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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.)
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It really won't matter, because the odds that any star would come close enough to our system to either A) directly hit anything, or B) even disturb the orbits of any planet with gravitional pulls, would be so remote that it would not be worth calculating.
As well, the "collision" would probably take several hundred thousand years, so defining a point of collision would be relatively pointless.
Lastly, if anything negative (IE: the Earth was going to be creamed by a slow moving star) was going to happen, we would have a simply goofy amount of time to do anything we could. On the flip side, there really isn't anything you can do to stop a star from doing whatever it wants to (stars are stubborn that way, something to do with the "inertia section" in their "Laws and Code of Honour For Stars" book). Aside from a *mass* migration (to, say, somewhere nearby, like the Greater Magellanic cloud), the human race would simply have to put their collective heads between their collective knees and kiss their collective asses goodbye. In about half a million years.
My question is this: how do galaxies collide? I mean, I thought that everything started at point A, there was this Big Bang thingy, and everything flew apart from the point A. If that was the case, it should be impossible that anything flung out of the explosion should be on an intersecting path with anything else from the explosion. Think of it this way: isn't it impossible for the light from the sun to "collide" with other sun light, because they start at the same point, and move outward and apart from each other. Why do the paths of galaxies cross?
"Don't mind me cutting myself on Occam's Razor"
did what we're seeing occur 206 million years ago?
Short answer: yup :-)
Does the expansion of the universe affect that amount of time?
Overly simplistic answer: not really. If you have the math, you might want to look at a book on general relativity, find the chapter on the Robertson-Walker-Friedmann cosmological model, skip the section on solving the Einstein equations, and read up about comoving coordinates.
Slightly better answer: For "comoving" observers, the time on their clock is the same as the time it takes light to travel a given number of light-times (light-minutes, light-seconds, etc...). Thus, if we were comoving, the light-time would be exactly the clock time. We aren't actually comoving observers, but we aren't moving too fast, so it is a good approximation to pretend that we are.
In other words, is our "now" the same as the "now" currently at that point in space?
Yes, if we are both comoving. Both "nows" are at the same cosmic time, but it makes no practical difference, since their "now" won't be apparent to us for 206 million years. Now, if both are non-comoving, then no, the times their clocks would measure would differ.
I guess what I'm trying to ask is can you compare clocks that are 206 million light years apart
You can send a signal from one clock to the other (Einstein, among others, invented a procedure to allow comoving observers to do so), but light must still travel the distance between them, so there is no instantaneous way to do so.
So, like the rest of your question asked, if both clocks are synchronized and are comoving, they will always remain synchronized. Otherwise, no.
I don't know if I'm phrasing this comprehensibly
I'm almost certainly positive that my answers aren't comprehensible, so it doesn't much matter :-)
As a side note, people have tried to create maps of the "acceleration vectors" of galaxies in the local universe, but not by studying motions over time -- rather, you look at the density distribution of matter and try to infer a potential and acceleration field. Yes, it's a little sketchy.
> the gas should probably behave in some
> interesting ways
Like a cosmic wind that literally blows the Earth off course?
The shocks would be very interesting; I am assuming you mean the earth being hit with what would amount to a cosmic wind gust.
I understand your points, and how this could be devastating, but is the density of the ISM really that powerful? Granted that all of the arguements you have put forth are based on the density of the ISM being sufficient, but, in your opinion, do you think the ISM is that dense. I would not, at least, for *most* of the effects.
"it's a little sketchy" - Yes, but brilliant, nonetheless?
Thanks for the response! You are making me think; which, outside of comments in this article, is something that no-one else today can claim today.
"Don't mind me cutting myself on Occam's Razor"
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.
I'm not a PhD yet, but I am an astrophysics graduate student - and my research is in galaxy formation. As one of the other responses said, this is a pretty complicated (and not totally solved problem), but the general idea is known, thanks to some really interesting theories and lots and lots of computer simulations.
