1. The Solar System

2. Coming Down to Earth… Antares – a huge red giant
Betelgeuse – a large red giant
Aldebaran – a red giant
Rigel – blue star Arcturus – red giant

3. Coming Down to Earth… The Sun – an average size yellow star
Sirius – a white star
Pollux – a medium-large yellow star
Arcturus – a large yellow star

4. The Sun compared to the planets of the solar system
Coming Down to Earth…
The Sun compared to the planets of the solar system

5. What We Know About Our Solar System
A. 1 Sun and 8* planets spread across a flat disk B. All of the planets orbit in the same flat plane as the sun. C. All of the planets orbit in the same direction as the sun rotates.

6. Planets all orbit in the same flat orbital plane.

7. What We Know About Our Solar System
D. The sun rotates more slowly than expected. (Usually there is an increase in angular momentum near the center of a spinning system.) E. The solar system is loaded with rare elements (Pb, Au, U, Pt, etc.)

8. The Terrestrial Planets
F. The four inner planets are small and rocky and have very thin atmospheres.

9. The Jovian Planets
G. The outer planets are large, with thick, dense atmospheres.

10. The Jovian Planets
…are also called the “Gas Giants”

11. The Jovian Planets
G. The outer planets are much larger than the inner planets.

12. ***Any good hypothesis has to explain all of these facts.***

13. The Inner (Terrestrial) Planets

14. 1. Mercury is the smallest planet. Its diameter is 3032 miles across.
One year on Mercury (time it takes to orbit the Sun) is only 88 Earth days.

15. 1. Mercury
One sidereal day (the time it takes Mercury to revolve once) takes about 59 Earth days
However, due to the fast orbital speed of Mercury, one solar day (the time between one sunrise and the next) is almost 176 days. It takes 2 years to finish 1 day!!

16. 1. Mercury
d. …This slow revolution causes extreme night and day temperature differences. The side of the planet that is exposed to the sun can reach 800 F. The side that is opposite the sun can drop to F.

17. 1. Mercury
d. Mercury is a very dense planet – more so than the Earth. It is covered with craters and cracks that may be the result of cooling and shrinking of the surface due to the extreme temperature changes.

18. 2. Venus
a. is about the size of Earth and is often called our “Twin” planet. b. Is the hottest planet. Temps can reach 900 F. This high temperature is due to Venus’ dense sulfuric acid clouds that trap heat.

19. 2. Venus
c. One year on Venus is 224 Earth days (time it takes to circle the Sun).
d. One sidereal day on Venus (the time it takes for Venus to finish one rotation) is 243 Earth days. Venus takes more than a year to finish 1 rotation!
Venus has a retrograde rotation - it rotates backwards - Sun rises in the west! As a result, one solar day (the time between one sunrise and the next) is only 116 days.

20. 2. Venus
d. The surface of Venus was not seen until 1975 due to its thick cloud cover, but radar mapping has allowed astronomers to discover a planet littered with volcanoes. The majority of the topography resembles a gloomy orange/red desert.

21. 3. Venus

22. 2. Venus
e. Venus’ atmosphere reflects much of the sun’s rays, causing Venus to appear very brightly in the night sky. Venus is often referred to as the evening star. It is often the first star visible at night.

23. 3. Earth
a. is the only planet known to support life. Earth’s location and the presence of liquid water has allowed life to exist.

24. 3. Earth (Moon)
b. Earth has one satellite: the Moon. The moon is about one quarter of the Earth’s size, which is relatively large for a moon.

25. 3. Earth (Moon)
c. The Earth’s moon has no atmosphere, which is why it is covered with craters. (Most asteroids burn in the Earth’s atmosphere before they are able to land.)

26. 3. Earth (Moon)
c. (cont.) The dark spots, named maria (seas) by Galileo, were created by solidified lava flows.

27. 3. Earth (Moon)
d. The moon rotates at the same speed that it orbits Earth. As a result, the dark side of the moon is always facing away from Earth.

28. 3. Earth (Moon)
d. (cont.) The dark side of the moon has only been viewed by space probes and a few astronauts.

29. 3. Earth (Moon)
e. The moon takes 28 days to orbit the Earth. This combined with light from the sun being reflected by the moon accounts for the different appearing shapes or phases of the moon.

30. Dark Side of the Moon

31. 3. Earth (Moon)
f. The temperature of the moon may reach as high as 253 F on the exposed side and drop to -261 F on the dark side This is due to a lack of atmosphere and rotation.

32. 3. Earth (Moon)
g. The moon probably formed when a giant object the size of a small planet collided with the Earth causing an enormous amount of rocky debris to be ejected into space. This debris joined in a single mass, forming the moon.

33. 4. Mars
a. is the Red planet. Mars is the most studied planet due to its close proximity to Earth and features. b. One year on Mars is about 687 Earth days. One day on Mars is 24 hrs, 37 mins.

34. 4. Mars
c. Mars has two moons: Phobos and Deimos. These odd shaped moons are small: 17 and 9 miles across. The common theory is that these moons are asteroids that were trapped in orbit around Mars many millions of years ago.

35. 4. Mars
d. Mars has been the target of several unmanned probes and satellites. These missions have revealed that Mars’ topography is very rugged.

36. 4. Mars
d. (cont.) The largest mountain in the solar system in Olympus Mons, which stands over 78,000‘ (15 miles) high and covers an area the size of Ohio (340 mile diameter) (Mt. Everest, by comparison is 29,000‘ - 5 ½ miles high.)

37. Olympus Mons
Largest Volcano in the Solar System!

38. 4. Mars
d. (cont) Mars also has ice caps, similar to Earth’s at each pole.

39. 4. Mars
d. (cont) Mars has large canyons and dry stream beds that may have at one time held water. It is unlikely, however that Mars has ever had a water cycle similar to Earth.
Valles Marinaris