Does other galaxies exist with planets in them or are we the only one???
Other galaxies will definitely have stars systems with planets.
Now that we have telescopes on satellites, we can detect planets orbiting nearby stars. Over 3,000 exoplanets have been discovered and the number is increasing.
Given that these exoplanets are orbiting stars in the nearby region of our galaxy, there must be many more. I fact many think that most star systems have planets.
Given that our Milky Way galaxy is one of billion, there must be planets in most if not all of them.