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

Nice pictures, but the real science....

[warpeightbot]

is in the infared, ultraviolet, and radio/x-ray detectors, which have nothing to do with the visual-spectrum pictures. All that big lens is there for is to sell the project to the taxpayers... which is, of course, why the big panic to replace that lens despite the fact it wasn't affecting any of the research projects... as one of the Mercury Seven astronauts said, "No Bucks, No Buck Rodgers." No pretty pics, no constituent letters to Congress saying "Save Hubble."

Helluva way to sell a science project.

There is no Momentum generated by the BB

[efuseekay]

It is a general misconception that the BB gives a "momentum impulse" the causes the expansion of the universe. Expansio of the U is expansion of space itself, whicih has nothing to do with "total momentum" or things like that.

Also there is no "point zero" in a BB for the current "favourite" flat universe model. The idea of a BB "exploding from a point into void" is also false. In the current Omega=1 (i.e. asymtotically expanding) universe, there is not even a concept of a "single point", i.e. the Universe came into being as infinite space in the BB (hard to visualize, but true). The simple proof is that an Omega=1 U is an infinite U, so extrapolating infinite back a finite amount of time (i.e. the age of the Universe) will still lead to an infinite universe. So the Universe has no boundaries (a single point, on the other hand, has a one-dimensional boundary so to speak very loosely).

Now, to answer the question of the original poster :

Colliding galaxies are common place. During the early universe, purturbations in the density field "seeded" the universe, causing stars and galaxies to form. Some purturbations are larger than others, and those which is larger than the so called "Jeans Mass" will collapse to form objects in the universe, creating a local overdensity of mass whose gravitational effects overcome the inherent "expansion" of space. Thus, we see many so called "galaxy clusters" in space, of which Virgo is the closest. In such clusters, galaxies are gravitationally bounded to each other, and eventually will collide to form one gigantic galaxy. (Such gigantic galaxies which are >1000 times more massive the the Milky Way are called cD galaxies and are not uncommon.)

... 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.

Hubble & Pluto/Kuiper Belt objects

[Smitty825]

While I'm far from an astronmer, I was wondering if we could somehow use the Hubble Space Telescope to study the planets in our solar system? Would Hubble give us a good view of the Outer planets, especially ones we haven't studied like Pluto or the new Kuiper belt object, or are they too close to us for Hubble to focus in on?

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?

Pay attention to those pictures!

[Pacer]

We have our own collision coming up, with Andromeda, fairly soon (possibly within the lifetime of our own sun, something like 5 billion years from now). I wonder if it will look this cool, and who will be watching?

http://oposite.stsci.edu/pubinfo/pr/97/34/af1.ht ml has some more info, although I think this page is getting a bit dated.

Pacer

Question for the Physics doctorates

[Sawbones]

I simple question for the physics docterates here in /.

How does this phenomenon fit into the expanding universe model? Perhaps my understanding of the model is too simplistic or flawed, but I would have thought that in general the galaxies would all be flying apart from eachother at some relatively high speed - making this apparent head on colosion a bit improbable.

Would it require that the two clusters have a similar enough trajectory and have just pulled towards eachother via combined gravitational effects over eons?

Is it likely that - even though stars won't colide - the two galaxies will become one double dense one - perhaps collapsing inward to a singularity?

Yes, this is probably better suited for Ask Slashdot, but there's no way that would ever get accepted let alone on the front page ;)

All pretty facinating though...

Astronomy Picture of the Day

[A nonymous Coward]

For fans of these kinds of pictures, Astronomy Picture of the Day is hard to beat. They have a this same picture for today.

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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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