When galaxies collide

[worthj1970]

I was looking at UniverseToday.com slideshow, and came across a pic of NGC2207, where a smaller galaxy is colliding with a larger one. My question is, how would we know if a similar event was happening on the far side of our own galaxy? I assume there are 'shock waves' (or something of the sort) that would be felt, right?<br /><br />Thanks!<br /><br />John W.<br />

 

[bbrock]

I don't think so. The stars are so spread out, they would essentially pass through each other. There would be some collisions, but on a galactic scale, it would take millions of years. Imagine a cloud of marbles, each one several miles apart, merging into one cloud. Although there may be billions of them, the event would not be that dramatic or sudden. Remember, one light year is still ~ 6 trillion miles. Most stars are separated by several hundred or thousand LY's. <br /><br />Bill

 

[bbrock]

I did some rough calculations to put the scale of distance in perspective. If you have two stars that are ten times the diameter of our sun, one light year apart. this would be equivalent to two 1/2" marbles separated by 5.92 miles. The closest star to our sun is Alpha Centauri which is 4.5 light years. If these two stars were the size of 1/2" marbles, the separation between them would be 26.6 miles. <br /><br />It would be tough playing marbles on a galactic scale.<br /><br />Bill

 

[worthj1970]

Thanks for the replies (and feeding my curiosity:>)!<br /><br />John W.

 

[thalion]

If another galaxy were colliding with the Milky Way on the opposite side from us, we would definitely notice it. There would be a strong infrared signal from dust, probably much stronger radio activity, and many supernova signatures visible across the spectrum.

 

[qzzq]

Worthj1970 posted: --<i>I assume there are 'shock waves' (or something of the sort) that would be felt, right?</i><br /><br />ESA's webportal featured a nice artist's impression of merging galaxies, shockwaves included: <ul type="square">Massive merger of galaxies is the most powerful on record<br /><br />23 September 2004<br />With ESA’s XMM-Newton observatory, an international team of scientists has observed a nearby head-on collision of two galaxy clusters that has smashed together thousands of galaxies and millions upon millions of stars. It is one of the most powerful events ever witnessed. Such collisions are second only to the Big Bang in total energy output.</ul> <img src="/images/icons/cool.gif" /><br /> <div class="Discussion_UserSignature"> <p> </p><p>***</p> </div>

 

[astrophoto]

Just wait a few years (ok more than a few!) and see what happens when we hit Andromeda. And I think we're currently swalling a small galaxy as we speak.

 

[nexium]

The shock waves from the collision 70,000 lightyears from here on the far side of our galaxy will take 700,000 years to reach Earth, if these waves propagate at 1/10 th the speed of light. Do we have satellites that detect shockwaves, extremely weak as they have traveled great distances? I recall one probe detected faster than solar wind particals, apparently coming from beyond our solar system. Is this possibly a shock wave?<br /> The infrared from dust collisions will arrive in 70,000 years at the speed of light.<br /> Perhaps more correctly, we are seeing now, what happened 70,000 years ago.<br /> I do not expect an increase in super novas, as Jupiter size collisions with stars will stir up the core, bringing fresh hydrogen to the core thus delaying and/or weakening the supernovas about to occur. If the black hole forms gradually over millions of years in the core of a star (instead of quickly) the star would have a strange spectra just before it winked out, as the black hole finally captured the last of the star from the inside.<br /> The acreation disk of an off center black hole should bring fresh hydrogen deep into the core allowing part of the core to continue to fuse hydrogen. Gravitational collapse would be local, instead of core wide. Is it possible that this is why some stars are variable?<br /> Novas should double, as the density will be about double where the galaxies over lap. Neil