APOD: The Colliding Spiral Galaxies of Arp 271 (2013 Aug 25)

[geckzilla]

How do we know that these two galaxies have not already collided and are now emerging into their post collision states?

'Cause they aren't crazy enough looking. End of layman's explanation.

...Actually, it's all about simulations, looking at other galaxies in various states of merging and making an informed guess, otherwise known as a hypothesis.

[Chris Peterson]

'Cause they aren't crazy enough looking.

I just sat down to construct a nice reply invoking gravity, shock fronts, and tidal distortion, but on second thought I think your answer will do just fine.

[rstevenson]

Just curious, how long would it take using conventional technology to travel perpendicular to the plane of our galaxy before a reasonably good view could be had to confirm that the milky way is a barred galaxy?
Conversely, if we had a starship that could erase the limitations of speed and time, how far would one have to go to confirm the same?

Just glancing mentally at the geometry, I'd say you'd want to rise up about half the diameter of the Milky Way or about 50,000 light years at a minimum. Given that our current fastest spacecraft can't even manage 1% of the speed of light, that means you're going to have to wait at least 5 million years for the picture to be taken, and another 50,000 or so for it to get back to you -- assuming: we could make a camera and spacecraft that would last 5 million years and a comm system that could deliver the picture, and that there'd be anyone here to care to receive it.

Given the magic of star trek-level technology, we might get an answer in a century or so.

Rob

[Chappy]

There sure are allot of active star forming regions in both of these Galaxies spiral arms, makes for a beautiful image. It would be so cool to revisit this collision in another million years to see how things have changed.
Dang, Space is such an amazing place!