When beauty and science collide

By Phil Plait | March 31, 2011 7:00 am

I’ve been posting a lot of nice astronomical images lately, but sometimes one comes along and blows me completely away. How fantastically gorgeous is this?

Holy Haleakala! [Click to galactinate.]

That spiral galaxy is NGC 6872, and as you can see in this image from the Gemini South telescope it’s getting its clock cleaned by the littler spiral — IC 4970 — just to the right. The two are undergoing a galactic collision, a colossal event playing out over hundreds of millions of years. NGC 6872 is currently the victim here; its spiral arms are clearly distorted and being flung wide by the gravitational interaction. However, the smaller IC 4970 will be the ultimate loser in this battle: it will fall into the bigger galaxy, be torn apart, and eventually consumed in its entirety, becoming a part of NGC 6872. Bigger galaxies do this to smaller ones all the time; the Milky Way is in the process of eating several small galaxies even as you read this (I have details in articles linked below; see Related Posts).

This pair has been observed by other telescopes, including the composite picture here of images by the Spitzer Space Telescope (which sees in the infrared), The Very Large Telescope (visible light), and Chandra (X-rays), which I rotated to match the Gemini shot and rescaled a bit.

Interestingly, in the Chandra image the smaller galaxy has a bright point source core blasting out X-rays, indicating it’s an active galaxy, meaning the supermassive black hole there is actively gobbling down matter. That’s not obvious in the Gemini image because dust in the galaxy’s core hides the energy, but X-rays can get through it. Astronomers think there’s not enough material in IC 4970 to feed the hole, so it must be stripping off cold gas from the bigger galaxy. You can see a hint of that in both images here.

Another cool thing about this image is that the target galaxies were actually suggested by high school students for a contest! The Australian Gemini Office organizes the contest every year, which is to find scientifically important and aesthetically pleasing astronomical targets for the monster telescope. In 2010 the Sydney Girls High School Astronomy Club won (pictured). My pal Travis Rector then organized the observations and put together this incredible image.

And the new contest for 2011 is already underway. If you know some high school students who’d like the chance to point an 8 meter telescope, then send them to the contest website! Imagine having that on your college application.

Image credits: Sydney Girls High School Astronomy Club, Travis Rector (University of Alaska, Anchorage), Ángel López-Sánchez (Australian Astronomical Observatory/Macquarie University), and the Australian Gemini Office; NASA/CXC/SAO/M.Machacek, ESO/VLT, NASA/JPL/Caltech

Related posts:

Awesome Antennae!
Hubble grills a confused galaxy
Andromeda born out of a massive collision?
Evidence and theory collide with galactic proportions
In galactic collisions, might makes right

CATEGORIZED UNDER: Astronomy, Pretty pictures

Comments (42)

  1. Robert E

    WOW! That image is stunning.

  2. Peter

    “Collide????”: coincide!

  3. Nigel Depledge

    Most excellent!

  4. Allen L

    Wow. A new candidate for the desktop.

    I just noticed that there have been no trolls complaining about BA straying away from astronomy topics.

  5. mike burkhart

    Amazing ,When I see pictures of other galaxys I wonder how are they like our Milky Way ? How are they different ? How many planets may be orbiting the stars ? and most important is there life on any those planets ? I think we may never know it would take millons of years to reach other galaxys and I do’nt see a way we can detect planets and other things in other galaxys useing the same methods we use in our own galaxy. (one more thing we will never find out :whats on the other end of a black hole you would never survive a trip into one so you never find out if black holes are connected to white holes, or if they leed to other universes or parts of this universe.)

  6. Conshycrush

    Never say never Mike!

  7. What effect will a collision like that have on their insurance rates?

  8. DrBB

    @3 Peter Says: “’Collide????’: coincide!”

