Explanation: Why are stars forming in the bridge between these colliding galaxies? Usually when galaxies crash, star formation is confined to galaxy disks or tidal tails. In Arp 194, though, there are bright knots of young stars right in a connecting bridge. Analyses of images and data including the featured image of Arp 194 from Hubble, as well as computer simulations of the interaction, indicate that the bottom galaxy passed right through the top galaxy within the past 100 million years. The result has left a stream of gas that is now falling toward the bottom galaxy. Astronomers hypothesize that stars form in this bridge because of the recent fading of turbulence after the rapid collision. In about a billion years, the galaxies -- including a smaller galaxy superposed on the upper galaxy (see it?) -- will all merge into one larger galaxy.
Re: APOD: Arp 194: Merging Galaxy Group (2019 Mar 25)
Posted: Mon Mar 25, 2019 4:44 am
by Nitpicker
APOD Robot wrote: ↑Mon Mar 25, 2019 4:07 am
including a smaller galaxy superposed on the upper galaxy (see it?)
I will play the game, but I'm not sure. Is it the one I've marked below as "??? 1" or "??? 2"?:
(The whole thing looks like a question mark to me.)
Re: APOD: Arp 194: Merging Galaxy Group (2019 Mar 25)
Posted: Mon Mar 25, 2019 5:13 am
by RocketRon
Would gravity be enough to reverse both these in their tracks, so to speak.
Thats a colossal amount of momentum they each have,,,,
Re: APOD: Arp 194: Merging Galaxy Group (2019 Mar 25)
Posted: Mon Mar 25, 2019 5:37 am
by Nitpicker
Another curious puzzle ... I've just noticed a number of different websites that say that Arp 194 is in Cepheus, when it is nowhere near Cepheus. It is in Ursa Major. I wonder who was the initial culprit to so successfully propagate this misinformation?
Unless I have been similarly misinformed, Arp 194 is a very small target, as well as a very dim one. From top to bottom, it probably only spans about four three Jupiters. Pretty impressive, even for the HST. (And very nice processing, geck.)
Re: APOD: Arp 194: Merging Galaxy Group (2019 Mar 25)
APOD Robot wrote: ↑Mon Mar 25, 2019 4:07 am
including a smaller galaxy superposed on the upper galaxy (see it?)
I will play the game, but I'm not sure. Is it the one I've marked below as "??? 1" or "??? 2"?:
apod_hack.jpg
(The whole thing looks like a question mark to me.)
I guess that the small galaxy is definitely "??? 2". I must say that the small galaxy is rather well-formed and not very affected by the titanic tidal forces battering it.
I'll skip the question marks now and call the galaxy "behind and on top of" the large one "1". "1" looks like a pretty large galaxy to me, probably as large as the obvious forefront galaxy.
Note that the forefront galaxy and the "1" galaxy seem to have equally large yellow bulges. If anything, the bulge of the "1" galaxy might be larger. My guess is that the "1" galaxy might be a bulge-dominated galaxy, although I believe that it did have a spiral system of its own, whereas the forefront galaxy was probably a gas-rich spiral before the crash. Admittedly it is possible that the "1" galaxy was equally gas-rich and spiral-dominated as the forefront galaxy. If so, galaxy "1" might have "spread its spiral arms like wings" due to the tidal forces wrecking it.
Note the brilliantly turquoise color of the nebulas at the end of the stellar bridge pointing towards the galaxy at the bottom of the picture. Geck, since you processed this image, can you explain why the nebulas look so turquoise here? Do they contain unusual amounts of both Hα and OIII?
Look at the galaxy at the bottom of the picture. Look at the smooth gas-poor arms. It seems to me that this galaxy might have lost quite a bit of its gas as it crashed through the galaxy complex "above" it.
What an incredible cosmic wrecking ball.
