Hubble Captures Colliding Galaxies

ackthpt writes: "I used to enjoy simulating model galactic collisions on my desktop but, CNN is featuring a find for the Hubble Space Telescope -- a collision between two galaxies 206 million lightyears away in the direction of the constellation Lyra. The picture is spectacular." It's this sort of thing that makes the Hubble's continued success, in light of it's famous earlier misadventures.

Comments

... is hiding in the same pictures

[mattorb]

Yes, they're pretty, but that doesn't mean they're scientifically useless. I've harped about this before, but the point is that there's a lot to be had from pictures like these; I don't know the details of this particular image, but in general, you can often get a sort of "poor man's spectroscopy" using narrow-band pictures. By taking images centered around some wavelength of particular interest (say the [OIII] doublet at 5007 angstroms, and hbeta at 4861), and doing some appropriate calibrations (subtracting the "continuum" level from the images, and calibrating to some absolute flux units), you can even get maps of the temperature or density of these objects. (Err, okay, so this doesn't really apply to this particular picture, but you get the idea -- I've used this technique successfully with HST WFPC2 imagery of planetary nebulae before.) In the particular case of colliding galaxies, there's also a lot to be said for "fuzzier" science, looking qualitatively at what happens in this kind of situation and trying to generalize it. You might look at the morphology of the spiral arms, or where you see the most star formation (by looking in Halpha) -- is the region of most star formation highly correlated with some aspects of the collision? Can you maybe infer something about the gas dynamics in this system, just by looking at enough pictures like this? The answer is yes, though of course there are limits.

End result: certainly I agree with you that media other than imaging have their place -- spectroscopy is the way to go for a lot of things. And other wavelength bands (as you say, IR, UV, x-ray, etc.) are important, too -- but don't knock the visual band! :-) And "nice pictures" and nice science aren't necessarily mutually exclusive.

Re:Question for the Physics doctorates

[Masem]

You've got the competition from the momentum generated from the Big Bang, which slowly decreases over time due to 'friction', and gravitational acceration from the galaxies, which also slowly declines (in most cases) with increasing distances between galaxies. While within the first few nanoseconds after the BB, all trajectories of all particals were away from point zero, gravity began to overtake the momentum forces and lead to agglomeration of particles. In the case of galaxies at this point in time, some are close enough to have gravity overcome the increasing distances between galaxies, while others are too

Which is why we're not sure if there will be a big crunch or if the universe simply wimpers out spread out over an amazing distance. The balance between momentum and gravity is not well understood and without being able to accurate map all major bodies in space, there's no way to easily predict it.

And when the galaxies are done colliding, there's a lot of outcomes (I remember a good segment in Cosmos) -- One could 'eat' the other, as the picture in this article shows (where the core of one would be destroyed), they could combine cores if their movement vectors are slow enough, or both could completely kill each other leaving only a dense core of stars and several more flying away from each other and the core well above the rate which gravity could recapture them.

To me, what's amazing is the fact that there are no significant stellar events associated with the collision: no novas or the like, though I'm sure any local solar systems are majorly distributed.

Yesterdays news

[Anonymous Coward]

This happened years ago. Why are we only hearing about it now?

Ban the universe

[Private Essayist]

Man, first we see a skull in outer space, and now we see a violent collision between galaxies. Doesn't anyone think of the children? We need to ban these violent space images before they turn the hearts of our children dark!
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