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Hubble Captures Colliding Galaxies 116

Posted by timothy from the like-a-blind-date-gone-wrong dept.
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.
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Hubble Captures Colliding Galaxies More

Hubble Captures Colliding Galaxies

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  • 206 million lightyears away ???

    Are we sure? Didn't General Motors make the mirrors in the Telescope? Did they take into account that "OBJECTS IN MIRROR ARE CLOSER THAN THEY APPEAR"?

    Hahahahahaha, I kill me.

    --
  • If, hypothetically, galaxies moved at any significant fraction of the speed of light, I would suspect that we wouldn't *have* any galaxies; gravity would work so slowly that agglomeration would never occur save for the rare head-on collision of two stars. Or, to put it more interestingly, your galaxy would now behave more like a gas at conditions where fusion is possible.

    Heck, at 0.9c, would stars even exist? Cold, hard planets, maybe, but I think even a small gas giant would be impossible.

    Even if galaxies could stay together at this speed, relatively won't matter; the probably outcomes of a galaxy that is moving at another at 0.9c (fixed reference point) is probably the same as both galaxies moving at each other at 0.9c (fixed reference point) (which in this case is simply as if one galaxy as moving at the other at 0.9x c assuming the other galaxy was fixed in space). Exactly the outcome probably is dependant on if it's a direct hit or close shave.

  • Nice pictures, but the real science.... (Score:4)

    by warpeightbot ( 19472 ) on Thursday November 02, 2000 @12:22PM (#654618) Homepage
    is in the infared, ultraviolet, and radio/x-ray detectors, which have nothing to do with the visual-spectrum pictures. All that big lens is there for is to sell the project to the taxpayers... which is, of course, why the big panic to replace that lens despite the fact it wasn't affecting any of the research projects... as one of the Mercury Seven astronauts said, "No Bucks, No Buck Rodgers." No pretty pics, no constituent letters to Congress saying "Save Hubble."

    Helluva way to sell a science project.

  • is here [stsci.edu]

    Lots of great pictures and hubble info. Of course, this should be in the related links. :)
  • I thought he was referring to: "Scientists with the Hubble Heritage created the image using archive data recorded by the Hubble telescope in 1996."

    I was curious about the same thing.
  • thanks for the link

  • Geeeeze I hate that. At least link to the source of the item, not some lame news story.

    Oh well I guess Tim's time is better spent doing important things ;).

    Here's the right link
    Hubble Homepage [stsci.edu]


    CC
  • Yeah, but what a way to go! =)


    --
  • Is it me... Or does that photo look like the head of (some of) our beloved Linux Penguin????
  • another lawsuit against Firestone tires.
  • 100km across? It's the Death Star! Run!

  • There is no Momentum generated by the BB (Score:4)

    by efuseekay ( 138418 ) on Thursday November 02, 2000 @12:49PM (#654627)
    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.)

  • 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?

  • This totally reminds me of something I once saw on xscreensaver!

  • 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 :-)

  • The key word is 'relativity'. Velocities are can only be measured relative to a particular frame of reference, and no frame of reference is considered preferred. Hence, there is no such thing as a 'fixed reference point'. You may see a galaxy zipping along at 0.9c, but someone travelling along with the galaxy would perceive it as standing still. The laws of physics don't change just because somebody else thinks you're moving quickly. Formation of stars and planets would be unaffected because they're all in approximately the same frame of reference.

    The question, as I understand it, relates to two galaxies coliding at 0.9c relative to each other (that is, my galaxy is standing still, but I think yours is about to run into me at 0.9c).

  • 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.

    Well, for one thing, it's space itself that is expanding. Things aren't flying away from each other in the same way that a billiard ball flies away from the tip of the cue.

    Now, in this expanding space, it is certainly possible for objects - whether they be galaxies or billiard balls - to collide with each other. It's just that galaxies are a little further apart than billiard balls.

  • The trouble isn't collisions between stars themselves, but between the interstellar medium in the two colliding galaxies. The space between stars is filled with gas and dust (albeit at densities which are many orders of magnitude lower than what you find in any terrestrial environment); when galaxies collide, the gas should probably behave in some interesting ways -- shocks, ionization fronts, etc. I won't even guess what that would do to any given place in one of the galaxies, on average, but my hunch is it wouldn't be good. :-)

    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.

