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KIDS LEARNING SOLAR SYSTEM Solar System: Our solar neighborhood is an exciting place. The Solar System is full of planets, moons, asteroids, comets, minor planets, and many other exciting objects. Learn about Io, the explosive moon that orbits the planet Jupiter, or explore the gigantic canyons and deserts on Mars. What Is The Solar System? The Solar System is made up of all the planets that orbit our Sun. In addition to planets, the Solar System also consists of moons, comets, asteroids, minor planets, and dust and gas. Everything in the Solar System orbits or revolves around the Sun. The Sun contains around 98% of all the material in the Solar System. The larger an object is, the more gravity it has. Because the Sun is so large, its powerful gravity attracts all the other objects in the Solar System towards it. At the same time, these objects, which are moving very rapidly, try to fly away from the Sun, outward into the emptiness of outer space. The result of the planets trying to fly away, at the same time that the Sun is trying to pull them inward is that they become trapped half-way in between. Balanced between flying towards the Sun, and escaping into space, they spend eternity orbiting around their parent star. How Did the Solar System form? This is an important question, and one that is difficult for scientists to understand. After all, the creation of our Solar System took place billions of years before there were any people around to witness it. Our own evolution is tied closely to the evolution of the Solar System. Thus, without understanding from where the Solar System came from, it is difficult to comprehend how mankind came to be. Scientists believe that the Solar System evolved from a giant cloud of dust and gas. They believe that this dust and gas began to collapse under the weight of its own gravity. As it did so, the matter in this could begin moving in a giant circle, much like the water in a drain moves around the center of the drain in a circle. At the center of this spinning cloud, a small star begin to form. This star grew larger and larger, as it collected more of the dust and gas that were collapsing into it. Further away from the star that was forming in the center were smaller clumps of dust and gas that were also collapsing. The star in the center eventually ignited forming our Sun, while the smaller clumps became the planets, minor planets, moons, comets, and asteroids. Solar System Facts: Each page is full of fun and exciting facts about our Solar System. Take your time, and enjoy exploring our solar family. http://www.kidsastronomy.com/solar_system.htm Page 1 of 6 KIDS LEARNING SOLAR SYSTEM The Earth's Moon Luna is a beautiful world that lies some 384,400 kilometers from Earth. It is littered with mountains, valleys, old volcano sites, and many bowl like holes called Craters. Luna is a neat world to explore because you can see it without any telescope, or binoculars. I know you have seen it, in fact you may even see it tonight that is because Luna is our moon. OKAY! Let's start here... So you're asking, what is ASTRONOMY? Well... Here's our best definition. Astronomy is the study of SPACE and the changes that take place in and around all objects moving through space. It's more than just Earth and our Solar System. The study of astronomy covers every planet, object, and bit of energy flowing through the universe. So where did the word cosmos come from? It's actually a Greek word that describes an orderly and interconnected universe. Astronomy is the study of that universe and as you learn more, you will discover how each part is connected to the others. But where do you start? There are moons, planets, stars, systems, and galaxies. We'll start with the big picture and a general overview of the universe. Go take a look! A SOLAR SYSTEM FROM DUST Our system of one star and eight planets was born about 4.6 billion years ago. All of the pieces were created at the same time. But wait! It wasn't a big "POOF!" and everything was here. It took billions of years for the entire system to develop. All of the gases, dust, and pieces of the system were around at the start. Eventually a star, eight planets, some smaller dwarf Page 2 of 6 KIDS LEARNING SOLAR SYSTEM planets (like Pluto), and an asteroid belt developed. There wasn't even a star when the Solar System started out. START WITH A STAR The system began as a spinning blob of gases. As the blob spun for millions and millions of years, it began to flatten. It probably looked like that shape for a flying saucer. It was a round, flattened disk with a bulge in the middle. That bulge was the beginning of the Sun. Scientists call that "baby" sun a protosun. The last step for the Sun was the magic that ignited it and caused it to shine. Do you remember that dust and gas swirling around that didn't become the Sun? The disk flattened even more and the planets began to develop. PLANETS FROM THE PIECES Eight planets developed and now orbit the Sun. As you move away from the Sun, you will first find four planets, then a group of small asteroids, and four large Jovian planets. There are also objects called dwarf planets that include bodies such as Pluto and Charon. In the past few years, astronomers have started to discover smaller objects beyond Pluto