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.""

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.

No, you're all wrong!!

[Anonymous Coward]

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

Nope. Read again, more closely.

Astronomers Witness Whopper Galaxy Collision

The implication is that Burger King intends to merge with Dairy Queen and will be introducing its line of BK burgers at DQ. Honestly.

Re:

[morgan_greywolf]

The implication is that Burger King intends to merge with Dairy Queen and will be introducing its line of BK burgers at DQ. Honestly.

No, no. It's a merger of four giants! The implication is that Burger King, Subway, McDonald's and Taco Bell are all merging, and soon you'll be able to get McBurritos and Whopper subs on whole wheat.

Re:

[xENoLocO]

We already have that bullshit in Orlando. ugh.

Re:

[microTodd]

They're all over. KFC and Pizza Hut. Taco Bell and Long John Silver's. Or my personal favorite...Baskin-Robbins and Dunkin Donuts.

Its really weird to be able to order pizza, tacos, and friend fish at the same counter.

Re:

[Masami Eiri]

That's because KFC, Taco Bell, and Pizza Hut are already owned by the same corporation. I didn't think LJS is though... Anyway, that's why you see those combo restaurants. I think its convenient. Some family members want Pizza Hut, others want Taco Bell, they're in the same place.

Re:

[Luyseyal]

Not to mention the hospitals.
-l

Re:

[tomhudson]

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

Or one of the nastier black holes, sort of like what happens with corporate mergers gone wrong, or the federal deficit, for that matter.

Re:

[mwvdlee]

What I find most fascinating about this is that they have apparently found a way of knowing there won't be many bigger galaxies in the universe we aren't able to see.

Re:

[Brian Gordon]

Yes, this is a ridiculous claim. There's no way to possibly know how big the biggest galaxies are. Also, does anyone realize how stupid that analogy is of "sand trucks flinging sand everywhere"? What?!

Re:

[Ambitwistor]

It's not a ridiculous claim, if they're talking about the observable universe. We can't see every galaxy, but there's no reason to believe that what we are seeing is not a representative sample. It's harder to study the very earliest galaxies, because they're the farthest away and therefore faintest, but we can see galaxies all the way back to when galaxies probably first formed, and we can see things even earlier than that (e.g., the cosmic background radiation).

Re:

[KingPrad]

Holy Hell...that's the scariest thing I've ever heard of.

Re:

[notnAP]

We're Beatrice.

Re:

[JohnFluxx]

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.

Really?

[Funkcikle]

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

Re:

[Hoi Polloi]

I hope they have insurance.

We need goverment intervention!

[faloi]

We need to stop galaxies from forming a monopoly on being the only galaxy in the universe now, while there's still time. If we sit back and let these galaxies continue merging, it will be too late!

4 way stop?

[SQLGuru]

So, how long is this going to take? What happens when the black holes at the center of each one collide? And, if as we say yesterday, they are really worm holes, what will that imply? Will the wormholes be the 4-way stop of the galaxy?

Layne

Re:

[Ambitwistor]

What happens when the black holes at the center of each one collide?

You get one big black hole and a bunch of gravitational radiation.

Can singularities actually collide?

[Colin Smith]

Supposed to be infinitely small and all that.

 

Re:

[Josh Booth]

Well, their event horizons can collide, but once that happens, all bets are off, until some einstein 2.0 can figure out what happens in a black hole.

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:

[drooling-dog]

Not an astrophysicist, but... Sure, if the General Theory of Relativity has anything to say about it. I think what was unexpected in the paper was how rapidly the gas cloud collapses into a disk around the binary black holes, and how quickly the drag from the gaseous disk degrades their orbit around each other. A million years isn't a long time before the black holes merge...

1 + 1 + 1 + 1 = 10? Huh?

[ip_freely_2000]

"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."

4 galaxies the size of the Milky way create something 10 times bigger? Either the galaxies are much larger than the Milky Way or the result is not 10 times bigger...maybe only 4 times bigger?

Re:

[EggyToast]

I believe the "at least" means that the smallest one is still larger than the Milky Way. Meaning that all are greater than 1.

Re:

[Scarblac]

It says at least.

Re:

[danbert8]

The first part suggests that the galaxies are similar in size (either diameter or volume), whereas the second part refers to mass. It is entirely possible that each of the 4 galaxies is the same diameter as the Milky Way, but has combined mass of 10 Milky Ways.

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.

Re:

[backwardMechanic]

Astronomers don't usually worry too much about the math, so long as the powers of 10 are good to +/- 10ish, so you're well within bounds.

