1. Chapter 28 Our Solar System

2. Big Idea: Using the laws of motion and gravitation, astronomers can understand the orbits and the properties of the planets and other objects in the solar system

3. Our Solar System 28.1 – Formation of the Solar System 28.2 – The Inner Planets 28.3 – The Outer Planets 28.4 – Other Solar System Objects

4. Our Solar System Quick facts It is likely that Jupiter was the first planet in the solar system to form It rains sulfuric acid on Venus Mercury’s days are two-thirds the length of its years

5. 28.1 Formation of the Solar System

6. Objectives Explain how the solar system formed Describe early concepts of the structure of the solar system Describe how our current knowledge of the solar system developed

7. Formation Theory Theories of the origin of the solar system rely on direct observations and data from probes Scientific theories must explain observed facts Shape of the solar system Differences among the planets Nature of the oldest planetary surfaces Asteroids Meteoroids Comets

8. Big Bang Theory No one knows what happened exactly All the scientists know it that a marble sized universe was produced by a big bang and a large ball of heat started to grow This ball kept expanding, but it didn’t contain matter it was all energy Mass and energy are interchangeable It changed these particles and matter Short Explanation

9. Big Bang Theory There was so much energy, the particles slowed down and created matter The universe was then expanding It all cooled, when protons and neutrons cooled They combined to form Helium an Hydrogen Video

10. Collapsing of Interstellar Clouds Stars and planets form from interstellar clouds These clouds are made mostly from hydrogen and helium gas with small amounts of other elements and dust There is a gravitational force between all of these materials which is how it is thought our planets and stars formed

11. Collapse Accelerates At first a collapse is slow but it gradually accelerates It becomes much denser in the center Eventually, the cloud becomes a rotating disk with a dense concentration of matter at the center

12. Matter Condenses Because of this spinning and condensing of Hydrogen and helium scientists believe this is how the sun formed There is high pressure and high temperature with this matter condensing Because of this temperature gradient, different elements and compounds condensed at a certain distance away from the sun This affected the distribution of elements in the forming of planets

13. As a result Inner planets are higher and richer in melting point elements and the outer planets are more volatile elements This also explains why the outer planets consists of gases and ices

14. Planetesimals Because of these different particles were now condensing in our solar system, they grew as grains and collided These colliding particles merged to form planetesimals Planetesimals are objects hundreds of kilometers in diameter

17. Gas giants form The first large planet to form was Jupiter It grew from merging of icy planetesimals that contain lighter elements Saturn grew similarly but not as large Because each gas giant attracted material they all started to form rings and satellites

18. Terrestrial Planets Form The terrestrial planets started to form from elements that resisted vaporization from the sun Scientists also believe the sun swept much of the gas in the area of the inner planets Thus, the inner planets didn’t develop satellites Video

19. Debris Material that remained after the formation of the planets and satellites is called debris Eventually this debris diminished as they hit other planets or were diverted out of the solar system Others formed into asteroids or comets The asteroid belt formed because of Jupiter’s gravitational force

20. Kepler’s First Law The laws are named after a German astronomer named Johannes Kepler (1571–1630), who proposed them in the early 1600s. Kepler was able to summarize the carefully collected data of his mentor—Tycho Brahe—with three statements that described the motion of planets in a sun-centered solar system. The laws are still considered an accurate description of the motion of any planet and any satellite.

21. Kepler’s First Law An ellipse is an oval shape that is centered on two points instead of a single point These two points are called foci

23. Kepler’s Second and Third Law In addition to discovering the shapes of the planetary orbits, a planet does not orbit at a constant distance from the sun Kepler has also shown that planets move faster when they are closer to the sun The length of time it takes for a planet to travel a complete orbit around the sun is called its orbital period Pg. 801 in your text Video