exoplanets
You don't.
A huge mass of stars and planets is called a galaxy.
An astronomer.
Astronomers
Planets orbit stars. Our planet (earth) orbits a star we call the sun.
This will never happen.
Planets orbit stars.
On the contrary! A star has planets, which circulate it. And planets have moons. Stars do not circle planets.
Anything outside the Earth is astronomy.
Planets and stars have gravity.
Those are called "planets". The ancient Greeks distinguished "fixed stars" - which is what we nowadays simply call "stars"; and the moving stars, which in Greek is called "planets".A planet certainly looks like a star (a very bright star, in some cases), but nowadays they are not usually called "stars".
the Greeks called the planets wanderers