Ann
Re: APOD: Arp 194: Merging Galaxy Group (2019 Mar 25)
Posted: Mon Mar 25, 2019 6:20 am
by geckzilla
Nitpicker wrote: ↑Mon Mar 25, 2019 5:37 am
Unless I have been similarly misinformed, Arp 194 is a very small target, as well as a very dim one. From top to bottom, it probably only spans about four Jupiters. Pretty impressive, even for the HST. (And very nice processing, geck.)
Thanks! I'd put Arp194 at around 1.5 Jupiters, possibly more if you count extended, dim regions that aren't visible in this image.
Re: APOD: Arp 194: Merging Galaxy Group (2019 Mar 25)
Posted: Mon Mar 25, 2019 6:24 am
by geckzilla
Ann wrote: ↑Mon Mar 25, 2019 5:42 amNote the brilliantly turquoise color of the nebulas at the end of the stellar bridge pointing towards the galaxy at the bottom of the picture. Geck, since you processed this image, can you explain why the nebulas look so turquoise here? Do they contain unusual amounts of both Hα and OIII?
Absolutely. The H-alpha emission is contained largely in the green channel here, and [OIII] is in the blue channel. No narrowband filters were used, so only the most significant emission nebulas are having any effect on the colors. That bridge is certainly impressive.
Re: APOD: Arp 194: Merging Galaxy Group (2019 Mar 25)
Posted: Mon Mar 25, 2019 6:26 am
by Nitpicker
oops ... duplicate
Re: APOD: Arp 194: Merging Galaxy Group (2019 Mar 25)
Posted: Mon Mar 25, 2019 6:28 am
by Nitpicker
geckzilla wrote: ↑Mon Mar 25, 2019 6:20 am
Thanks! I'd put Arp194 at around 1.5 Jupiters, possibly more if you count extended, dim regions that aren't visible in this image.
Yes, my numbers are entirely questionable. Just before you posted, I narrowed my "four" Jupiters to "three" (top to bottom of image frame), but the more I read about this object, the more contradictions I find.
Re: APOD: Arp 194: Merging Galaxy Group (2019 Mar 25)
geckzilla wrote: ↑Mon Mar 25, 2019 6:20 am
Thanks! I'd put Arp194 at around 1.5 Jupiters, possibly more if you count extended, dim regions that aren't visible in this image.
Yes, my numbers are entirely questionable. Just before you posted, I narrowed my "four" Jupiters to "three" (top to bottom of image frame), but the more I read about this object, the more contradictions I find.
I'm not very sophisticated. I just pulled up a picture of Jupiter taken with the same detector and compared them from there. No reading required. hehe
Re: APOD: Arp 194: Merging Galaxy Group (2019 Mar 25)
Posted: Mon Mar 25, 2019 7:42 am
by Nitpicker
geckzilla wrote: ↑Mon Mar 25, 2019 6:35 am
I'm not very sophisticated. I just pulled up a picture of Jupiter taken with the same detector and compared them from there. No reading required. hehe
(Jupiter never appears much bigger than 50" from Earth. Two Jupiters would fit top to bottom.)
Re: APOD: Arp 194: Merging Galaxy Group (2019 Mar 25)
Posted: Mon Mar 25, 2019 8:41 am
by De58te
Uhm I might bring a controversy but doing a google search I found several sites including Wiki that say that the trio of colliding galaxies are in the top section. The two on the west side that are in direct collision and the smaller spiral galaxy on the east that is relatively unaffected. The arm of new star formation to the south is now thought to just be superimposed over the southern galaxy which isn't connected but just happens to be in the line of sight.
Re: APOD: Arp 194: Merging Galaxy Group (2019 Mar 25)
Posted: Mon Mar 25, 2019 9:02 am
by Nitpicker
Yeah, I read similar contradictory stuff too, De58te. Apart from the image's scale and its similarity to a question mark, I am not willing to speculate.
