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Milky Way & Andromeda Collision
Frédéric writes: "A lof of people know that our Sun will be a red giant in about 15 billion years, and its size will increase dramaticaly beyond the Mercury orbit and we will burn. But do you know that the Andromeda Galaxy will collide with our Milky Way in about 3 billion years, a first time, then another time after 1 billion years to merge themselves, what a mess! There is some pretty nice simulations in MPEG, and a lot of pictures with some explanation. The simulator use 24 million particles, they are planning a 120 million particles simulation."
Your sig should be attributed to A.C. Clarke, not Issac Isamov. (Due to the nature of sigs on slashdot, if you fix this my comment will look weird because the fix will appear retroactively in your post, but hey, I can live with that.
Don't label something "offtopic" unless you know the topic well enough to tell what's on topic.
How does a galactic collision affect planets in a galaxy?
Consider a single star, not in a galaxy, with a planetary system like the sun. Nice and stable. But if it should be heading for a galaxy, what are the chances of it passing through without gravitational forces disrupting the planets?
Interstellar separation may be large compared to stellar radii, but if you pass through enough stars there's an increased chance that you come near enough to one to affect the planets. Maybe.
Baz
This event will completely overshadow the release of kernel 388472466124525.27324.212
I am sure everyone will forget to update their kernel when the galaxies collide.
On a less humorous note, has anyone read that a scientist claims that the Earth can be gradually moved away from the Sun, using the gravitational force of a comet? The side effect will be that we may lose the Moon in the process...
http://www.space.com/scienceastronomy/planetearth/ earth_move_010207.html
The side effect will be that we may lose the Moon in the process
That would be nothing short of a disaster. I remember seeing a documentary on TV a couple of years ago where they showed that it was the gravitational pull of the moon in its particular orbit, that holds earth's axis in place. Thus stopping the spin of the earth from upending the poles or placing them somewhere completely different. We'd suffer terrible climate instability if the moon didn't exist where it does, and it's possible that life might never have developed here at all.
Macka
I'm pretty sure it's estimated the sun will burn out and become a red giant in about 4 billion years.
All you people working on infinite lifespan projects might as well hang it up now. Just 3bil years is hardly worth it now is it?
You never really know how close to the edge you can go until you fall off.
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"Of course, that's just my opinion. I could be wrong." --Dennis Miller
Of course, in 3 billion years, this might not much matter, but for two colliding galaxies, its quite possible for both of them to pass through each other without any stars colliding. However, its extremely likely that one or two stars will come within a light year of Earth. What will happen is a lot of the debris in the Oort cloud which usually remains in long period orbits way way out there can be flung into the inner solar system (the same effect happens every 60 million years or so when the solar system passes through one of the spiral arms.
:)
When this happens, there are suddenly a lot more big rocks roaming around the inner solar system, and the chances of Earth getting hit by one of them increases dramatically.
Of course, I personally don't plan to lose any sleep over this.
-Restil
Play with my webcams and lights here
Both galaxies have lot of void space. Only here and there an object can be found so there's not much chance for real collisions. Off course gravite will pull all objects closer to another but because of their speed, I doubt many will actually collide. Can anybody give an estimate of how many objects will actually collide and what this means for live on earth?
0x or or snor perron?!
Really nice guy, too. In '93 I wrote him a letter and asked him what the status of the Nemesis Hypothesis was, and he wrote a very nice and thorough reply in which he indicated that Hipparcos, a satellite which was supposed to resolve it once and for all, suffered an instrumentation failure. They were falling back to a manual sky-search and were hoping to have it done by 2000.
Given that it's now 2001 and we haven't heard anything, I think we can conclude either
- The search is taking far longer than expected
- Fundamental problems in the search methods kept it from being a productive observation
- The search was concluded and nothing was found, and Nemesis is pretty much a dead theory
... That being said, Richard Mueller is a very serious scientist. It angers me when I hear people call him a kook for the Nemesis Hypothesis (not that the original poster did).The Nemesis Hypothesis was classic scientific work. It was a blindingly creative look at a very difficult problem. It explained past observations and made predictions for future observations. The hypothesis was, is, testable (admittedly, not easily testable).
