We currently find most exoplanets based on how they affect the light around them, (known as Transit Photometry), so revolving around a sun helps, but there are also rouge planets that are not orbiting around a sun. Not all galaxies look like ours, The Milky Way, that is sort of flattened and spiral. I’ll see if I can find a good video to help explain. As for your idea of 10 dimensions, that is not in anyway provable. Colleagues working on String Theory are working hard to make the math work and they love to talk about all the dimensions and parallel universe theories, but it is in no way provable or testable at the moment (but neither is Cyclical Time, but it seems to fit better with what we currently know) There are two main schools of thought when it comes to this. One is based on Cyclical Time and the other is String Theory. I’m team Cyclical Time, until something better comes along, simply because when they start talking about the creation of infinite parallel universes, it is totally a anthropocentric construct, and we know the Universe, and what is has always done, doesn’t give a damn about one human’s decisions on this insignificant planet. Decisions one tiny human makes on this planet is not going to splinter the Universe off in a new direction. Anyway, here is a good video about finding Exoplanets.
https://www.youtube.com/watch?v=Zt7WPXZVzFA Here is a video that explains different types of galaxies we have identified (three main types).
https://www.youtube.com/watch?v=B7q0Z19sKdM