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.""

Comments

Merger?

[MECC]

"When this merger is complete, this will be one of the biggest galaxies in the universe,"

Kind of like if Walmart, Target, Sears, and the DoD merged?

One wonders what the galactic lawyers will get out of this.

Really?

[Funkcikle]

So a galaxy is not like a series of tubes, it is like a truck? Fascinating insight there.

Its Galacta-mania IV!

[sizzzzlerz]

Its an four-way inter-galactic throw-down to determine the true Champion of the Universe!

Four galaxies enter. One galaxy leaves.

Let me guess...

[cosmocain]

...the new-formed galaxy will be named:

BEOWULF!

Re:One of the biggest in the universe?

[Anonymous Coward]

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.

One of the biggest in the Universe?

[kalirion]

Shouldn't that be "One of the biggest in the known Universe"?

Expanding Universe?

[slapout]

I thought that galaxys where all moving away from each other. How did these manage to colide?

Re:Expanding Universe?

[Ambitwistor]

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.

Re:Expanding Universe?

[Control Group]

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.

But...

[hcdejong]

There was no kaboom! There is supposed to be an earth-shattering kaboom!

Re:1 + 1 + 1 + 1 = 10? Huh?

[Yusaku Godai]

Well, as a programmer, the way I see it is that it should be 1 + 1 + 1 + 1 = 100, so that should *really* blow your mind.

This type story doesn't do much for me

[alta]

Now, when someone can show me some live footage of two stars crashing into each other and a really big explosion, then I'll be impressed. Something far enough away so I can actually see it all happening, but not so far that it looks like a few grains of sand crashing into each other.

The other thing that keeps me getting excited about this stuff is when something REALLY COOL is going to happen, and then they say. "It will be in the very near future, realativly, in the next 5 million years."

I got more out of the banner ads for self aiming telescopes in the $400-$500 range. I never was good at aiming my old telescope. I could find the moon, but not anything smaller.

Re:4 way stop?

[drooling-dog]

What happens when the black holes at the center of each one collide? Glad you asked that question... Just read a couple of papers about that yesterday in the 29 June issue of Science. From one of the abstracts: It is normally assumed that after the merger of two massive galaxies, a SMBH [supermassive black hole] binary will form, shrink because of stellar gas dynamical processes, and ultimately coalesce by emitting a burst of gravitational waves... We report hydrodynamical simulations that track the formation of a SMBH binary down to scales of a few light years after the collision between two spiral galaxies. A massive, turbulant, nuclear gaseous disk arises as the a result of the galaxy merger. The black holes form an eccentric binary in the disk in less than 1 million years as a result of the gravitational drag from the gas rather than from the stars. - Meyer et.al., Rapid Formation of Supermassive Black Hole Binaries in Galaxy Mergers with Gas, Science 316,1874 (2007).

Re:We're in the middle of a galactic accident now

[Yusaku Godai]

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.

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-t he-sun-from-another-galaxy

And the wonkiness about the angle we see the Milky Way at from Earth is just plain bad math.

That link is false

[Ambitwistor]

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.

Re:1 + 1 + 1 + 1 = 10? Huh?

[Mikkeles]

It's probably related to the Banach-Tarski paradox!

It's sorta like this

[Moraelin]

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.