"Just a minute..."
"That's odd".
When it comes to probing dwarfs, NASA's New Horizons Pluto probe has been hogging the limelight. But the Dawn spacecraft orbiting tiny Ceres, which is hidden in the asteroid belt between Mars and Jupiter, is back in operation – and has sent back the first full maps of the sort-of planet. Crucially, the latest pictures fail to …
. . . on either Ceres or Pluto it is still true that there could be almost unlimited alien activity around various parts of the solar system that we just haven't looked at (or closely enough) yet.
So long as they're sensible enough not to broadcast using EM (or only using tightly focussed beams) we would never know.
Probably not though . . .