Re:

[Mikkeles]

It's probably related to the Banach-Tarski paradox! [wikipedia.org]

Re:

[gatkinso]

Did the term "at least" elude you?

Re:

[Lithdren]

All four are AT LEAST as large as our own.

Meaning, none smaller. Doesn't mean they cant be bigger.

Order of Magnitude

[neurostar]

Well, in some cases, astronomy is an order of magnitude science. As this collections of objects doesn't seem to have any gravitational lensing associated with it, there is no way to independently determine the mass of the system. A rough guess at the mass can be determined by assuming a mass to light radio since we know how bright it is (and presumably how far). That would lead to the mass estimates.

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:

[Opportunist]

Yeah, but will it run Linux?

Re:

[UbuntuDupe]

New galaxy? Why do people keep acting like this is something new? It's unbelievably old and out of date, and I don't know how it got on a *news* site. If the light from this eveny is just getting to us, it happened millions of years ago. Oh, I know, the old excuse, "well, it's new to *this* light cone". Kinda like how that '86 Chevy is a "new car" ... to me.

Re:

[Control Group]

If I had mod points and I hadn't already commented, I'd bump you.

I haven't laughed out loud at something on /. for a while. Thanks.

Re:

[HTH NE1]

Oh, I know, the old excuse, "well, it's new to *this* light cone".

Hey, stop taking words out of my mouth!

Mod that man up Funny with a hint of Insightful.

Re:

[thePsychologist]

Technically since this is observed hundreds of thousands light years away, it's already happened hundreds of thousands (perhaps many millions) of years ago.

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:

[UnanimousCoward]

Think Lindsay Lohan and rehab...

Re:

[spun]

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.

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 [ucr.edu] and this [ucla.edu] and this [faqs.org] 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 [hubblesite.org] 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.

Analogy breaking down

[Bazman]

So when four galaxies collide, they make a huge super-galaxy...

Now is that how they make those monster trucks?

But...

[hcdejong]

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

Re:

[Chris Mattern]

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

No boom today. Boom tomorrow. There's always a boom tomorrow.

I doubt a "star crash" will happen

[Opportunist]

Consider the amount of stars and the room between them. It's quite unlikely that many stars will actually "collide". Although it's fairly certain that due to gravity some will lose or gain a few planets and debris, some will start moving in a very different way around the center and so on. We'll certainly get a lot of "spill" from gravity desasters, but I don't really think that there will be many head-on collisions of entire stars or systems.

Insurance

[gsslay]

I hope neither galaxy is admitting culpability and have got those witnesses names and addresses.

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:

[Ambitwistor]

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.

That's exactly what some gamma ray bursts [wikipedia.org] are thought to be: colliding stars. However, since they're colliding neutron stars, we can't really see them before the explosion, so all you see is a great big flash at the end. You don't see two stars zooming toward each other before they collide.

So typically human...

[Ralph Spoilsport]

See a galactic train wreck, and EVERYONE has to slow down and look.

Move along, people - nothing to see here...

;-)

RS

Wild eyed exaggeration

[Flying pig]

A normal galactic collision is like compact cars smashing together?

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:

• Ought to be made to read Douglas Adams on how big the Universe is
• Ought to get taught about valid and invalid metaphors and similes at school
• Ought to stop whoring for research budget by trying to attract the mass media and dumbing down reality.

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?"

Biggest ?

[bytesex]

I thought the biggest galaxy was that one that covered about thirty degrees of the night sky all around, yet was invisible to naked eye - whatever happened to that story ?

Re:

[Ambitwistor]

You're thinking of the Saggitarius dwarf galaxy, which subtends 10 degrees. That's the largest in apparent size (other than the Milky Way, of course) because it's so close, but it's not the largest in actual size.

Galaxies - God - Cosmology

[MobyDisk]

Scientists now have a clear image of the God of the Whopper galaxy [businessweek.com].

Most massive extinction event yet

[mattr]

This sounds like awful news for anyone in or near any of those galaxies. We just had news that scientists had good reason to believe the Earth's own biodiversity is severely affected by nearby galaxies' radiation when we pop up over the plane of the galaxy and lose our shielding. When you add the beams of radiation from central black holes and other sources, and four times as many novas and supernovas in the same volume as usual, it sounds very inhospitable to life. And then think about an Earth like ours w

On the other hand ...

[jbeaupre]

Lots of aliens are having sex that normally wouldn't. "Grashnar, hold me! I don't want to die a virgin!"

