The Solar System: Patterns and Origins

1. Chapter 6 What are the basic properties of the solar system? What are some of the general patterns in the solar system? What do these patterns tell us about the how the solar system formed? Is (was) there life beyond Earth? Other Worlds: An Introduction to the Solar System Astronomy 2010

2. 6.1 Overview of Our Planetary System • We have sent spacecraft to every planet except Pluto. • Also to moons, comets, and an asteroid. • We’ve learned much about the planets and the solar system. • We want to get an overview of the solar system, and then discuss in more detail in chs. 7 to 13. Astronomy 2010

3. Our Planetary System is the Solar System Astronomy 2010

4. 6.1.1 An Inventory Most of the mass of the solar system is in the Sun. In this chapter we are discussing everything else. Astronomy 2010

5. The Nine Planets Astronomy 2010

6. The Nine Planets • The masses of the Sun, Earth, Jupiter, and other objects are measured by observing the effect of their gravity. • All the planets orbit the Sun in the same directions. • All the orbits lie (almost) in the same plane. • All the planets rotate (spin) about an axis. • Most rotate in the same direction as they orbit. • Venus rotates backwards • Pluto and Uranus spin “on their sides” Astronomy 2010

7. The Orbits of the Planets Astronomy 2010

8. Terrestrial Planets Mars • The four innermost planets: • Mercury • Venus • Earth • Mars • Small, composed of rock and metal, with solid surfaces. Astronomy 2010

9. Jovian Planets • The next four planets are called Jovian or giant planets • Jupiter • Saturn • Uranus • Neptune • Mostly liquids and gases • No solid surface we can stand on. Astronomy 2010

10. 6.1.2 Smaller Members of the Solar System • Satellites or moons • All the planets except Mercury and Venus have moons (small “m”) • Rings • All the giant planets have rings • Asteroids • Rocky metallic objects, mostly in the asteroid belt • Comets • Chunks of ice, mostly beyond the orbit of Pluto Astronomy 2010

11. A Scale Model of the Solar System Astronomy 2010

12. 6.2 Composition and Structure of Planets • Three groups by composition • Giant planets: Jupiter, Saturn, Uranus, Neptune • Terrestrial planets: Mercury, Venus, Earth, Mars • Pluto • The different compositions and locations can help us understand how they formed. Astronomy 2010

13. 6.2.1 The Giant Planets • Core of metal, rock, and ice • Surrounded by hydrogen and helium • Strong gravity holds and compresses the hydrogen and helium into liquid form • The pressure at the core is so great that any material will be crushed  no solid surface to land on. Astronomy 2010

14. 6.2.2 The Terrestrial Planets • Composed primarily of rocks and metals • Silicon, oxygen, nickel, iron • Densest metals in the central core • Differentiated • Interior of the planets are or were molten long enough to allow the heavier elements to settle to the core Astronomy 2010

15. 6.2.3 Moons, Asteroids, and Comets • Earth’s Moon is like the terrestrial planets • Mars’ moons look like captured asteroids • Other moons more similar to the cores of the giant planets they orbit -- differentiated • Asteroids and comets are probably unchanged since they formed. Astronomy 2010

16. 6.2.4 Temperatures: Going to Extremes • Generally, the farther something is from the Sun, the colder it is. • Mercury: 500K • Pluto: 50K • Venus breaks this rule, since at 700K it is hotter than Mercury but further from the Sun. • Earth is the only planet at about the right place to have liquid water Astronomy 2010

17. 6.2.5 Geological Activity • Planetary crusts are modified by both internal and external forces. • Good evidence that all the planets have seen considerable number of impacts. • Impacts more frequent in the early history of solar system • Volcanos and seismic quakes produced by internal heat. Astronomy 2010

18. 6.3 Dating Planetary Surfaces • We’d like to know the age of a planet’s surface • Two techniques: • Counting the craters • Radioactive rocks Astronomy 2010

19. 6.3.2 Radioactive Rocks • Relies on the natural abundances of certain radioactive isotopes • Used to determine the age of the Earth and Moon • 4.5 billion years • Radioactive isotopes are atoms that decay and transform into a different atom. • In a half-life, half of the radioactive isotopes decay. Astronomy 2010

20. 6.4 Origin of the Solar System • Where did the solar system come from? • How did it form? • Look at the patterns in the solar system as a whole to get a clue. Astronomy 2010

21. 6.4.1 Looking for Patterns • All the planets revolve around the Sun in the same direction, and in nearly the same plane • The Sun rotates in the same direction • Hypothesis: the Sun and planets formed from a spinning system called the solar nebula. (discuss angular momentum) Astronomy 2010

22. 6.4.2 The Evidence from Far Away • In cool gas clouds, like the one pictured on the cover of the book, we find evidence for new star formation. • In some instances we see evidence of a disk of material around the star, a stellar nebula. Astronomy 2010

23. Recent Photo from Spitzer Space Tele. Astronomy 2010

24. The Search for Life Beyond Earth • We are searching for evidence of life within our solar system. • Advantages: we can send probes or humans to the locations to perform direct tests • Disadvantages: limited possible locales • The search is concentrated on Mars and Europa, one of Jupiter’s moon’s. Astronomy 2010

25. Dear Professor Robert Harr       Good morning,  I like to present for you these lines of our recently published book about Astronomy, that I have translated, and which you can see at our website.      Your brother       E. A. Nassir    The Mistake of Astronomers about Mars   Mars is bigger than Earth; it is about one and a half times (less than! two times) that of Earth.Click here  - [The Wrong Calculations of Astronomers Concerning Mars]: If it were smaller than Earth, it would be nearer than Earth to Sun.Click on:   the cause of a planet being near the sun and another being far  , and see- at our website- the diagram 3 of a simple experiment.     Mars is inhabited: having rivers, seas, deserts, plains, mountains, day and night, and the plant, the animal and intelligent human beings to whom God has sent their apostles a! nd prophets, out of themselves.   Click here      The Planets Are Inhabited    There will be an anticipated meeting between the people of Earth and the people of Mars, which may be a fruitful one.   Click here      An Anticipated Meeting between the Inhabitants of Earth and some other Planets    The circumstances and conditions on Earth will become bad in the future (when Earth will stop its axial rotation; like what happened to Venus and Mercury before, on which life was exterminated), then there will be a migration from Earth to Mars.   Click here         The Traveling to Mars Is Successful Astronomy 2010

26. Discussion Question • Here is planet Earth • Which other object in the solar system do you think is most interesting for the next NASA mission, and why? Astronomy 2010