1. Components of the Solar System Chapter 16

2. Our Solar System ► The solar system is the name given to the planetary system of which the Earth is a part. It also contains planets, moons, comets, meteors and asteroids which are all held together by the gravitational pull of a star named the Sun. ► As the Sun began to heat up, gravity began to pull-in dust an gases, which clumped together and form our planets. Rocks that did not become large enough to form planets remained as asteroids.

3. 16-1 Describing the Solar System ► Ancient Greeks watched the stars in the sky. They noticed that some stars moved, they called the objects “planets” which meant wandering star. ► Geocentric System-Most Greek astronomers believed that Earth(geo) was at the center of the universe and everything revolved around it. ► Ptolemy believed in a geocentric system and that planets move on little circles that move on bigger circles. His ideas were believed for over 1,400 years.

4. ► Copernicus believed the sun was at the center of the universe. ► Heliocentric System-stated that Earth and the other planets revolved around the Sun(Helios) ► Galileo believed in the heliocentric system. He was the 1 st scientist to use a telescope to look at objects in the sky. He saw moons revolve around Jupiter and Venus go through phases similar to our moon. ► This explained that Ptolemy’s geocentric system could not be correct, so we have now named our universe the Solar System.

5. ► Heliocentric System Geocentric System

6. ► In the late 1500’s Tycho Brahe(Danish), observed the positions of the planets for almost 20 years. ► In the 1600’s Johannes Kepler(German mathematician), discovered that the orbits of each planet is an ellipse, elongated circle or oval shape. ► Isaac Newton concluded that two factors keep the planets in orbit-gravity and inertia. ► Inertia is the tendency of a moving object to stay in motion and a stationary object to stay in place.

7. ► Gravity is the force that attracts all objects toward one another. Gravity depends on the masses of the object and the distance between them. ► The solar system is a large system that consists of a combination of many smaller systems and objects. ► It is hard to determine where our solar system ends. It ends at the point at which objects are no longer affected by the sun’s gravitational pull, solar wind and the sun’s magnetic field. Some believe it ends at the Oort Cloud outside the Kuiper Belt.

8. 16-2 Characteristics of the Sun ► The sun is a ball of glowing gas and does not have a solid surface. The sun produces energy in a process know as nuclear fusion. ► Nuclear fusion is where hydrogen atoms join together to form helium-this occurs under extreme temperatures and pressure in the sun’s core. ► The energy released includes light and heat, when it reaches Earth it is our main source of energy.

9. ► The sun has three layers: ► The photosphere(light)-the inner layer, what you see when you look an image or photograph of the sun ► The chromosphere(color)-the middle layer, what you see at the beginning and end of a total solar eclipse. ► The corona(crown)-the outer layer, a white layer around the sun only visible during eclipses.

10. ► Solar winds are a stream of electrically charged particles sent out from the sun’s corona. They can cause auroras if they enter our atmosphere. ► Sunspots-dark areas of gas on the sun that are cooler than other gases around them. Sunspots go through cycles every 10-11 years. ► Prominences-reddish loops of gas that link sunspot regions. ► Solar Flares-explosions of hydrogen gas formed when loops in sunspot regions suddenly connect. They increase the solar winds, cause magnetic storms and can interfere with satellite signals.

12. 16-3 The Inner Planets ► Known as the terrestrial planets(land/Earth)-the four inner planets are small and have rocky surfaces. ► Mercury-Closest to the sun with no moons, due to no known atmosphere it has the greatest range of temperatures of all planets. ► Venus-Second planet from the sun, known as Earth’s twin-it shines very bright in the sky. It’s day is longer than its year and it has a retrograde rotation which means it rotates backwards. Venus has a very thick, hot atmosphere caused by the trapping of heat or the greenhouse effect.

13. ► Earth-Third planet from the sun and the only planet with water and life as we know it. ► Mars-Fourth planet from the sun and known as the “red planet”. Mars has 2 moons and an atmosphere made mostly carbon dioxide. It has seasons like Earth because of the tilt of its axis.

14. 16-4 The Outer Planets ► The first four outer planets are much larger than Earth, do not have solid surfaces and are known as gas giants. They are believed to have partly solid cores. ► Jupiter-The largest planet in the solar system. It has a Great Red Spot storm, similar to a hurricane on Earth. Jupiter has four main moons and about 17 others. ► Saturn-The second largest planet in the solar system and the only planet less dense than water. Saturn has a visible ring system and several moons.

15. ► Uranus-The first planet discovered since ancient times by William Herschel, it looks blue due to methane in its atmosphere. Uranus has many moons and rotates on its side. ► Neptune-Like Uranus, it has a blue, methane atmosphere. It was discovered as a result of a mathematical prediction. Neptune has faster winds than any other planet. ► Pluto-The fifth outer planet, it is different from the other outer planets, because it is small and rocky like the inner planets.

16. ► Pluto was discovered in 1930 by Clyde Tombaugh. Pluto has one main moon Charon and two other smaller moons. Pluto and its moons are so far away from the sun that it takes 248 Earth years to make one orbit of the sun.

17. 16-5 Comets, Asteroids and Meteors ► Like each planet, each comet is a small system within the large solar system. ► Comets(long haired stars)- are large chunks of ice and dust whose orbits are usually very long, narrow ellipses. They are similar to a “dirty snowball” about the size of a mountain on Earth. Comets have three parts: The coma-an outer layer made of dust and gas, the nucleus-the inner layer and the tail-gas and dust pushed away by solar winds. Halley and Hale-Bob are two well known comets.

18. ► Asteroids are objects too small and numerous to be called planets. Asteroids were first discovered in 1801-1807 between the orbits of Mars and Jupiter, an area now known as the asteroid belt. Some well known asteroids are Ceres, Pallas, Juno, and Vesta. An asteroid hit Earth about 65 million years ago and Scientists believe this caused dinosaurs to become extinct. Asteroid Belt

19. ► A meteoroid is a chunk of rock or dust in space that usually comes from comets or asteroids. ► A meteor is a streak of light you see when a meteoroid has encountered friction in Earth’s atmosphere and burned up. Meteor showers occur several times a year. ► A meteorite is a meteoroid that has passed through Earth’s atmosphere and hit Earth’s surface. If large enough they can cause craters.