Tau was an uninhabited world, so it wasn't being 'invaded' so much as 'colonized.'

Our ship became stranded in the void. I'm not actually sure what happened after that.

[ Not until later. ]

It's a little more complicated than that, but theoretically yes. But you don't want to go somewhere that you'd be unable to use or construct a solar rail on the other side to return.

Most solar rails are constructed in the orbits of planets or major celestial bodies.