  • Re:Yesterdays news (Score:1)

    by Anonymous Coward
    Satellites, including the Hubble Space Telescope, can collect so much data that it may take years for scientist to get around to it. For example the Voyager spacecrafts visited Saturn in the early 80s, (1981 I think), and discovered a couple new moons. In 1990, while digging through and examining the data from the Voyagers' visits, they found a another new moon. The Clemintine spacecraft which orbited the moon a few years ago, if my memory serves me, collected THOUSANDS of images a day. Do you think they have thousands of paid scientist working around the collect to look at and analyze all the data in real time?
  • the momentum generated from the Big Bang, ... all trajectories of all particals were away from point zero, ...

    There is no point zero. Space itself is expanding. There is no momentum in the conventional sense here.

    It's not like an explosion; in an explosion you can identify the point at the center that everything started at. There is no `central point' in the universe that identifies a `location' for the initial singularity (the Big Bang).

  • > 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.
  • Actually, if you look at this link [stsci.edu] it looks like a computer generated image. In fact when I take a second look at it, most CGI planets look better!

  • ... is hiding in the same pictures (Score:5)

    by mattorb ( 109142 ) on Thursday November 02, 2000 @02:24PM (#654638)
    Yes, they're pretty, but that doesn't mean they're scientifically useless. I've harped about this before, but the point is that there's a lot to be had from pictures like these; I don't know the details of this particular image, but in general, you can often get a sort of "poor man's spectroscopy" using narrow-band pictures. By taking images centered around some wavelength of particular interest (say the [OIII] doublet at 5007 angstroms, and hbeta at 4861), and doing some appropriate calibrations (subtracting the "continuum" level from the images, and calibrating to some absolute flux units), you can even get maps of the temperature or density of these objects. (Err, okay, so this doesn't really apply to this particular picture, but you get the idea -- I've used this technique successfully with HST WFPC2 imagery of planetary nebulae before.) In the particular case of colliding galaxies, there's also a lot to be said for "fuzzier" science, looking qualitatively at what happens in this kind of situation and trying to generalize it. You might look at the morphology of the spiral arms, or where you see the most star formation (by looking in Halpha) -- is the region of most star formation highly correlated with some aspects of the collision? Can you maybe infer something about the gas dynamics in this system, just by looking at enough pictures like this? The answer is yes, though of course there are limits.

    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.

  • Gravity sucks.

    registered the domain yet?

    so this thing happened 206 million years ago - how does one proof the theory of "light years" in any case? surely, they can calculate it using a bunch of mathematical expressions - but how does gravity affect the "line of sight" concept? maybe the light rays are being warped in some manner such that they seem to be further away than they really are?

  • Re:Question for the Physics doctorates (Score:3)

    by mattorb ( 109142 ) on Thursday November 02, 2000 @03:02PM (#654640)
    it's pretty interesting stuff, isn't it? :-)

    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, [harvard.edu].) Certainly the very long-term effects would be enormous, though.

    Hope that helped clear things up...

  • Hubble & Pluto/Kuiper Belt objects (Score:4)

    by Smitty825 ( 114634 ) on Thursday November 02, 2000 @11:49AM (#654641) Homepage Journal
    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?

  • galaxies colliding (Score:3)

    by blakduk ( 166007 ) on Thursday November 02, 2000 @11:52AM (#654642)
    Check out this link [stsci.edu] for a spectacular HST image of colliding galaxies taken in 1995.

  • Re:Question for the Physics doctorates (Score:5)

    by Masem ( 1171 ) on Thursday November 02, 2000 @11:53AM (#654643)
    You've got the competition from the momentum generated from the Big Bang, which slowly decreases over time due to 'friction', and gravitational acceration from the galaxies, which also slowly declines (in most cases) with increasing distances between galaxies. While within the first few nanoseconds after the BB, all trajectories of all particals were away from point zero, gravity began to overtake the momentum forces and lead to agglomeration of particles. In the case of galaxies at this point in time, some are close enough to have gravity overcome the increasing distances between galaxies, while others are too

    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.