    So this touches on a confusion I have about this whole galaxy collision thang. Various pop-TV accounts of such matters (I’m looking at you, “History” Channel) always portray ’em in the most dramatic and doomsday-ish terms, a mega-catastrophe on an inter-galactic scale. But somewhere I seem to have picked up a comment of some astronomical authority to the effect that these “collisions” are from the point of most sentient beings living on the planets in question (we assume scads of such aliens, because why not) these would be largely theoretical rather than practical events because the lion’s share of any galaxy’s make-up is empty space. Stellar orbits get shoved around in veeeerrrrrrryyyy slow motion, some new star forming regions spark up and you wouldn’t necessarily want to be living in one of those neighborhoods, but on the whole it’s not like you’re sitting there getting battered by planetary collisions every five minutes or millenia, stuff crashing into other stuff etc.

    So in a general way I’m wondering which is it? If the Kolossal Kataclysm of Doom scenario is more or less right I’d just as soon be disabused of my misconception so I don’t embarrass myself at any more cocktail parties by holding forth on this in error. Hate it when that happens.

  9. How fantastically sexy is it that you find this fantastically gorgeous? I LOVES me some Phil Plait!

  10. Joseph G

    Wow!!! To tell you the truth, I half-expected to see “Artist’s impression of colliding galaxies” in small print somewhere! :)

  11. wew..i hope i can see one of those before i die..
    :( t its one of my wish..

  12. Joseph G

    Ahh damnit! My post got sucked into a black hole altogether, apparently. I think it didn’t like when I used the word A$$holes (it was apropos – I was describing people selling books and whatnot based on 2012 hysteria).

  13. foxxbott

    The coolest thing about this picture is all those colorful little dots in the background aren’t stars, they are other galaxies!! 😀

  14. Robert

    Maybe it’s because I haven’t taken Advanced Astronomy courses, but how to we know that the galaxies are actually colliding? As a 2-dimensional picture, it seems obvious. But 3-dimensionally, one galaxy can millions of light years farther away along the Z-axis.

  15. Have you noticed there is a very bright spot on the Chandra picture that is completely absent in the Gemini picture? On the Chandra picture, it is horizontally on the same level at the galaxy center, but right on the left edge. Anybody know what that is?

  16. CB

    @ DrBB:

    It’s Doomsday from the perspective of the victim galaxy, since it will no longer exist as an entity. From the perspective of the bigger galaxy, it’s lunch time. From the perspective of most of the stars and planets in either galaxy participating in the collision, mostly no big deal (though I’d imagine the chances of having a foreign star sweep through your star system are higher in a galactic collision than other times). So it’s all a matter of perspective. :)

  17. CB

    @ Michel:

    I’m guessing it’s a strong source of X-rays. But beyond that banal observation, I’m clueless. =D

  18. Tom Huffman

    Wowsers!!!! Is there a wallpaper-sized version of this?

  19. amphiox

    From the perspective of most of the stars and planets in either galaxy participating in the collision, mostly no big deal (though I’d imagine the chances of having a foreign star sweep through your star system are higher in a galactic collision than other times). So it’s all a matter of perspective.

    And from the perspective of any astronomers who might be on any of the planets in either galaxy, it’ll probably be “drooling-in-excitement” time.

  20. JB

    Has anyone contacted the Galactic Empire?

  21. @ Bon Joseph:

    Read your post again, really closely, especially that last line… hehehehe! Trust me to notice! 😉

  22. ASFalcon13

    So here we are, turning our telescopes toward billions of stars. Who knows how many of them harbor life?

    Think about that for a second. Think about all the civilizations you might be looking at in a single frame.

    Also, how many of those civilizations might be turning their telescopes and looking right back at us?

    On another note, and I’ve said this before…when on Earth did I tell Spitzer to do this?!? :)

  23. Messier Tidy Upper

    How fantastically gorgeous is this?

