Well, no one knows the answer to this question for sure - since stars are so much brighter than planets, it turns out that it's really hard to see planets directly because the light from their sun swarms any light they might be reflecting back at us (well, besides the planets in our own solar system, obviously!). But recently, NASA launched a space telescope designed to try to find as many planets around other stars as it could. So far, it's found tons! I'm not an expert on this, but the last I heard, it had found around seven hundred planets or so. But those are just the planets closest to us, and the ones that are most visible; based on that number, if you try to estimate how many solar systems there are in the Milky Way, it turns out there might be as many as 100 BILLION solar systems in our own galaxy! Keep in mind that there are something like 300 billion stars in total, so it's possible that a good chunk of the stars you see in the sky have their own solar system!