9.2 - Our Solar System

Transcription

1 9.2 - Our Solar System Scientists describe our solar system as the Sun and all the planets and other celestial objects, such as moons, comets, and asteroids, that are held by the Sun s gravity and orbit around it. Unit 4 - Exploring Our Universe 1 / 8

2 The Formation of our Solar System The most accepted theory on how our solar system was formed is called the nebular theory. A nebular is a cloud of dust and gases in space, which is essentially an area of star formation. Unit 4 - Exploring Our Universe 2 / 8

3 Summary of the Nebular Theory: After the Sun was formed, the solar wind blew against the nebula from which it is formed, pushing the gas and dust away from the Sun. The leftover dust continued to spin, creating a thin disk around the new star. Small bodies began to form in the disk, forming into planets, moons, asteroids, and comets. Watch: The Nebular Theory Unit 4 - Exploring Our Universe 3 / 8

4 The Planets A planet is an astronomical body that orbits one or more stars and is capable of forming into a spherical shape under its own gravitation force. In our solar system, there are eight planets. There are two broad categories to classify these planets: the rocky inner planets and the gas giants. Unit 4 - Exploring Our Universe 4 / 8

5 The Planets A planet is an astronomical body that orbits one or more stars and is capable of forming into a spherical shape under its own gravitation force. In our solar system, there are eight planets. There are two broad categories to classify these planets: the rocky inner planets and the gas giants. Watch: The Planets Unit 4 - Exploring Our Universe 4 / 8

6 The Rocky Inner Planets The four rocky inner planets are called: Mercury, Venus, Earth, and Mars. These planets formed similar to how a small snowball, when rolling it on sticky snow, can grow in size. When particles of dust and gas slammed into each other during our solar system s formation, some began to stick together, resulting in these planets. Unit 4 - Exploring Our Universe 5 / 8

7 The Four Gas Giants The four gas giants are called: Jupiter, Saturn, Uranus, and Neptune. The solar wind blows gases away from the Sun; however, not all the gases escape the solar system. Beyond the asteroid belt is the snow line. On the Sun side of this line, the Sun s radiation keeps water in its gaseous phase. Past this line, water can cool to form droplets and then freeze. The gas giants may have grown as they did because ice acted as a kind of glue to cause gas particles to stick together. Watch: Why does Saturn have rings? Unit 4 - Exploring Our Universe 6 / 8

8 Measuring Distances in Space One unit used to measure distances in space is the astronomical unit (AU). One AU equals the average distance between the Sun and the Earth, about 150 million km. Common Distances from the Sun (AU): Mercury: 0.4 AU Mars: 1.5 AU Jupiter: 5.3 AU Neptune 30.0 AU View: Our Solar System (to scale) Watch: Visualizing the Size of the Planets Unit 4 - Exploring Our Universe 7 / 8

9 Other Objects in the Solar System The Asteroid Belt - Circling the Sun at about 3 AU is a huge band of billions of rocks called asteroids. Dwarf Planets - similar to planets (have a spherical shape), but have an unusual orbit that contains many other objects. (ex: Pluto) Unit 4 - Exploring Our Universe 8 / 8

10 Other Objects in the Solar System Comets - a celestial object made of ice and dust which travels in an elliptical orbit around the Sun. Meteors and Meteorites - A meteor (a shooting star ) is a meteoroid that collides with the gas molecules in Earth s atmosphere and heats up to very high temperatures. If a meteor does not burn up and strikes Earth, it is called a meteorite. Unit 4 - Exploring Our Universe 9 / 8