Yes, that is right. And whoever "owns" that planet should have a name, so you can tell that the planet is occupied. Be sure you have good defense left on your planet before sending off attacks to someone else's planet. It takes about a day [or more] for your fleet to even to get to that person's planet, and he will know you are coming and could launch against you! He will also have defenses that could defeat your fleet. He can also send fleets from his other planets to the planet you plan to attack [wo you knowing it]. So, don't get trigger happy until you are a tad more familiar with things.