Yup.
But, I take such a probe very seriously. So I declared war, and will destroy his fleets. He may retaliate in great force. If so, I am ruined. Alternatively, he may decide I'm not worth the effort, and leave me alone. Either way, I've re-routed scouts to the planets between me and him, and will send some subspacers and blackbirds as well later, just to make sure I have plenty of advance warning.
If it was me, I would just send my main fleet at you and take the capital, but then I'm a jerk and don't mind wasting 10 battleships and 30 cruisers at this stage of the game, since I have no real targets anyway.