-- Earth is one planet is a "Solar System", that consists of everything that's gravitationally hooked to the Sun ... one star. This system contains 7 other other significant planets, more than 100 of their moons, and huge numbers of comets, asteroids, dwarf planets, and countless bodies in a giant shell that are so small and so far away that we can only see a few of them so far. Every one of these items orbits the sun. The ones that are farthest out may take thousands of years to complete one orbit.
That's the 'kingdom' of ONE star ... the sun.
-- It's very likely that there are similar gatherings of different-size objects around MOST stars ... maybe ALL stars. Those objects are tremendously difficult for us to see. We're just beginning to be able to see the most massive planets that go with other stars, and already, something like a thousand of them have been discovered. We know that they're there, but we can't see things like their actual size or surface markings yet.
-- Stars are clumped in gatherings of several billion, called 'galaxies'. Our sun is one of an estimated 300 to 400 billion stars in one galaxy, which we call the "Milky Way Galaxy".
-- Astronomers estimate that there are billions of other galaxies.
So there are billions of billions of other stars, and most of them may have several planets.
That's an awful lot of OTHER physical systems out there, that contain other planets and moons.
Having trouble wrapping your mind around all of that ? Don't worry, you're not the only one. It's easy for us to talk about it, but impossible for our minds to actually understand it. It's just too big.
