The Solar System The solar system consists of the sun, the nine planets and their moons, and other small bodies, including the asteroids and comets. Many of the planets are also orbited by one or more moons. "Lie on your back and look at the stars." - H. Jackson Brown, Jr. (from Life's Little Instruction Book) The Center of the Solar System - the Sun For the Egyptians, the sun was Ra, the Greeks called it Helios and the Romans gave it the name Sol. These ancients, among others, studied and pondered this vast presence in the sky, its presence seen as a sign of divinity by many. Despite the interest in the sun and other celestial bodies, the sun's position as the center of our solar system was not understood for millenia. It once was the center of a huge debate, with science at conflict with spiritual authorities. Those who dared suggest the sun was the center of our solar system were regarded as blasphemers, and Galileo was condemned for heresy for his support of Copernicus' theory that the earth orbited the sun, not vice versa. It wasn't until later in the 17th century that it generally became accepted that the sun was the center of the solar system and not the earth. "Willingly would I burn to death like Phaeton, were this the price for reaching the Sun and learning its shape, its size, and its distance." -Eudoxus Today, the study of the sun continues. The Ulyssess satellite, launched in 1990 by the Space Shuttle Discovery, has been sending back data on the sun to scientists and will continue to do so at least until 2008. The Genesis spacecraft has completed its mission of collecting particle samples from the sun's solar winds and is on its way home. It is scheduled to be recovered in mid-air using helicopters in September, 2004. The Nine Planets The study of our solar system began in prehistoric times. There was the sun and the moon, but early astronomers, using only the naked eye, recognized certain bodies in the sky, known as "wanderers", or planetes in Greek. The wanderers were eventually given names, and are now known to us as Mercury, Venus, Mars, Jupiter and Saturn. Galileo was the first to use the new-fangled telescope to search the skies in 1610, and discovered the four large moons of Jupiter. Others also used this new technology, which was being improved continuously. Finally, in 1930, the last of the known planets of our solar system, was discovered. The knowledge of our solar system continues to grow, and new moons are still being discovered orbiting the outer planets. The Cassini satellite has recently entered orbit around Saturn, and two Rovers scurry across the surface of Mars. Our neighboring planets continue to intrigue us, and like our planet Earth, will continue to beckon explorers to study and probe their mysteries. The following table lists the nine planets, in order of their distance from the sun, with some additional information for each planet: Planets of Our Solar System ------------------------------------------------------------------------- Average Dist. Average Name From Sun Diameter Temp. Gravity Moons ------- ---------------- ----------- -------- ------- --------------- Mercury 57,909,175 km 4,879.4 km 452 K 0.376 No moons Venus 108,208,930 km 12,103.6 km 726 K 0.903 No moons Earth 149,597,890 km 12,756.3 km 281 K 1 The Moon Mars 227,936,640 km 6787 km 310 K 0.375 Phobos, Deimos Jupiter 778,412,020 km 142,800 km 120 K 2.34 Ganymede, Callisto, Io, Europa (61 total) Saturn 1,426,725,400 km 120,660 km 88 K 1.065 Titan, Rhea, Iapetus, Dione, Tethys, Enceladus, Mimas (31 total) Uranus 2,870,972,200 km 51,118 km 59 K 0.905 Miranda, Titania, Oberon, Umbriel, Ariel (26 total) Neptune 4,498,252,900 km 49,528 km 48 K 1.14 Naiad, Thalassa, Despina, Galatea, Larissa, Proteus, Triton, Nereid (13 total) Pluto 5,906,376,200 km 2,300 km 37 K 0.059 Charon This information has been compiled from the Planetary Fact Sheets, the Planet Profiles and the Solar System page, which are Internet pages provided by the National Aeronautics and Space Administration (NASA).