Re: APOD: Arp 194: Merging Galaxy Group (2019 Mar 25)
Posted: Mon Mar 25, 2019 9:19 am
by Ann
De58te wrote: ↑Mon Mar 25, 2019 8:41 am
Uhm I might bring a controversy but doing a google search I found several sites including Wiki that say that the trio of colliding galaxies are in the top section. The two on the west side that are in direct collision and the smaller spiral galaxy on the east that is relatively unaffected. The arm of new star formation to the south is now thought to just be superimposed over the southern galaxy which isn't connected but just happens to be in the line of sight.
I read that too, but frankly, I doubt it. To me it is too much of a coincidence that a fantastic bridge emanating from a pair of interacting galaxies would just by chance happen to point at another extremely nearby galaxy, which, however, is not at all involved in the interaction.
I think that the explanation in the caption of the APOD makes much more sense:
APOD Robot warote:
Analyses of images and data including the featured image of Arp 194 from Hubble, as well as computer simulations of the interaction, indicate that the bottom galaxy passed right through the top galaxy within the past 100 million years.
Ann
Re: APOD: Arp 194: Merging Galaxy Group (2019 Mar 25)
De58te wrote: ↑Mon Mar 25, 2019 8:41 am
Uhm I might bring a controversy but doing a google search I found several sites including Wiki that say that the trio of colliding galaxies are in the top section. The two on the west side that are in direct collision and the smaller spiral galaxy on the east that is relatively unaffected. The arm of new star formation to the south is now thought to just be superimposed over the southern galaxy which isn't connected but just happens to be in the line of sight.
I read that too, but frankly, I doubt it. To me it is too much of a coincidence that a fantastic bridge emanating from a pair of interacting galaxies would just by chance happen to point at another extremely nearby galaxy, which, however, is not at all involved in the interaction.
Re: APOD: Arp 194: Merging Galaxy Group (2019 Mar 25)
Posted: Mon Mar 25, 2019 12:37 pm
by orin stepanek
Is the little galaxy to the right of the three part of the merge? It looks like it may be more distant from Earth; and I'm not seeing any disruption in it's arms!
Re: APOD: Arp 194: Merging Galaxy Group (2019 Mar 25)
Posted: Mon Mar 25, 2019 1:03 pm
by neufer
orin stepanek wrote: ↑Mon Mar 25, 2019 12:37 pm
Is the little galaxy to the right of the three part of the merge?
It looks like it may be more distant from Earth; and I'm not seeing any disruption in it's arms!
The probability of two galaxies interacting (i.e., in close proximity in ALL 3 dimensions) at any one time is quite low.
The probability of three (or more) galaxies interacting is close to nil.
Re: APOD: Arp 194: Merging Galaxy Group (2019 Mar 25)
Posted: Mon Mar 25, 2019 1:04 pm
by Chris Peterson
RocketRon wrote: ↑Mon Mar 25, 2019 5:13 am
Would gravity be enough to reverse both these in their tracks, so to speak.
Thats a colossal amount of momentum they each have,,,,
These are not isolated bodies. They are gravitationally bound- in orbit around each other (or in more complex mutual orbits with other components of a galaxy cluster). That is, they are not two bodies moving in straight lines, but rather, two bodies, each in an elliptical orbit, where those orbits crossed each other closely enough that much of their extended volume collided. They will continue in their orbits (as modified by their extended nature and nearby galaxies) until they collide again, either merging, or continuing in similar cycles until they do.
Re: APOD: Arp 194: Merging Galaxy Group (2019 Mar 25)
orin stepanek wrote: ↑Mon Mar 25, 2019 12:37 pm
Is the little galaxy to the right of the three part of the merge?
It looks like it may be more distant from Earth; and I'm not seeing any disruption in it's arms! :?
The probability of two galaxies interacting (i.e., in close proximity in ALL 3 dimensions) at any one time is quite low.
The probability of three (or more) galaxies interacting is close to nil.
