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SgrA* The center mystery of our galaxy - amazingly rarely imaged

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#1 freestar8n

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Posted 19 June 2019 - 05:58 AM

This is a view into the very center of our own Milky Way Galaxy - where the SgrA* black hole lurks. For some reason this patch of sky is rarely imaged - I guess because you can't actually see anything right there. But it is nonetheless where many things important to our galaxy are happening.

 

This is an image that has been calibrated and imaged in Sloan i' r' g' filters to show the colors exactly as they are measured - and clearly it is a very orange/red region obscured by dust. North is up - and it is about 0.4" per pixel.

 

SagAGood_irg_xgrads.jpg

 

Full res astrobin link:

get.jpg?insecure

 

Imaged with EdgeHD11 at f/7 with ASI1600 on cge-pro guided by MetaGuide. Not much time with only 6 exposures of 300s in each Sloan filter: i' r' g' mapped to RGB. No processing or sharpening other than gradient removal and stretch with levels to reveal faint stars. Photometrically calibrated based on APASS field magnitudes with over 200 field stars.

 

The inset in the upper left is a zoomed in view of the central region where the black hole is presumed to live. You can see an asterism on the left and an overall ring shape of stars that is identifiable. The ring presumably has no physical meaning since the stars shown are likely foreground stars that have nothing to do with the black hole itself. But nonetheless - this is a view directly into the center of our galaxy. And for some reason - few imagers look there.

 

Here is a link that shows the region and the asterism right near the center that helps locate it:

http://ircamera.as.a...s/galcenter.htm

 

Here is a plot of the field stars used to calibrate the three Sloan filter channels - which span slightly beyond visible into the IR:

 

PhotoFitPlot.png

 

It took me a while to find example images that allowed me to confirm this really is the right place to look - but I think I have it right.  I want to go deeper but I'm not sure what else can be revealed.  The main thing for me is - this is a view of a fairly important part of the sky for us.  And it's interesting to see new asterisms and a ring pattern that I never knew before - but know now.

 

Frank


Edited by freestar8n, 19 June 2019 - 07:13 PM.

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#2 ChrisWhite

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Posted 19 June 2019 - 06:21 AM

Frank,

 

Very cool.  I've been reading up about our supermassive black hole in astronomy publications, and the topic is fascinating.  Other than knowing that there is something hidden in there, it's a pretty boring stretch of sky (visually) which as you mentioned is probably the reason it's not imaged frequently.  So, not so amazingly enough it is skipped over...

 

The link you posted has some truly fascinating information in there!  Seeing the stellar orbits around the black hole is quite dramatic.  It's hard to imagine how volatile that region must be!



#3 freestar8n

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Posted 19 June 2019 - 06:36 AM

Thanks Chris.  Yes - I didn't expect to actually "see" anything there.  But I was surprised to realize there are certain identifiable asterisms that help locate it - that no one including me knew about.  And I was very surprised that in searching the web I couldn't find examples to help me locate the particular point in the image.  The link I provided was a fairly rare example that I could find.

 

It's also confusing because there are several "SgrA's" corresponding to different radio sources.  As I understand it, SgrA* corresponds to the actual center - which is what I present.  Other components of "SgrA" are some distance away.

 

To me it's odd we know the big dipper and Orion and the southern cross - but we don't know this little patch of stars - including the very identifiable asterism on the left of the inset - and the ring I point out.  I couldn't think of something to call it because it isn't really a dipper or a buttonhook - but it is distinctive.  And it is right next to the center of our galaxy - which astronomers may or may not image in detail in the coming 10-20 years.

 

So - to me it's a good patch of sky to get familiar with and appreciate - even if it doesn't reveal something amazing in the very center.  So far, anyway.

 

Frank


Edited by freestar8n, 19 June 2019 - 09:04 PM.

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#4 Astroman007

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Posted 19 June 2019 - 07:00 AM

Very interesting, very mentally expansive...just thinking of and imagining what lies beyond that rich field of stars.

 

I often take a look at that patch of sky through the summer months.



#5 happylimpet

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Posted 19 June 2019 - 07:07 AM

What a great idea to image this famous area. I would love to see a stretched version of your image down to the noise floor to see how many of the sources visible in the linked IR image are visible.



