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A Crack at Sgr A*

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#1 BQ Octantis

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Posted 14 May 2022 - 07:55 PM

You've probably heard by now that we have an image of Sgr A*—the black hole at the center of our galaxy. The Event Horizon Telescope Collaboration published the image on 12 May 2022—after a whopping 5 years of processing:

 

SgrA.jpg

[Source]

 

Having oogled, imaged, and studied the core of the Milky Way for 5 years, I know the approximate location of the galactic center—about 1/4 of the way from 2 Sgr to HIP 87220. But the press release of the black hole piqued my curiosity as to how I well had captured it. Sadly, the longest I shot it was at 50mm—there were no nebulosities between the Lagoon Nebula and the Lobster Nebula worth shooting, so I only ever shot it at wide field.

 

Still, I wondered…

 

So I pulled up the stack from my last shot of the Great Sagittarius Star Cloud—shot last July from a Bortle 1 site:

 

get.jpg?insecure

 

Surely I captured something!

 

I pulled up Sgr A*'s exact location in Stellarium. I made a screen grab, and I gingerly overlayed the coordinates and star field on a highly-zoomed view of the region in my image. And there it was:

 

gallery_273658_12412_60288.gif

 

So here is my rendition of our central black hole, covered by one 3.9 arcsec pixel:

 

SgrA_px.gif

 

For reference, the glowing event horizon in the published image of Sgr A* is 0.16 milliarcseconds across. So I have a reasonable degree of confidence that the light I captured from it is entirely contained in the pixel. laugh.gif

 

Cheers,

 

BQ


Edited by BQ Octantis, 14 May 2022 - 07:59 PM.

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#2 ram812

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Posted 14 May 2022 - 08:13 PM

Looks good....☺. Really, though. I can't wait for JWST to point that way. But I like your pixelated rendition with SagA* overlay. Great catch
Now, if we could just SEE it😉😁!

CS, Ralph😉

#3 vidrazor

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Posted 14 May 2022 - 09:51 PM

Looks good....☺. Really, though. I can't wait for JWST to point that way. But I like your pixelated rendition with SagA* overlay. Great catch
Now, if we could just SEE it!
CS, Ralph

...but.............................................................it's black...
 


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#4 BQ Octantis

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Posted 15 May 2022 - 07:51 AM

Technically, the superheated gases on the event horizon are as hot and bright as the surface of our sun. Their orbital period (at an orbit the size of Mercury's) is a matter of minutes, which produces a lot of friction. But the galactic dust is thickest along the Great Rift, and Sgr A* is at the dead nuts center. So very few visible photons make it to us; and indeed, I can't help but wonder exactly how many photons that registered on my pixel were actually from Sgr A*. I'm going with >1.


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#5 kathyastro

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Posted 15 May 2022 - 08:39 AM

I can see why they call it a black hole!


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#6 BQ Octantis

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Posted 15 May 2022 - 09:19 AM

Well it was certainly black-ish in my image! But the just the size of the event horizon presents a greater challenge: the dust notwithstanding, no amount of point spread from any of my optics is going to pick up a sun-luminoisty-level, Mercury-orbit-sized source at 27,000 light years. Even if it did, my most extreme setup gives me a spatial sampling of 50 milliarcsec—about 1000 times too big for any detail.

 

The EHT team used a telescope with the diameter of the Earth and a wavelength of 1.3mm for their image. By my calculus, that gave them a resolution (Rayleigh criterion) of 0.026 milliarcseconds! jawdrop.gif



#7 Dagryl

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Posted 15 May 2022 - 03:15 PM

Here you can check a pretty good video about the image.

 

https://www.youtube....h?v=Q1bSDnuIPbo



#8 BQ Octantis

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Posted 15 May 2022 - 03:33 PM

A nice description of angular resolution and interferometry, too!



#9 BucketDave

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Posted 17 May 2022 - 04:12 PM

If you squint at it, isn't one of the pixels SLIGHTLY brighter than the others..... or have i i halecmd too much beer?

Good effort for trying to locate it. If I tried with my LX85 mount, it would either:
A) smear it over 10 arc seconds, or
B) suffer a loose encoder wheel and point at my garden hedge instead.

0.001 arc seconds? Must have been a computing nightmare to get all those images in-phase.

PS. At 50 degs N, the garden hedge is not so far off Sag A*. I envy you folks who can see it at a sensible altitude.

Clear skies!
Bucket

#10 BQ Octantis

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Posted 19 May 2022 - 08:29 PM

I don't know…it might be your monitor. Or maybe mine. With enough beer, blame is unimportant! (And the LX85 is more tolerable, too.)

 

Sadly, I'm now at 40˚N. Well, it would be sad if the sky wasn't always so bloody cloudy. And for that, there's just not enough beer…



#11 unimatrix0

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Posted 20 May 2022 - 03:22 PM

It's so black, it made me see all the dust on my monitor. 




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