Discussion: New View of Colliding Galaxies

[Fraser]

SUMMARY: The W.M. Keck Observatory in Hawaii took this photograph of two galaxies about to collide over 5 billion light-years away from us. The image was possible because of the new laser guide star system for adaptive optics which corrects the distorting effects of the Earth's atmosphere. This allows Keck to have nearly the same view as space-based observatories like Hubble. Both galaxies in this collision are mature, and seem to have used up all their gas. This won't create spectacular amounts of new star formation, which is what happens with less mature galaxies.

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[antoniseb]

This is great news about Keck being fitted with Laser Adaptive Optics. Now most of the sky can be observed with these incredible tools.

[Eric Vaxxine]

I would love to witnes such a collision...and we are looking so far into the past. If you were to approach these two..at the speed of light, would you see the collision happening at normal speed?

[antoniseb]

Originally posted by Eric Vaxxine@Jan 14 2005, 02:18 PM
If you were to approach these two..at the speed of light, would you see the collision happening at normal speed?

I'm not sure what you mean by normal speed.

If you were to travel toward them at nearly 'C', you'd see them collide much more rapidly. If you were going close enough to 'C', you could see the whole dance happen in a few minutes, even though it requires the movement of stars across tens of thousands of lightyears, and took hundreds of millions of years in the reference frame of those galaxies.

One of the downsides is that the light from these galaxies would be blueshifted into the high energy gamma ray range, so you wouldn't be able to see it, and might have to increase the budget for shielding.

[Greg]

I hadn't heard of the concept of dry mergers before, but the idea makes alot of sense. This sort of thing should be more likely in large galaxy clusters where large galaxies can get stripped of dust and gas by their numerous neighbors as they approach. Otherwise we are probably looking at two dwarfs merging. I woul dspeculate that if you waited long enough, the activity of the black hole might begin fueling star formation even in this relatively dead galaxy merger.