Why do you say that? Perhaps you mean "colliding" rather than "interacting"? After all, we see two or more nearby galaxies interacting in clusters all over the place.
Re: APOD: Arp 194: Merging Galaxy Group (2019 Mar 25)
De58te wrote: ↑Mon Mar 25, 2019 8:41 am
Uhm I might bring a controversy but doing a google search I found several sites including Wiki that say that the trio of colliding galaxies are in the top section. The two on the west side that are in direct collision and the smaller spiral galaxy on the east that is relatively unaffected. The arm of new star formation to the south is now thought to just be superimposed over the southern galaxy which isn't connected but just happens to be in the line of sight.
I read that too, but frankly, I doubt it. To me it is too much of a coincidence that a fantastic bridge emanating from a pair of interacting galaxies would just by chance happen to point at another extremely nearby galaxy, which, however, is not at all involved in the interaction.
We have analyzed in detail the photometric properties and the kinematics of the strongly
interacting system Arp 194. The main constituents of this system are a collisional ring system
(A194N) and an intruder (A194S) that have experienced an interpenetrating, head-on encounter a
few 108 yr ago. We have shown that tidally stripped gas is falling toward the center of the intruder,
A194S, and that it is fueling a strong nuclear and circumnuclear Starburst. Arp 194 is therefore
one of the few known objects for which convincing evidence of cross-fueling exists. Considering
that gas is usually confined in a “dynamically cold” configuration in disk galaxies, the Arp 194
case indicates transfer of orbital energy to the internal motion of gas during the the encounter. We
suggest that gas motions in superwind galaxies – which are mostly interacting systems – could also
be affected by the same mechanism.
Several aspects of the Arp 194 system deserve further scrutiny. The morphology of A194N
is fairly complex, and the distorted morphology of the ring as well as the bright arc of A194N
indicate the possibility of perturbations by a third party
Ann
Re: APOD: Arp 194: Merging Galaxy Group (2019 Mar 25)
Posted: Mon Mar 25, 2019 2:35 pm
by Chris Peterson
De58te wrote: ↑Mon Mar 25, 2019 8:41 am
Uhm I might bring a controversy but doing a google search I found several sites including Wiki that say that the trio of colliding galaxies are in the top section. The two on the west side that are in direct collision and the smaller spiral galaxy on the east that is relatively unaffected. The arm of new star formation to the south is now thought to just be superimposed over the southern galaxy which isn't connected but just happens to be in the line of sight.
There are two galaxies colliding in the northern component. The third galaxy visible in the north may or may not be involved (it looks like a background object to me). The galaxy that forms the southern component may or may not be interacting significantly with the pair (or trio) of galaxies to the north, or with their tidally ejected material.
Re: APOD: Arp 194: Merging Galaxy Group (2019 Mar 25)
De58te wrote: ↑Mon Mar 25, 2019 8:41 am
Uhm I might bring a controversy but doing a google search I found several sites including Wiki that say that the trio of colliding galaxies are in the top section. The two on the west side that are in direct collision and the smaller spiral galaxy on the east that is relatively unaffected. The arm of new star formation to the south is now thought to just be superimposed over the southern galaxy which isn't connected but just happens to be in the line of sight.
There are two galaxies colliding in the northern component. The third galaxy visible in the north may or may not be involved (it looks like a background object to me). The galaxy that forms the southern component may or may not be interacting significantly with the pair (or trio) of galaxies to the north, or with their tidally ejected material.
It looks like that to me, too.
Ann
Re: APOD: Arp 194: Merging Galaxy Group (2019 Mar 25)
Posted: Mon Mar 25, 2019 4:21 pm
by zendae1
Is there no way to perhaps see this amalgamation from 'the side'? We have had simulations that offer supposed views before. I do wonder what this looks like from any perpendicular location! From the real view, it looks like a train wreck.
Arp 194: Merging Galaxy Group
My final answer on the image scale is here:
