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Bigger Galaxy Eats Smaller Neighbor

Posted by michael on from the tastes-like-chicken dept.

Mr.Happy3050 writes "CNN is reporting here that the large galaxy Centarus A absorbed a smaller neighboring galaxy 200-400 million years ago. The absorption created a line of blue stars thousand of light-years across."

23 of 40 comments (clear)

  1. Terrorism? by misfit13b · · Score: 5, Funny

    CNN also reports that they have heard from certain "federal sources" that this attack may in fact have been either connected to Saddam Hussein or the Al-Quida network.

    1. Re:Terrorism? by gehrehmee · · Score: 5, Funny

      I can't believe we just let this happen. The Milky Way must wake up to the world of galactic terror that's been surrounding us for years. It's now clear that the Local Group of galaxies is paralized to act on this clear and present threat. I hearby propose that all solar systems hand over power to Sol, so as to promote a centralized bureau Homegalaxy Security.

      Subsequently, all solar systems may be subject to thorugh examination by the Hubble Space telescope, and any other mechanisms available to us (which we cannot disclose for threats of this information falling into enemy hands) to ensure that any threats from within our galaxy are squashed. If you're not involved in galactic terror, you have nothing to hide.

      Remeber: In the war against galactic terror, you're either with us or against us.

      --
      "You know, Hobbes, some days even my lucky rocketship underpants don't help" -- Calvin
    2. Re:Terrorism? by PhilHibbs · · Score: 2

      Fortunately for the galaxy in questions, the Statute of Limitations protects it from prosecution, unless it can be brought under the jurisdiction of Michigan.

  2. The trouble with those little galaxies by JUSTONEMORELATTE · · Score: 5, Funny

    On about 500 million years later, you're hungry again.

  3. When I get hungry by isorox · · Score: 5, Funny

    I usually go for a mars bar, not an entire galaxy!

  4. Is it "Eat a Star" month and nobody told me? by greenhide · · Score: 4, Informative

    Look at this other article posted on CNN.com yesterday, about an astronomer (Feng Ma) observing a black hole eating another star.

    It looks like CNN was actually a little late on reporting this actually, here's an article on the 7th about the same event. Actually, it looks like Feng Ma actually observed the "belch" the black hole gave out after consuming the star.

    --
    Karma: Chevy Kavalierma.
  5. A question by Syncdata · · Score: 5, Interesting

    I was of the understanding that, were two galaxies to cross through each other's paths, that it would be more or less clean, due to the sheer ammount of space in comparison to the matter in the galaxies.

    --
    "Inattention makes clowns of us all" -Bean
    1. Re:A question by drudd · · Score: 5, Interesting

      It is true that none (or very few) of the stars which make up the two galaxies will collide. But the gas will collide (often leading to starformation, or the stripping of gas from galaxies).

      Also, all components are interacting gravitationally, so the structure of the galaxies does not survive "cleanly." Instead there are very interesting features, tidal tails, spherical shells, and usually the major fractions of the two galaxies settle down into a single system very different from the two progenitors (assuming the two initial galaxies are roughly the same size).

      Doug

      --
      Venn ist das nurnstuck git und Slotermeyer? Ya! Beigerhund das oder die Flipperwaldt gersput!
    2. Re:A question by u19925 · · Score: 2

      Within the galaxy if there is a civilization, they want get affected by this merger. Nothing spectacular at small scale. But at large scale, the whole galaxy morphology can change. Also the interstellar gas density increases which gives rise to rapid star formation with different characteristics then the older stars. It is just like two clouds colliding. The gap between two molecules in a cloud is huge. Even then, when they collide, they can produce lighting and thunderstorm and rain.

    3. Re:A question by Alsee · · Score: 2

      Did you just say that when interstellar gas collides it can produce RAIN!? chuckle

      -

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      - - You can't take something off the Internet! That's like trying to take pee out of a swimming pool.
  6. Simulation by mbrubeck · · Score: 4, Funny

    So what? From my experience running 'xlock -mode galaxy', this sort of thing happens all the time.

  7. Old news by shrikel · · Score: 5, Funny
    absorbed a smaller neighboring galaxy 200-400 million years ago

    Come on, editors. This is getting ridiculous.

    --
    Any sufficiently simple magic can be passed off as mere advanced technology.
    1. Re:Old news by teamhasnoi · · Score: 2

      Just wait 100 million years and they'll repost it.