Compare this to superstring theory, which has no observational support, no experimental support, no predictions for future observations. While I like superstring theory--it's a really cool thought exercise--it's not science.
So why is it so many hail Brian Greene (superstring theory luminary) as the next Einstein, and in the next breath condemn Mueller as a kook?
It's just like how two cars can collide despite the expansion of the universe. Our two galaxies are not big enough or distant enough to be affected by the large-scale expansion of the universe. Other effects are much more significant at these small scales.
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Patrick Doyle
I mod down every jackass who puts his moderation policy in his sig. Oh, wait a sec....
Sun's gonna go Red Giant in 5 billion years, not 15.
Picky picky picky.
--Nuintari
slashdot : where an opinion can be wrong.
I wonder if my collision insurance from State Farm covers galaxies. Which driver would be at fault?
I'm trying to teach myself to set people on fire with my mind... Is it hot in here?
Arthur C. Clarke
Because typical distances between objects in the universe (such as superclusters) are a lot Lot LOT bigger than the measly 2,300,000 light years between Milky Way and Andromeda.
The expansion of the universe means things which are already very far apart will get farther apart -- "the rich get richer...". It has miniscule effect at the level of individual galaxies, where gravity is firmly in charge.
You should now feel a whole lot smaller than you did a few minutes ago. On the bright side, you're still way bigger than quarks. :-)
Note that you're using the word "soon" in conjunction with an event 3 billion years from now. It seems to me that if we can get a self-sufficient Mars base within the next thousand years, and colonize other solar systems within the next million years, then we're way ahead of the game.
Overpopulation, biological warfare, mutating viri.Overpopulation is generally self-correcting (starvation). It's also easily handled by public education and women's rights (see western europe). And as for biowar/mutation, I have justified belief in medical progress and the human immune system.
Will Mozilla be finished by then so people can watch the live webcast?
Oops - my bad; it's just LA that're taxing stuff that isn't even on their planet.
To spell out "numerically": in each iteration, you basically compute for each particle the total vector of gravity pulling at it and then move it a bit in that direction. Lather, rinse, repeat. Many, many times.
The illegal we do immediately. The unconstitutional takes a little longer.
--Henry Kissinger
Anyone interested in this should really check out the book The Mote In Gods Eye by Larry Niven and Jerry Pournelle. Mankinds first encounter with an alien species is with a species in much the situation described above. They can't efficiently get out of their solar system, which has led to all sorts of changes in their society, biology, traits, etc. Makes for an excellent read.
Just as water vapour moving very energetically in clouds produces lightning, I would imagine that colliding gas clouds would cause a lot of unimaginably intense electric charges.
These clouds are also a plasma similar to the inside of a fluorescent tube, so the lightning would cause very intense bright flashes.
Imagine the night sky being lit up by hundreds or thousands of bright flashes.
Dude, that's like saying, "Your going to spend all this time and effort building this huge Widget factory, when you can just carve Widget's out yourself?". Yes, of course there is a high up-front cost, but it's made up for in the long run. Economies of Scale, hello?
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True enuf, although I suppose the article cannot get everything right.
Time to get out the 5000 rated sunblock
;-)
Check out the Vinny the Vampire comic strip
"It is a greater offense to steal men's labor, than their clothes"
I'm going to have to start taking bets on the outcome
Check out the Vinny the Vampire comic strip
"It is a greater offense to steal men's labor, than their clothes"
Why are they using the Startrek font on that "Quicktime" mpeg? Are they trying to get some funding for an escape plan?
Good thing that galactic spirals aren't due to winding, then, isn't it?
An excellent online reference on density waves (the phenomenon currently thought to be responsible for the appearance of spiral galaxies) is at http://fuse.pha.jhu.edu/~danforth/spiral
Density waves were proposed in the mid-60s and have (so far) stood up pretty well. What this has to do with the big bang or evolution is beyond me.
5 Gy is the rule of thumb figure. I even just asked a passing solar physicist about it... :-)
Employee of Inrupt, Project Release Manager and Community Manager for Solid
As a layman, I would have thought that all galaxies would be moving generally away from one another.
