Galaxy cluster collision makes a splash… a million light years long!

By Phil Plait | December 15, 2011 7:00 am

In what has become an annual tradition here at BA Central, literally the day I post my gallery of best pictures of the year, something comes along that really would’ve made it in had I seen it even a few hours earlier. In this case, it’s a combined Chandra X-Ray Observatory and optical Very Large Telescope image of galaxy clusters colliding that’s so weird that at first I thought for sure it was Photoshopped! But it’s real, so check this out:

What you’re looking at is a collision on a massive scale: not just two galaxies, but two clusters of galaxies slamming into each other, forming this object, called Abell 2052. The total mass of this combined cluster is almost beyond imagining: something like a quadrillion times the mass of the Sun — 1,000,000,000,000,000 Suns! Note that our galaxy has about a hundred billion stars in it, so Abell 2052 is about 10,000 more massive. Yikes.

Something that big has a lot of gravity, and that’s the key to what happened here (PDF). As the clusters approached each other prior to the collision, gas in one cluster was drawn off and headed toward the other. Once the clusters passed, the gas got whipped around by gravity, reversing direction, and essentially, well, sloshed. The analogy the astronomers used was wine in a wineglass as you swirl it; if you suddenly whip the glass a bit faster the wine will slosh up the side in a wave.

That long blue curved streamer? That’s the wave: extraordinarily hot gas (30 million degrees C!) that got sloshed around by the cluster’s gravity. The scale of it is simply epic; that streamer is over a million light years long! Again, for comparison, the Milky Way is 100,000 light years across, 1/10th as big as that wave. Craziness.

The interior portion is no less amazing. You can see swirls in there too, as well as two holes that look a bit like eyes. Those aren’t really holes so much as bubbles of hot gas expanding inside the surrounding cooler gas; they’re also buoyantly rising, pushing on the surrounding gas and compressing it. That’s what hot gas does, whether it’s in a balloon here on Earth or heated to millions of degrees in the center of a cosmic collision 500 million light years away.

But as I looked at that image of the core, I couldn’t help but think it looked familiar… and somehow sad. And then I realized, ironically…

Even when two galaxy clusters merge, they’re still forever alone.

Image credit: X-ray: NASA/CXC/BU/E.Blanton; Optical: ESO/VLT

CATEGORIZED UNDER: Astronomy, Cool stuff, Pretty pictures

Comments (28)

Links to this Post

  1. eBookitude » Blog Archive » Bad Astronomy | December 25, 2011
  1. lol, a galactic troll!
    Expect it to start regurgitating right wing talking points.

  2. It’s not a coincidence that you receive photos right after posting “The Best Photos…” because you have a bazillion people visiting your site who are interested in Astronomy. Somebody is going to feel slighted that you didn’t include their favorite photo and probably tell you about it. :)

  3. Whoa. What an image! The universe never fails to amaze and awe. (But now I can’t stop seeing that face in the center…)

  4. Steuard

    Are images that appear (or appear on your radar) in late December eligible for the following year’s list, or are they just out of luck? (I’ve always wondered why so many “Best of the Year” lists get published before the year is in fact over.)

  5. HRJ

    Your post reminded me of this APOD:

    which I think is even more impressive than this one.

  6. OtherRob

    Steuard makes a good point. Maybe you should wait until early January to post your year’s best pics.

  7. Zafod

    I just read the PDF and found it interesting that so much information can be gathered from such a distant object. I also ROFLOL the troll face in the center.

  8. It kind of looks like a blue version of the Ghostbusters ghost. Protect your hot dogs and don’t get slimed!

  9. Relativity

    It looks more like Fatso in the Casper movie…

    But really, that 30 million degrees thing…Is that measured as a whole (million ly) condensed to a point (summed up by integration) or a scale down to where we can understand like a “point” in that cloud swirl? For example, it is cold in Minnesota as I can see the thermometer measuring a volume of say 1 cubic ft? How is temperature measured on that massive scale?

  10. Nobody

    Next year there isn’t going to be a next year, so he has to get them done a little early.

  11. Prufrocker

    I’m going with the baby from 2010: The Year We Make Contact.

  12. David

    Please do not make references to obscure stupid internet memes. Especially ones that start at a forum where pictures of animal abuse are routinely posted i.e. 4chan.

  13. Björn Lammers

    WHOAH. This makes your galactic collision image in the year’s best series look a bit… puny? I guess you would most certainly notice this if it were happening in your vicinity…
    Thanks for the explanation yesterday, I really enjoyed the whole thing! It was certainly worth the hour and a half of lost sleep.