NASA Link

[hawkfish]

For anyone who finds space.com as annoying as I do, here [nasa.gov] is the link to the original story at NASA's Spitzer site.

Astrophysical Journal LETTERS?!

[Shag]

Dear Astrophysical Journal Letters,

Late one night while I was working on my dissertation on polarimetry of active galactic nuclei, I was surprised by Maria, the physics department's delicious young cleaning lady. Her janitorial uniform did little to conceal her large, perky breasts, which were spherical and of uniform density...

I'm not sure this is a good idea...

Re:

[fr4nk]

It is assumed that the universe is not infinite in size.

Re:

[bazorg]

and that this scientist has seen enough galaxies to be sure of what he's saying.

Re:

[Ambitwistor]

No, it's just assumed that we're talking about the observable (or more likely, observed) universe.

Re:

[smooth wombat]

It is assumed that the universe is not infinite in size.

Which always brings up my question: if the universe is not infinite in size, what is it expanding into or sitting in? I.e. if you place a drop of ink into a glass container full of water, the drop will expand (eventually) until it meets the glass.

That is not what is happening according to current theories of the universe. The most common answer I get is that is loops back upon itself. Fine. That still doesn't explain what the universe sits

Re:

[JesseMcDonald]

Which always brings up my question: if the universe is not infinite in size, what is it expanding into or sitting in?

I'm not a physicist, but I'll take a stab at this anyway. Basically, the universe isn't expanding into anything. There isn't empty space beyond the universe's boundaries; there isn't anything beyond those boundaries. It doesn't even make sense to say "beyond the boundaries of the universe". There is no frame of reference anywhere in the universe than could possibly observe or interact wit

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.

Re:

[Yusaku Godai]

I don't have any mod points, so I'm replying to this AC to bump his comment up.

As he says, this is a fallacy. Even if there were an infinite number of galaxies, that does not mean that each galaxy is necessarily larger than any other. You could, in fact, have an infinite number of galaxies that are all the exact same size.

Re:

[Ambitwistor]

Yes, there can be a largest galaxy in an infinite universe, but the probability that these particular galaxies will be it, is infinitesimally small.

Re:

[Ambitwistor]

You are assuming certain things to come up with that probability.

Yes, but it's pretty ridiculous to assume otherwise: that "the largest galaxy" is going to get finite probability mass out of an infinite collection of galaxies.

Unlikely? sure, but that's not the point.

Yeah, it kind of is the point: it is not mathematically impossible, but still absurd, to believe that we have actually run across the largest galaxy out of an infinitude of galaxies.

Re:

[MBGMorden]

But the number of galaxies is not infinite. The universe itself has a finite ammount of mass and energy inside it, and that is used to make up a finite number of galaxies. Now from some texts I have read the number of galaxies numbers at least in the high billions, possibly trillions, but that's a LOT smaller than infinity ;).

Re:

[codeButcher]

And for them to know that this particular galaxy (when it eventually comes around) is bigger than all others, they'd have to compare it to all others. In an infinite universe, this will take, like, forever. Luckily for them the merger will not be completed anytime soon.

Re:

[thePsychologist]

Sorry, but your logic is flawed! The universe is not a continuum of sizes. There IS a smallest size, so there are a finite number of sizes in [0,k] intersect the set of possible sizes.

Give you a simple example: between 0 and 100ML of water, there are only a finite number of volumes that can exist, since the minimum size for anything is the water molecule.

Re:

[Chris Burke]

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 a

Re:

[4D6963]

If the universie in infinite, then there are an infinite number of galaxies that are even bigger.

Well the universe is not believed to be infinite but more like 150 Gly in diameter. And even then, there may be a limit to how big a galaxy can possibly be.

Re:

[MBGMorden]

That brings up yet another interesting point. If such stars have been shed in the past, then obviously they will be thrown out of the galaxy, but a star's fusion process and lifespan are not dependent upon the galaxy itself. I wonder how many "homeless" stars are floating in the spaces between two galaxies. I'd also wonder if they might have a greater chance of their planets (assuming they had any and that they maintained a stable orbit as the star was ejected from the galaxy) harboring life, given that

Completely off topic.

[jdray]

10 beware of goto
20 goto 10

Re:

[neoform]

Nah, that was just for G.W.

Re:

[Opportunist]

Well, his administration is much like a black hole. Sucking up everything that gets into its reach, letting no info out...

