What evidence is there to prove that galaxies collide and merge?
These pictures...
If when Galaxies collide, the dark matter keeps moving without being affected by the collision. Why doesn't the resultant single galaxy fly apart?
Actually, that's what happens most of the time. The galaxies don't so much "fly apart" as "pass right through each other". Remember that galaxies are mostly empty space: our .0000001 light-year diameter sun is 4 light years from its nearest neighbor. The centers are considerably denser, but still, if the galaxies are moving together fast enough, the pass right through each other. It sucks for whoever happens to be living on a planet near a star that does get sucked into somebody's galactic black hole, but the galaxy as a whole doesn't care all that much.If the galaxies collide slowly, they may merge. And in that case, it's possible that what you're predicting happens: the galaxy loses some of its dark matter, giving it insufficient mass to keep its stars rotating the way they are. But that's not the only possible outcome. It depends a lot on how the galaxies are oriented towards each other, with respect to their angular momentum. Sometimes they'll add, sometimes they'll cancel out, and then the entire thing can indeed go kablooey. Sometimes they'll sneak up on each other, and the dark matter's gravitational pull will end up making the whole mass form a new, larger galaxy around the barycenter. It's a many-body problem, and tracing the history of all the stars and all the matter is very hard. Some stars will always be flung out of a galactic collision; others will be assimilated, and everybody will shift around, looking for a new equilibrium (over the course of millions of years). We haven't observed nearly as many galaxies colliding as it would take to consider all of the possibilities, but it can all be simulated in a computer. The results vary widely, depending on just who hits whom, and how hard.
What happens when galaxies collide? If two galaxies collided, would existing life be destroyed?
The chances are that life will be just fine.Galaxies are unimaginably large, but to get an idea of how Earth might be affected by a collision between the Milky Way and Andromeda, think about the Sun.The Sun is 1.4 million km wide, or 0.00000015 lightyears.The distance between the Sun and Earth is 150 million km, or 0.000016 lightyears.The distance between the Sun and Pluto at it farthest point is 7.38 billion km, or 0.00078 lightyears.The distance between the Sun and the edge of its magnetic field is 14.5 billion km or 0.0015 lightyears.The distance between the Sun and the nearest star (Alpha Centuri - actually 3 stars orbiting each other A, B and Proxmia) is 4.3 lightyears away.For arguments, sake, lets say these are typical distances between stars and solar systems within all galaxies.This means you can fit 2,900 of our solar systems between the Sun and Alpha Centauri, and the Solar System itself between the Sun and its edge is 99.999924386% empty.So the chances of the Earth, or the Sun colliding with another star or planet in the mashing of the two galaxies is actually incredibly remote. What’s more likely to happen is that the introduction of new gravity sources of so many new stars will disorient the orbits of the planets of the Solar System, which could still result in life on Earth ending.
What does that mean that 2 spiral galaxies have collided?
Well Ann, it means just what you wrote : two spiral galaxies that have collided.Two “objects” in the global Universe that were moving towards each other, due to their initial directions and reinforced by the gravity between them, having made them collide.Off course it is a huge “event”, that collision, but it took millions of years to complete. Suppose even if they move head on, the relative speed of approach is so tiny in comparison to their dimensions it takes millions of years before their centres can “meet”! The outcome of any collision depends on a lot of factors. Sometimes it will become one bigger (new to be named) galaxy. Sometimes they “fly” thru each other, both coming out differently.
What are 3 possible outcomes for plants that washed up on shore?
Before the colonization of plants on earth, earth was mostly covered by water. The parts that were land were barren and inhospitable. What are 3 possible outcomes for plants that washed up on shore?
What happens when our galaxy collides with the Andromeda galaxy?