#6 freestar8n

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Posted 19 June 2019 - 07:34 AM

What a great idea to image this famous area. I would love to see a stretched version of your image down to the noise floor to see how many of the sources visible in the linked IR image are visible.

Thanks - I do want to go deeper and sharper with this image - but it is winter in Melbourne and imaging is harder to do - so I went with what I have.  It was imaged from a fairly bright suburban backyard with about 18.5 mag light pollution - and the seeing wasn't great at around 2.2" fwhm or so.  I hope to get more time in the future - but someone at a dark site with good seeing would be able to go much deeper and see more stuff in the center of the "ring."

 

In the very center there are professional images at high res showing stars swirling around what is likely a black hole - and that stuff is very dynamic.  But the view at this level and for most amateurs would be fairly constant over time - even if it is fairly deep and high res.  So I would be interested to see what can be observed over time in this particular very special part of the sky.

 

Frank


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#7 PeteM

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Posted 19 June 2019 - 07:38 AM

Nice work on this Frank. I have wondered in the past what it would look like with modest amateur equipment. Here at 42N latitude it does not get very high and imaging that low never crosses my mind. Maybe I will have to give it a go and find the asterism. Thanks for sharing this.



#8 OldManSky

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Posted 19 June 2019 - 09:36 AM

Nice, Frank.

From what I understand, the stars in the asterism you highlighted are zipping along with a very high proper motion -- largely due to their proximity to the black hole.

It would be interesting for you to image the same region in a year, with the same gear, and compare the two images to see how much the stars have moved :)



#9 freestar8n

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Posted 19 June 2019 - 06:31 PM

Nice, Frank.

From what I understand, the stars in the asterism you highlighted are zipping along with a very high proper motion -- largely due to their proximity to the black hole.

It would be interesting for you to image the same region in a year, with the same gear, and compare the two images to see how much the stars have moved smile.gif

Thanks for the comments, everyone.  By coincidence the current APOD is also a view of SgrA*.

 

What was frustrating for me with my image was determining the scale of images such as the APOD - since they usually don't indicate the size of the field in arc-minutes.

 

Many high res images of it, including the APOD, show a small arc of stars nearby that is very recognizable.  But it's hard to tell how big the arc is and how faint the stars are.

 

Below is a similar image that does show scale, and you can see that the arc is actually only a few arc-seconds wide - and presumably it is very faint.  So the size of my image is huge in comparison.

 

As for stars moving quickly - I think the stars in my image are relatively ordinary and nearby stars that aren't affected by the black hole.  They just happen to be along the line of sight.  I think you need to go deep in the IR to see the stars that are whipping around - and you need very high res.

 

The very deep red stars in my image are likely very small and faint stars that are close by - and the blue ones are brighter and farther away.  But still relatively close.

 

I hope to go deeper with more time if I can get it.

 

Frank

 

 

 

lgs_rgb_narrow_large_label.jpg


Edited by freestar8n, 19 June 2019 - 07:14 PM.

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#10 freestar8n

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Posted 19 June 2019 - 07:11 PM

I just realized I used the wrong abbreviation.  It is SgrA* and not SagA*

 

I don't know how to change the title of a thread in CN.  Is there a way?

 

Frank



#11 AKHalea

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Posted 19 June 2019 - 08:30 PM

I just realized I used the wrong abbreviation.  It is SgrA* and not SagA*

 

I don't know how to change the title of a thread in CN.  Is there a way?

 

Frank

Frank : First let me say that it is a nice capture of a generally neglected area by amateur APers because the area sort of of ordinary looking, but very important for our Milky Way to exist. 

 

Regarding your question above - Simply request the moderators to change the title to what you want it to, They usually oblige ..... Anil



#12 flyingcougar

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Posted 19 June 2019 - 08:56 PM

I just realized I used the wrong abbreviation.  It is SgrA* and not SagA*

 

I don't know how to change the title of a thread in CN.  Is there a way?

 

Frank

 

Got you covered Frank.wink.gif

 

 

And that is a very interesting subject, well done!



#13 freestar8n

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Posted 19 June 2019 - 09:00 PM

Got you covered Frank.wink.gif

 

 

And that is a very interesting subject, well done!

Great!  Thanks very much.  I wouldn't want others using the wrong abbreviation.

 

And thank you, Anil!

 

Frank




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