Re:

[steveo777]

You don't want that. If Voltron is forming that close, then it is inevitable that we'll end up on the business end of a Blazing Sword.

Re:

[Ambitwistor]

So this leads me to wonder, will a merger of this size cause a larger gravitational force as 4 swirling masses converge.

Not really. There will be more mass concentrated in the center of wherever the final galaxy ends up, but the gravitational field outside the boundary of where the current galaxies are won't really change.

Would this draw other galaxies closer to the newly merged one, ever increasing the size of the merged one?

No more so than the current galaxies are doing now; the final galaxy will have more or less the same mass as the originals, after all.

Re:

[Control Group]

the final galaxy will have more or less the same mass as the originals, after all

Less. It will have less.

Re:

[Ambitwistor]

That's technically true, due to mass loss from ejection, but the overall mass is still going to be pretty much the same, which was my overall point.

Re:

[gordo3000]

less, gravitational waves will draw a great deal of that mass-energy out of the local system..

Re:

[Ambitwistor]

Gravitational waves will be quite negligible compared to the total mass energy of the galaxies (though they will be a significant fraction of the mass-energy of the central black holes). Greater mass loss will be due simply to stars being ejected from the galaxies during the collision, but the end result will still be pretty close to the original mass of the system.

Re:

[gordo3000]

I'm not actually versed on the math, but I'd wonder what it would be like with teh collisions(ie in large galaxies what percent of mass is centered in teh central black hoels and surrounding things and how much of that gets radiated during a collision)....all I'm sure about is it will be less...

Re:

[Ambitwistor]

Not much mass is centered in central black holes, compared to the galaxy they're in. Our galaxy is around 100 billion solar masses, and the central black hole is only a few million solar masses — that's like 1/1000 of a percent of the total mass. Some supermassive black holes in quasars can be billions of solar masses, but that's not the sort of galaxy we're talking about here.

Colliding black holes can radiate a lot of their mass-energy as gravitational waves, though; something like 30-40% in the be

Not true

[Have Blue]

This was debunked by badastronomy.com. (Or at least that article is a bad argument for it.)

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/ [virginia.edu]
And take a look at a debunking here: http://www.badastronomy.com/bablog/2007/06/27/is-t he-sun-from-another-galaxy [badastronomy.com]

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 [virginia.edu] and here [badastronomy.com]. The Sun's orbit in the galaxy indicates that it did indeed originate in the Milky Way.

Arrghh mods, don't believe everything you read!

[Sibko]

The things this guy says on his website don't even make sense!

The fact that the Milky Way is seen in the sky at an angle has always puzzled astronomers. If we originated from the Milky Way, we ought to be oriented to the galaxy's ecliptic, with the planets aligned around our Sun in much the same angle as our Sun aligns with the Milky Way.

If our sun is from the Sagittarius Dwarf Galaxy, which is merging almost vertically with the Milky Way, you'd kinda assume then, that our orbit would be more 'galactic up-down' than the actual full orbit it has in the galactic plane. But I couldn't possibly explain it better than this guy: http://www.badastronomy.com/bablog/2007/06/27/is-t he-sun-from-another-galaxy/ [badastronomy.com]

Re:

[Ambitwistor]

will this start to see this happening during our lifetime, or has it already?

Unfortunately, no.

Old news

[pedestrian crossing]

No. Galaxies are huge, and these are very far away, so even if they are moving really fast they won't appear to move on a human time scale.

But the cool thing IMHO is that we are literally looking 5 billion years back in time.

Earth hadn't even formed when this collision took place, but we're looking at it right now.

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.

Re:

[Chris Burke]

Well, I suggest you take your untrained eye out of the city to someplace nice and dark, and preferably with someone who can find some good objects for you to look at. But really you only need to look at two things -- any star in the sky (not a planet, look for the twinkle, if it doesn't twinkle it's a planet), and then look at Andromeda. Andromeda is easy to see with binoculars, and you can tell it isn't a star with the naked eye. Anyway, that'll show you how stars and galaxies can be distinguished. The

Re:

[viewtouch]

Don't forget that this all happened 5 billion years ago.

Re:

[Basehart]

Jeez, talk about old news. Come on Slashdot, get with the program already.

Re:

[dakameleon]

Next few million years should suffice.

Re:

[pclminion]

From this distance, one vantage point, how can they know for sure this convergence is actually going to "collide" as opposed to just skim past each other? You can't tell how far apart they are in all 3 axii, just 2.

You get the third axis by comparing the Doppler shift with the apparent lateral speed. It's basic trig.