Then again perhaps I'll catch that ride on one of those Vogon ships .. which reminds me ... plenty of time to invest some cash in a towel company..
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Jon - TheSpork
I thought that was about 8 billion years? Anyone?
This is indeed highly cool and it's nice to see some astronomy on /. ... it's now comonly accepted that our galaxy has already borged many smaller less-fortunate ones in the local group; shreds of their corpses (I'm not making this up! have been located in our galaxy by looking for stars with anomalous motions, ie fossilised fragments of things we ate long ago.
Thing that gets me is, given that the Sloan Digital Sky Survey just found a quasar at redshift 6.2 (ie about 10 billion years old)... this is getting pretty close to the Big Bang... this doesn't give much time for our galaxy (or any others) to actually form, before we're switched on, full of stars, and eating our neighbours.
The more I write, the more this sounds like some sick geek in-joke... [*1 10 points if you spot the reference
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"I'm not downloaded, I'm just loaded and down"
Every day the sun gets hotter and in a little under one billion years the earth will be too hot for life as we know it. My suggestion would be start snapping up that cheap Mars real estate right now. It's always best to get in on the ground floor for the best prices.
Smeghead every day of the week.
In another 3 billion years, according to moore's law, our processors are going to have enough transistors to attract nearby galaxies just by turning on. i bet that didnt go into the particle field.
I am trying to quit smoking
Someone call our galaxy's insurance agent, and be sure to get some
photos of the accident. I'd sure hate to be stuck with the
repair bill on this one.
I assume that's at least marginally more accurate than the screen saver that comes with my Linux distribution, eh?
Seeing this woke my curiosity...
;)
How carefully and realisticly can they predict all this? It must be very close to a chaos-theory if you ask me, *EVERYTHING* affects *EVERYTHING* and here they are saying what's going to happen in 4 billion years - bold.
Of course people can guess and make it a good guess at that but really, how much time and knowledge have been put into these simulations. How much do we know about the world/universe around us to accuratly predict "so and so will happen..."? Is everything just based on what we know every starsystem looks like and it's position or is there more stuff to back it up?
And besides, who cares? I'm long gone when these 3.9999999999999999 billion years has passed
Anataka suki desu. Itsumo. Itsumademo.
See the rather tasty java applet by Leonardo Boselli, Galactic Collider 1.0, which shows how spiral arms are created when galaxies pass close by each other. You could change the start positions to whack two galaxies together, if that's what you really want to do...
The child's site you point to correctly points out that the sun will * burn out* in about 5 billion years, however, it will turn into a red giant about a billion years before that.
As for the 15 billion figure that is the estimated age of the *entire frikkin' universe* so I guess the author should get credit for having been able to attach a cosmological number with a subject of cosmology, but it's kinda like saying that Lincoln was assasinated in 1066.
KFG
One statement there says "the gap is closing at 500000 km/hour". I am not a professional astronomer, but I understand that we can not currently determine the proper motion of objects farther away from us than a few tens of light years. So although we know that Andromeda and the Milky Way are hurtling toward each other at 500 thousand kilometers per hour, we do not know how fast they are moving with respect to each other in the sideways direction. It is highly likely that the proper motion component of the relative velocities is greater than zero. If there is a high enough proper velocity, this would mean that the two galaxies, being in orbit about a common point, would miss when they came to their closest point and just fly right by each other.
The article touches on this with "the best explanation is that the Milky Way and Andromeda are in fact a bound pair of galaxies in orbit around one another." But they make no reference to the unknown proper motion.
Also, it is possible that the galaxy we live in now may well be the result of a historic collision of two smaller galaxies. The evidence for this is that the Magellinic Clouds are now in orbit around the Milky Way and are irregular. Now, this is speculation on my part, but that's allowed, isn't it.
