The solar system consists of the Sun; the eight official planets, at least three “dwarf planets”, more than 130 satellites of the planets, a large number of small bodies (the comets and asteroids), and the interplanetary medium. (There are probably also many more planetary satellites that have not yet been discovered.) The inner solar system contains the Sun, Mercury, Venus, Earth and Mars. The main asteroid belt (not shown) lies between the orbits of Mars and Jupiter. The planets of the outer solar system are Jupiter, Saturn, Uranus, and Neptune (Pluto is now classified as a dwarf planet).
The sun is a star, a hot ball of glowing gases at the heart of our solar system. Its influence extends far beyond the orbits of distant Neptune and Pluto. Without the sun's intense energy and heat, there would be no life on Earth. And though it is special to us, there are billions of stars like our sun scattered across the Milky Way galaxy. If the sun were as tall as a typical front door, the Earth would be the size of a U.S. nickel. The temperature at the sun's core is about 27 million degrees Fahrenheit.Average diameter: 864,000 miles, about 109 times the size of the Earth.
Sun-scorched Mercury, the smallest planet in our solar system, is only slightly larger than Earth's moon. Like the moon, Mercury has very little atmosphere to stop impacts and it is covered with craters. Mercury's dayside is super-heated by the sun, but at night temperatures drop hundreds of degrees below freezing. Ice may even exist in craters. Distance from the sun: About 36 million miles, slightly more than 1/3 as far as the Earth. The emperatures range between 279 degrees Fahrenheit on the side away from the sun; 801 degrees Fahrenheit on the side facing the sun.
Venus is a dim world of intense heat and volcanic activity. Similar in structure and size to Earth, Venus' thick, toxic atmosphere traps heat in a runaway 'greenhouse effect.' The scorched world has temperatures hot enough to melt lead. Glimpses below the clouds reveal volcanoes and deformed mountains. Venus spins slowly in the opposite direction of most planets. Distance from the Sun: About 67 million miles, about 3/4 as far as the Earth is from the Sun. The surface temperature: 864 degrees Fahrenheit and the atmosphere: Carbon dioxide, nitrogen.
Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large amounts of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surface is made up of the ocean, dwarfing Earth's polar ice, lakes and rivers. The remaining 29% of Earth's surface is land, consisting of continents and islands. Earth's surface layer is formed of several slowly moving tectonic plates, interacting to produce mountain ranges, volcanoes and earthquakes.
Mars is the fourth planet from the Sun and the second-smallest planet with a thin atmosphere, having the surface features reminiscent both of the impact craters of the Moon, and the valleys, deserts and polar ice caps of Earth. It is the most widely searched planet for life. Mars has been observed by many different cultures from around the world since hundreds of years. Because of this it is impossible to credit anyone with its discovery, Mars being easily visible with the naked eye. It is named after the Roman god of war due to its red appearance.
Jupiter is the fourth brightest object in the sky, visible to the naked eye. It shines so brightly that even Venus dims in comparison. Because of this, it has been observed since ancient times by many different cultures. The discovery of Jupiter cannot be attributed to someone. However, Galileo Galilei is the first astronomer to have observed Jupiter through his telescope. He began extensive observations of the planet in 1609. During this time and until 1610, Galileo discovered the four largest moons that orbit Jupiter: Io, Europa, Ganymede, and Callisto. They are called the Galilean moons in his honor.
Adorned with thousands of beautiful ringlets, Saturn is unique among the planets. All four gas giant planets have rings -- made of chunks of ice and rock -- but none are as spectacular or as complicated as Saturn's. Like the other gas giants, Saturn is mostly a massive ball of hydrogen and helium. Distance from the sun: About 900 million miles, nearly 10 times as far as Earth is from the sun. It was named after the Roman god of wealth and agriculture Saturn, which is the equivalent of the Greek god of time, Cronos.
Uranus is the only giant planet whose equator is nearly at right angles to its orbit. A collision with an Earth-sized object may explain the unique tilt. Nearly a twin in size to Neptune, Uranus has more methane in its mainly hydrogen and helium atmosphere than Jupiter or Saturn. Methane gives Uranus its blue tint.Discovered: March 13, 1781 by William Herschel. Distance from the Sun: About 1.8 billion miles, about 19 times further than the Earth. The atmosphere consists of hydrogen, helium, methane.
Neptune is the fourth largest and the farthest planet of the Solar System with the most powerful wind speeds out of all the planets. It is the smallest of the gas giants and is the first planet to be discovered by mathematical predictions in 1846. Neptune was observed in 1613 by Galileo Galilei however, he taught that it was just a star, and when he wanted to further research it, the motion of the planet began to be far too slight to be detected again. The greatest factor of the discovery was the planet Uranus, whom astronomers were calculating its orbit and observed that Uranus wasn’t following their models.
Pluto is the largest known dwarf planet in the Solar System, discovered in 1930. It was thought to be the 9th planet of our system for 75 years until the discovery of Eris and other similar objects that led to its demotion from a planet to a dwarf planet in 2006. Pluto is the largest member of a group of objects that orbit in a disc-like zone beyond the orbit of Neptune, called the Kuiper Belt. This far away realm is populated with thousands of miniature icy worlds, which formed early in the history of our Solar System about 4.5 billion years ago.