[SampleMan]

Some astronomers have recently suggested that neutron-rich heavy elements such as gold might be most easily made in rare neutron-rich explosions such as the collision of neutron stars.

On the Discovery Channel an astrophysics guru was stating that the collision of two galaxies would likely result in zero star collisions, so how do they explain the frequency of neutron star collisions?

[OSHA]

so how do they explain the frequency of neutron star collisions?

Binary star systems which are very common.

[sig226]

so how do they explain the frequency of neutron star collisions?

They don't. Proxima Centauri is 4.2 lightyears away and is our nearest neighbor. There is enough distance for another star to pass between us without seriously disturbing either system. In order for a stable system to decay into a collision, a third object would have to be involved. Or the colliding object could be a runaway star, possibly liberated when another multiple system broke down.

Interestingly, the study of mass extinctions led to the belief that we've suffered massive comet impacts about every 27,000,000 years. This could happen if we had an undetected binary star and it's orbit dislodged objects from the Kuiper Belt at this interval. Some astronomers are taking the suggestion seriously enough to look for the object. And if there are two massive objects circling the solar system, we may be screwed. :)