A few years ago, astronomers announced that a dwarf galaxy in the direction of Saggitarius was colliding with the Milky Way. I'm not sure it's exactly within our galaxy's borders [I'd thought it was, but the only reference I could find after a minute of googling said otherwise], but it's orbiting (every billion years or so), and the galaxies have had an effect on each other. Check out this FAQ about the dwarf and the referred page. Key quote: "It [SagDEG] is apparently in process of being disrupted by tidal gravitational forces of its big massive neighbor in this encounter. "
xlock -inwindow -mode galaxy &
:)
Bowie J. Poag
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Mod up a post Rob doesn't like and you'll never mod again
Galaxies collide all the time. It's not a real destructive process. Look at the distance between stars. A "collision" of galaxies is like the collision of dust particles in a wind. There are very few stars that actually come into contact with each other, it simply increases the mass of the galaxy as a whole. We add a lot more stars to the galaxy and that's pretty much it.
Never mind the fact that, unless we start to migrate to other star systems in the next few hundred years, there's little chance that any of our descendants will be around to see it.
We're at a very delicate time in the history of our race. If we don't begin to migrate to other planets and other star systems soon, we'll be doomed. Overpopulation, biological warfare, mutating viri. All these things can lead to the destruction of all life on this planet. Then there are the less likely scenarios: Asteroid collisions, comet collisions. These too will happen, it's just a matter of when.
But the actual collision of the galaxies, as I see it, is just another opportunity for us to have more planets to colonize.
It also raises the possibility of us finding other life out there.
Scientific American ran a great article here about how the chances are, we're the most advanced species in our galaxy and why. It makes a great deal of sense. A collision with Andromeda could change that, and that I find interesting. Especially given the time frame. If we're to migrate through the galaxy, we could be in very good shape if Andromeda itself is already populated.
But I'm just wandering off into all kinds of stuff completely unrelated. Sorry... I love this stuff, though.
solving the ODE's is done numerically.
the main problem is of calculating the force on every star at every iteration.
the problem was thought to be quadratic , but a decade ago was shown to be linear (by a PhD student named greengard) using spherical harmonics expansions.
a very nice layman's introduction is at:
http://www.amara.com/papers/nbody.html
there are other sources linked there as well.
keywords:
N-body problem
Barnes-Hut algorithm
Fast Multipole Method (FMM)
BTW I wonder what method they used, my guess is that at 10^8 stars an adaptive FMM variant is fastest.
Working for necessity's mother.
Galactic collisions are actually relatively common in Nature; typical galactic separations are of order hundreds to thousands of kiloparsecs (kpc), whereas a typical galaxy is of order a few kpc in radius. Moreover, galaxies form along a highly filamentary spiderwork of structure in the early universe, and tend to flow inwards to more massive galaxies.
This situation is to be contrasted with the fate of stars during a galactic collision. Stellar radii are about 10^8 times smaller than the typical interstellar separation, so the vast majority of stars will simply fly right by another. A few stars will probably encounter a direct encounter (particularly if the initial pass is close enough to raise subtantial tides on the stars, which would act to drain energy and angular momentum from the system), but the vast majority fly by unscathed.
It is true, however, that gaseous clouds in the interstellar medium are much more extended that stars, and collision between clouds (particularly giant molecular clouds) will be quite spectacular. It is hypothesized that cloud collisions as well as gaseous flows (bringing tremendous influxes of mass to the galactic nuclar region) resulting from galactic collisions can account for the tremendous bursts of star formation seen in "starburst" galaxies such as NGC 1808.
In any case, the future collision of the Milky Way with Andromeda will be quite fascinating for far future Milky Way astronomers (if any are still around). Or perhaps for astronomers in other galaxies, far, far away...
Bob
Science, like Nature, must also be tamed, with a view turned towards its preservation.
3 billion years, eh? That ought to give California plenty of time to figure out how to tax Andromeda.
Look, there's no point in acting all surprised about it! The plans for the destruction of the Milky Way have been up at your local planning office in the Lesser Magellanic Clouds for the last one and a half Hubble Times so there's no point complaining now! I don't know, stupid bloody apathetic Galaxy, I've got no sympathy at all!
Phear my l33t homepage.
"A lof of people know that our Sun will be a red giant in about 15 billions years, and its size will increase dramaticaly beyond the Mercury orbit and we will burn. " Who needs demotivators?