We call it the solar system because it is made up of our star, the Sun, and everything bound to it by gravity. The solar system has one star, eight planets, five officially named dwarf planets , hundreds of moons, thousands of comets, and more than a million asteroids. Our solar system is located in the Milky Way, a barred spiral galaxy with two major arms, and two minor arms. Our Sun is in a small, partial arm of the Milky Way called the Orion Arm, or Orion Spur, between the Sagittarius and Perseus arms. Our solar system orbits the center of the galaxy at about 515,000 mph (828,000 kph). It takes about 230 million years to complete one orbit around the galactic center. Planets following Sun in nearer to farther order Mercury, Venus, Earth, Mars, Jupiter, Uranus, Neptune SUN : The Sun center of our solar system is a huge glowing sphere of hot gas. Most of this gas is hydrogen (about 70%) and helium (about 28%). Carbon, nitrogen and oxygen make up 1.5% and the oth...