  • Sorry, i don't have a physics doctorate, but your conception of "everything moving outward" isn't quite right. Our universe right now has a gradient towards moving outwards, but that doesn't mean everything is moving in a straight line from a single point. Remember, our universe is BIG. Try to imagine the imensity... No, bigger than that. Yet bigger than that. Now take that and raise it to the power of a hundred. Now what you're imagining is just our neighborhood. You see, when you have something that big, stuff gets pulled around and it goes in all directions. Since the biggest bang of them all (affectionately known as "The Big Bang", amazingly enough) was so powerful, everyone is still moving in a net outward direction, but that still leaves a variance. Think of an atomic explosion: everything is moving outwards very rapidly, but eventually it runs into stuff and changes direction. Okay, not the best analogy, but i think you can get the point by now.

    ~Chad
  • Let's let this troll die quickly....can't....resist...gotta throw in my .02

    Flynt has only alleged this and has no evidence to back the claim since the informant and him could not agree on a price. The woman at the center of the controversy denied ever having intercourse with Bush has blasted Flynt telling him to "put up, or shut up" with the facts on the Drudge Report [drudgereport.com] last week.

  • One more reson to avoid long term commitments (Score:3)

    by slickwillie ( 34689 ) on Thursday November 02, 2000 @11:57AM (#654646)
    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.

  • Re:Hubble & Pluto/Kuiper Belt objects (Score:3)

    by GiantKeith ( 225194 ) on Thursday November 02, 2000 @11:58AM (#654647)
    There are pics available of the planets, comets and other objects within the solar system on the Hubble site. Go to;

    http://oposite.stsci.edu/pubinfo/SolarSystemT.ht ml#Venus

  • 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

  • Why are NASA's pics so small and low quality.. give us some DECENT high quality digital images!!
  • They jammed our radar!
  • I'm guessing the stars with lens flare are nearby (relatively) stars -- part of our own galaxy -- that are "in the way". Because they are closer, they seem much brighter, so they are overexposed.
  • That's right, our galaxy is currently in the process of merging with the Large Magellanic Cloud, an irregular dwarf galaxy visible in the southern hemisphere.
    ^. .^

  • 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].


    --

  • We'd have enough time to hire a bunch of oil drillers, throw them into two spacecraft...
    Okay, I've had my fun. I'll stop now.
  • Well, I'm not a doctorate, but I have a simple explanation.

    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!

  • 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!).


  • 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?


    First of all, the Big Bang isn't a matter of everything in the universe exploding from point A. The Big Bang didn't happen at a point, it's the universe itself (not just the stuff in it, but spacetime itself) expanding everywhere at once. A common 2-D analogy is spots on the surface of a balloon, when you inflate the balloon the spots get further apart, the surface of the balloon has no center, every point is moving away from every other.

    As for why the paths of galaxies cross, although the universe is expanding and most galaxies are moving away from any given galaxy, locally that can be different, as gravitational attraction can bring things together if they are close enough to begin with.

  • You are right on that account, but it still rules out head-on collisions.

  • How do galaxies collide? Why do the paths of galaxies cross?

    If the galaxies are close enough to each other to start with, gravitational attraction will be sufficient to overcome the separation caused by cosmic expansion.

    Don't think of an explosion...the BB wasn't an explosion. Things aren't flung outward. In a certain very well defined sense, nothing in the universe is moving. It is the stuff (space) between the stuff (galaxies, etc) that is expanding, but it isn't "pushing" the galaxies apart. In a certain rigorous sense, to first approximation, the galaxies aren't moving (their cosmic coordinates are not changing with time, but the space between coordinates is increasing).

    Beyond the first approximation, since galaxies are kind of heavy, they are gravitationally attracted to each other. If when they were formed they were close enough to each other, their mutual attraction would cause them to be drawn together faster than the space between them could stretch, and they would gain speed towards each other.


  • > 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 [stsci.edu] are huge. [stsci.edu]

  • Turn the hearts of our children dark? George Bush is *definitely* not up on the technology. Hearts are made of meat, and the way to keep meat looking nice and red in the butcher shop display case is to add a small amount of sulfites to it. Duh.

