Smash galaxies together… for SCIENCE!

By Phil Plait | November 30, 2009 9:26 am

galaxyzoomergerMost people think that science is done by, well, scientists. Men and women in white lab coats buzzing away in a lab somewhere.

There are a lot of stereotypes in that description, but the important thing to note here is that science can be done by anyone. You don’t need to be in a lab or at the eyepiece or up to your knees in pond scum to be able to make important contributions to science.

In fact, with all the digital data coming down from telescopes, just in astronomy alone there are marvelous ways anyone can pitch in. Galaxy Zoo is just such a "citizen science" project — you can classify galaxies at home, on your computer, perusing their vast database of starry island universes. It’s highly addictive — over 50,000,000 galaxies have been classified by the public so far!

And now the folks behind Galaxy Zoo (including my friend Chris Lintott) have a new product that will eat up all your spare time: Galaxy Zoo Mergers. Instead of normal workaday galaxies, this new project displays two or more galaxies undergoing violent collisions, many of which will one day result in the two merging into one bigger galaxy. Our own Milky Way has suffered through many such mergers, growing over time to its present size. Mergers are a basic process in galaxy evolution, and are vitally important to study.

In GZM, you are shown a collision image, and you can fiddle with various parameters in a computer model of the event, eventually trying to get your model to look like the actual image. You can change the galaxies’ masses, direction, speed, angles, and number of stars in the simulation — and it uses real physics to determine the shapes of the galaxies as they interact gravitationally! As you tune the simulation, the result is displayed in real time so you can see how well you’re doing (and I’ll note it ran smoothly, even on my three-year-old Mac laptop). Here’s an example I played with:

galaxyzoo_merger

As you can see, I didn’t do too badly. By making the left galaxy lower mass and changing the direction and speed of the collision, I was able to get a simulation that is reasonably close to the real image.

I’ll note that while it’s not too hard to get started, it does take a little bit of patience — but after only a few minutes I was colliding away. And if it’s not easy to start, it’s impossible to stop. Like Galaxy Zoo itself, this is the crack cocaine of the internet. If you value your spare time away from the computer, you may not want to get involved with this!

I of course mean that in the best way: merging galaxies is fun. There is something ultimately cool about letting billions of stars interact over vast scales of distance and time… and there is real science here. By creating a database of such events, scientists can use the data to look for trends. Are most collisions at certain angles? That might imply how the galaxies collide when they are in clusters, gigantic collections of thousands of galaxies. Are the mergers high speed, low speed? Are the victims wildly disparate mass galaxies, or usually two of roughly the same mass? What are the highest and lowest speeds of collision?

All of this is important to know. The more basic info we get about collisions, the better we can understand them. For scientists studying collisions, it’s almost hopeless to get enough simulations for this, but by crowd-sourcing it they get all that for free. The data from Galaxy Zoo indicate that people are quite good at classifying galaxies with only minimal training (done right there on the site in a couple of minutes), and we can hope the same is true for mergers; they’ll run tests to make sure.

So everyone wins here. Scientists get data they can use to understand the Universe, and the public has the knowledge that they are contributing to that understanding… and having fun all the time.

Science! I love this stuff!

CATEGORIZED UNDER: Astronomy, Cool stuff, Science

Comments (18)

  1. Gary

    Yes, it is cool. But what is simple at first, gets harder as you try to fine-tune the simulations.

  2. jim moore

    How does the simulation handle dark matter and dark energy? Because galaxies spin so fast that they would fly apart without dark matter and dark energy holding them together.

  3. I’m pretty sure I tried that same one. I got pretty close but ruined it when I tried tweaking the “depth” parameter. That and the “speed” parameter are really sensitive.

  4. And if it’s not easy to start, it’s impossible to stop. Like Galaxy Zoo itself, this is the crack cocaine of the internet. If you value your spare time away from the computer, you may not want to get involved with this!

