By far the largest member of the Solar System is the Sun, which contains over 99% of the total mass of the Solar System. The planets Mercury, Venus, Earth, and Mars are small, rocky worlds relatively close to the Sun. The giant gaseous planets, Jupiter, Saturn, Uranus, and Neptune, are considerably larger and are further from the Sun. The last planet, Pluto, is small and cold. Sharing the Solar System with the planets are the much smaller asteroids and comets.
The Sun is a star, one of the 100 billion that constitute our galaxy, the Milky Way. The stars in the Milky Way are grouped into a spherical shape at the center of the galaxy, and a thin disk around it; the Sun and the Solar System are located in the disk, over 10^17 km from the center. Just like the planets orbit the Sun, the Sun and the entire Solar System orbit the center of the galaxy every 240 million years. Our Sun is not unusual; there are many stars like it in the Milky Way. For this reason, many scientists believe other stars in the galaxy may have planets of their own, perhaps even planets bearing other forms of life.
