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Hubble Captures Colliding Galaxies
ackthpt writes: "I used to enjoy simulating model galactic collisions on my desktop but, CNN is featuring a find for the Hubble Space Telescope -- a collision between two galaxies 206 million lightyears away in the direction of the constellation Lyra. The picture is spectacular." It's this sort of thing that makes the Hubble's continued success, in light of it's famous earlier misadventures.
Helluva way to sell a science project.
It is a general misconception that the BB gives a "momentum impulse" the causes the expansion of the universe. Expansio of the U is expansion of space itself, whicih has nothing to do with "total momentum" or things like that.
Also there is no "point zero" in a BB for the current "favourite" flat universe model. The idea of a BB "exploding from a point into void" is also false. In the current Omega=1 (i.e. asymtotically expanding) universe, there is not even a concept of a "single point", i.e. the Universe came into being as infinite space in the BB (hard to visualize, but true). The simple proof is that an Omega=1 U is an infinite U, so extrapolating infinite back a finite amount of time (i.e. the age of the Universe) will still lead to an infinite universe. So the Universe has no boundaries (a single point, on the other hand, has a one-dimensional boundary so to speak very loosely).
Now, to answer the question of the original poster :
Colliding galaxies are common place. During the early universe, purturbations in the density field "seeded" the universe, causing stars and galaxies to form. Some purturbations are larger than others, and those which is larger than the so called "Jeans Mass" will collapse to form objects in the universe, creating a local overdensity of mass whose gravitational effects overcome the inherent "expansion" of space. Thus, we see many so called "galaxy clusters" in space, of which Virgo is the closest. In such clusters, galaxies are gravitationally bounded to each other, and eventually will collide to form one gigantic galaxy. (Such gigantic galaxies which are >1000 times more massive the the Milky Way are called cD galaxies and are not uncommon.)
Mode (3) smart-aleck mode. Press * to return to main menu.
End result: certainly I agree with you that media other than imaging have their place -- spectroscopy is the way to go for a lot of things. And other wavelength bands (as you say, IR, UV, x-ray, etc.) are important, too -- but don't knock the visual band! :-) And "nice pictures" and nice science aren't necessarily mutually exclusive.
the questions you pose don't have straightforward answers -- at least not ones that appear straightforward to me. But you can come up with some broad estimates.
A rough estimate of interstellar gas density is on the order of 1 particle per cm^3 -- a bit lower (0.1) between clouds, a bit higher (20) in diffuse clouds, much higher (10^3 - 10^6) in molecular clouds.
At these densities, it turns out that the likely effect of galaxy - galaxy collisions may be to strip out a large portion of the gas in both galaxies. Certainly the large-scale effects are enormous, and you can see them in our own Milky Way -- the galactic disk is "warped" upwards by as much as 4Kpc (12,000 light years) at large (20 kpc) distances from the nucleus, and this is thought to be a result of a tidal interaction long ago with the Large/Small Magellanic Clouds. Also, one of the most popular theories for how elliptical galaxies (or at least some elliptical galaxies) form is via collisions between spirals -- ellipticals have very little gas and dust. This theory is borne out somewhat by the fact that the concentration of ellipticals is much higher in rich clusters of galaxies than it is in the "field" -- as the density goes up, you would expect more collisions, hence more formation of ellipticals.
And hey, while we're at it, the process of gas stripping is a fundamental issue in the study of clusters of galaxies. As galaxies in a rich cluster move through the (very hot) intracluster medium, a shock develops and basically pushes a bunch of the gas out -- for a relatively simple physical analysis of this situation, see for instance Shore's book on Astrophysical Hydrodynamics.
But to get back to the original issue: if we were sitting on Earth when the MW collided with Andromeda, what would it be like? The answer is that I don't really know -- my hunch is that the local (in both space and time) effects would not be all that great; life around the Sun would probably get along just fine. But I don't know, because I'm too lazy to work out the problem. :-) (I'm sure this is in the literature somewhere, if you're truly dedicated -- try the Astronomy and Astrophysics data abstract service,.) Certainly the very long-term effects would be enormous, though.
Hope that helped clear things up...
While I'm far from an astronmer, I was wondering if we could somehow use the Hubble Space Telescope to study the planets in our solar system? Would Hubble give us a good view of the Outer planets, especially ones we haven't studied like Pluto or the new Kuiper belt object, or are they too close to us for Hubble to focus in on?
Doh!
Check out this link for a spectacular HST image of colliding galaxies taken in 1995.
Which is why we're not sure if there will be a big crunch or if the universe simply wimpers out spread out over an amazing distance. The balance between momentum and gravity is not well understood and without being able to accurate map all major bodies in space, there's no way to easily predict it.
And when the galaxies are done colliding, there's a lot of outcomes (I remember a good segment in Cosmos) -- One could 'eat' the other, as the picture in this article shows (where the core of one would be destroyed), they could combine cores if their movement vectors are slow enough, or both could completely kill each other leaving only a dense core of stars and several more flying away from each other and the core well above the rate which gravity could recapture them.
