The start of a long, long dance

By Phil Plait | May 11, 2012 6:30 am

A hundred million light years away, two gorgeous spiral galaxies are locked in an embrace that may end with them merging, a dance spread across a hundred thousand light years in space and a hundred million years of time.

[Click to galactinate, and yeah, just do it. The hi-res version is big and lush and lovely indeed.]

This image, taken by frequent BABlog contributor Adam Block, shows this cosmic waltz in lovely detail (another wonderful image is available via the ESO as well [UPDATE: … and from Gemini, with a diagram of the two and a nice explanation]). The two galaxies (NGC 5426 on the left, and NGC 5427 on the right) are just starting this eons-long encounter, but affects are already visible. You can see tendrils of material stretching from NGC 5426 to its companion, drawn out by the force of NGC 5427’s gravitational attraction.

Inside the galaxies, you can easily see the pink glow of gas clouds, disturbed by the interaction, starting to furiously churn out hot young stars. Actually, stars of all masses are born in these clouds, but it’s the rare massive stars that have the most impact. They blast out ultraviolet light which makes the gas glow, and will explode as supernovae, lighting things up even more.

In galactic collisions like this the outcome can be difficult to ascertain. Perhaps they’ll pass this one time and do so with sufficient velocity to make this a one-eon stand, continuing on into the night. Or, if their relative speeds aren’t enough, they’ll pull apart, only to be drawn inexorably together once again. Even then they may pass, but this time in an ever-decreasing arc, until finally they merge into one bigger galaxy. Although this plays out over far too long a timespan to watch in real time, we see so many colliding galaxies that it’s like having snapshots at all different stages of evolution (see Related Posts below for lots of collidey goodness).

The general steps here are known, but the specific outcome of this particular encounter is still to be seen.

And we’ll see something like it up close, if not for quite some time: the Andromeda Galaxy will one day collide with our Milky Way, and when that happens we’ll be able to see what a galactic collision looks like… from the inside. Buy your tickets now. The show begins in just a billion years or two.

Image credit: Adam Block/Mount Lemmon SkyCenter/University of Arizona

Related Posts:

Desktop Project Part 25: Chaos in a galactic nursery
Sometimes a cigar galaxy is just a cigar galaxy
Galaxy cluster collision makes a splash… a million light years long!
First light for ALMA
Gorgeous galaxies celebrate Hubble’s 21st birthday
The delicate aftermath of cosmic violence

CATEGORIZED UNDER: Astronomy, Pretty pictures

Comments (18)

  1. [pedant]

    The two galaxies (NGC 5426 on the left, and NGC 5427 on the right) are just starting this eons-long encounter, but affects* are already visible.

    *effects 😛

    Sorry, I myself have trouble figuring out which one to use from time to time, so it’s one that slaps me in the face when I see it improperly applied.


    Still, very pretty photos. Added to my desktop slideshow! :)

  2. Other Paul

    Actually could be affects, as in ‘affected things’, a little old-fashioned but who here would eschew such stylistics?

    But – to the matter at hand – just imagine living over there! Where would you want to be to get the best view, even only the tiny moment you’d get (have got, a hundred megayears ago)? Right there in the melange, or properly ensconced in one of the rims? Or maybe the best view would be from some nearby satellite galaxy?

  3. Jon Hanford

    This page at the Gemini Observatory site includes a discussion of this galaxy pair, a beautiful image taken with the 8-meter Gemini-South telescope and a (very helpful) diagram outlining the possible 3D configuration of the encounter, based on a 2004 study:

    As Phil pointed out, signs of the interaction between the two galaxies are already evident. From my link:

    “…the giant HII regions in NGC 5427’s disk [the galaxy to the right in the image above] are forming at a higher rate, and are more plentiful, than expected for a galaxy of this type. One giant star-forming region at the tip of NGC 5427’s western (top) spiral arm, looks especially large and disturbed, as does the arm itself, which is unusually straight, as if strong tidal forces have broken the arm in two, causing it to bleed starlight.”

    In addition, young newly formed stars are seen in the bridge between the two galaxies. It’ll sure be interesting to see how this encounter plays out, though it’s a bit off in the future. :)

    Oh yeah, that 2004 study of NGC 5426/27 (aka Arp 271) is available here:

  4. Renee Marie Jones

    What would the night sky look like if you were right in the middle, part of one of those tendrils? Would you see both galaxies in the sky, or would they be too dim?

  5. AliCali

    @3 Renee Marie Jones:

    “What would the night sky look like if you were right in the middle, part of one of those tendrils? Would you see both galaxies in the sky, or would they be too dim?”

    Let’s assume each galaxy’s size is similar to the Milky Way. We’re 2/3 away from the center, but because of all the interstellar dust, we can’t see the core; just see a cloudy band of stars representing our disk. And because of the dust, the disk doesn’t appear brighter toward the center; like we’re in a fog.

    If you’re on a planet in the middle of the interacting pairs, you’d be further than 2/3 away from either core. I imagine the dust would block even more. Thus, you’re left with a band of stars…or perhaps two bands of stars. I could see having two bands crisscross each other in the sky. Imagine being on the planet and trying to figure out what the heck those two bands are, and imagine what it’d be like when you figure out that you’re in the middle of two galaxies coming together.