    2. Re:Old news by falzer · · Score: 2

      In other news, man invents the wheel!

  8. Question by photon317 · · Score: 4, Interesting


    Now I can see a large galaxy colliding with a smaller cluster of dwarfs or whatever it was - but at the end of the article they talk as if it's a fairly well-known fact that the Milky Way and Andromeda will collide at some point in the distant future. Now, I seem to remember the classic marker-spots-on-a-balloon explanation that so long as the universe is expanding each galaxy continues to get further and further away from each at a high speed (near light speed but not quite?). Is this simplistic explanation wrong, and in fact large stable galaxies can and do collide into each other, or are they talking in terms of after a theoretical turning point where theuniverse starts shrinking again?

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    11*43+456^2
    1. Re:Question by drudd · · Score: 5, Informative

      The simplistic explanation doesn't take gravity into account. Think of it as ants walking around on the surface of a balloon which is being blown up.

      So if the ants stand still, they all get further away from each other (the classic analogy).

      Next level of complexity: the ants are walking around with some random direction and speed. Some will be getting closer to each other, as long as their velocity is greater than the spread of the balloon's surface between them (i.e. distance grows by one inch, but they walked an inch and a half, so the two ants are now half an inch closer than they were initially).

      Now you add in gravity (I don't know how to express this with ants... let's just say they feel some desire to walk towards each other, and that desire is related to their distance). So nearby ants feel some force which causes them to walk towards each other. If they are sufficiently close, this force will cause them to move faster towards each other than the inflation of the balloon is moving them apart (as in the second case).

      This is why the stars in galaxies don't fly apart as the universe expands. The gravitational force at those scales is much greater than the expansion.

      Doug

      --
      Venn ist das nurnstuck git und Slotermeyer? Ya! Beigerhund das oder die Flipperwaldt gersput!
    2. Re:Question by jaakkeli · · Score: 5, Insightful

      "Now I can see a large galaxy colliding with a smaller cluster of dwarfs or whatever it was - but at the end of the article they talk as if it's a fairly well-known fact that the Milky Way and Andromeda will collide at some point in the distant future."

      Yes, they will collide.

      "Now, I seem to remember the classic marker-spots-on-a-balloon explanation that so long as the universe is expanding each galaxy continues to get further and further away from each at a high speed (near light speed but not quite?)."

      Remember that in the real world galaxies aren't fixed marks drawn on a balloon. They are free to move around space any way they want to in addition to this "cosmic recession" due to expansion of space. So, in terms of the balloon analogy, the galaxies can move freely around the surface of the balloon while it's inflating; their velocity will be the sum of this recession velocity (which they would have if they weren't moving on the balloon) and the velocity at which they are moving on the balloon.

      Another important thing to note is that not every galaxy is receding at the same velocity. If you measure the velocities from one galaxy, those galaxies which are further away from this one will appear to have a larger velocity. The recession speed is given by a formula known as Hubble's law:

      v = H*d

      where v is the velocity, H is a constant (known as the Hubble constant - Google will give you a numerical value) and d is the distance from the Milky Way (or any other galaxy where you could be measuring these things) to the other galaxy. In addition to this velocity (which won't nowhere near light speed unless the other galaxy is *very* far away), the galaxy can have any other velocity due "ordinary" movement through space, but these velocities are randomly determined (they are due to collisions with other galaxies and such "ordinary" things), so on average galaxies will tend to follow Hubble's law and recede from us. Also, since the recession velocity increases in proportion to distance, distant galaxies will follow this law much better than nearby galaxies, so there will be much fewer exceptions.

      OK, so that should be clear by now. Now, forget everything I just said! The above is all true and nice to know, but it isn't at all relevant for the Milky Way and Andromeda. I just wanted to make a few other things clear before moving on to this one...

      Andromeda and the Milky Way do not recede at all due to expansion of space. They are bound together by gravity, just like (for example) the Earth and the Moon. If you still like to think in terms of the balloon analogy, imagine that some of the marks (which would have to be something a bit more substantial than pen marks) would be tied together with a piece of rubber band. As the balloon inflates, the marks would try to separate from each other, but the band would pull them back together. So, things that have some kind of a force holding them together ("bound systems") don't expand while most of the universe does.

