Explanation: Will our Milky Way Galaxy collide one day with its larger neighbor, the Andromeda Galaxy? Most likely, yes. Careful plotting of slight displacements of M31's stars relative to background galaxies on recent Hubble Space Telescope images indicate that the center of M31 could be on a direct collision course with the center of our home galaxy. Still, the errors in sideways velocity appear sufficiently large to admit a good chance that the central parts of the two galaxies will miss, slightly, but will become close enough for their outer halos to become gravitationally entangled. Once that happens, the two galaxies will become bound, dance around, and eventually merge to become one large elliptical galaxy -- over the next few billion years. Pictured here is a combination of images depicting the sky of a world (Earth?) in the distant future when the outer parts of each galaxy begin to collide. The exact future of our Milky Way and the entire surrounding Local Group of Galaxies is likely to remain an active topic of research for years to come.
Explanation: Will our Milky Way Galaxy collide one day with its larger neighbor, the Andromeda Galaxy? Most likely, yes. Careful plotting of slight displacements of M31's stars relative to background galaxies on recent Hubble Space Telescope images indicate that the center of M31 could be on a direct collision course with the center of our home galaxy. Still, the errors in sideways velocity appear sufficiently large to admit a good chance that the central parts of the two galaxies will miss, slightly, but will become close enough for their outer halos to become gravitationally entangled. Once that happens, the two galaxies will become bound, dance around, and eventually merge to become one large elliptical galaxy -- over the next few billion years. Pictured here is a combination of images depicting the sky of a world (Earth?) in the distant future when the outer parts of each galaxy begin to collide. The exact future of our Milky Way and the entire surrounding Local Group of Galaxies is likely to remain an active topic of research for years to come.
Given that to our eyes we only see the central part of Andromeda, and it's about the same brightness as the Milky Way, I'd expect this view to have both components look similar (and to our eyes, faint gray).
Re: APOD: Milky Way Galaxy Doomed: Collision... (2022 Jun 06)
Given that to our eyes we only see the central part of Andromeda, and it's about the same brightness as the Milky Way, I'd expect this view to have both components look similar (and to our eyes, faint gray).
I also think that the colors and brightness values were not exactly adjusted here and it is more a "picture collage". Still, I'm amazed at how far away the center of Andromeda is in the image shown. I would expect a lively interaction there already, with the effect of tidal forces, interacting satellite galaxies and a lot more active (red) star-forming regions than today...
Re: APOD: Milky Way Galaxy Doomed: Collision... (2022 Jun 06)
Posted: Mon Jun 06, 2022 9:07 am
by heehaw
Fasten your seatbelts !
Re: APOD: Milky Way Galaxy Doomed: Collision... (2022 Jun 06)
Posted: Mon Jun 06, 2022 12:08 pm
by De58te
Sheesh, I know it is the D-Day anniversary and all, but couldn't you have found a more gentler headline for today than Galaxy Is Doomed the Sky is Falling!
Re: APOD: Milky Way Galaxy Doomed: Collision... (2022 Jun 06)
Given that to our eyes we only see the central part of Andromeda, and it's about the same brightness as the Milky Way, I'd expect this view to have both components look similar (and to our eyes, faint gray).
I also think that the colors and brightness values were not exactly adjusted here and it is more a "picture collage". Still, I'm amazed at how far away the center of Andromeda is in the image shown. I would expect a lively interaction there already, with the effect of tidal forces, interacting satellite galaxies and a lot more active (red) star-forming regions than today...
Maybe Andromeda and the Milky Way are in the "Butterfly galaxies" stage of their merger, when they are still relatively undisturbed?
Ann
Re: APOD: Milky Way Galaxy Doomed: Collision... (2022 Jun 06)
Posted: Mon Jun 06, 2022 12:52 pm
by orin stepanek
It is a very entertaining video of the two galaxies merging! Still I
suspect that by the end of 7 billion years that the sun will have
burned out@ Mankind will probably be extinct by then; or evolved
into extra galactic travelers!
cats+entangled.jpg (50.59 KiB) Viewed 3832 times
Kitties are already entangled!
Re: APOD: Milky Way Galaxy Doomed: Collision... (2022 Jun 06)
Posted: Mon Jun 06, 2022 1:15 pm
by E Fish
The step by billion-year-step toward full collision is really interesting in the link given. The idea of an eventual collision is a fascinating one, if only because of the likelihood that there won't be any direction physical collision, only gravitational interactions.
(And the mountains in silhouette sure look a lot like the Tetons, although as Orin said, they're not likely to be around by the end.)