It all goes back to the big bang. After recombination (when quarks and other fundamental particles recombined to make hydrogen, helium, etc.), the distribution of matter in space wasn't completely uniform (ie some parts were denser than others), and as the universe expanded and things cooled off, these denser areas became centers of gravitational attraction and became the first stars and clumps of stars. In turn, these clumps attracted each other and formed galaxies, and so on and so forth, giving the really cool hierarchical structure that we observe today. This is known as the bottom-up theory of galaxy formation, by the way. For more information, and if you like math, check out _Physical Cosmology_ by Peebles. Another excellent book is _A Short History of the Universe_ by Joseph Silk. It's at the level of Stephen Hawking's popular books, and really interesting.
Anyhow, things that are relatively close together (such as our galaxy and those in our local group, and other clusters of galaxies) will stay near each other, since the gravitational potential holding them together is much, much stronger than the expansion of the universe. Since all of the galaxies in a cluster are moving around as well as being attracted to all of the other galaxies, their orbits are generally very complicated and can't be modelled analytically. Probability dictates that it is practically inevitable that a few will hit each other. As a matter of fact, the general consensus in the cosmology community is that most large galaxies (such as Andromeda) were created when smaller galaxies collided.
As far as the fates of the colliding galaxies, individual stars are generally unaffected since, after all, there's a lot of empty space in a galaxy. However, tidal forces typically distort or completely destroy at least one of the galaxies, or make them into one larger galaxy. Another interesting effect is that the hydrogen gas clouds in the galaxies are disturbed, which causes lots of new stars to form during or right after the collisions. A huge singularity wouldn't form because the density of stars, gas, etc. isn't high enough (by many orders of magnitude) for that to happen. If two big stars happen to collide, it is entirely possible that a black hole will form, though I don't know how probable that is.
Of course, what I have said is merely the "prevailing wisdom" of cosmologists. Computer simulations (including my own) support this theory, but the debate certainly isn't over.
-Brian
They jammed our radar!
"Don't mind me cutting myself on Occam's Razor"
Simple question: What is the nature of time? [heh]
Since the collision is 206 million light years away, then did what we're seeing occur 206 million years ago? Does the expansion of the universe affect that amount of time?
[Warning: I'm not sure exactly how to phrase what I'm thinking for the following] And more esoterically, I know that time and space are intertwined in complex ways. Does it make sense to talk about what is happening at that point in space "now" in time, relativistically speaking? In other words, is our "now" the same as the "now" currently at that point in space?
I guess what I'm trying to ask is can you compare clocks that are 206 million light years apart, or does the nature of space/time make it that two clocks are considered synchronized when you can compare the signals from two clocks received at light speed? [ugh -- I don't know if I'm phrasing this comprehensibly].
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Sometimes it's best to just let stupid people be stupid.
Gravity sucks.
As for them ending up as a double-galaxy singularit, I don't think that they'll become a singularity, but current theory considers the probability/liklihood, that most normal galaxies contain a central black hole. Becomming a black hole would require more than two black holes passing through each other on a cyclical basis.
I would expect that they'll end up intertwining over time. If we're alive a couple hundred million years from now, we might even see the next iteration. (presuming that the sun hasn't melted down by then). I guess that that leads to the next question:
Are there any signs of globular clusters (or whatever galexies turn into post-collision) going for a second try?
`ø,,ø`ø,,ø!
Free Software: Like love, it grows best when given away.
Erm, "friction"? With what?
"Gravitional acceration from the galaxies"
Assume you mean "accreation", how would accreation slow anything down to a measurable degree? And where are the galaxies picking up this extra mass? Pre "Big Bang" proto matter litter?
So, at the end of your first paragraph, you are saying, that the galaxies are NOT colliding head on, but are "glancing through each other", so to speak.
Galaxy self-canabilism, on the grandest scale, in the end, would cause another Big-Bang type singularity, correct?
I thought we had a rather detailed map of all of the galaxies in a 20 megaparsec sphere, including a lot of information regarding their velocity vectors and mass. Admittedly, acceleration vectors would take a tremendous amount of time gather.
