Where are the other solar systems?
Somewhere in the Universe. Andromeda is the galaxy closest to ours (The Milky Way). Our solar system is packed with minor planets (those much smaller than Pluto). Many more than people in general are aware of. Scientists know of around 707.000 minor planets.
The stars you see in the sky are kinda like our sun - they have things orbiting them; planets, minor planets, asteroids etc. Our sun is, afterall, just a star itself.
There are I believe around 3500 known exoplanets that we humans are aware of. They are naturally very hard to discover, as they are so extremely far away from us. An exoplanet is a planet that orbits another star than our star (the sun). So knowing how difficult it is to take pictures of Neptune, one can realize how difficult it is to take pictures of exoplanets!
A quick little Google search: Among the estimated 1400 stars located within 50 light-years, 40 had been confirmed to have planetary systems with 14 other stars having unconfirmed exoplanet candidates.
The solar system closest to us is called Proxima Centauri. It's located about 4 light-years from us. It wasn't until August 2016 (!!) that scientists could confirm that Proxima Centauri has a planet that is now called Proxima b (why such a boring name?!)
But considering these discoveries are happening now and then in our time now, the number of discovered stars & planets are constantly increasing.
How do they find these planets, considering how far away they are, one asks? They observe the stars and if they find that a shadow is passing that star with even intervals, they can count how big it is and then determine if it's a planet or something else orbiting.