    Very! :-)

    Superluminous (beyond merely brilliant) image there. Thanks Gemini, Spitzer, Chandra & BA. :-)

  24. Brian Too

    Re: “NGC 6872[‘s]… spiral arms are clearly distorted and being flung wide…”

    The BA has much more sensitive perception than mine. I look at that picture and I’m thinking, “I wonder if those 2 galaxies are even close enough to interact…”

  25. Gonçalo Aguiar

    The thing that amuses me is that, by now the big galaxy has eaten the smaller one for sure, but we haven’t yet to see it…

  26. DrBB

    @18: I suppose the simplest response is to note that our own galaxy is involved in an ongoing collision or three itself. We seem to be surviving it ok so far.

    @16, @26: it seems pretty obvious to me that there’s a tail of material being drawn off from the lower right arm of the large galaxy to the small one. Pretty big “kink” in the arm at that point. The tail looks a bit foreshortened, at least to my eye, because the smaller galaxy is in the foreground with respect to the larger. Looks like the small one has been spiralling closer to the large one over the aeons and that’s more or less what’s been drawing the latter’s arms out as they gyre around each other.

  27. Gerard

    Potential lay person epiphany here.

    They’re each spinning counter-clockwise!

    I hope. Is that right?

  28. DrBB

    Just imagine what the night sky looks like to someone on a planet on the outer edge of the smaller galaxy facing in toward the big one. Must be lots of star systems with a clear view across the intervening void. We had to painstakingly deduce the shape of our galaxy, looking through the thing edge on from inside one of the spiral arms, and once you know where you are in the whole thing you can sort of get an impression of it when looking up at the Milky Way if you have a good visual imagination and a view of Sagittarius. But imagine looking out from your own galaxy across that gulf and having that whole huge structure spread right out all across the sky in front of you. Wow.

  29. ASFalcon13


    I think they’re spinning clockwise, but that makes sense because they’re in the southern celestial hemisphere. On the other hand, galaxies in the northern celestial hemisphere spin counter-clockwise 😉

  30. Anchor

    Phil, you might have mentioned that NGC 6872 is famed for being one of the largest galaxy structures known: those extended arms stretch over three-quarters of a million light-years, and they’re apparently still in the process of extending their reach. Compare that with the estimated diameter of our Milky way, at a ‘mere’ 100,000 light-years, and it gives you an idea of how collosal this beast is – if our Milky Way was replaced by NGC 6872, those arms would easily extend beyond the Magellanic Clouds, and reach nearly about a sixth of the way to the Andromeda galaxy!). It always reminds me of a twin tape-measures being played out from their common spool.

  31. Nigel Depledge

    @ Anchor (33) –
    And that’s a big tape measure!!

  32. sophia8

    DrBB @30: That’s exactly what I was thinking. Are we twins or something? 😀
    Every time I see one of these images, I really, really wish that reincarnation is real – then I’d have a chance of standing on a planet in one of those galaxies, marvelling at the night skies…..

  33. Gary Ansorge

    Wow! Thanks for the new desktop.

    18. CB.

    Just as in the ingestion of a living critter, it matters greatly to the critter but not at all to the atoms and molecules comprising that critter.

    ,,,we’re the atoms,,,

    Gary 7

  34. Gerard


    You are a riot. Nice post for this morning :)

    And, thanks for the reply, but it pains this polite person to still think they’re going counter-clockwise. Otherwise the little galaxy is having it’s greatest effect on stars that haven’t reached it yet.

    I like the glob at the point where some of the stuff is getting redirected towards the little one and some is seemingly escaping the system. That leaving stuff has to be going slower than what’s coming up behind it. And there’s a bit of knot there. Can that knot between them grow? Large enough to hasten the smaller’s collision?

  35. Capt Tommy

    Imagine your solar system is in one of those distorted arms with the Eye of God in your night sky. Or just a large and incredably beautiful galaxy to fill half your sky.


  36. Jesus

    I wish I could witness Andromeda engage in Galactic Cannibalism with the Milky Way.


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