A collision... With broadly speaking, 2 outcomes : 1) they pass through each other then go their separate ways. 2) they merge into one galaxy. Apparently option (2) is going to happen, but not necessarily on the first pass. The two galaxies are essentially already orbiting each other. In an elliptical orbit. The period may be 20 million years or longer. After the first pass, which will occur in about 5 billion years, the period of the ellipse will reduce to perhaps just one billion years. The following close pass will see the final merger of the two galaxies. There is a "fly in the ointment". As you alluded, both galaxies contain a SMBH. (Super Massive Black Hole) Almost independently of the rest of the collision, the 2 SMBHs will take up an orbit around each other, say, when they approach within 100,000 light years of each other. They will then commence to lose gravitational energy and spiral toward each other. They will merge after perhaps several hundred million years. In the process of merging they will "eat" millions, perhaps billions of stars from both galaxies. The core of each galaxy will be particularly likely to be absorbed. Maybe the earth/sun will remain unscathed to witness the events. Or maybe the sun is fated to be lunch for one of the SMBHs.
What happens when 2 stars collide?
There are several possibilities. If the collision speed is higher than a particular threshold speed, say about 300 miles per second, enough kinetic energy would be imparted to the two masses that the stellar material would dissipate into a vast expanding cloud of gas, never to reassemble itself into a new star. If the speed were very slow, the stars would merge into a new, more massive, star. The evolution of the new star would begin with a rejuvenated core of fresh fuel since the merging of the two stars would have mixed new hydrogen fuel into the core of the new star. If the speed of the impact is moderate and off center, the stars will go into a very tight orbit around one another, perhaps even sharing a common gaseous envelope. Over time, the two separate cores would spiral into each other, and you would again be left with one new, massive star. Since the escape velocity of the Sun is about 1.3 million miles per hour, this is about equal to the threshold speed of the impact. If a smaller star, like a white dwarf or neutron star, smashes into a bigger star, like a red giant, most of the giant's outer envelope would be blown off as it absorbs the impact. The results get a little more violent when two smaller stars collide. Neutron stars are very small and dense. If a neutron star reaches a certain mass, it will implode and form a black hole. Therefore, if two neutron stars merge but their combined mass is more than the maximum mass a single neutron star can have, they implode into a black hole. If the circumstances are the same when two white dwarf stars collide, they will implode into a neutron star.
When the Milky Way and Andromeda galaxies merge, what would cause that new galaxy to become a spiral galaxy?
The outcome will not end up as a spiral galaxy. As of now our galaxy and Andromeda are spirals. But, in some four billion years when our galaxy begins to merge with Andromeda, things are gonna be a chaotic mess. The merging galaxies are gonna become all distorted and unrecognizable as the gravitational effects of all the stars, black holes, planets and other objects passing each other in the merging process will alter the orbital paths of pretty much every star and other objects in both galaxies. A large number of stars and other objects will most likely be gravitationally ejected from the merging galaxies in some four to six billion years, especially if they get close enough to either of the supermassive black holes that reside in our galaxy or Andromeda, to either get eaten up or gravitationally thrown out of the galaxies entirely. After the dust settles, which will take another three billion years after the galaxies start colliding, the final outcome will be a mega elliptical galaxy. The chances of the final outcome being a new spiral galaxy are pretty much zero percent.
What would happen to Earth if the Andromeda galaxy collides with ours right now?
That will happen in about four billion years. The sun and earth will be quite different by then. If the sun hasn't evolved into a red giant by then, it's certainly thinking about it. Whether or not a red giant sun would obliterate the earth is hard to say. The limb of the sun may reach earth, which will be farther away from the sun, but red giants are quite nebulous and far less dense than middle age stars. The earth will definitely be too hot to support life by then. If the melted, barren, desolate rock survives in some form or fashion one of two things will happen when the milky way collides with andromeda.Either the solar system will be flung into intergalactic space like millions of other stars, or it will eventually fall into a stable orbit around the newly formed mega galaxy.The collision will take about two billion years if memory serves correctly, making the sun 6 billion years older than it is now. The sun will eventually become a white dwarf with an awesome planetary nebula surrounding it.