The long expected end of the Galaxy is the collision with Andromeda, in a symphony of gravity, interstellar matter and a whole load of destruction and subsequent creation of a monster galaxy. However, through my subscription to New Scientist I read of emerging evidence that may perhaps indicate we do not yet fully understand the chain of cosmic events – so I will share these ideas with you. The ideas are complex, so I am presenting them simply as I do not have the full picture myself yet. If I find the time to drill into the detail I will update you.
The disturbance in the current understanding came from the observation that the break away galaxies around the edge of our galaxy appear to have some sort of correlation… a rough alignment that suggests they may be a trail from some form of cosmic collision. So an alternative view is that two galactic discs came together, colliding with great force leaving tails of dust much like that you might see in the tail of a comet but on a grander scale. If you imagine two spinning discs being pulled into each other, colliding, and then ripping away from each other – leaving parts of one in another and vica vera. Then when the dust began to coalesce around the edge of the galaxy they form the breakaway galaxies which are observed when we look at the universe today.
Whist it sounds far-fetched, and I stress there is much more work to do in this area, what would be most interesting is it would require a total rethink of dark matter. In our current models the dark matter creates random scatterings of galaxies – not correlated ones like the skies seem to suggest. But dark matter seemed so neat, and mysterious so the topic wasn’t explored too much further.
In 2005 some scientists made the important observation that there in fact exists some very similar structures of dwarf galaxies around the poles of Andromeda. This brings forward the incredibly bold idea that Andromeda and our Galaxy have already collided.
However: This theory is defeated by time. That is, there is not enough time since the big bang for the galaxies to have collided and to have pulled apart to their present point – which means the observed correlations are meaningless? Rarely. This just leads to more questions we need to address.
Currently there are some very exciting and very complex areas of research that are trying to test and prove this area. The most notable is modified Newtonian dynamics.
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