Our Solar System

1. Our Solar System

2. NEBULA THEORY • A large cloud of gas and dust • Gravity – pulls material together, material spins faster and faster • Most of the gas is pulled into the center of the disk, becoming hot enough for nuclear fusion to begin A SUN IS BORN!

3. Planets Form

4. Steps in Formation • The most abundant element in the universe is HYDROGEN • In areas where there are more hydrogen atoms, they coalesce (join together) to form a protostar ("before or first" star). • Everything drawn around the protostar, some falling into it - some having the mass and velocity to stay in orbit. The proto-Sun becomes more massive, it acquires the gravity in its core to fuse hydrogen into helium (due to tremendous pressures and temperatures acting on the core). • Once fusion begins, the SUN IS BORN! (now a "star," instead of a protostar)

5. Steps in Formation (cont.) • PLANETESIMALS - In the outer parts of the disk, gas and dust formed small asteroid-like and comet-like bodies. These collided and grew larger by sticking together • INNER PLANETS – At formation, the temperatures were very HOT. Most water and other ice-forming materials vaporized (carbon dioxide, ammonia, methane). Most gas escaped the gravity of these planets. • OUTER PLANETS – At formation, temperature here was much COOLER. Planets have a planetesimal core, but grew in size, gravity increased, able to capture lots of hydrogen and helium in the surrounding space.

6. Early Solar System

7. PLANET SIZES

9. Star -fueled by fusion.

10. INNER PLANETS • Terrestrial Planets • terra – Latin for “Earth” • Definition of a planet • a celestial body that is in orbit around the sun • has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a nearly round shape • has cleared the neighborhood around its orbit

11. Mercury

12. Mercury Passing Sun

13. Venus

14. Venus • Known as the “evening star” or “morning star” • Density and Internal structure similar to Earth • Day is longer than its year • Rotates in a direction opposite to most other planets and moons (east to west) • Greenhouse effect of the atmosphere

15. Venus’ Surface

16. Earth

17. Mars

18. Mars • “Red Planet” – break down of iron-rich rocks • Thin atmosphere – mostly CO2 • Liquid water existed in the distant past • Where is the water today? • thin atmosphere does not allow water to stay liquid (becomes a gas) • polar ice caps or frozen underground • OLYMPUS MONS - Largest volcano in the solar system (covers an area the size of Missouri and 3x height of Mt. Everest)

19. Mars

20. OUTER PLANETS • Gas Giants • Composed mostly of hydrogen and helium • Much of the hydrogen and helium is actually liquid phase due to enormous pressure inside planet • Because of their size, much stronger gravitational force than inner planets • ALL have rings – small particles of ice and rock

21. Jupiter Mass is 2½ times that of all other planets combined!

22. JUPITER

23. Ganymede – largest moon

24. Io – most volcanic

25. Europa – possible ocean of H20

26. Callisto – most craters

27. Saturn

28. Uranus 2 times as far from the SUN as Saturn is!

29. Uranus Axis of rotation is tilted about 90 from vertical

30. Neptune

31. Orbits Planet orbits a star pathway, elliptical Satellite orbits a planet

32. Gravitational Attraction • All matter has mass • All mass attracts other masses by a force called gravity. • The force of gravity depends upon the • MASS of the two objects • DISTANCE between them • The attractive force (F) between two bodies is • DIRECTLY proportional to the product of their masses (m1 and m2), • INVERSELY proportional to the square of the distance (r) between them

33. F F Newton’s Law of Universal Gravitation

34. Astronomical Unit (AU) The distance from the Earth to the Sun • 93,000,000 miles • 150,000,000 km Used to measure distances in the solar system, able to work with reasonable numbers.