1. 21 Sep 2000ASTR103, GMU, Dr. Correll1 Build Your Foundation II

2. 21 Sep 2000ASTR103, Sec 3, GMU, Dr. Correll2 The Solar System How many stars are there in the solar system? Was the solar system created as a direct result of the birth of the universe? How long has the Earth existed? Is Pluto the farthest planet from the sun? What typical shapes do moons have?

3. 21 Sep 2000ASTR103, Sec 3, GMU, Dr. Correll3 The Solar System The solar system formed from an interstellar cloud of gas and dust--the solar nebula –Mostly hydrogen and helium (created in the big bang) –Also contain heavier elements--silicates, iron, etc (created in larger stars)

4. 21 Sep 2000ASTR103, Sec 3, GMU, Dr. Correll4 The Solar System Solar nebula contracts –flattens and spins –Sun begins to shine –gas expelled from inner disk by solar radiation –ice and dust accrete to form planetesimals (~10 km in size) and then planets

5. 21 Sep 2000ASTR103, Sec 3, GMU, Dr. Correll5 The Solar System Computer simulations show formation of inner solar system takes as little as 150 million years--only about 1/30 the age of the solar system

6. 21 Sep 2000ASTR103, Sec 3, GMU, Dr. Correll6 The Solar System Stellar nebula seen in other star formation regions

7. 21 Sep 2000ASTR103, Sec 3, GMU, Dr. Correll7 The Solar System

8. 21 Sep 2000ASTR103, Sec 3, GMU, Dr. Correll8 The Solar System

9. 21 Sep 2000ASTR103, Sec 3, GMU, Dr. Correll9 The Solar System

10. 21 Sep 2000ASTR103, Sec 3, GMU, Dr. Correll10 The Solar System

11. 21 Sep 2000ASTR103, Sec 3, GMU, Dr. Correll11 The Solar System Thought experiment: –If I’m looking at a star with one large planet in orbit around the star, what kind of motions do I see? Remember Newton’s 3rd law of motion--for every action there is an equal and opposite reaction –If planet is very tiny? –If planet is very large?

12. 21 Sep 2000ASTR103, Sec 3, GMU, Dr. Correll12 The Solar System Thought experiment: –OK, so I see both the star and the planet circling each other (or more accurately, there common center of gravity) –If I’m looking at the light from the Star, using a spectroscope, what do I notice about the absorption and emission lines?

13. 21 Sep 2000ASTR103, Sec 3, GMU, Dr. Correll13 The Solar System Thought experiment: –Right, I’ll see the absorption/emission lines Doppler shifted. From this I can measure relative velocities. –From the velocities and periods of orbits, I can calculate the masses of the star AND the planet!

14. 21 Sep 2000ASTR103, Sec 3, GMU, Dr. Correll14 The Solar System

15. 21 Sep 2000ASTR103, Sec 3, GMU, Dr. Correll15 The Solar System How many stars are there in the solar system? –One, our Sun. Was the solar system created as a direct result of the birth of the universe? –No, the universe was created 13-18 Billions years ago; the solar system is about 4.6 Billion years old How long has the Earth existed? –About 4.6 Billion years old Is Pluto the farthest planet from the sun? –Sometimes Neptune is What typical shapes do moons have? –Irregular spheroids, e.g.--potatos