Re: APOD: Milky Way Galaxy Doomed: Collision... (2022 Jun 06)
Posted: Mon Jun 06, 2022 1:56 pm
by Keyman
Chris Peterson wrote: ↑Mon Jun 06, 2022 4:15 am
Given that to our eyes we only see the central part of Andromeda, and it's about the same brightness as the Milky Way, I'd expect this view to have both components look similar (and to our eyes, faint gray).
Spoilsport.
Re: APOD: Milky Way Galaxy Doomed: Collision... (2022 Jun 06)
Posted: Mon Jun 06, 2022 2:09 pm
by AVAO
E Fish wrote: ↑Mon Jun 06, 2022 1:15 pm
The step by billion-year-step toward full collision is really interesting in the link given. The idea of an eventual collision is a fascinating one, if only because of the likelihood that there won't be any direction physical collision, only gravitational interactions.
(And the mountains in silhouette sure look a lot like the Tetons, although as Orin said, they're not likely to be around by the end.)
Maybe it will be faster than we think until the battle of the titans begins.
Re: APOD: Milky Way Galaxy Doomed: Collision... (2022 Jun 06)
Posted: Mon Jun 06, 2022 2:21 pm
by Chris Peterson
E Fish wrote: ↑Mon Jun 06, 2022 1:15 pm
The step by billion-year-step toward full collision is really interesting in the link given. The idea of an eventual collision is a fascinating one, if only because of the likelihood that there won't be any direction physical collision, only gravitational interactions.
Gravity is enough! The problem is that planetary systems are inherently chaotic in their orbital dynamics. Once you get a star inside a light year or so of another, their planetary systems are likely to be perturbed, and it doesn't take much to shift a planet with life on it into an orbit that is incompatible with that life. Galaxy collisions, while producing no physical collisions, are likely very disruptive to systems that harbor life.
Re: APOD: Milky Way Galaxy Doomed: Collision... (2022 Jun 06)
Posted: Mon Jun 06, 2022 2:44 pm
by Bird_Man
It would be interesting to see the interaction between the black holes at the centers of each galaxy during the collision.
Re: APOD: Milky Way Galaxy Doomed: Collision... (2022 Jun 06)
Posted: Mon Jun 06, 2022 2:53 pm
by Chris Peterson
Bird_Man wrote: ↑Mon Jun 06, 2022 2:44 pm
It would be interesting to see the interaction between the black holes at the centers of each galaxy during the collision.
Most of the interaction is likely to be between the black holes and the shifting bulk mass of all the stars in both galaxies. The central black holes themselves represent such a tiny fraction of the entire galactic mass that unless they pass very close together, they probably won't have much influence on each other.
Re: APOD: Milky Way Galaxy Doomed: Collision... (2022 Jun 06)
Bird_Man wrote: ↑Mon Jun 06, 2022 2:44 pm
It would be interesting to see the interaction between the black holes at the centers of each galaxy during the collision.
Most of the interaction is likely to be between the black holes and the shifting bulk mass of all the stars in both galaxies. The central black holes themselves represent such a tiny fraction of the entire galactic mass that unless they pass very close together, they probably won't have much influence on each other.
Thanks Chris for this explanations.
This also answers the implicit question from my previous post regarding the degree of mutual interference between the core regions of the two galaxies. I am really surprised that the supermassive black holes are extremely small with less than 0.0043% for our galaxy and less than 0.1% for the Andromeda galaxy in terms of total stellar mass (excluding dark matter). Of course, there can also be other reasons why the eye of the Andromeda galaxy turns towards us.
AVAO
Re: APOD: Milky Way Galaxy Doomed: Collision... (2022 Jun 06)
Given that to our eyes we only see the central part of Andromeda, and it's about the same brightness as the Milky Way, I'd expect this view to have both components look similar (and to our eyes, faint gray).
I also think that the colors and brightness values were not exactly adjusted here and it is more a "picture collage". Still, I'm amazed at how far away the center of Andromeda is in the image shown. I would expect a lively interaction there already, with the effect of tidal forces, interacting satellite galaxies and a lot more active (red) star-forming regions than today...
I don't understand what exactly Chris meant by his post. Is the featured image of the much closer Andromeda galaxy an accurate depiction of what our eyes would see? I think he's saying that we'd only be able to see the core area of Andromeda with our naked eyes and so it would look a lot smaller than shown here.
Re: APOD: Milky Way Galaxy Doomed: Collision... (2022 Jun 06)
Chris Peterson wrote: ↑Mon Jun 06, 2022 4:15 am
Given that to our eyes we only see the central part of Andromeda, and it's about the same brightness as the Milky Way, I'd expect this view to have both components look similar (and to our eyes, faint gray).
