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Milky Way & Andromeda Collision
Posted by
Hemos
on Wed Jul 11, 2001 03:52 AM
from the pretty-pictures dept.
from the pretty-pictures dept.
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."
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Milky Way & Andromeda Collision
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Pretty sim of colliding galaxies (Score:3)
The first gentleman had it about right (Score:3)
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
Re:So what does this mean? (Score:3)
the chance that none of the 1e11 stars in Andromeda will collide with one of "our" stars is approximately 1 - (1e11 x 8.3e-19) = 1 - 8.3e-8, very close to 1
Don't you mean (1 - 8.3e-19) ^ 1e11? I mean, assuming each potential collision is an independant, random event. However, according to maple, this is still roughly 1. Huh. Imagine that.
By the way, if anyone around here actually read articles, someone might note that one of the researchers said that in the case where the sun ends up in the thick of things, the risk to the Earth is minimal, though the night sky would be quite bright due to all the starbursts going on.
But I think the coolest part is right before the collision, when an entire half of the night sky is filled with a great big spiral galaxy! Holy mind blow!
Some Important Things to Note (Score:3)
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.
Big deal. It's happening already. (Score:4)
Who needs MPEG? (Score:4)
xlock -inwindow -mode galaxy &
:)
Milky Way and Andromeda merge? (Score:4)
--
Not such a big deal (Score:4)
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 [sciam.com] 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.
Re:15 billion years? (Score:4)
n-body problem resources. (Score:4)
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.
Galactic Collisions and Starburst Galaxies (Score:5)
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 [nasa.gov].
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
Re:How far gone are they? (Score:5)
4,000,000,000 years - 3,999,999,999.9999999 years /.
= 0.0000001 years = 0.0000365 days = 0.000876 hours = 0.05256 minutes = 3.1536 seconds until you'll be "long gone". Since it's now considerably more than 3 seconds since the parent post was made, I'd like to offer my deepest condolences to the family and friends of Faile. Perhaps Slashdot could put up a black colour-scheme every July 11th in rememberence of this noble member of the community, who used his dying breaths to post to
California (Score:5)
Don't Panic... (Score:5)
What a way to start a morning (Score:5)
Re:So what does this mean? (Score:5)
The main danger, if I recall correctly, comes from colliding gas clouds. These are much bigger than stars, and about as common, so the chances this will happen are far greater. Colliding gas clouds tend to form stars, as their densities suddenly increase due to the shock, and some of those stars will be super massive ones that go supernova in a few million years. A supernova right nextdoor (on an astronomical scale, at least) is not something you want to happen, believe me.
- Kite
Re:Not such a big deal (Score:5)
Some scientists are speculating on 'Nemesis', a dwarf star on a very wide orbit (period 30 million years) around the Sun. They claim Nemesis is responsible for the mass extinctions, dropping comets to inner Solar System as it passed through the Oort cloud.
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.
I agree that we should be going ASAP. However, it is not possible to colonize the stars before have lots of experience on colonization in the Solar System. There's also some propulsion research to be done.
Mars is probably within our reach, but it is not politically feasible. Even a simple manned mission to Mars would need global cooperation of all the major space players (USA, EU/ESA, Japan, Canada, Russia, maybe even China) as no-one has the money and political will to do it alone. I think the cost of a Mars-flight would be somethink like 1 Trillion US dollars. That would mean the American share would be of the order 400 Billion dollars.
I think a permanent lunar base would be feasible. (I have read some ILEWG publicationts for this, and recommend them for anyone interested in lunar exploration. A google search should get you started.) The cost is estimated to be of the order 200 Billion US dollars, so it is a little more than ISS or NMD. However, there is lots of small-scale developments that could be done with less money. ESA and NASA are doing some small-scale research already. The Moon base could could be financed as a US/EU cooperation. Maybe Canada and Japan could also join. Thus the US share would be of the order 100 Billion dollars. So, all we need is the political will that makes the decision: Forget the NMD, we settle the Moon instead. Sigh....
I'm sure one day we will turn the Moon to a real spaceport. Launching something from the Moon to low Earth orbit requires less energy than launching it from Earth. As Moon has no atmosphere, the satellites and spacecrafts could be build easily (no messing with cleanrooms, no out-gassing problems) over there from local raw materials. There's plenty of solar energy available in the Moon, so raw material extraction is possible.
The lack of atmospehere could also allow launching of satellites with coil/railgun like devices powered by solar electricity. This would mean no cumbersome rockets wasting chemical fuel. (HCNO elements are not easily available on the moon, so chemical fuel would be stupid)