I was presuming that nobody has any ftl tech, given that it seems to violate the laws of physics for such a technology to exist. And you can look virtually everywhere, in the galaxy at least, with the right technology (and probably less advanced a tech than needed for manned space travel, what you need is a machine, capable of using the resources available in some asteroid to construct more of itself, and send those copies off towards other star systems. These probes would multiply exponentially until they've explored every star in the galaxy, with no further input required beyond building the first one)