    Too late…

  5. Mike Wagner

    I’m afraid to try. Not something a person with any level of OCD wants to go near. :)

  6. I am wondering what happens in the aftermath of a collision, of say, 2 spiral galaxies. Would they, over time, regain the spiral shape, or would they be permanently changed?

  7. Gary Ansorge

    Hmmm, smashing galaxies. Sounds like a band.

    Reminds me of the old joke about why particle physicists make lousy biologists(“Now, let’s carefully analyze the resultant debris,,,”).

    Beautiful images. Mike Wagners comment should be a warning to all. If I get started on this, I’ll have no time to put my contrarian viewpoints on this blog and THEN where will Y’All be? Missing my indescribable wisdom, that’s where.

    I think I might go hear a band called Smashing Galaxies,,,once,,,

    Gary 7

  8. Simon

    Oh, thanks a lot. I have a day job, you know! Tweaking galaxy simulations = not doing my day job… :-)

  9. Torbjörn Larsson, OM

    I think I might go hear a band called Smashing Galaxies,,,once,,,

    Great idea, do what they did with the big bang and express characteristic frequencies as sound. The big bang is a dying chirp, but does smashing galaxies go snap, crackle and pop?

  10. Gary Ansorge

    9. Torbjörn Larsson, OM Says:

    “,,,does smashing galaxies go snap, crackle and pop?”

    More like SMASH, BOOM, CRASH, SCREECH!!!

    MAybe I’ll skip the band.

    Gary 7

  11. @Michael L. they generally become more eliptical galaxies (if I remember my lessons correctly). I assume you are wondering about the eventual fate of our own Galaxy?

  12. tyler

    “Most people [____] that science is done by, well, scientists. Men and women in white lab coats buzzing away in a lab somewhere.”

    You forgot a word in your first sentence. =)

  13. Tom

    I like Chris Lintott. Not least of all for his co-hosting of one of, if not THE longest running astronomy TV shows here in the UK, The Sky at Night, still presented (though he’s starting to show his age hence, I imagine, Chris’ presence) after 52 years by Patrick Moore. Moore is a famously eccentric Englishman who has dedicated well over half of his 86 years to popularising and educating the public on astronomy, and I love him for it. How many people still on TV today actually *met* Einstein? ;)

  14. I promise I’m not just commenting because Tom was nice (thanks Tom), but I thought it was worth answering a couple of the questions.

    1. Dark matter – is included. In fact, the simulations assume that everything in the galaxy behaves like dark matter, in the sense that it has gravity but doesn’t form stars, emit light or so on. We’ll go back and run simulations with baryonic (normal) matter in once we know how the gravitational picture unfolds. Dark energy, on the other hand, doesn’t matter on these scales. Once two galaxies have attracted each other like this, their mutual gravitational pull is much more significant than the expansion of the Universe or dark energy.

    2. Trying to work out what is going to happen to these systems is the point! Once we have a matched simulation, we can let it evolve and find out under what circumstances adding two spirals together gives you an elliptical.

    Thanks for all your help.

    Chris

  15. Nigel Depledge

    The BA said:

    You don’t need to be in a lab or at the eyepiece or up to your knees in pond scum to be able to make important contributions to science.

    Wait, what?

    Now you tell me!

  16. #13 Tom:
    For the record, The Sky at Night is not only the longest running astronomy or science series; it’s the longest continuously running TV series, of any kind, in the world!
    In those 52 years, Sir Patrick himself has presented every episode except one; he missed just one due to illness, after an unbroken run of 47 years.

  17. Elias Tandel

    Woooah! I just love’em mergers. Large Hadron What?

  18. Ubiquitous

    You can change the galaxies’ masses, direction, speed, angles, and number of stars in the simulation — and it uses real physics to determine the shapes of the galaxies as they interact gravitationally! As you tune the simulation, the result is displayed in real time so you can see how well you’re doing

    What about those of us who don’t have the millions of years to spare to watch? :-)

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