General > General Technical Chat
Sagittarius A*
<< < (4/20) > >>
TimFox:
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
TimFox:
"not a math rorscharch wankfest" is a puerile insult, not lessened by your idiosyncratic spelling of "Rorschach".
RoGeorge:
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
aetherist:

--- Quote from: TimFox 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.

--- End quote ---
Here are the lies in the earlier BH image.
aetherist:

--- Quote from: TimFox 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".
--- End quote ---

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.
Navigation
Message Index
Next page
Previous page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod