Donuel,

Sorry, any radioactive isotopes of gold would have decayed away, if they are not being produced in the solar system. Where do you think transmutation is happening?

https://en.wikipedia.org/wiki/Isotopes_of_gold

Please note the half-lives- any trace amounts left after 4.5 to 5 billion years would not be a risk.

And we do not (yet) have gravity tractors of warp drives, in any deployable form. I have no problem working on them, but it would be nice to have some means of changing the orbits of bodies that would otherwise collide with the earth ASAP.