from say 5 pixel info is i think a long ways away from being a true image, but others might disagree.
 

Offline TimFoxTopic starter

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Re: Sagittarius A*
« Reply #22 on: May 13, 2022, 09:28:55 pm »
https://www.space.com/webb-flaring-milky-way-black-hole
JamesWebb probly wont be able to make a good image. But at least its image will be a true image, not a math rorscharch wankfest.
https://en.wikipedia.org/wiki/Rorschach_testre-creation .
You can define "true image" any way that pleases you. Just be aware that other people might disagree. Do that often enough and others will stop paying attention to you.
Cosmologists & JamesWebb & Co use artificial colour etc, that’s ok.
Creating a 100,000 pixel image from say 5 pixel info is i think a long ways away from being a true image, but others might disagree.

Read section 3 to see how the authors crunched the data.  There is a lot of discussion of statistical methods to generate a best estimate, using different approaches to compare results.  This is not hand-waving.  Have you ever done maximum-likelihood data processing?  Are you familiar with the concepts of resolution and pixel?  A pixel is the quantization of the display, and very often is finer than the actual resolution.  In general, it wastes whatever resolution you have to display it with coarser pixels.  I often digitize my (non-periodic) 4x5 inch film images at 2400 dots/inch, to not lose resolution in that process, which takes forever.
« Last Edit: May 13, 2022, 09:57:47 pm by TimFox »
 

Offline raptor1956

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Re: Sagittarius A*
« Reply #23 on: May 13, 2022, 09:57:01 pm »
Every consumer digital camera in use today makes use of math to reconstruct the image.  When taking still images the data is expressed in a Bayer pattern and demosaicing, a mathematical process, must be done to reconstruct the image.  An even more complex process is involved with video as the enormous data rate is way too high for consumer cameras to handle uncompressed.  Math is required for everyday images and video and anyone that uses digital cameras knows that the end result is an accurate representation of what the photographer was shooting, given limitations of exposure and technique.

A more direct comparison to the methods used to capture the BH image is the interferometric approach needed to combine the images captured by telescope using multiple imagers or when multiple telescopes are combined. The VLT is a four telescope installation that can use each telescope independently or they can be combined using interferometry. 

The techniques used to capture an image of Sag A* is simply an extension of techniques already in use everyday.  I'm disturbed that we have a member that has his head up his, well, black hole, and fawns over a YT charlatan! 


Brian
 

Offline TimFoxTopic starter

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Re: Sagittarius A*
« Reply #24 on: May 13, 2022, 10:01:08 pm »
Yes, long before current interferometry with Earth-dimension long baselines, "regular" interferometers were used (in 1920) to measure the disc diameter of distant stars, which could not be resolved directly with telescope optics.
https://en.wikipedia.org/wiki/Michelson_stellar_interferometer
 


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