Moons are objects that orbit planets.  Astronomers now count nearly 150 moons around the planets.  We find a great variety of 
  natural satellites in our solar system.  Some of the larger moons were almost certainly formed at the same time as their parent 
  planet.  Others are obviously captured objects with wildly eccentric orbits.  Still others orbit near the planet and have the job of 
  keeping planetary rings in line.