When galaxies collide, how many stars actually collide?

Question

Of course this takes millions of years.

Answer 1

The distance between the stars in a galaxy is very large, When two galaxies pass through each other, there is very little probability of a star hitting another.

However, the gravitational forces between the stars in the galaxies do affect the other stars. I saw a computer simulation of two galaxies colliding and the result was stars scattering all over, some clumping together. The action was not caused by stars colliding but by their gravitational fields interacting.

Answer 2

Let's do a quick, back-of-the-envelope type calculation of how many star collisions you might expect if two galaxies like our own collide with each other.

Our galaxy is basically disk shaped with a radius of 50,000 light-years. This translates to around 2.5*10^20 kilometers. This gives an area for the disk of about 2*10^41 square kilometers.

Let's say a typical star has a radius of around 2*10^6 kilometers (this may be a bit off, but not by much). With this, the typical cross sectional area will by 1.2*10^13 square kilometers. There are about 10^11 stars in our galaxy, so the total cross sectional area coveres by stars is around 1.2*10^24.

Dividing, we find that the proportion of the cross section of our galaxy covered by stars is (2*10^41)/(1.2*10^24) which is 1.6*10^-17. This represents the probability that a star will be hit by one individual other star in the other galaxy. Now multiply this by the number of stars in the other galaxy, 10^11, to find that the approximate probability of a collision is 1.6*10-6.

In other words, the probability of two stars colliding is on the order of 1 in 600,000. Even with our estimates, this shows that it is pretty unlikely that any stars at all will actually collide when two galaxies collide. Even if the average size of a star was 100 times as great as in this estimate, the likelihood would still be very small.

Answer 3

Interacting galaxies (Colliding galaxies) is the result of one galaxy's gravity disturbing another galaxy. An example of minor interaction would be a satellite galaxy disturbing the primary galaxy's spiral arms. An example of major interaction would be a galactic collision.

[edit]
Satellite interaction

The Whirlpool Galaxy with its satellite NGc 5195A giant galaxy interacting with its satellites is common. A satellite's gravity could attract one of the primary's spiral arms. Or even the satellite could dive in to the primary (e.g. Sagittarius Dwarf Elliptical Galaxy). This could trigger a small amount of star formation. The satellite could be a vacuum cleaner and suck up some of its primary stars or vice versa.

[edit]
Galaxy collision

The Mice GalaxiesColliding galaxies are common in galaxy evolution. Colliding may lead to merging. Merging is the most violent of all galaxy interactions. This occur when two galaxies collide and find they do not have enough momentum to continue traveling after the collision. Instead, they fall back into each other and eventually merge together, forming one galaxy. If one of the colliding galaxies is much larger than the other, it will remain largely intact after the merger; that is, the larger galaxy will look much the same while the smaller galaxy will be stripped apart and become part of the larger galaxy. Collisions are less violent than mergers in that both galaxies remain separate after the collisions.

Answer 4

Yes, of course, a very long time.

Sorry, not enough data! Glancing blows or solid SMACK! How large are each of the galaxies in width and depth? --And what is the distribution pattern (globe, pinwheel, spiral, bar shape?) and density? How many stars in each under those conditions to start with?

If the centers are densely populated and collide, then you are talking about--on the average--of millions, just countless millions--and perhaps even the creation of a super black hole. --If just a glancing blow, then perhaps as few as a couple of thousand.

Sorry, not enough data, and even with precision data, the number would only be an approximation because 3-D in the round observation of ALL collision events between individual stars would not be possible without repeated circumnavigation of the entire mess and that would not be possible before the event would be concluded because of the distances and speeds required.

Answer 5

Very likely, none.

Stars are millions of miles across, true. However, even during a collision between galaxies, they are separated by thousands or millions OF millions of miles. It's like two bullets colliding in mid-air: possible, but highly unlikely. Space is really, really empty, even within a galaxy.

Now, immense clouds of gas are a different story. They will collide during galaxy collisions and mergers, setting off episodes of large-scale star formation.

JIM

Answer 6

When galaxies collide the stars do not collide. They are thrown as far as 3-5 light years away due to intense shockwave.

Answer 7

Galaxies often crash into one another. Even our own galaxy has had others pass right through it. Don't worry though, galaxies can pass through each other quite safely. Stars are so far apart that the chances of two colliding is very unlikely

http://www.kidsastronomy.com/galaxys.htm

Answer 8

Actual collisions between stars would be very rare, given the huge distances between stars. When we observe interacting galaxies, the most noticeable effect is usually the intense star birth activity due to the effects on the galactic gas clouds. But the most spectacular collision in the merger of two galaxies may be the merger of their central black holes.

Answer 9

The number of stars within any galaxy is an estimation. It would be impossible to know the exact number of stars involved in a collision, let alone how many different kinds of stars were involved.

Answer 10

As I understand it, very few if any actually collide. There is so much space between the systems that they usually just pass each other by or merge together with very little contact between bodies.