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Astronomers Witness Whopper Galaxy Collision
Raver32 writes "A major cosmic pileup involving four large galaxies could give rise to one of the largest galaxies the universe has ever known, scientists say.
Each of the four galaxies is at least the size of the Milky Way, and each is home to billions of stars.
The galaxies will eventually merge into a single, colossal galaxy up to 10 times as massive as our own Milky Way.
"When this merger is complete, this will be one of the biggest galaxies in the universe," said study team member Kenneth Rines of the Harvard-Smithsonian Center for Astrophysics.
The finding, to be detailed in an upcoming issue of Astrophysical Journal Letters, gives scientists their first real glimpse into a galaxy merger involving multiple big galaxies.
"Most of the galaxy mergers we already knew about are like compact cars crashing together," Rines said. "What we have here is like four sand trucks smashing together, flinging sand everywhere.""
It is assumed that the universe is not infinite in size.
Your logic is flawed.
There are an infinite real numbers between 0 and 1 inclusive, but there is a largest element in the set (specifically, 1.0).
Likewise, even given an infinite set of galaxies, there can be a largest galaxy.
Not all galaxies are moving away from each other. Due to gravity and local variations in density, some are moving towards each other. For instance, andromeda will crash into our galaxy in a billion years or so.
- None can love freedom heartily, but good men; the rest love not freedom, but license. -- John Milton
This is definitely a cool idea. But it's just a myth. Take a look at that site--lots of wonky pseudo-science to be had. And I especially knew something was wrong when they started talking about the Mayan calendar and global warming.
t he-sun-from-another-galaxy
At any rate, take a look at the original press release that was misinterpreted to come up with this theory here: http://astsun.astro.virginia.edu/~mfs4n/sgr/
And take a look at a debunking here: http://www.badastronomy.com/bablog/2007/06/27/is-
And the wonkiness about the angle we see the Milky Way at from Earth is just plain bad math.
The astronomer quoted in that link has specifically stated that his work was misrepresented; see here and here. The Sun's orbit in the galaxy indicates that it did indeed originate in the Milky Way.
If galaxies are close enough, they can collide. Generally, a gravitationally bound system will resist the Hubble expansion (which is why our solar system and galaxy are not expanding at the rate the universe does). Only when the bodies are spread far apart and not gravitationally bound to each other does the universe's expansion dominate. See this FAQ and this and this for details.
Wrong scale. On the macroscopic scale - the same scale where the universe looks the same in all directions - everything is moving away from everything else. On smaller scales, of course, this isn't the case*. To see the "everything expanding" universe and the "everything homogenous" universe, you need to lower the granularity of your observations to the point that this sort of localized clustering isn't measurable. A good start would be to take Hubble's Ultra Deep Field image as your basic unit of observation (and that's still only 0.000008% of the area of the sky). In that image, only five of the objects visible (the ones with lens flare crosses) are stars, every other object is a galaxy. You can see the homogeneity of the universe in that image. Four of those galaxies colliding - even the four largest that are visible - wouldn't change the overall character of the image at all.
*Well, this may or may not be the case, depending on how well I understand the expansion of space. If the apparently-faster-than-light expansion of the early universe is, in fact, due to a combination of things flying apart and the space between them expanding, it's reasonable to think that space is still expanding. In which case, literally everything is moving apart from everything else, from the neutrons and protons in your average nucleus to galactic clusters. But I may be misunderstanding the expansion of space.
Reality has a conservative bias: it conserves mass, energy, momentum...
Yes, because obviously when a couple of small cars collide it takes place over a few hundred thousand light years and lasts for a million years or so (the warranty on the airbag may be voided).
And this one is like trucks smashing together?
I am now firmly of the view that astronomers:
How about "This in no way whatsoever resembles any kind of collision you have ever witnessed on Earth, it dwarfs your imagination, and by the way any kind of anthropocentric comparison should have been buried with Galileo?"
Pining for the fjords
It's sorta like this:
Some time ago, we figured out that:
1. All type 1a supernovae are exactly as bright when they blow up, because that's a star going a tiny bit over the Chandrasekhar limit. So basically they're all very nearly exactly the same weight stars, and blow up in the same way. So since seen brighness decays with the square of the distance, you can calculate how far it was when you see one.
2. (Based on 1 too.) The farther something is, the more re-shifted its spectrum will be. Basically the faster it moves. So you can know fairly accurately how far away these 4 are.
And it would have to be a freakin' big star to be _that_ bright at that distance. You're asking for a galaxy sized star.
3. We also know how big a main sequence star can possibly get, and that's only about 120 solar masses, but the closer you get to that limit, the faster it burns and the more unstable it is. The ones over 100 solar masses burn extremely fast and tend to regularly blow up huge chunks of their mass.
At any rate, we know that a star can't possibly be as big as those things at that distance. Even a star with 100 solar masses, won't have 100 times the Sun's volume. Gravity compresses them a bit more. And even 100 times the Sun's volume would be only a bit over 4.5 times the Sun's radius. It's just not even _near_ the size of a galaxy.
Also, in spite of their massive mass and fast burning rate, the hypergiant stars seem to be "capped" in brightness, so they won't get as bright as a whole galaxy anyway.
Also, remember when I said they burn very fast? A hypergiant burns and blows up in 1 to 3 million years, give or take a few. That's about 4 orders of magnitude shorter than our Sun. They just don't live long enough for 4 of them to come anywhere near each other.
A polar bear is a cartesian bear after a coordinate transform.
For anyone who finds space.com as annoying as I do, here is the link to the original story at NASA's Spitzer site.
You will not drink with us, but you would taste our steel? - Walter Matthau, The Pirates
His logic did not depend on the set being continuous. It would have worked just as well using rational numbers in the range [0, 1], of which there are an infinite number and which still has a largest element (again, 1).
And while there may in reality be a finite number of possible sizes, the argument the OP made and the GP rebutted was about an infinite universe with an infinite number of galaxies, which are not necessarily each a different size than every other galaxy. The argument still works exactly as well in that case.
The enemies of Democracy are
Space is big. Really big. Really really fucking big.
During the collision of the galaxies, it's unlikely that any of the suns will even hit each other. That's how freaking big space is.
Consider that we are in a galaxy. Now consider our nearest star (other than the Sun) is so far away that it takes _years_ for light to reach us.
If our galaxy collided with another galaxy (as it will - we are set to collide with the Andromeda galaxy), we probably wouldn't see much.