Did the Milky Way Have a Galactic Collision in the Past?

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Discussion Overview

The discussion centers on the possibility of past galactic collisions involving the Milky Way, particularly with the Andromeda Galaxy. Participants explore evidence for such events, the dynamics of galaxy interactions, and the implications of these encounters on stellar and galactic structures.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants express curiosity about evidence for past collisions between the Milky Way and other galaxies, specifically the Andromeda Galaxy.
  • One participant asserts that Andromeda is moving towards the Milky Way and will collide in the future, but has not done so in the past, emphasizing the vast distances between stars in both galaxies.
  • Another participant questions the timeline of the collision, suggesting that the timeframe should be in billions of years rather than millions, and discusses potential dynamical effects despite the low likelihood of direct star collisions.
  • There is a mention of gravitational interactions during galactic encounters causing significant disruptions, rather than physical collisions between stars.
  • Some participants note that while stars do not collide, galactic encounters could still have severe effects, such as triggering comet showers from the Oort cloud due to tidal perturbations.
  • Evidence is presented regarding the merging of dwarf galaxies with the Milky Way, specifically referencing the Sagittarius Dwarf Galaxy.
  • One participant discusses theories about the formation of spiral galaxies involving mergers of older galaxies, leading to the creation of spiral arms.

Areas of Agreement / Disagreement

Participants generally do not agree on whether the Milky Way has experienced past collisions with other galaxies, particularly Andromeda. Multiple competing views remain regarding the nature and effects of galactic interactions.

Contextual Notes

Participants express uncertainty regarding the timelines of galactic collisions and the specific effects of gravitational interactions. There is also a lack of consensus on the implications of these interactions for stellar dynamics.

Aidyan
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I'm wondering if there is any evidence that our own Galaxy 'crashed' with other Galaxies in the past (e.g. with the Andormeda Galaxy?). Is there any evidence for this? Googled... but couldn't find much. If so can someone point me at some research on this?
 
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My understanding is that the Andromeda galaxy is moving toward our galaxy and will pass through it some time (millions of years- I wouldn't worry about it!) in the future so has NOT passed through it in the past.

I also seem to recall (people with better knowledge can correct this) that the distance between stars in both galaxies is so great that there would be relatively little disturbance in either galaxy.
 
HallsofIvy said:
My understanding is that the Andromeda galaxy is moving toward our galaxy and will pass through it some time (millions of years- I wouldn't worry about it!) in the future so has NOT passed through it in the past.

I also seem to recall (people with better knowledge can correct this) that the distance between stars in both galaxies is so great that there would be relatively little disturbance in either galaxy.
Millions?? I hope you mean billions, since 'millions' would be just 'tomorrow' in evolutionary time. Sure, stars do not collide in such a 'collision-less' encounter, but I'm not at all sure that it would have no dynamical effects. Just look at the pictures of other colliding galaxies.
 
HallsofIvy said:
I also seem to recall (people with better knowledge can correct this) that the distance between stars in both galaxies is so great that there would be relatively little disturbance in either galaxy.

A collision between two galaxies would not be like a collision in a normal sense as most of the disruption would be caused not be physical collisions between stars and stuff but by the gravitational mayhem as the galaxies gravitational fields move through each other.
 
Aidyan said:
I'm wondering if there is any evidence that our own Galaxy 'crashed' with other Galaxies in the past (e.g. with the Andormeda Galaxy?). Is there any evidence for this? Googled... but couldn't find much. If so can someone point me at some research on this?

Yes, we have evidence that several dwarf galaxies have merged (or are in the process of merging) with our galaxy. See, for example, the Sagittarius dwarf galaxy.
 
Aidyan said:
Millions?? I hope you mean billions, since 'millions' would be just 'tomorrow' in evolutionary time. Sure, stars do not collide in such a 'collision-less' encounter, but I'm not at all sure that it would have no dynamical effects. Just look at the pictures of other colliding galaxies.

Right, STARS don't, but galaxies do. Very few stars in either galaxy will have actual collisions, although some solar systems will be perturbed.

EDIT: hm ... I think I may have misunderstood your post. Perhaps you were already saying that stars don't?
 
Yes, star's don't collide. But I think that nevertheless a galactic encounter could have devastating effects on life. For example the tidal perturbation would probably trigger huge comet 'showers' from the Oort cloud.
 
Aidyan said:
Yes, star's don't collide. But I think that nevertheless a galactic encounter could have devastating effects on life. For example the tidal perturbation would probably trigger huge comet 'showers' from the Oort cloud.

Yeah, sure could be. It IS surprizing though how empty galaxies are.
 
From http://en.wikipedia.org/wiki/Andromeda–Milky_Way_collision
While the Andromeda Galaxy contains about one trillion (1012) stars and the Milky Way contains about three hundred billion (3x1011); the chance of even two stars colliding is negligible because of the huge distances between each star. For example, the nearest star to the Sun is Proxima Centauri, about 3x107 solar diameters (4x1013 km or 4.2 ly) away. If the Sun were a ping-pong ball in Paris, the equivalent Proxima Centauri would be a pea-sized ball in Berlin (and our galaxy would be about 1.9x107 km wide, about a third of the distance to Mars).
 
  • #10
Right now I think that there is a dwarf galaxy called the Sagittarius Dwarf Galaxy that is colliding with the Milky Way. I think that some theories for the formation of spiral galaxies consist of older galaxies merging together and forming the central bulge, which is full of older stars, and then the violence of that interaction causes the spiral arms to form.
 

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