1. C12 : The Solar System

2. Section 1 : The Solar System
P. 337 Fig 1
Sun contains ______% of the mass of the solar system. → great gravity → holds the planets and other objects in the solar system.
1 Astronomical unit (Au) – the average distance between Earth and the Sun.
~ 150 million km.

3. Q: Any other body beyond Pluto in the solar system?
A: Astronomers are studying the movements of Pluto to det. whether the gravity of an object farther out is affecting Pluto.

4. Formation of the Solar System and Planets

6. A cloud of gas and dust in space was disturbed by supernova.
Explosion caused waves which squeezed the cloud.
Squeezing increased the gravity pull and and the cloud of gas and dust come together to form solar nebula.

7. The cloud began to spin faster as it collapsed.
The cloud grew hotter and denser in the center.
The edge gets thinner and cooler.
As the disk got thinner, ptles began to stick together and form clumps. Some clumps got bigger forming planets or moons.

8. Near the center of the cloud, only rocky material could stand the great heat. Example: Earth.
Icy matter settled in the outer regions of the disk.
The center eventually got so hot that it became a star, the Sun.

9. Lighter elements are scarcer in the planets near the Sun than in planets farther out in the solar system.
Planets closer to the Sun travel _______ than planets farther away from the Sun.

10. Section 2 : The Inner Planets
Mercury
Venus
Earth
Mars

11. Mercury
Venus
Earth
Mars

12. Mercury Many craters → like Earth’s Moon Cliffs ~ 3 km
Weak magnetic field → iron core
No atmosphere. Why?
Temps: 425°C →
- 170°C

13. Closest to Sun
2nd smallest planet in solar system
No moons

14. Venus Earth’s twin : size and mass very similar.
Clouds (carbon dioxide) are very dense → very little sunlight enters.
Heat is absorbed by CO2 in the atm →greenhouse effect
45°C → 475°C

15. Yellow color → clouds of H2SO4
Surface has craters, volcanoes
No moons

16. Earth Q: How does Earth’s atm helps to protect us?
A: It causes most meteors to burn up before they reach the surface. It also shields us from Sun’s intense radiation.
Q: Why does the Earth appear to be blue?
A: ocean color

17. Mars

19. Reddish yellow → iron oxide in soil.
Polar ice caps → made of frozen CO2 & H2O
Olympus Mons → largest volcano in the solar system.

20. Q: The two closest planets to Earth are Venus and Mars
Q: The two closest planets to Earth are Venus and Mars. But when astronauts from Earth visit another planet, it will be Mars rather than Venus. Why?
A: Venus has very high temps and atm press (dense clouds) → caused space probes to malfunction and conditions more hostile for humans.

21. Mar’s atm is much thinner than Earth’s → mostly CO2.
Surface temp : - 125°C → 35°C
2 small moons – heavily cratered
- Phobos
- Deimos (farther away)

22. Section 3 : The Outer Planets

23. Jupiter

24. 5th planet from Sun
Atm : hydrogen and helium
Largest planet in solar system
Great Red Spot : giant storm about km
At least 61 moons

25. 4 Large Moons of Jupiter Io : active volcanoes
: red and orange → sulfurous compounds
: atm – thin oxygen
: closest to Jupiter

26. Europa : rocky interior
: 100 km thick crust of ice
: thin O2 atm
: possible ocean as deep as 200
km under the ice

27. 3. Ganymede : crust of ice ~ 500 km thick
: rocky core
: thin oxygen atm
: largest moon (bigger than
Mercury)

28. 4. Callisto : crust of ice and rock a few
hundred km thick
: crust might surround a salty
ocean
: rocky core
: thin CO2 atm

30. Saturn

31. Sixth planet
2nd largest in solar system
Lowest density
Thick atm : hydrogen & helium
Complex ring system

32. Structure of Saturn

33. Saturn’s rings → ice and rock ptles
At least 31 moons
Largest moon : Titan
Atm : Nitrogen; Argon; Methane

34. Uranus

35. 7th planet
~ 21 moons
Largest moon : Titania
: craters & deep valleys

36. Gaseous planet
Atm : hydrogen; helium; methane
Bluish green → CH4

37. Neptune

38. 8th planet
Atm : similar to Uranus
Bluish green → methane

39. At least 11 moons
Largest moon : Triton
Atm: nitrogen
Gaseous planet

40. Pluto

41. Smallest planet in solar system
Orbit round the Sun → 248 years
Different from other outer planets:
- thin atm
- solid, icy rock surface
1 moon : Charon (half the size of pluto)

43. Section 4: Other objects in the Solar System
Comets
Meteoroids
Asteroids

44. Comets

45. Halley’s Comet
Composed of dust & rock ptles (like large dirty snowball) mixed with frozen water, CH4 & NH3

46. Oort Cloud Billions of comets surround the solar system
Located beyond the orbit of Pluto
Gravity of the Sun and nearby stars gravities interact with the comets in the cloud
Either escape from the solar system or get captured into smaller orbits

47. Structure of Comet
Approaches Sun → frozen ice, CH4, NH3 vaporize → release dust and bits of rock
Coma: the gases and released dust form a bright cloud
Nucleus: solid part of comet (unmelted frozen ice)
Solar wind pushes on the gases and dust in the coma → form tails

48. Meteoroids
When comets vaporize and break up → small pieces from the comet’s nucleus spread in the original orbit of the comet → These pieces of dust and rock is called meteoroids

49. Meteoroids which enter Earth are small → burn up in Earth’s atm → meteor
Meteor Showers : more meteors enter the atm of Earth. Occurs when Earth crosses the orbital path of a comet.
Meteorite : big meteoroid not burning up in the atm and hits the Earth. They are debris from asteroid collisions or broken up comets.

50. Asteroids Rock similar to the planet
Located in asteroid belt – between orbits of Mars and Jupiter
Tiny ptles to rocks 940 km in diameter