      In fact, speaking about galaxies in the balloon analogy is somewhat misleading, since they are usually gravitationally bound to many other galaxies, so galaxies really aren't the objects Hubble's law is all about. For example, the Milky Way is bound to Andromeda, the Magellanic Clouds and a huge number of other galaxies which have much more cryptic names. Together these are all known as the "local group" of galaxies. Some of its members are much further away from us than Andromeda and still not receding from us.

      Oh, and I must say one thing: the balloon analogy is nice and quite illustrative, but taking it too seriously can lead to some pretty horrible misconceptions. You shouldn't trust too much on any conclusions drawn from it.

    3. Re:Question by jaakkeli · · Score: 5, Insightful

      "This is why the stars in galaxies don't fly apart as the universe expands. The gravitational force at those scales is much greater than the expansion."

      Some nitpicking: this is not right. You can't do this kind of a "strength comparison" between some force and the expansion of the universe. In fact, whether or not some system holds together in the process has absolutely nothing to do with the strength of the attractive forces between its individual parts.

      For example, consider yourself just standing on the surface of the Earth. You are bound to the Earth by its gravity. To travel to outer space you would need to somehow obtain enough energy kinetic to climb out of the Earths gravitational well. If you somehow managed to do this and would start traveling around in space with a huge speed (greater than the Earths "escape velocity"), you would still feel the effect of the Earths gravity, but the difference would be that you'd have enough energy to escape the well and travel where ever you'd want to go. Similarly, the Moon is bound to the Earth since it doesn't have enough kinetic energy to escape the Earths potential well.

      For another example, consider an electron and a proton traveling around freely in space close to each other. There is of course an attractive force between the two of them. The most important question then is whether they have enough energy to overcome this attractive force and travel freely to infinity or will the attractive force be strong enough to keep them together. If they are moving too fast for the force to hold them together, they'll move around as independent free particles; if they are moving so slowly that the force will always be strong enough keep them together they will form a bound state. (This particular bound state is better known as the hydrogen atom.)

      The essential question here is whether or not the system is bound or not: if it is, the distance between its parts will not increase due to the expansion of the universe; if the system isn't bound, the distance will increase. This has really nothing to do with the strength of the interaction, but depends entirely on whether the internal forces are strong enough to hold the system together, given the energies of the internal parts.

      The Milky Way and Andromeda are gravitationally bound in this sense: they don't have enough energy to escape each others potential wells, so they don't recede from each other when the universe expands. While the space between them expands, gravity will still always have the same distance-dependence, so it will keep the galaxies together exactly the same way.

      (The collision is likely to change all this, though. At least some parts of our two galaxies are going to acquire enough kinetic energy to escape the new system, whatever that is going to look like.)

  9. Re:A question - answered. by saskboy · · Score: 5, Insightful

    As an Anonymous person here said, the stars interact because of gravity, so even though there is some space between the stars, the two [?] galaxies that come out of the collision will look nothing like they did when they entered it.
    For a smaller scale comparision, imagine 2 solar systems colliding. The odds of the planets, and stars hitting are not 100%, but you can bet the orbits are going to be drastically changed.

    --
    Saskboy's blog is good. 9 out of 10 dentists agree.
  10. Dust clouds by Gerry+Gleason · · Score: 2

    The bands of blue stars suggests that there is quite a bit of large star formation triggered by the collision. It could be either or both dust clouds from one galaxy triggered into star formation by star masses in the other, or merged clouds that are now above some critical density.

    1. Re:Dust clouds by Alsee · · Score: 3, Interesting

      The perfect gas law is a pretty poor approximation of interstellar gas. Gravity, magnetism and radiation pressure have substantial effects. The gasses is also generally not in equlibrium. Remember these are distances of thousands of light years, an effect like a nova can create disruptions and "winds" that last millions of years. A galactic collision would throw it far out of equilibrium for 100's of millions of years.

      -

      --
      - - You can't take something off the Internet! That's like trying to take pee out of a swimming pool.
  11. Just like what happened to Tadpole and The Mice... by mraymer · · Score: 3, Informative

    Here are some pretty Hubble pictures of galaxies feeding. Both the Tadpole galaxy (UGC 10214) and The Mice (NGC 4676) are the result of merging galactic masses.

    --

    "To confine our attention to terrestrial matters would be to limit the human spirit." -Stephen Hawking

  12. Yankee bastards. by rjw57 · · Score: 2

    Surely this should be 'neighbour'

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    Rich