Are UFOs a part of the solar system?
The existence of the so-called UFOs has not been conclusively confirmed. Therefore, we may be receiving visitors from other planets or moons of our own solar system, from other stars, or we may be receiving no visitors at all.
There is only one star that is part of our solar system. That is the sun. The stars we see are outside our solar system. "Solar" refers to our star. It holds the solar system together as it is through its gravity that everything orbits it, creating the solar system. So it is the key part of our solar system. That is why it is part of it.