Starship Asterisk*

Ann wrote: ↑Fri Jul 30, 2021 8:16 pm Speaking of ring galaxies, I just found a picture of the Andromeda Galaxy in radio waves (at 6.6 GHz) and I just have to share it with you.

The Andromeda Galaxy in radio waves at 6.6 GHz. Picture: The Sardinia Radio Telescope in Italy. Credit: S. Fatigoni et al (2021).

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I hope this link isn't going to break! But in any case...

Is the Andromeda Galaxy a ring galaxy, or is it a ring galaxy?

Ann

Chris Peterson wrote: ↑Fri Jul 30, 2021 10:49 pm

JohnD wrote: ↑Fri Jul 30, 2021 10:27 pm

Chris Peterson wrote: ↑Fri Jul 30, 2021 5:27 pm

It's not. Black holes can't be optically resolved. They're far too small.

Not the BH itself, but the accretion disk, around the event horizon?
Like this?
Black hole EHT image.png

No. A BH and an accretion disc are unresolvable in light at any distance from us where we expect to find them. Images like you provide are produced by radio telescopes with planetary scale apertures (interferometers), yielding a resolution of about 20 microarcseconds, and therefore able to resolve structures in nearby galaxies with sizes of a few hundred AU (or a few hundredths of a light year).

Whatever that spot in this image is (I'm inclined to agree with Ann, that it's a dust cloud), it must be many light years across.

JohnD wrote: ↑Fri Jul 30, 2021 10:27 pm

Chris Peterson wrote: ↑Fri Jul 30, 2021 5:27 pm

roland jochems wrote: ↑Fri Jul 30, 2021 5:20 pm If you zoom in on the eliptical galaxy left mid. you see something that actual looks like a black hole as it would be in visible light passing in front of it low right. I can't upload pictures otherwise I could show it.

It's not. Black holes can't be optically resolved. They're far too small.

Not the BH itself, but the accretion disk, around the event horizon?
Like this?
Black hole EHT image.png

Chris Peterson wrote: ↑Fri Jul 30, 2021 5:27 pm

roland jochems wrote: ↑Fri Jul 30, 2021 5:20 pm If you zoom in on the eliptical galaxy left mid. you see something that actual looks like a black hole as it would be in visible light passing in front of it low right. I can't upload pictures otherwise I could show it.

It's not. Black holes can't be optically resolved. They're far too small.

johnnydeep wrote: ↑Fri Jul 30, 2021 6:59 pm

Chris Peterson wrote: ↑Fri Jul 30, 2021 5:27 pm

roland jochems wrote: ↑Fri Jul 30, 2021 5:20 pm If you zoom in on the eliptical galaxy left mid. you see something that actual looks like a black hole as it would be in visible light passing in front of it low right. I can't upload pictures otherwise I could show it.

It's not. Black holes can't be optically resolved. They're far too small.

Any thoughts on what the black spot is? Perhaps there's just not enough here to tell. I presume the poster was referring to this spot:

Click to view full size image

Chris Peterson wrote: ↑Fri Jul 30, 2021 5:27 pm

roland jochems wrote: ↑Fri Jul 30, 2021 5:20 pm If you zoom in on the eliptical galaxy left mid. you see something that actual looks like a black hole as it would be in visible light passing in front of it low right. I can't upload pictures otherwise I could show it.

It's not. Black holes can't be optically resolved. They're far too small.

roland jochems wrote: ↑Fri Jul 30, 2021 5:20 pm If you zoom in on the eliptical galaxy left mid. you see something that actual looks like a black hole as it would be in visible light passing in front of it low right. I can't upload pictures otherwise I could show it.

Ann wrote: ↑Wed Jul 28, 2021 7:24 pm
Note that when a pebble is dropped in a pond, waves appear to push water outwards.

I guess we are seeing the same effect in the "ponds" (that is, disks) of galaxies that get hit by a galaxy-sized "pebble".

https://en.wikipedia.org/wiki/Deferent_and_epicycle wrote:

Water particle motion of a deep water wave

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The complexity to be described by the geocentric model

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<<In the Hipparchian, Ptolemaic, and Copernican systems of astronomy, the epicycle was a geometric model used to explain the variations in speed and direction of the apparent motion of the Moon, Sun, and planets. In particular it explained the apparent retrograde motion of the five planets known at the time. Secondarily, it also explained changes in the apparent distances of the planets from the Earth.

It was first proposed by Apollonius of Perga at the end of the 3rd century BC. It was developed by Apollonius of Perga and Hipparchus of Rhodes, who used it extensively, during the 2nd century BC, then formalized and extensively used by Ptolemy of Thebaid in his 2nd century AD astronomical treatise the Almagest.