    The internet doesn't cause it. Exposure to oxygen causes hearts of children, cows, and pigs dark.
  • I ran your comment through the fish, but I still couldn't figure out what the hell language you are talking in. Can someone please translate??
  • If you are talking about the cross-shaped spikes of light that come from the brighter stars, those are actually diffraction effects caused by the secondary mirror holder in the telescope. the smaller secondary is held in place by a mount shape like a + and this causes the diffraction spikes. they don't show up on the fainter stars so well because they are, um, fainter.
    ^. .^
  • Is this the height of arrogance or what? They turned an entire galaxy (two, in fact) upside down just because it looks nicer!

  • Yesterdays news (Score:5)

    by Anonymous Coward on Thursday November 02, 2000 @11:29AM (#654665)
    This happened years ago. Why are we only hearing about it now?
  • They both must report to their respective insurance companies of course. If the companies can insure SUVs it can't be that much more expensive to insure galaxies.
  • Couldn't they just digitize all the pics, put them online and tell people what to look for? If you find something and it turns out it is what they wanted, you get a free poster of that shot or something. Or they could write some software that could analyze the pictures and pick out the top 10% that are likely to be interesting.

    This could at least filter out the really obviously wrong stuff. They could then put the cruft online and let the public search through those for fun on the chance that the computers missed something.

    Thousands of pics per day would be difficult to go through, but sifting out the crap should not be THAT hard to do these days.

  • The really interesting part about this is that two galaxies can collide and the stars inside feel almost 0 difference. The reason being that the space between individual stars in a galaxy is so expansive compared to the actual mass of the star (and hence any sort of significant gravitational pull).

  • Heck I think it would be cheaper to insure galaxies. They have a much lower accident rate, and cause less damage when they colide, as they mostly just pass through eachother

  • 206 million years ago to be exact, but even /. obeys the speed of light. Still, it looks pretty impressive for what has been described as a two swarms of gnats passing through one another, except for that each gnat is 15 miles from the next.

  • Pay attention to those pictures! (Score:4)

    by Pacer ( 153176 ) on Thursday November 02, 2000 @11:36AM (#654671) Homepage Journal
    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?

    http://oposite.stsci.edu/pubinfo/pr/97/34/af1.ht ml has some more info, although I think this page is getting a bit dated.

    Pacer
  • What a marvellous image from the Hubble crew, yet again!

    And yet.. the scentists totally overlooked one of the most inspiring and self-validating discoveries about this cataclysm: they rotated the image Too Far! Yes, rotating the image just 90 degrees to the right instead of 180 degrees, the photo is quite obviously Tux.

    It may be interpreted as an Emperor penguin staring regally off into the reaches of space, or (more likely) his wings close against his body after their downbeat against the freezing depths he swims, our mascot is about to swallow a most appealing morsel of a miniature galaxy.

    Come to think of it, no matter which way you rotate this pic it is most definitely a penguin. Where did those scientists learn taxonomy? A golf club? Feh! Maybe they need to rethink their choice of OS?... And how do they know it wasn't just a penguin galaxy to start off with? The dopplers should show the little fishie galaxy fleeing most convincingly.
  • Oh wait, that wasn't colliding galaxies..someone smeared grape jelly on the lens!

  • Another great pic (Score:3)

    by discore ( 80674 ) on Thursday November 02, 2000 @09:35PM (#654674) Homepage

    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 tml [mtu.edu]

    And 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 [seds.org] NGC 2207 and IC 2163 will slowly pull each other apart, creating tides [utk.edu] of matter, sheets of shocked gas [slashdot.org], lanes of dark dust [slashdot.org], bursts of star formation [slashdot.org], and streams of cast-away stars [slashdot.org]. Astronomers predict [stsci.edu] that NGC 2207, the larger galaxy on the left, will eventually incorporate [stsci.edu] IC 2163, the smaller galaxy on the right. In the most recent encounter [harvard.edu] 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 [slashdot.org], the stars in them usually do not [nasa.gov] collide.

  • How much warning time do you think we would have?

  • Question for the Physics doctorates (Score:4)

    by Sawbones ( 176430 ) on Thursday November 02, 2000 @11:36AM (#654676)
    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...
  • So how come some stars show lens flare, and
    other stars are perfectly clear????

    Is the lens flare caused by the Hubble optics, or
    is it something in the path between the star and
    us???

