What happens when a smallish galaxy plows right through the center of a bigger one?
This:
Holy Haleakala. That’s Arp 148, and it’s magnificent. That elongated galaxy was probably not quite so stretchy before it hit, but the gravity of the other galaxy drew it out. In turn, its own gravity drew in stars and gas from the bigger galaxy, which then expanded as a ring as the smaller galaxy plunged on. It almost looks like a freeze-frame image of a bullet shattering a drum head.
If you like that, you’ll love this: Hubble has released 59 such images of galaxy collisions today (the US version of the release is here), celebrating Hubble’s 18th anniversary in space. It launched on April 24, 1990.
The galaxy pictures are stunning. The one on the left is Arp 256, two spiral galaxies interacting as they pass each other for the first time. Long tendrils are being drawn from both galaxies, and the blue regions indicate epic bursts of star formation (young, massive stars are blue and extremely luminous). Someday the Milky Way and Andromeda galaxies will look very much like this… a billion years from now, when they pass each other. I’d write more here, but golly, I have a book coming out in October with lots more details. 
This one is even weirder: it’s a red elliptical galaxy and a bluish spiral interacting. The blue galaxy looks to be small to my eye; it’s getting totally disrupted by the elliptical. There’s some indications of dust getting blown every which-way in the elliptical too. This will be a very interesting system in about another 500 million years or so.
I’ll leave you with one more: NGC 6050.
Two magnificent spiral galaxies, each about the same size, slide toward one another and are just now beginning their slow dance. I can almost imagine them spinning like buzz saws into each other, tearing both to shreds (in fact, they look a whole lot like the animation of colliding galaxies used in my short astronomy video on Hulu — and yes, we’ll be posting that on internationally-accessible servers soon). The two spirals will no doubt merge completely into an elliptical… unless they’re moving too quickly. They are both part of the Hercules Cluster of galaxies, 650 million light years away (the press release says 450 million, but the 2MASS catalog says 650). Hercules has over 100 galaxies in it and is therefore pretty massive; all that mass means a lot of gravity, and that in turn means the component galaxies are screaming along at high velocity. It’s possible these two beauties will continue on their way, passing through each other, distorted, beaten, but surviving.
I wonder how that story will end; lover’s embrace or ships passing (literally) in the night? With images like these, astronomers will learn a lot more about how galaxies behave when they collide, and that will point the way to better, more detailed observations. Eventually we’ll know how the story goes, from start to finish.
Our own future is wrapped up in these images, writ large across the sky. As usual in astronomy, and in science as a whole, by looking outwards we learn more about ourselves.
Happy anniversary, Hubble.
April 24th, 2008 at 8:52 am
Oh man, these are sweet. I really adore pics like that. Puts you right back in your place. We’re just not worthy.
April 24th, 2008 at 8:55 am
Phil, in the fourth image, what is that grouping that sort of looks like a barred-spiral at the very top and dead center of the collision? Is that a globular cluster, a third galaxy, a feature of the collision?
April 24th, 2008 at 8:59 am
Okay, I can’t help thinking the first picture looks like the effect used in the Stargate SF shows when they activate the gate.
April 24th, 2008 at 8:59 am
And YOU thought you were having a bad day!
April 24th, 2008 at 9:00 am
Moose, funny you’d ask. I had written a bit about that, but took it out. I’m not sure what it is! It might be a background galaxy, or a companion galaxy (like M51′s).
April 24th, 2008 at 9:04 am
@Anonymous
Hmm…does that mean that every time they activate a stargate, they’re ripping a galaxy or two apart?
April 24th, 2008 at 9:09 am
How else would they get the energy needed?
April 24th, 2008 at 9:19 am
So maybe someday, our semi-bio-robotic decedents with three eyes, (because humans have long since departed Earth to colonize a newer planet 287 light years away and evolution there continues,) will look up and see the Milky Way much as we do. However, they will also see another “Milky Way” (called Andromeda,) stretching up in the opposite direction, with lots of bright blue stars in many far away clusters.
April 24th, 2008 at 9:19 am
[...] Phil Plait) posted 4/24/08 at 11:19am to Nerdery, Science! · 0 replies · [...]
April 24th, 2008 at 9:32 am
[...] was reminded of all these thoughts this morning by a post on Bad Astronomy Blog. Check out Bad Astronomy’s write up of some great Hubble shots of galactic collisions and interactions. As you’re looking at the [...]
April 24th, 2008 at 9:45 am
That first pic Arp 148 looks more like Pac-Man is vomiting.
April 24th, 2008 at 10:11 am
Hurrah for Hubble!
April 24th, 2008 at 10:23 am
Is it possible that companion galaxies are ejected from the central galaxy because they tend to align themselves along the minor axis of the ‘parent’ galaxy?
April 24th, 2008 at 10:54 am
After classifying thousands of galaxies on the Galaxy Zoo website, I have to admit that the last one looks to be 3 galaxies instead of two. The third, in the top middle can be a star forming region I suppose, but there looks to be a clear bar like structure that may represent a galactic core. Does anyone know more about this particular interaction? How are we certain there are only two galaxies instead of three?
April 24th, 2008 at 11:02 am
Nice pictures!
So the milky way is going to collide with Andromeda some time from now. What kind of collision will that be? Is that known? I mean, what is the angle of impact and so on?
April 24th, 2008 at 11:15 am
The universe is not only a violent place, its a more violent place that we can even imagine! I wonder what creatures who lived in those galaxies must have seen so very long ago.