In both Hipparchian and Ptolemaic systems, the planets are assumed to move in a small circle called an epicycle, which in turn moves along a larger circle called a deferent. Both circles rotate clockwise and are roughly parallel to the plane of the Sun's orbit (ecliptic). Despite the fact that the system is considered geocentric, each planet's motion was not centered on the Earth but at a point slightly away from the Earth called the eccentric.

In the Hipparchian system the epicycle rotated and revolved along the deferent with uniform motion. However, Ptolemy found that he could not reconcile that with the Babylonian observational data available to him; in particular, the shape and size of the apparent retrogrades differed. The angular rate at which the epicycle traveled was not constant unless he measured it from another point which he called the equant. It was the angular rate at which the deferent moved around the point midway between the equant and the Earth (the eccentric) that was constant; the epicycle center swept out equal angles over equal times only when viewed from the equant. It was the use of equants to decouple uniform motion from the center of the circular deferents that distinguished the Ptolemaic system.

Epicyclical motion is used in the Antikythera mechanism, an ancient Greek astronomical device for compensating for the elliptical orbit of the Moon, moving faster at perigee and slower at apogee than circular orbits would, using four gears, two of them engaged in an eccentric way that quite closely approximates Kepler's second law.

Epicycles worked very well and were highly accurate, because, as Fourier analysis later showed, any smooth curve can be approximated to arbitrary accuracy with a sufficient number of epicycles. However, they fell out of favour with the discovery that planetary motions were largely elliptical from a heliocentric frame of reference, which led to the discovery that gravity obeying a simple inverse square law could better explain all planetary motions.>>

johnnydeep wrote: ↑Wed Jul 28, 2021 7:29 pm Thanks, Ann. So I was mostly on the right track with my self-supplied answers.

johnnydeep wrote: ↑Wed Jul 28, 2021 4:21 pm Another ring galaxy?

Click to view full size image

Some questions:
- How do we know the "intruder" galaxy passed through rather than just nearby this ring galaxy? Is it just the symetrical ring itself that's the tell tale sign?

- Why should the star formation be mostly confined to the evident ring? Why not more uniformly throughout the entire galaxy? Is it just because there is more dust in the fringes? Is it because the pressure "ripples" traveled outward from the site of penetration and any blue stars that were created first toward the center are now older and no longer blue?

bystander wrote: ↑Wed Jul 28, 2021 3:12 pm

Ann wrote: ↑Wed Jul 28, 2021 8:23 am
In my opinion, the most likely galaxy to have passed through the disk of AM 0644-741 and turned it into a ring galaxy is the galaxy that I have labelled 5 in my annotated image. The number 5 galaxy is smaller than AM 0644-741, it appears to be at the same distance as AM 0644-741 (because it has the same overall color profile), and it seems to lack any outer features (which were presumably ripped off during its passage through AM 0644-741).

The APOD text identifies "1" as the intruder. This post from Chandra X-ray Observatory in Sept 2018 also identifies "1" as the intruder.

viewtopic.php?t=38664

Sorry, I didn't read all the way through. I missed shaileshs's post.

Ann wrote: ↑Wed Jul 28, 2021 8:23 am
In my opinion, the most likely galaxy to have passed through the disk of AM 0644-741 and turned it into a ring galaxy is the galaxy that I have labelled 5 in my annotated image. The number 5 galaxy is smaller than AM 0644-741, it appears to be at the same distance as AM 0644-741 (because it has the same overall color profile), and it seems to lack any outer features (which were presumably ripped off during its passage through AM 0644-741).

shaileshs wrote: ↑Wed Jul 28, 2021 2:58 pm

Ann wrote: ↑Wed Jul 28, 2021 8:23 am

shaileshs wrote: ↑Wed Jul 28, 2021 4:38 am What's the name of that "intruder" galaxy ? Seems to be that eliptical galaxy w/ no spehrical arms and no band at the center.. And, surprisingly, it passed through this main galaxy, triggered such violent destruction/displacement as well as creation but on looks almost untouched in it's own appearance (except floating connecting gas clouds that give away the secret). As if it has nothing to do with this chaotic impact triggered and left behind. Unless someone researches the interaction and proves that that it was culprit, normally no one would have a slightest doubt that it caused such havoc.. Right ? So interesting..

Well, clearly AM 0644-0741 has taken a hit that made it throw out all that gas and dust that subsequently formed a fantastic lopsided starforming blue ring around the main body of AM 0644-741, which, by the looks of it, started out as a barred grand design (that is, two-armed) spiral galaxy.

