Galaxy SMASH!

By Phil Plait | August 7, 2009 12:00 pm

30 years ago, astronomers started playing around with making simulations of colliding galaxies. Computers were slow, so they could only keep track of a few hundred or thousand stars, which limited the models severely. The software had to keep track of every star, its location, velocity, and mass… the number of calculations is forbidding.

Things have come a long way. Now astronomers can track millions of stars using hydrodynamics codes, and then graphically display them giving them color, adding in dust, the effects of cloud collisions, supernovae… and the results are stunning.

Have a look. This is not just some animation; this is an actual result using complicated math and physics. It’s also lovely.

You can read more about this here.

Tip o’ the spiral arm to Pamela Gay, aka StarStryder, who is reporting from the IAU meeting in Rio.

CATEGORIZED UNDER: Astronomy, Cool stuff, Science

Comments (48)

  1. Logan

    Seems a big violent.

  2. The one time that violence is beautiful. At least when you’re far,far away.

  3. The explosion of stars in the first pass is amazing!

  4. Here’s an astronomy question for you: could a galactic collision like the one in the simulation result in “rogue stars”, stars that get flung away from either galaxy and into deep space?

  5. Phil, I bow to no one in my liking for the video or in my belief in simulation, but an “actual result” in simulation is what you get when your simulation makes predictions of unexpected behavior which are then confirmed by the real physical process. This is a lovely simulation, with lovely and fascinating results, but it has no more information content than it started with.

  6. Nicely done video. I’d choosed some other background music.

    Ok, I’m in some grunge phase right now… :/

  7. IBY

    Very cool video, with a nice background music. Although the collisions themselves are beautiful, it sacrifices the beauty of the spirals, turning the joined galaxies into a red elliptical galaxy. That is the fate of Milkomeda, I guess.

  8. dhtroy

    [to the tune of Monster Mash]

    They did the Mash.
    They did the Galaxy Smash.
    The Galaxy Smash!
    It was a Universal Clash!
    They did they Mash!
    It blew up in a flash.
    They did the Smash!
    It was the Galaxy Smash.

  9. Time for me to head to my galactic collision shelter in the back yard.

  10. NewEnglandBob

    Awesome and lovely.

  11. Overall a very impressive piece. It expresses my dreams from 20+ years ago when I once swam among the astro-fishes. Of course, I also did radio back then. I can’t help but think what the film would look like with the individual star version choreographed to the tune of “The Flight of the Bumble Bee” and the gas version with an acid rock background.

  12. Brando

    Ah, the things you can do with a PhD in Computational Physics.

  13. nawitus

    Darren, yes it’s possible, and we even know one of such: a star named SDSS J090745.0+024507.

  14. It seems that page was last modified June 2008. The internet’s a funny place.

  15. That’s awesome. I’ll have to watch the high-quality version, because even the HQ Youtube vid looked heavily artifacted (is that a word) on my nice monitor.

    It reminds me of my favorite screensaver (which I’ve been using for like 10 years), galaxies.scr. There’s a better version bundled in some KDE distros for Linux I think.

  16. Every time I see a simulation like this, I can’t help thinking of the inhabitants of the stars that get flung out into space.

    Imagine a technological civilization arising on a planet with a double milky way in the sky, and then figuring out that they’ll never get to visit their neighbors because two billion years ago their sun got ejected in a collision.

    Has anyone written a filk song about this yet?

  17. I read in a book somewhere that these galactic collisions will be the death of us all! Death!!!! DEATH FROM THE SKIES!!!

    Lovely background music. Reminds me a lot of the original Vangelis score from Cosmos – not the jangly stuff that was tacked on for the DVD release.

  18. StevoR

    Awesome! Thanks for posting this BA. 8)

    These sort of animations have indeed come along way quickly – as, not-so co-incidentally, have improvements in our computers.

    @ 20 Harold :

    I read in a book somewhere that these galactic collisions will be the death of us all! Death!!!! DEATH FROM THE SKIES!!!

    Well death could come from the skies but it won’t be in the form of Galactic collisions. Too long term a threat and our only risk here is the Milky Way – Andromeda Galaxy “fender bender ” in many aeons time hence.

    Unless a (possible?) merger with the Large or Small Magellanic Cloud ends up being much more destructive than currently considered – but even then it will be many millions of years away after we’re all dead and quite likely Humanity will already be extinct. As the book says.

    Good ref though! ūüėČ

  19. T.E.L.

    Very nice. Now compare to the treatment of colliding galaxies (at about 24:30) in this classic documentary film:

  20. bradley547

    If this were real, I’d have to envy the inhabitants of the outlying clusters for their night skies.

  21. HWRmaupin

    On the ‘read more’ page it mentions 2Myr per frame. For a laymans info, does that indicate that the merger would take many millions of years?

  22. T.E.L.

    HWRmaupin Said:

    “On the ‚Äėread more‚Äô page it mentions 2Myr per frame. For a laymans info, does that indicate that the merger would take many millions of years?”