    Thanks in advance!
    -Jim
  • Dick Clark..... and hosting a rockin new years eve special too.
  • I don't have a PhD .. but here's a rough guess at how it could have happened.
    Assuming everything was moving outward, some further out than others, then I suppose it's possible for galaxies to start slipping in towards each other as space-time bends and ripples. If a large star collapsed into a blackhole, it would create that dent in the "fabric of space/time".

    http://www.intothecosmos.com/faq/ is a spiffy sight for beginners on the subject of black holes.. http://www.ncsa.uiuc.edu/Cyberia/NumRel/GravWaves. html - and a good sight to understand gravitational waves.

    Hopefully someone with more education on the subject can give a better answer ;>
  • Well, I'm not a doctorate, but I'll take a crack at this one.

    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.

  • The question of the 'clumpiness'. . . (Score:3)

    by kfg ( 145172 ) on Thursday November 02, 2000 @12:03PM (#654681)
    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.
  • We'd have enough time to launch an anti-galaxy nuclear missile and destroy the rogue galaxy before it has a chance to collide with us and possibly wipe out all life on Earth.

    (note: it's funny)
    --
  • Was Captain Hazelwood at the wheel?
  • We all get lots of cool desktop wallpaper out of the deal.

    Judging by this story scientists get lots of entertainment value out it as well as they all try to decide what terrestrial or supernatural image the space photos most look like.

    Kinda like playing "clouds" with a multi billion dollar budget.

    They could save time and money by working smarter, not harder, if they all had their analysts sit on the arguments of image interpretation as well.

    Hey, maybe I should patent that idea.
  • Wow from the looks of it [cnn.com], the yellow one kicked the purple one's ass up and down the quadrant!
  • here you can find higher quality images you can scale down for your desktop:

    http://oposite.stsci.edu/pubinfo/PR/2000/34/pr-p hotos.html

  • Insurance rates (Score:3)

    by BMonger ( 68213 ) on Thursday November 02, 2000 @12:45PM (#654687)
    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...

    :)
  • 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).

    From what I understood of my Quantum I class, we cannot measure anything moving away from us at many times c. (Except, IIRC, for weird particles like neutrinos, which travel faster than c but never drop below it). The simple Einstein velocity addition formula states that v=(u1+u2)/(1+u1*u2/c^2). Thus, nothing is ever faster than c, no matter how many times you speed it up.
  • More information on this can be found here [nasa.gov].
    --
    *Condense fact from the vapor of nuance*
    25: ten.knilrevlis@wkcuhc
  • This space expanding principle, is this an intergalatic principle, or does it have intragalactic ramifications, too?
  • "We used to call it the golf club but then we turned it upside down and it looked like a bird," said Hubble scientist Keith Noll of the Space Telescope Science Institute in Baltimore, Maryland.

    Isn't science great!
  • We should also ban the public use of those nasty space words like: "moon", "black hole" or even "venus" 'cause it makes a link to nudity. Those scientists are a menace for the peaceful society.
    :)

    --
  • And this STScI page [stsci.edu] offers a much better look at today's new image than CNN's coverage does, and the science isn't dumbed down for the drooling masses.
  • Indeed I believe that is the currently favored hypothesis. It's as good as any other.

    One of the key questions is just when did physical law as we know it begin to exist. We KNOW that a short time before that it did not.

    The window of time in which such quantum effects could have produced clumpiness is actually very small. If quantum effects began either too early or too late after the big bang the hypothesis dosn't work, and the window is nano seconds. Dosn't mean it couldn't have happened that way.

    Since quantum fluctuations are also about the most random physical event we know of and happen on an increadably tiny scale, were THEY clumpy?
  • !duh? light travels faster than sound. so if you saw it yesterday, and you heard it today, it's about 45000km from mhere you are. Hey that's not too far away....
  • It probably would have no effect on us at all, the distances between 'solid' matter is so great, physical collisions between object would be extremely unlikely.
    but if another star was going to come dangerously close to us we would have only about 100,000,000 years to prepare.
  • >You've got the competition from the momentum generated from the Big Bang...
    > While within the first few nanoseconds after the BB...

    But it is still a theory. A theory with, apparently, very little hard evidence to back it up. And that's interesting becasue poeple have been studing it for a generation.

    Did you know that most universe scale computer models only take into account gravity. What about electromagnatism? "Nope".

    Check out The Big Bang Never Really Happened by Eric J. Learner for more info.

