APOD: Ring Galaxy AM 0644-741 (2021 Jul 28)

[APOD Robot]

Ring Galaxy AM 0644-741

Explanation: The rim of the large blue galaxy at the right is an immense ring-like structure 150,000 light years in diameter composed of newly formed, extremely bright, massive stars. AM 0644-741 is known as a ring galaxy and was caused by an immense galaxy collision. When galaxies collide, they pass through each other and their individual stars rarely come into contact. The large galaxy's ring-like shape is the result of the gravitational disruption caused by a small intruder galaxy passing through it. When this happens, interstellar gas and dust become compressed, causing a wave of star formation to move out from the impact point like a ripple across the surface of a pond. Other galaxies in the field of view are background galaxies, not interacting with AM 0644-741. Foreground spiky stars are within our own Milky Way. But the smaller intruder galaxy is caught above and right, near the top of the frame taken by the Hubble Space Telescope. Ring galaxy AM 0644-741 lies about 300 million light years away toward the southern constellation Volans.

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[jks]

It is interesting that this galaxy has an offset core, and somewhat of a void at its center, presumably due to the interaction with its neighbor.

[shaileshs]

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..

[Ann]

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.

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.

---

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!

[JohnD]

Like the famous picture of Hoag's Object https://apod.nasa.gov/apod/ap100822.html in which another ring galaxy appears in the background, this picture does the same. Ann's Object No.4 (bottom left) appears to be very similar to AM 0644-741!

JOhn

[VictorBorun]

The near-core part of the disk of the Ring Galaxy AM 0644-741 seems to turn away from our line of sight more than the plane of the Ring.
Judging by the visibility of the dust lanes backlighted by the core:

[orin stepanek]

Eye candy in the heavens; after a vicious collusion

[neufer]

https://www.syfy.com/syfywire/an-ancien ... ero-galaxy

[shaileshs]

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.

---

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]

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.

---

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..

Thanks for setting me straight, shaileshs!

Ann

[bystander]

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.

[johnnydeep]

Another ring galaxy?

Another Ring Galaxy?

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?

[johnnydeep]

From http://www.astrosurf.com/uploads/monthl ... b164ac.jpg, here are three of the other galaxy's names (or at least, identifiers):

Other Galaxies Around AM0644-741

[Ann]

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.

Thanks for setting me straight, bystander and shaileshs!

Ann

[Ann]

Another ring galaxy?

Click to view full size image

Another ring galaxy? Could be!

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?

NGC 2207 and IC 2163. Image: NASA/ESA and The Hubble Heritage Team (STScI)

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The Tadpole galaxy, a collisional product. NASA, H. Ford (JHU), G. Illingworth (USCS/LO), M. Clampin (STScI), G. Hartig (STScI), the ACS Science Team, and ESA.

---

I think that if the galaxies just pass by each other, you don't normally get rings, just drawn-out spiral arms and other tidal features.

And you don't always get rings just because two galaxies collide head on. The Tadpole galaxy got its weird shape and extremely long tail when another galaxy collided with it, but we don't see a ring.

- 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?

Click to play embedded YouTube video.

The Cartwheel galaxy and satellites, Image: ESA/Hubble & NASA - http://www.spacetelescope.org/images/potw1036a/

---

Many if not most galaxies have yellow centers, because the reservoir of gas and dust in the center of a galaxy tends to get used up first. That's because the center of a galaxy typically sees many more episodes of star formation, because things are just more active and crowded there. Instead, there is often a relatively unused reservoir of gas and dust in the outskirts of a galaxy, and if this gas and dust gets stirred up, that can set up new episodes of star formation in these outer parts of the galaxy.

Note that the outer ring is the bluest part of the Cartwheel galaxy, while the inner rings are yellow. The "spokes" connecting the inner and outer rings are intermediately colored. Note that even the small blue satellite galaxy has what resembles a ring, which is bluer than the rest of the galaxy.

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".

Ann

[johnnydeep]

Thanks, Ann. So I was mostly on the right track with my self-supplied answers.

[Ann]

Thanks, Ann. So I was mostly on the right track with my self-supplied answers.

Thanks. Maybe I shouldn't have said that the Tadpole galaxy doesn't have a ring. Look closely, and you can see that it does have a ring - or two rings, though one is incomplete - which are centered on, well, the galaxy's center.

The rings are not as blue as the long tail of the Tadpole.

Ann

[neufer]

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".

Galactic collisions actually follow the physics of 'Doc' Edgerton's Milk Drops.

Doc's Milk Drops generate violent shock waves that devolve into expanding rings of milk droplets.

No gentle widening wave packets of water ripples.

Water particle motion of a deep water wave

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The complexity to be described by the geocentric model

---

<<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.>>

[roland jochems]

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.

[Chris Peterson]

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]

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:

What's This Dark Spot?

[Ann]

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

Well, if it isn't some sort of photographic "mistake" (or whatever you call them), my best guess is that it is a dust cloud of some sort.

The Mice Galaxies. NASA, H. Ford (JHU), G. Illingworth (UCSC/LO), M.Clampin (STScI), G. Hartig (STScI), the ACS Science Team, and ESA.

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Check out the picture of the Mice Galaxies. As you can see, the bright center of the galaxy on the right is severely dimmed by a thick dust cloud. I have a very low-resolution picture of these galaxies in The Color Atlas of Galaxies by James D Wray, and in that book Wray racked his brain over what could have caused the center of one of the Mice Galaxies to be so dark. Answer: Dust.

Ann

[Ann]

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).

---

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

[JohnD]

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?

[Chris Peterson]

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

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.