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A dark relativistic jet?

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#1 Ettu

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Posted 13 April 2021 - 10:29 AM

I've been doing the Astronomy Leagues Arp Peculiar Galaxy program, and came across this one

Arp 213 also IC 356

A 10' crop

 

ARP 213 10' fov 12-14-20.JPG

 

It sure looks like a relativistic jet coming out of the core, except dark! How can that be !?

Presumably something in our Milky Way?, but wow, what a fortuitous alignment of a uniquely shaped region of intervening dust!

Btw, my wife noticed along the lower edge of the galaxy that I may have captured a piece of the mysterious dark matter that scientists all over the world have been trying to find! ;-)

 

Scope = 11" Edge, at f10

Camera = Canon Ra

8 of 600 sec exposures

From my semi urban back yard, Bortle 4.5

ImagesPlus development.


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#2 whwang

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Posted 13 April 2021 - 11:03 AM

A small galaxy (with gas and dust) falling into the big one can easily produce that kind of feature.

Real relativistic jets should not be dark. In optical wavelengths, they should be either bright (like the M87 jet) or nearly transparent. Only electrons can be accelerated to close to speed of light to form relativistic jets, and electrons are not effective absorbers of optical light. Dust particles can absorb optical light effectively, but they are too massive to be accelerated to speed of light.
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#3 Ettu

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Posted 14 April 2021 - 11:51 AM

A small galaxy (with gas and dust) falling into the big one can easily produce that kind of feature.

Real relativistic jets should not be dark. In optical wavelengths, they should be either bright (like the M87 jet) or nearly transparent. Only electrons can be accelerated to close to speed of light to form relativistic jets, and electrons are not effective absorbers of optical light. Dust particles can absorb optical light effectively, but they are too massive to be accelerated to speed of light.

Interesting. If such a feature could easily be produced I suppose there should be more that us amateurs could see,

Do you or anyone else know of any other such examples? I'd like to get another picture.

 

In this specific case (IC 356), has it been convincingly determined that it is a dust inflow, or a M.W. foreground object, or something else?


Edited by Ettu, 14 April 2021 - 11:52 AM.


#4 whwang

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Posted 14 April 2021 - 09:33 PM

Interesting. If such a feature could easily be produced I suppose there should be more that us amateurs could see,

Do you or anyone else know of any other such examples? I'd like to get another picture.

 

In this specific case (IC 356), has it been convincingly determined that it is a dust inflow, or a M.W. foreground object, or something else?

Best other example is M81.  There are multiple subtle dark lanes that are not part of the spiral arms going through the galaxy.

 

On this page, you can find key astrophysical measurements about IC356:

http://ned.ipac.calt...wmap=4&corr_z=1

 

There is a tab "Reference (141)" containing 141 scientific papers that mentioned or studied IC356.  Unfortunately most of the papers study samples of galaxies, rather than focusing on just IC356.  You will need to read through them carefully to find the information you want.  What I said in my previous post is based on my general knowledge about galaxies, not based on something that I learned about IC356 particularly.  So it is not entirely impossible that I said something wrong.

 

Telling whether a feature is associated with a galaxy or with the Milky Way can sometimes be tricky.  However, based on the image of IC356, that dark lane is almost certain that it's associated with IC356 but not our Milky Way.



#5 Ettu

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Posted 15 April 2021 - 10:10 AM

Thanks very much whwang!

I looked up my last image (circa 2010) of M81, and unfortunately didn't see any of the subtle lanes you mentioned. Time for a revisit while it's still up there this year, now that my skills and equipment are better.

 

I did find this photo from Adam Block that shows several columns (left side especially) quite nicely.

http://www.caelumobs...llery/m81.shtml

So the IC 356 version then could be a remarkably large and obvious thoroughfare by comparison

 

Not that my picture is particularly sharp, But the lane appears to break up into 3 forks or funnels near "the big one" a sort of spaghettifying? Any thoughts on why more than one? 


Edited by Ettu, 15 April 2021 - 10:12 AM.


#6 whwang

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Posted 15 April 2021 - 12:09 PM

I also noticed that the dark lane breaks into multiple ones when I first saw your picture. (It appears less obvious to me in the Paloma plate.) A natural explanation is again that a small galaxy falls into it, and different parts of that galaxy have slightly different trajectories.

#7 Ettu

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Posted 20 April 2021 - 10:45 AM

I also noticed that the dark lane breaks into multiple ones when I first saw your picture. (It appears less obvious to me in the Paloma plate.) A natural explanation is again that a small galaxy falls into it, and different parts of that galaxy have slightly different trajectories.

Thanks again whwang!

Perhaps it's not appropriate in this forum about imaging, to continue a conversation about the dynamics going on in a galaxy? If the moderators feel it's not germane, let me know. On the other hand, others might be curious too, or be inspired to image this interesting and relatively large bright Arp Peculiar galaxy, - well within our capabilities.

As a layman, and after your comments, I find this galaxy to be all the more interesting.

For example, if M81 is one of the best "also" examples of the dark phenomena that appears central in IC356, then IC356's is truly unique in both its size and position. M81's lanes by comparison are thin, dispersed, feeble, numerous, and definitely not as easy to capture.

I'm wondering why the core IC356 isn't lighting up with the inflow of such a massive object. Perhaps it just hasn't started yet?

I was wondering too if determining more definitively the nature of this "dark jet" is a Masters degree caliber project?

 

Regards,

 

Ettu



#8 whwang

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Posted 21 April 2021 - 07:25 AM

Hi,

 

I don't believe M81 and IC356 are rare ones.  I encounter images like this from time to time.  Some of them have dust features more prominent than this like NGC 5128, which is an elliptical galaxy with a massive spiral galaxy falling in and forming a new disk.  Some of them have weaker dust features that require strong image enhancement to reveal.  I just can't remember the name or numbers of all of them.  Merging of large galaxies and accretion of small galaxies onto big ones happen all the time in the universe, and is the major way for galaxies to grow.

 

The dust lane in IC356 does not require a big galaxy to fall into it.  A small, LMC-like, or even-SMC like satellite galaxy can produce such dust shadow.  Perhaps aliens living in a distant galaxy far behind SMC would see such a dust feature against Milky Way's disk but would not see SMC.  The dust lane is easy to see when it is in front of a bright background galaxy like IC356 or Milky Way, but a small satellite galaxy can be difficult to see when we are very far away.

 

I think one interesting project is to look for a galaxy atlas and look at the images carefully.  Or you may download the public Palomar photographic images of galaxies and give them strong contrast stretch.  I believe you will see many interesting phenomena.  The galaxy world is messy.  Many things can be going on.


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