in the Kuiper Belt. The distance from the Sun to the Earth is considered "1" (scientists call that distance an astronomical unit).The average distance to Pluto from the Sun is 39.5. The Voyager probes launched decades ago are just now reaching the outer edges of our Solar System. That edge, called the heliopause, is far beyond the orbit of Pluto. SOLIDS AND GASES As the planets developed, two types began to emerge. In our system, we have planets that are mainly made of rock and those that are mainly made of gases. The official names are terrestrial (rocklike) and Jovian (those with gases). Of the eight planets in our system, Mercury, Venus, Earth, and Mars are the terrestrial planets. The Jovian planets include Jupiter, Saturn, Uranus, and Neptune. The Jovian planets are all much larger and have a lower density when compared to terrestrial planets. Astronomers have recently decided that there are objects in the Universe that are larger that asteroids and comets, but smaller than real planets. These dwarf planets also orbit the Sun and include Pluto, Charon, and others discovered in the Kuiper Belt. You may also hear the term trans-Neptunian objects used to describe those distant dwarf planets. MORE THAN PLANETS Page 3 of 6 KIDS LEARNING SOLAR SYSTEM If you finished the main Solar System section, you now understand that our system has one star and nine accepted planets. Given that basic information, we want to let you know that there is much more in our little system than those ten objects. WHAT YOU CAN SEE Sure, you can see a planet. They are tough to miss. As you continue exploring, you will find moons around almost every planet. While the Earth only has one, other planets have more than twenty moons. You also know that you can see rings made of small pieces of dust and ice that circle Saturn and other gas giants. As you look for smaller objects in the system, you will find a field of asteroids in orbit around the Sun between Mars and Jupiter. There are also stray asteroids flying through the Solar System. Comets are also found orbiting the Sun. The amazing thing is that there may still be other objects in our Solar System. That's one of the exciting things about astronomy... There are still millions of things to discover in the universe. WHAT YOU CAN'T SEE There are also many things we can't see in the Solar System. There are small particles and energies swirling throughout the system. Many of these unseen energies are created by the Sun. We have a heliosphere that surrounds our entire system and Voyager has just reached the heliopause (the edge). The Sun also gives off small particles called the solar wind, light, and various types of radiation. While Earth needs to be protected from some of these forces, the energy that creates the heliosphere is protecting every object in our system. STAR LIGHT, STAR BRIGHT What is a galaxy without thousands of stars? A vacuum. Those thousands of stars grouped together form the galaxies you can see with a telescope. Stars are the objects that heat and light the planets in a system. Everything revolves around stars. Thousands of stars cover our galaxy and when you look at our star, the Sun, you will see it is quite small. Throughout the universe, there are big ones, small ones, and different colored ones. We're going to discuss the way scientists study stars and how stars affect the planets that orbit them. Page 4 of 6 KIDS LEARNING SOLAR SYSTEM WHAT MAKES A STAR? So you're out one night and you look up into the sky. Assuming you aren't in a city with tons of smog or clouds, you will probably see a sky filled with little dots of light. Those dots (this should not be a surprise) are stars. Some are only a few hundred light years away and some are thousands of light years away. They all have some things in common. You see, stars are huge balls of fire. They aren't just any fire. That fire is from a constant number of nuclear reactions. LIGHTING THE WAY Not all stars have solar systems spinning around them. Some stars are just sitting out in the middle of nowhere. Some stars have a companion star nearby, kind of like a twin. When you have a twin, astronomers call you a binary star. A star is a huge ball of plasma, usually made of hydrogen (H) and helium (He). That ball of fire also gives off light. All kinds of light. There are visible, infrared, ultraviolet, and X-rays constantly emitted into space. You may find planets that are almost identical to the makeup of stars, like Jupiter, but something has not ignited their nuclear reaction. Mercury Venus Page 5 of 6 Earth KIDS LEARNING SOLAR SYSTEM Mars Jupiter Saturn Uranus Neptune Pluto http://www.windows.ucar.edu/tour/link=/our_solar_system/solar_system.html The Solar System The solar system is made up of the Sun, the 9 planets and their 169 known moons, asteroids, comets, dust and gas. The planets, asteroids, and comets travel around the Sun, the center of our solar system. Most of the bodies in the solar system travel around the Sun along nearly circular paths or orbits, and all the planets travel about the Sun in the anticlockwise direction (when viewed from above). Click on image for full size version (15K) other bodies of the solar system. Solar system formation began billions of years ago, when gases and dust began to come together to form the Sun, planets, and Page 6 of 6