    Oh yes. One revolution of a spiral galaxy out in our neck of the woods is on the order of 1/4 billion years. Collisions take even longer. These things are exercises in patience. :)

    Incidentally, our galaxy, the Milky Way, is destined to collide with the Andromeda galaxy several billion years from today.

  23. fatherdaddy

    Nice, but, I’d like to see how that simulation compares to reality. Show me the pictures of galaxies in some stage of this type of collision. They don’t look like what they’re showing me on Galaxy Zoo.

  24. It was very pretty but a little dull after the first pass.

  25. IBY

    Yeah, scientists call the hypothetical unified future galaxy “Milkomeda,” a bit corny, but appropriate enough.

  26. Okay, totally off topic, but is anyone else getting really sick of accidentally rolling over that Pfizer ad?

  27. Wow. astounding. I remember a much simpler bit like this from Cosmos. I remember being slightly horrified at the perceived destruction. I mean, an event like that would cause incalculable damage to millions of worlds.

    Wait, I’m still slightly horrified.

  28. marianna

    fatherdaddy….type in “colliding galaxies” into Google, click the Images tab, then Enter. That will provide you with what you seek. :-)

  29. Buzz Lightyear

    Gravity Rules!!!

  30. Torbjörn Larsson, OM

    Re Logan, I think these mergers are emviolinated enough. Are all galaxy neighborhoods this rough-and-tumble?

    an ‚Äúactual result‚ÄĚ in simulation is what you get when your simulation makes predictions of unexpected behavior

    Um, why?

    To confirm the simulations are correct, which for all practical purposes must be considered a result (that we reasonably understand the physics, say), wouldn’t all we need for them to match some other predictions (or observations)? Say, some distribution of merger times, if such a distribution exist in some meaningful way.

    If OTOH only unexpected behavior would be tested against not many simulations could be considered good models. That doesn’t seem to be the case.

    Incidentally, our galaxy, the Milky Way, is destined to collide with the Andromeda galaxy several billion years from today.

    IIRC some claimed somewhere that it will be one of the last observable major mergers.

    Is that so, and does that take the accelerating expansion into consideration to inflate [sic?] the rareness of the event? (I.e., the observable universe will then be less rich in galaxies, mergers or not, as they drop out of sight.)

    If it’s true, I don’t know if our descendants are to be congratulated for the long last act of the local volume, or not.

  31. Muzz

    Some of you folks might know Gravity 3D already;

    It’s a bit old now but you can do similar looking stuff with that, although not as physically/light accurate. Fun though.

  32. Andy Diamos

    Anyone know what song is played in the background? I’d be interested in getting it.

  33. Beautiful program there.

  34. Gary Ansorge

    31. Buzz Lightyear;

    Naw! Earth Rules,,,gravity sucks.

    Great imagery. Hydrodynamic codes? Hmmm, yes, I guess I see how that would apply.

    GAry 7

  35. marianna

    @Andy Diamos….the composer of the music is Nancy Ellen Abrams. She has a website of her music. You may be able to find that song there at expandinguniverse_dot_org. The credits of the simulation do not list the name of the song.

    If the song isn’t already on the website, there is an email address there that should eventually get to her.

    I downloaded the high definition version of this simulation from the original website Phil has linked. It is extraordinarily beautiful with each star seeming to be a separate point. If you like this low resolution youtube version, you really should download the HD version. Put it on full screen and sit in a darkened room. I would love to see this displayed in a planetarium. I think the beauty of the model, and the immensity of time and forces I can’t comprehend would make me weep.

  36. Patrik

    Hi and thanks for all the nice comments. It’s always fun when your work is appreciated.

    HWRmaupin: Yes, the total time shown in the movie is about 3 billion years.

    Marianna: I believe the name of the song is “All’s well that ends well”, and it’s on Nancy’s website. Unfortunately you can’t listen to it, though. And about planetariums, we have a project underway to bring realistic movies of simulations to planetariums, which should be pretty awesome.

  37. Gary Ansorge

    38. Patrik:

    Thanks Patrik, for all your hard work. It is beautiful.

    Gary 7

  38. marianna

    That is totally exciting about bringing these type of things to a planetarium, Patrik. Good luck with that. Please let Phil know the details when this comes about so he can notify us.

    This colliding galaxies animation is a wonderful blending of art and science. As one of Phil’s posts said, Science is Imagination, and you’ve certainly demonstrated that.

  39. Apocalypse Cow

    I’m fascinated with this video, especially the completely(to me) random element that forms on the upper left around 1:10, and collides with the main body around 1:25.

  40. Beautiful.

    I would really like to see this shown from the point of view of one of the stars that survive – like, and animation of what would be seen in the night sky of one of its planets, adjusted to point in the same direction every night, then speeded up (a LOT!)

  41. To Marianna and Andy Diamos — glad you liked the music. The scientists (collaborator Joel Primack is my husband) borrowed it from a song on my album, ALIEN WISDOM. And yes, Patrik’s right: the song is “All’s Well That Ends Well,” and it has words. ALIEN WISDOM is for sale at the wonderful independent artist website,


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