1. The Solar System

2. Size matters: radii of the Planets

3. Sun: Jupiter: Earth: Moon = 110:11:1:1/4

4. The Astronomical Unit A convenient unit of length for discussing the solar system is the Astronomical Unit (A.U.) One A.U. is the average distance between the Earth and Sun –About 1.5  10 8 km or 8 light-minutes Entire solar system is about 80 A.U. across

5. The solar system is a disk, not a sphere

6. The Terrestrial Planets Small, dense and rocky Mercury Venus Earth Mars

7. The Jovian Planets Large, made out of gas, and low density Jupiter Uranus Saturn Neptune

8. Asteroids, Comets and Meteors Debris in the Solar System

9. Asteroids Most asteroid orbits are situated between Mars and Jupiter

10. Asteroid Discovery First (and largest) Asteroid Ceres discovered New Year’s 1801 by G. Piazzi, fitting exactly into Bode’s law: a=2.8 A.U. Today more than 100,000 asteroids known Largest diameter 960 km, smallest: few km Most of them are named about 20 of them are visible with binoculars

11. Most asteroids are very small

12. Comets - Traveling Dirty Snowballs Small icy bodies, “dirty snowballs” Develops a “tail” as it approaches the Sun

13. Comet Anatomy Tail may be up to 1 A.U. long Ion tail points away from sun

14. Shapes Comet Giacobini- Zinner (1959) Ion tail 500,000 km long Coma: 70,000 km across Comet Hale-Bopp (1997) Tail 40° long as seen from earth

15. Halley’s Comet – a typical Comet Highly eccentric orbit, inclined substantially

16. Halley’s Comet – Now and then Halley’s Comet in 1910 Top: May 10, 30° tail Bottom May 12, 40° tail Halley’s Comet in 1986 March 14, 1986

17. Meteor Showers – caused by comets RadiantDuration Quadrantids (QUA)Dec. 28-Jan. 7 Lyrids (LYR)Apr. 16-25 Eta AquaridsApr. 21-May 12 Beta TauridsJune 30 Delta Aquarids July 25-31 Perseids (PER) Aug. 10-14 Draconids Oct. 6-10 Orionids (ORI) Oct. 15-29 TauridsOct.12- Dec 2 Leonids (LEO) Nov. 14-20 Geminids (GEM)Dec. 6-19

18. Impact on Earth Most probably caused the extinction of the dinosaurs

19. Impact Craters Quebec's Manicouagan Reservoir. Large meteorite landed about 200 million years ago. The lake, 45 miles in diameter, now fills the ring. Barringer Crater, AZ 0.8 mi diameter, 200 yd deep; produced by impact about 25,000 years ago

20. Tunguska ~30 m body struck Siberia in 1908 Energy equal to that of a 10 Megaton bomb! Detonation above ground; several craters

21. 2013: Siberia Again! 1000 people injured as 20m rock strikes Explodes about 20km overhead 16 hours before known non-fatal asteroid encounter

22. Frequency of Impact Events

23. Formation of the Solar System Features to explain: –planets are far apart, not bunched together –orbits of planets are nearly circular –orbits of planets lie mostly in a single plane –directions of revolution of planets about Sun is the same, and is the same as the direction of the Sun's rotation –directions of rotation of planets about their axes is also mostly in the same direction as the Sun's (exceptions: Venus, Uranus, Pluto) –most moons revolve around their planets in the same direction as the rotation of the planets –differentiation between inner (terrestrial) and outer (Jovian) planets –existence and properties of the asteroids –existence and properties of the comets

24. Formation of the Solar System Condenses from a rotating cloud of gas and dust –Conservation of angular momentum flattens it Dust helps cool the nebula and acts as seeds for the clumping of matter

25. Formation of Planets Orbiting dust – planitesimals Planitesimals collide Different elements form in different regions due to temperature Asteroids Remaining gas

26. Formation of Planets

27. Differentiation of gas and terrestrial planets

28. Cleaning up the Solar System Small objects are forced out of the inner Solar System by gravitational pull of bigger planets Small planetesimals collide and form planets -- or are thrown out!

29. Structure of the Planets explained Temperature and density of materials drop with distance to sun

30. Different formation mechanisms of terrestrial and Jovian planets This explains why they are of different size and material