Ring galaxy widefield NASA ESA Jonathan Lodge annotated.png

In my opinion, the most likely galaxy to have passed through the disk of AM 0644-741 and turned it into a ring galaxy is the galaxy that I have labelled 5 in my annotated image. The number 5 galaxy is smaller than AM 0644-741, it appears to be at the same distance as AM 0644-741 (because it has the same overall color profile), and it seems to lack any outer features (which were presumably ripped off during its passage through AM 0644-741).

Interestingly, there are some similarities between AM 0644-741 and NGC 7318B in Stephan's Quintet.

Stephan's Quintet, with yellow galaxies NGC 7318B (top) and NGC 7318A (bottom) at center. Note the ring that has been thrown out by NGC 7318B. Image: NASA, ESA, and the Hubble SM4 ERO Team.

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Stephans Quintet annotated NASA ESA and the Hubble SM4 ERO Team.png

The ring of NGC 7318B.

What are the names of the galaxies close to AM 0644-741? I have absolutely no idea. Please note that with a name like that, AM 0644-741 itself is sure to be very faint and far away. The same goes for its neighboring galaxies, but they, unlike AM 0644-741, are not interesting in themselves and are sure to have their designations listed only in more obscure and hard-to-access catalogs of faint galaxies.

Ann

P.S. Have to edit my post to note that I now have a nice palindrome number of posts, namely 11411 posts. I like it!

Hi Ann,

As always, your comments and sharing of knowledge is appreciated. Just wanted to mention, the post text says intruder galaxy is #1 in your annotated picture. And I think we can see it with the signs of interacting gas between the 2 galaxies.. I am not seeing any signs of interaction with #5..

Ann wrote: ↑Wed Jul 28, 2021 8:23 am

shaileshs wrote: ↑Wed Jul 28, 2021 4:38 am What's the name of that "intruder" galaxy ? Seems to be that eliptical galaxy w/ no spehrical arms and no band at the center.. And, surprisingly, it passed through this main galaxy, triggered such violent destruction/displacement as well as creation but on looks almost untouched in it's own appearance (except floating connecting gas clouds that give away the secret). As if it has nothing to do with this chaotic impact triggered and left behind. Unless someone researches the interaction and proves that that it was culprit, normally no one would have a slightest doubt that it caused such havoc.. Right ? So interesting..

Well, clearly AM 0644-0741 has taken a hit that made it throw out all that gas and dust that subsequently formed a fantastic lopsided starforming blue ring around the main body of AM 0644-741, which, by the looks of it, started out as a barred grand design (that is, two-armed) spiral galaxy.

Ring galaxy widefield NASA ESA Jonathan Lodge annotated.png

In my opinion, the most likely galaxy to have passed through the disk of AM 0644-741 and turned it into a ring galaxy is the galaxy that I have labelled 5 in my annotated image. The number 5 galaxy is smaller than AM 0644-741, it appears to be at the same distance as AM 0644-741 (because it has the same overall color profile), and it seems to lack any outer features (which were presumably ripped off during its passage through AM 0644-741).

Interestingly, there are some similarities between AM 0644-741 and NGC 7318B in Stephan's Quintet.

Stephan's Quintet, with yellow galaxies NGC 7318B (top) and NGC 7318A (bottom) at center. Note the ring that has been thrown out by NGC 7318B. Image: NASA, ESA, and the Hubble SM4 ERO Team.

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Stephans Quintet annotated NASA ESA and the Hubble SM4 ERO Team.png

The ring of NGC 7318B.

What are the names of the galaxies close to AM 0644-741? I have absolutely no idea. Please note that with a name like that, AM 0644-741 itself is sure to be very faint and far away. The same goes for its neighboring galaxies, but they, unlike AM 0644-741, are not interesting in themselves and are sure to have their designations listed only in more obscure and hard-to-access catalogs of faint galaxies.

Ann

P.S. Have to edit my post to note that I now have a nice palindrome number of posts, namely 11411 posts. I like it!

shaileshs wrote: ↑Wed Jul 28, 2021 4:38 am What's the name of that "intruder" galaxy ? Seems to be that eliptical galaxy w/ no spehrical arms and no band at the center.. And, surprisingly, it passed through this main galaxy, triggered such violent destruction/displacement as well as creation but on looks almost untouched in it's own appearance (except floating connecting gas clouds that give away the secret). As if it has nothing to do with this chaotic impact triggered and left behind. Unless someone researches the interaction and proves that that it was culprit, normally no one would have a slightest doubt that it caused such havoc.. Right ? So interesting..