To me, what's amazing is the fact that there are no significant stellar events associated with the collision: no novas or the like, though I'm sure any local solar systems are majorly distributed.
"Pinky, you've left the lens cap of your mind on again." - P&TB
"I can see my house from here!" - ST:
Asteroids, gamma ray blasts, mass insanity, deadly viruses, divine intervention, etc.
Now we have to worry about colliding with another galaxy. What next?
Oh shit, there's an election next week.
This happened years ago. Why are we only hearing about it now?
We have our own collision coming up, with Andromeda, fairly soon (possibly within the lifetime of our own sun, something like 5 billion years from now). I wonder if it will look this cool, and who will be watching?
t ml has some more info, although I think this page is getting a bit dated.
http://oposite.stsci.edu/pubinfo/pr/97/34/af1.h
Pacer
Wow, that site is really cool. I remember going to it a long time ago, they certainly have kept it going.
Anyway, here's another great pic of 2 more galaxies collding.
http://www.phy.mtu.edu/apod/ap991109.h tmlAnd hell, I might as well borrow their html of the description:
Billions of years from now, only one of these two galaxies will remain. Until then, spiral galaxies NGC 2207 and IC 2163 will slowly pull each other apart, creating tides of matter, sheets of shocked gas, lanes of dark dust, bursts of star formation, and streams of cast-away stars. Astronomers predict that NGC 2207, the larger galaxy on the left, will eventually incorporate IC 2163, the smaller galaxy on the right. In the most recent encounter that peaked 40 million years ago, the smaller galaxy is swinging around counter-clockwise, and is now slightly behind the larger galaxy. The space between stars is so vast that when galaxies collide, the stars in them usually do not collide.
I simple question for the physics docterates here in /.
;)
How does this phenomenon fit into the expanding universe model? Perhaps my understanding of the model is too simplistic or flawed, but I would have thought that in general the galaxies would all be flying apart from eachother at some relatively high speed - making this apparent head on colosion a bit improbable.
Would it require that the two clusters have a similar enough trajectory and have just pulled towards eachother via combined gravitational effects over eons?
Is it likely that - even though stars won't colide - the two galaxies will become one double dense one - perhaps collapsing inward to a singularity?
Yes, this is probably better suited for Ask Slashdot, but there's no way that would ever get accepted let alone on the front page
All pretty facinating though...
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In most situations I don't think you would have a galaxy collision at that high of a speed. Since the universe is supposidly expanding, we measure most things as moving away from us with velocities close to c and sometimes for the really far objects many times greater than c (redshift in the light). The concept to note here is that it is the actual space that is expanding, and hence it looks like the galaxies are travelling that much faster. So I guess you probably wouldn't find galaxies colliding at near-c speeds. Maybe if the universe starts to contract it might become more common ;)
Now, If you could get two galaxies to approach each other at near the speed of light you would definately have to take relativity into account. What that would entail exactly is far above my head, since it lies in the domain of general relativity (of which I'm not well versed) but suffice to say I wouldn't expect anything less than an interesting situation - one of the interesting problems in physics is the n-body problem, which is just the problem of describing the motion of n different objects under the laws of general relativity. Suffice to say it hasn't been solved for even 3 objects, so I would suggest that relativistic galaxy collisions are probably pretty complicated events.
UBU
of the material universe is as yet unsolved.
In the vernacular of the profession it is refered to as " not well understood," which is code for " We havn't the slightest fscking idea."
Your question is thus actually not only not a trivial one, but a rather profound one that is one of the major questions that actual cosmologists wrestle with.
If the universe is expanding evenly, and all evidence shows that it is, WHY isn't the matter in it evenly distributed? Especially taking into account that for some time after the big bang all matter had so much energy and was composed of such small particles that no known attractive force would have had any significant effect on them.
Good question. DAMN good question. Its solution is left as an exercise for the student, and when you find it teacher wants a good look at it because he wants to know too.
I'll offer you my own best guess though. In the nanoseconds after the big bang space itself was 'clumpy,'which naturally created 'pockets' of congregated matter. As the universe expanded these 'clumps' of space and matter expanded into each other and evened out, leaving space a single entity, but leaving the clumps of matter, now attracting under subatomic, and then later, gravitational forces.
What made space 'clumpy.'
Glad you asked. That'll be 90% of your final grade because I havn't got an fscking clue.
I bet their insurance rates are gonna go WAYYYYY up. Maybe the two galaxies can settle without telling their insurance agencies... or maybe not since it's on CNN and they've probably already heard about it. Damn CNN...
:)
For fans of these kinds of pictures, Astronomy Picture of the Day is hard to beat. They have a this same picture for today.
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Infuriate left and right
Man, first we see a skull in outer space, and now we see a violent collision between galaxies. Doesn't anyone think of the children? We need to ban these violent space images before they turn the hearts of our children dark!
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Private Essayist
He has worked on simulation programs that model this exact situation - the most interesting is the example showing the collision of our poor galaxy with Andromeda! (It's actually going to happen - don't worry though, it won't be for a long time...)
UBU