    All in all, though, I’m happy with our seat in the Milky Way.

  6. aleksandar

    Caught myself trying to comprehend the scale and size of what is pictured. Doing very rough estimates in my head, looking at that picture. Earth would be about the size of and atom, and one kilometer the size of a atomic nucleus.

  7. Jess Tauber

    Where have I seen this before… I know, STNG, the Farpoint mission. Or, as Troi might say, ‘great joy, and gratitude’…

  8. Ross

    I would like to read this post, but I can’t because the ad next to it is IMHO NSFW (woman standing with her jeans unbuttoned showing her underwear)

  9. kat wagner

    “a dance spread across a hundred thousand light years in space”. So it’s a good thing we’re so far from those galaxies so we get the big picture. Blows my pea-brain away.

  10. artbot

    #8 – Um, Adblock?

  11. Ross – you get distracted by a woman in her underwear when such a gorgeous picture as this is on the screen? Your geek license has been suspended.

  12. Paul A.

    I would love to see a simulation of what the night sky of a planet in one of the galaxies looking towards the other galaxy looks like.

  13. OneofNone

    @#5 Alicali

    The core of your calculation is only two-dimensional. We see our own galaxy as an obscured band of stars, because we are part of the disc. There are better point of views however.

    Just think of the magellanic clouds. Dwarf galaxies, in roughly the same distance as the tendrils between the two galaxies. And for full correction, think of Andromeda: roughly ten times as far away, but clearly visible.

    In the given image, I clearly see the two galaxies are in an angle with each other. And of course they did pass, but not right through the center. Instead it was like gently touching each others, if any direct crossing at all.

    So clearly, from the tendrils you see both galaxies. From a shallow angle, agreed. But both are clearly visible in the sky. If you see our Milky Way from a distance of 100kly, it is about 55 degrees wide. Pretty big. Two of these objects in the night sky, I would regard that as pretty impressive.

  14. Messier Tidy Upper

    @ ^ OneofNone : Yup. That’s how I’d think of this question too – we can see the Magellanic clouds pretty clearly from this close despite all that galactic dust mentioned by (#5.) AliCali.

    Now it could be that with the different geometry some of the other spiral here would be blocked and it may depend on exactly where your home star there is located but I tend tothink it would be a pretty spectacular sight – like the LMC supersized & taking up say a third of the sky – or more! 8)

    @8. Ross :

    “I would like to read this post, but I can’t because the ad next to it is IMHO NSFW (woman standing with her jeans unbuttoned showing her underwear.”

    At least she has her underwear on! Could be worse! 😉

    That’s not too NSFW I think and given its just an ad, not so bad. Anyhow there’s always adblocker or something like that.

    Personally, I think Discover & the BA are usually pretty good on keeping this blog family friendly and safe for work and I’ve never seen anything too bad in that regard here.

    Oh & if you didn’t read the post because its NSFW ad~wise then how come you’re commenting on it here? 😉

  15. Infinite123Lifer

    “Caught myself trying to comprehend the scale and size of what is pictured.”
    Exactly. Catching my reality check in checking if I am really alive because some of Lifes actualities are increasingly breathtaking, with dreamlike qualities rich in beauty utterly and affectionately nigh describable with words. Reflection alters yet again the extraordinary sense of entitlement to be a witness of just a moment of time so magnificently distant, so revealing through the essence of our lense and so extremely incomprehensibly epic that in its magnificance resides the keys to the questions which its products eventually ask.
    And to share the experience with others…

    For dreamers only: FDO
    To the dreamers who wonder I think its safe to say that everything in space is pretty impressive, even empty space is impressively vast but if you want to know what it looks like there…try try real real hard to dream about it using your imagination(oh and I think it helps to do a little research on certain aspects of what your hoping to see, the more you think about it the more likely I think you might dream about it). This is the only true way to experience such a thing. I myself have had impressive dreams, well if you call visiting the sun, or moving the moon or taking earth elsewhere or witnessing all 996 forces of nature (that was a dream by the way) or residing on not one but 2 peaceful alien worlds impressive or fun dreams then if you really want to know I suggest you imagine it before good sleep. I have never forgotten the imensity of those dreams btw. When dreaming hold on to what you love and trust it. Hope that helps.

    I hope its glaringly obvious that I am not selling anything or suggesting that one can take rides through space in their sleep. Iam just saying I have and it is mindblowingly FUN everytime, maybe it is possible to happen again somewhere sometime somewhen. Oh jeez, iam just saying maybe you can dream about it. I do sometimes.

  16. Nigel Depledge

    @ Larian LeQuella (1) –
    Aw, you beat me to it!

  17. CR

    Aw, the ad I got is for a cel phone, no people in it at all. I missed the ‘exciting’ one, I guess. :(

    As for the galactic dance pic, wow. In a way, it’s almost sad, knowing that these two galaxies might be torn assunder by their mutual interaction… kind of like watching an accident in slow motion and knowing that nothing will alter the outcome.
    Then again, that’s the nature of, well, nature itself, and new things shall (eventually) rise from the old.

    Kind of makes some of our everyday problems seem not-so-terrible nor important in the long run. (For that matter, kind of makes our bigger problems seem kind of pointless, too.)

  18. Brian Too

    Hey, let’s give these 2 some privacy! I think they’re about to, you know, get busy.


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