I also think that the colors and brightness values were not exactly adjusted here and it is more a "picture collage". Still, I'm amazed at how far away the center of Andromeda is in the image shown. I would expect a lively interaction there already, with the effect of tidal forces, interacting satellite galaxies and a lot more active (red) star-forming regions than today...
I don't understand what exactly Chris meant by his post. Is the featured image of the much closer Andromeda galaxy an accurate depiction of what our eyes would see? I think he's saying that we'd only be able to see the core area of Andromeda with our naked eyes and so it would look a lot smaller than shown here.
Yeah, only the core is really bright enough for us to see naked eye. And the brightness is about the same as the brightest parts of the Milky Way.
Re: APOD: Milky Way Galaxy Doomed: Collision... (2022 Jun 06)
Chris Peterson wrote: ↑Mon Jun 06, 2022 4:15 am
Given that to our eyes we only see the central part of Andromeda, and it's about the same brightness as the Milky Way, I'd expect this view to have both components look similar (and to our eyes, faint gray).
I also think that the colors and brightness values were not exactly adjusted here and it is more a "picture collage". Still, I'm amazed at how far away the center of Andromeda is in the image shown. I would expect a lively interaction there already, with the effect of tidal forces, interacting satellite galaxies and a lot more active (red) star-forming regions than today...
I don't understand what exactly Chris meant by his post. Is the featured image of the much closer Andromeda galaxy an accurate depiction of what our eyes would see? I think he's saying that we'd only be able to see the core area of Andromeda with our naked eyes and so it would look a lot smaller than shown here.
Note in Lars Karlsson's picture how bright the core of Andromeda is. The core is what we would be able to see.
By the way, is that a black and white image? No, it's not, because you can see an obviously blue star some distance to the left of Andromeda. The blue star is Nu Andromeda, a B5V-type star with a blue B-V index of -0.14.
Ann
Re: APOD: Milky Way Galaxy Doomed: Collision... (2022 Jun 06)
Posted: Tue Jun 07, 2022 1:26 pm
by E Fish
Chris Peterson wrote: ↑Mon Jun 06, 2022 2:21 pm
Gravity is enough! The problem is that planetary systems are inherently chaotic in their orbital dynamics. Once you get a star inside a light year or so of another, their planetary systems are likely to be perturbed, and it doesn't take much to shift a planet with life on it into an orbit that is incompatible with that life. Galaxy collisions, while producing no physical collisions, are likely very disruptive to systems that harbor life.
Oh, true enough. When I teach about galactic collisions, I have to explain that this is likely a gravitational collision rather than a physical one simply because my students tend to think only in terms of something like a car crash. I used to have a simulation of a galactic collision where it showed stars simply flying off into intergalactic space as the two galaxies got close enough to interact. In the ways of YT, though, that simulation disappeared and I haven't found a good one to replace it yet.
Re: APOD: Milky Way Galaxy Doomed: Collision... (2022 Jun 06)
Chris Peterson wrote: ↑Mon Jun 06, 2022 2:21 pm
Gravity is enough! The problem is that planetary systems are inherently chaotic in their orbital dynamics. Once you get a star inside a light year or so of another, their planetary systems are likely to be perturbed, and it doesn't take much to shift a planet with life on it into an orbit that is incompatible with that life. Galaxy collisions, while producing no physical collisions, are likely very disruptive to systems that harbor life.
Oh, true enough. When I teach about galactic collisions, I have to explain that this is likely a gravitational collision rather than a physical one simply because my students tend to think only in terms of something like a car crash. I used to have a simulation of a galactic collision where it showed stars simply flying off into intergalactic space as the two galaxies got close enough to interact. In the ways of YT, though, that simulation disappeared and I haven't found a good one to replace it yet.
How about this one - it's less than a minute long, and shows the Milky Way gracefully colliding with Andromeda, with tens of thousands of stars (at least!) being flown off into space:
Click to play embedded YouTube video.
Re: APOD: Milky Way Galaxy Doomed: Collision... (2022 Jun 06)
I also think that the colors and brightness values were not exactly adjusted here and it is more a "picture collage". Still, I'm amazed at how far away the center of Andromeda is in the image shown. I would expect a lively interaction there already, with the effect of tidal forces, interacting satellite galaxies and a lot more active (red) star-forming regions than today...
I don't understand what exactly Chris meant by his post. Is the featured image of the much closer Andromeda galaxy an accurate depiction of what our eyes would see? I think he's saying that we'd only be able to see the core area of Andromeda with our naked eyes and so it would look a lot smaller than shown here.
Yeah, only the core is really bright enough for us to see naked eye. And the brightness is about the same as the brightest parts of the Milky Way.
Milky Way Galaxy Doomed: Collision with Andromeda Pending
Mankind will probably be extinct by then; or evolved 