>though I'm sure any local solar systems are
> majorly distributed.
Actually, I would disagree with you on that point. We don't feel any a affects of the tritary system only 4-5 light years away (the Centauri system). Ergo, calculate the odds of any star of, let's say, three times the sun's mass of the star coming within 5 light years of the Sun during a collision. Change the numbers to fit this equation:
Force of Gravity = product of masses * the gravitational constant / the distance squared
OR:
F = KmM/(d^2)
with:
F = force needed to affect the earth's orbit
M = mass of rogue star
m = mass of earth,
K = gravitational constant (what ever it is)
d = distance between the two
Assume the F to move the earth out of orbit by, say 0.1% is a constant (and average and scalar, for now), we would have
d^2 = (mK/F) * M
To make matters ease, we replace mK/F, all constants, with one constant, X.
d^2 = X*M
OR (d^2)/M = X
Now, with M = 3*our sun's mass, d = 5 light years, which is the minimum safe distance/mass ratio:
25/3*SunMass = X
So as long as the ratio between the distance of the rogue star and the rogue star mass is less or equal to 25 light years squared divided by three times the sun's mass, everything is okay (keep those units straight!).
"Don't mind me cutting myself on Occam's Razor"
> Why are NASA's pics so small and low quality..
You are mistaken sir. It's CNN and CBS who are the bandwidth cheapskates.
NASA's pics are huge.
Is this the height of arrogance or what? They turned an entire galaxy (two, in fact) upside down just because it looks nicer!
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.
here you can find higher quality images you can scale down for your desktop:
p hotos.html
http://oposite.stsci.edu/pubinfo/PR/2000/34/pr-
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...
:)
More information on this can be found here.
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*Condense fact from the vapor of nuance*
25: ten.knilrevlis@wkcuhc
*Condense fact from the vapor of nuance*
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
After switching to another glass cleaner, scientists discovered that the galaxies were no more than large deposits of space-bird poop on the main lens. Apparently, the birds had recently migrated to Mercury and had passed the telescope after ingesting too much Martian Beef Ravioli...
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No sig
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
What would happen if the galaxy movement was greatly sped up, like .9c (where c is the speed of light)? Would relativity become a greater factor?
- I don't care if they globalize against free speech. All my best free thoughts are done in my head.
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
Galaxy collisions are very common, actually. Not only is the Milky Way absorbing the Large Magellenic Cloud (why do you think it looks so large? It's friggin' close) over time - they're inspiraling, that is - but the Milky Way is also currently devouring a smaller irregular galaxy - or, to be more specific, *has* devoured, we're just seeing it now.
I wish I could provide URLs for proof for those, but I mainly remember them from the papers, which were published about two years ago (the small irregular galaxy, that is, the LMC's fate is well known).
But those are kindof like speed bumps for a galaxy- in fact, that's how they grow - and evolve, actually, which of course, makes sense. What about a major collision between us, and say, Andromeda?
Wait a few billion years - it's happening. Give it a few billion more, and the Milky Way and Andromeda will be one very large elliptical galaxy. Of course, the Sun could just as easily become ejected from the merging galaxies, and that's not entirely out of the question, since we're near the rim and have significant angular momentum about one of the colliding centers of mass.
But, then the question comes, who cares? What does it matter? The answer is, truly, very little. Being in a galaxy is great for forming stars, but once a star is formed, it has no more need to stick around in a galaxy. So, being ejected doesn't matter. Neither does the impending galactic collision - considering the massive amount of space involved, the main effect of galactic collision is nothing more than heating up a bit of space dust.
You are arguing against one of the central result of one of the most active area of cosmology based on a single popular book written by someone who has no background training in hardcore physics. It's called appealing to authority, and here, it's false authority.
Mode (3) smart-aleck mode. Press * to return to main menu.
Well it's not computer GENERATED, it's computer aided. Those pixels are likely the finest resolution hubble could make out at that time.