April 24th, 2008 at 11:17 am
So how big are the galaxies in the first(bullet/drumhead) pic? How do they compare with our galaxy?
April 24th, 2008 at 11:39 am
Wooooooooaaaaaaahhhhhhhhhhhhh………. more cool stuff for my screensaver…….. but I wish they’d moosh ‘em all up into a zip file so I wouldn’t have do DL them one at a time……..
April 24th, 2008 at 1:46 pm
Fun. A nice set.
April 24th, 2008 at 2:02 pm
All I can say to the first one is… SHOOP DA WHOOP!!!
April 24th, 2008 at 2:52 pm
Great pix……Hubble continues to deliver even after 18 years. Despite an initially flawed mirror and after a series of repairs and upgrades….still our best eye on the Universe!
April 24th, 2008 at 2:58 pm
Beautiful. Absolutely beautiful.
How can one reject study of the natural universe, when it presents us with wonders such as these?
April 24th, 2008 at 3:19 pm
The pictures from the ARP Atlas of Peculiar Galaxies are a really good reminder of how important Hubble is.
Here’s a link to ARP 148 (topmost picture in Phil’s post) from that Atlas:
http://nedwww.ipac.caltech.edu/level5/Arp/Figures/big_arp148.jpeg
This link is on the Hubble Web site’s page along with a link to the Arp Atlas on a Cal Tech Web site.
Wow! and Wow!
April 24th, 2008 at 3:57 pm
That first picture looks awfully familiar.
Or, if the HTML doesn’t work:
That first picture looks awfully familiar:
http://antwrp.gsfc.nasa.gov/apod/ap070819.html
April 24th, 2008 at 4:25 pm
Fantastic. Because of the sheer size of galaxies, we only get a freeze-frame of the collision, which is kind of sad, but wouldn’t it be great if we could discover and use tachyons in telescopes to study these? Since the theoretical particles travel at various speeds faster than light, if we had a detector that could image them and put them into a video based on their energies, we could see past the collisions’ light cones and view a time lapse of the thing starting from the current photonic image. D: Oh, science fiction, why can’t you be science fact?!
April 24th, 2008 at 7:46 pm
Here’s a cool time waster – galaxy collision simulations in Java.
http://burro.cwru.edu/JavaLab/GalCrashWeb/main.html
Click applet to start, you can vary a bunch of parameters. It doesn’t do stellar evolution, but you get to see a lot of common features of interacting galaxies develop – spiral arms, tails, ‘ionization’, galactic fusion and so on.
April 25th, 2008 at 3:12 am
[...] What happens when a smallish galaxy plows right through the center of a bigger one? [...]
April 25th, 2008 at 5:40 am
All these images go to show that even in violence, our universe is quite lovely. Well, to us, the observers.
I don’t know if we’d say the same if this happened to US.
April 25th, 2008 at 11:53 am
Wow, those images are stunning.
April 25th, 2008 at 3:51 pm
We had always been given the model of galaxies as raisons in a rising cake, i.e. always drifting further away from each other as the universe expands. If that model had any validity how do galaxies bump into each other? Anyone?
April 25th, 2008 at 4:56 pm
Peter:
On average, the galaxies are moving apart. But since they’re not actually embedded in a cake, they’re free to have their own individual motions, superimposed on the general expansion.
Most galaxies are in gravitationally bound clusters. I *think* that galaxies within a cluster don’t tend to move apart; rather, the clusters are moving away from each other. Thus the number of collisions is probably about the same as it would be in a hypothetical non-expanding universe. (This is about 80% speculation on my part.)
April 27th, 2008 at 1:36 am
[...] Bad Astronomy Blog » When galaxies collide Cool images from Hubble. (tags: space science Astronomy) [...]
April 30th, 2008 at 1:33 pm
The BA wrote :
“I wonder how that story will end; lover’s embrace or ships passing (literally) in the night?”
Literally?? Oh dear, sorry to be a grammar / lexicon nazi (& yeah, I’m ofetn lousy whenitcome stogrammar & don’t even start on typos) but .. Argh! NO! No & again no!
‘Night’ (and ‘day’) are in this context totally inapplicable words.
Ships = galaxies???
NO! Not literally! ;-(
Metaphorically sure but not literally.
So they’re colliding and maybe pasing each other like galaxies in the cosmos not ships in the night.. Literally speaking.
*Metaphorically*, like ‘ships in the night’ .. okay. Bit of a cliche but okay.
Still thanks Bad Astronomer for those awe-inspiring, breath-taking, thought-sparking images.
I’m thinking they’ll have to be in 2008′s top 10 astro-images .. !
April 30th, 2008 at 1:38 pm
Noted # Helioprogenus (= Sunchild?) on 24 Apr 2008 at 10:54 am :
“After classifying thousands of galaxies on the Galaxy Zoo website, I have to admit that the last one looks to be 3 galaxies instead of two. The third, in the top middle can be a star forming region I suppose, but there looks to be a clear bar like structure that may represent a galactic core. Does anyone know more about this particular interaction? How are we certain there are only two galaxies instead of three?”
My guess – maybe those extra ones could possibly be background ‘line-of-sight / chance’ galaxies – not one’s directly involved in the collision?
We’re looking at galaxy clusters and superclusters here so many galaxies at slightly differing distances in a relatively small area of sky .. Hmm .. I’m not really sure though ..
May 2nd, 2008 at 12:51 pm
[...] ? When galaxies collide [...]
May 7th, 2009 at 12:03 pm
[...] See also: When galaxies collide [...]