    "Lerner does a fine job poking holes in Big Bang thinking and provides a historical perspective as well, linking scientific theories to trends in philosophy, politics, religion and even economics...a most readable book." -- Chicago Tribune
  • Damn. If only I had moderation today. I could moderate this pile of crap "Troll".

    Hacker: A criminal who breaks into computer systems
  • Yes, Bush had his girlfriend have an abortion, but you can't blame Bush for it. He was high on cocaine.
  • ...and George Pal is dead so can't make a movie about it....

    Hacker: A criminal who breaks into computer systems
  • How does this phenomenon fit into the expanding universe model?

    The earth is not flying away from the sun, you are not flying away from the earth, comets and asteroids periodically come close enough to hit the earth. While on a universal scale, expansion is occurring, locally -- even between galaxies and galactic clusters -- gravity may be pulling things together.

  • Astronomy Picture of the Day (Score:4)

    by A nonymous Coward ( 7548 ) on Thursday November 02, 2000 @11:39AM (#654702)
    For fans of these kinds of pictures, Astronomy Picture of the Day [nasa.gov] is hard to beat. They have a this same picture [nasa.gov] for today.

    --

  • There are other factors, like how galaxys form, galaxy clusters, gravity, etc.

  • This Just In:

    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...

    =-=-=-=-=-=-=

  • I would assume that it would have intragalactic ramifications the same way that the gravity-attraction between you and your computer monitor has an effect.

    i.e. The effect is there, but on the given scale it doesn't matter.

  • What this is going to do to their insurance premiums...

  • Ban the universe (Score:5)

    by Private Essayist ( 230922 ) on Thursday November 02, 2000 @11:40AM (#654708)
    Man, first we see a skull in outer space [discovery.com], 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!
    ________________
  • Since someone already posted up a question for those who have more knowledge, I have one.

    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?

  • Old news, but interesting... (Score:3)

    by Mad Hughagi ( 193374 ) on Thursday November 02, 2000 @11:40AM (#654710) Homepage Journal
    Like it says in the article, much of this work dates back to '96. If you're really interested in this stuff, check out this page [utoronto.ca] made by one of the profs at the university where I work.

    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...)

  • Re:Hubble & Pluto/Kuiper Belt objects (Score:3)

    by toast- ( 72345 ) on Thursday November 02, 2000 @12:13PM (#654713)
    If you go to the Hubble pictures page you will find they did focus on Pluto and Charon..

    The pictures don't reveal much... not enough to wet my whistle, even though it's probably much better than they have ever observed. THe kuiper belt object is far too small to really get much from it.. i mean Pluto is a coupel thousand KM across (i believe) and this new object is like 100 KM

    Here [stsci.edu] Is a link to some pluto as seen by hubble.
  • Although universal expansion dominates over large distances, over short distances velocities are dominated by local gravitational effects - e.g. our galaxy and Andromeda are converging due to mutual gravitational attraction and may eventually merge.

    Galactic collisions or similar interactions are very common. Galaxies are large compared to the distances between them - e.g. Andromeda is about 750kpc away, and is on the order of 100kpc in radius (this is a bit fuzzy) so intergalactic distances are only a few times galactic sizes. In comparison, stars are tiny compared to separations, so stellar collisions are very rare indeed.

    The Arp catalog of unusual galaxies contains many interacting/colliding galaxies. Two famous nearby examples are M51 [nasa.gov] and Centaurus A [nasa.gov].

    (If anyone cares, I do have a doctorate in astrophysics, although I'm not working in astronomy.)

  • 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.

  • Re:Nice pictures, but the real science.... (Score:3)

    by Michael Woodhams ( 112247 ) on Thursday November 02, 2000 @01:52PM (#654724) Journal
    No, there is real science in visual wavelengths too.
    Yes, much of the 'real science' doesn't produce pretty pictures.
    Yes, some Hubble pictures are for PR rather than science. I doubt the time spent on PR pictures a significant percentage of total observing time.
    No, Hubble has a mirror, not a lens.
    Hubble does a lot of valuable science. One could debate whether the same amount of money spent on Earth would produce more/better science, but it isn't just job security for aerospace engineers.
  • 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.
  • Well it's not computer GENERATED, it's computer aided. Those pixels are likely the finest resolution hubble could make out at that time.

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