  14. Thomas Siefert

    It’s your own fault for posting too early. You don’t see shops putting up their Christmas decorations in October now, do you?… Oh wait…! Eh, never mind.

  15. David

    Beautiful descriptions of the scale of this thing. Just massive. I have but one question:

    How does something ‘buoyantly rise’ when there is no ‘up’?

    I take it that refers to moving from a high-pressure to low-pressure system. Is there really no way of describing that process within a free frame of reference?

  16. Wow. Just… wow…. ow. Ow! I sprained by awesome-lobe.
    Serious question, though – if that “arm” is ten times the size of the Milky Way, why can’t we see any individual galaxies in these clusters?

    @13 David: Please do not make references to obscure stupid internet memes. Especially ones that start at a forum where pictures of animal abuse are routinely posted i.e. 4chan.

    I see several problems with your post.
    -First, the meme is not obscure; in fact it’s one of the better-known memes on the intertubes.
    -Second, all internet memes are stupid, so a request for a non-stupid internet meme is an oxymoron.
    -Third, roughly 95% of internet memes originate from somewhere in or around the 4chan region of the internet (sometimes forming around the outskirts in the swirling accretion disk of lolcats and porn). Again, see my second point.
    Also, do you consider Limecat animal abuse? What standards are we using, here? In my experience, animal abuse is the one form a cruelty that 4chan et al will NOT tolerate. They’ll spend all day ridiculing a random blog entry or picture of someone, but mention someone mistreating animals and all of a sudden everyone’s a justice-obsessed vigilante.

  17. Messier Tidy Upper

    Superluminous image here. I love it. ūüėÄ

    The scale of this is just incomprehensible really – at first I thought it had to be nebulosity of some sort in our own Galaxy but to think of it, no, to know it as collision of two clusters of galaxies is .. whoah! ūüėģ

    Just puts everything into a mind blowing perspective. :-)

  18. I’m still not sure exactly what I’m looking at. Is this the entirety of the two clusters, or a close-up? Is the blue stuff all intracluster gas, or are we seeing individual galaxies?
    Are galaxies in these clusters more closely packed then the galaxies in our local group?

  19. Wow! A truly cosmic dance if ever there was one! How long will this phenomenon last?

  20. Nigel Depledge

    @ Joseph G (19) –
    If I have understood correctly, the blue stuff is the X-ray glow from gas that has been smashed or drawn out of some of the galaxies.

    It is, apparently, very very hot.

  21. Darrin


    Relax, man. 4Chan may be a wretched hive of scum and villainy, but animal abuse is the one thing NO ONE there tolerates. Gore and porn? Fair game. But post a video of abusing an animal? God help you. They’ll unleash internet justice. Hard.

    Besides, most memes start on Reddit or 4chan. “Forever Alone” is by no means an obscure meme, it’s quite well-known. Not to mention that Phil is a citizen of the interwebs, and so is most of his readership. Thus, there is absolutely nothing wrong with making what equates to an internet in-joke from time to time.

  22. DanO

    Phil, or anyone else here who can answer my query. When you say the gas is 30 million degrees, does that mean that the atoms and/or molecules are VIBRATING at 30 M degress or are they moving at a speed that equates to 30 M degrees? My understanding of how to measure temerature of a gas outside of a container is lacking, so I’d appreciate if someone here could explain it to me.

    Thanks in advance.

  23. Downer

    @Joseph G
    That tail is at least 10 times longer than the diameter of the Milky Way. Yet the total mass of these two clusters is 10,000 times greater than the Milky Way. I guess the reason you can’t see individual galaxies is because matter is too tightly packed in the center, which in turn has smeared galactic structures to oblivion when it stretched out the other cluster. The density of gas is still so huge the whole structure is, judging from the blue color, a ginormously humongous stellar nursery.

    If I’m totally off here, somebody please correct me.

  24. Anthony

    How long until we make contact with an advanced civilisation running from this?

  25. Joseph G

    @ Downer: Wow. That’s what I was wondering – is this thing dense enough to be a sort of super-galaxy?
    I wonder if there’s a mass limit to galaxies, for that matter…

  26. Warren

    In your book, DEATH FROM THE SKYS you mentioned that when two galaxies collide the mass of the BLAK HOLES in the center of each galaxy merge to become one supermassive black hole. Example: your book says the MILKY WAY blackhole mass is that of 4million suns and Andromeda’s is 30 million syuns. When they merge the new BLACK HOLE mass equals 34 million suns. Since there are trillions of black holes in thes galaxy clusters, won’t there be a significant chance that a monumental monster black hole will.


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