1. The Beginning of Our Solar System
Ch 27

2. Questions??
What are some theories about how our solar system began?

3. The Nebular Hypothesis
solar nebular a rotating cloud of gas and dust from which the sun and planets formed
In 1796, French mathematician Pierre Simon, advanced a hypothesis now known as the nebular hypothesis.

5. The Nebular Hypothesis
The sun is composed of about 99% of all of the matter that was contained in the solar nebula.
planetesimal a small body from which a planet originated in the early stages of development of the solar system

6. Nebular Hypothesis
Some planetesimals joined together through collisions and through the force of gravity to form larger bodies called protoplanets.
Protoplanets’ gravity attracted other planetesimals, collided, and added their masses to the protoplanets

7. Diagram of Nebular Hypothesis

8. Nebular Hypothesis Step 1: Step 2: Step 3:
The young solar nebula starts to collapse due to gravity.
Step 2:
As it rotates, it flattens and becomes warmer near the center…this is where our sun formed.
Step 3:
Planetesimals form within the swirling disk

9. Nebular Hypothesis Step 4: Step 5: Step 6:
As planetesimals grow, their gravitational pull increases. Larger planets collect mostly dust and gas.
Step 5:
Small planetesimals hit larger ones and planets begin to grow.
Step 6:
Left over dust and gas leave solar nebula and our solar system is formed!

10. The Planets The Inner Planets: The outer Planets:
Mercury, Venus, Earth, Mars
Smaller, rockier, more dense than outer planets
Contain heavier elements like nickel and iron
The outer Planets:
Jupiter, Saturn, Uranus and Neptune
Composed of lighter elements such as helium, hydrogen and their ices (water ice, ammonia ice & methane ice)
Called gas giants b/c made of gas and have low density

11. Pluto – The Different Planet
Farthest and smallest planet (smaller than Earth’s moon)
Ice ball made of frozen gasses and rocks
Scientist do not believe that Pluto qualifies as a real planet.
Question?? How is Pluto different from the outer planets?
Unlike the other outer planets, Pluto is very small and is composed of rock and frozen gas, instead of thick layers of gases.

12. The Formation of Solid Earth
First, Earth was very hot, then Earth cooled to form three distinct layers.
Differentiation – denser materials sank to the center and lighter materials were forced to the outer layers.
Center: dense core of iron and nickel
Mantel: surrounds core, think layer of iron & magnesium rich rock
Crust: outermost layer, less dense, silica rich rock

13. Earth’s Layers

14. Earth’s Atmosphere The atmosphere formed because of differentiation.
Earth’s gravity is too weak to hold high concentrations of hydrogen and helium gases and is blown away by solar winds.
Outgassing
Outgassing formed a new atmosphere as volcanic eruptions released large amounts of gases
The ozone formed from remaining oxygen molecules after solar radiation caused ammonia and some water vapor to break down.

15. Formation of Earth

16. Outgassing

17. Earth’s Present Atmosphere
The ozone collected in a high atmospheric layer around Earth and shielded Earth’s surface from the harmful ultraviolet radiation of the sun.
Organisms, such as cyanobacteria and early green plants, could survive in Earth’s early atmosphere by using carbon dioxide during photosynthesis
These organisms produced oxygen as a byproduct of photosynthesis and helped slowly increase the amount of oxygen in the atmosphere.

18. Question??
How did green plants contribute to Earth’s present-day atmosphere?
Green plants release free oxygen as part of photosynthesis, which caused the concentration of oxygen gas in the atmosphere to gradually increase.

19. Formation of Earth’s Oceans
Were the first oceans fresh water or salt water?
Fresh water
As rain continued to fall, rocks were dissolved into the oceans.
As evaporation occurred, some of the chemicals from the rocks combined to form salts, making the oceans increasingly more salty.

20. The Ocean’s Effect on the Atmosphere
The ocean affects global temperature by dissolving carbon dioxide from the atmosphere.
Since Earth’s early atmosphere contained less carbon dioxide than today, Earth’s early climate was probably cooler than the global climate is today.

21. Multiple Choice Chapter 27
Small bodies that join to form protoplanets in the early stages of the development of the solar system are
A. planets
B. solar nebulas
C. plantesimals
D. gas giants

22. Multiple Choice, continued
Chapter 27
Multiple Choice, continued
Small bodies that join to form protoplanets in the early stages of the development of the solar system are
A. planets
B. solar nebulas
C. plantesimals
D. gas giants

23. Multiple Choice, continued
Chapter 27
Multiple Choice, continued
2. Scientists hypothesize that Earth’s first oceans were made of fresh water. How did oceans obtain fresh water?
A. Water vapor in the early atmosphere cooled and fell to Earth as rain.
B. Frozen comets that fell to Earth melted as they traveled through the atmosphere.
C. As soon as icecaps formed, they melted because Earth was still very hot.
D. Early terrestrial organisms exhaled water vapor, which condensed to form fresh water.

24. Multiple Choice, continued
Chapter 27
Multiple Choice, continued
2. Scientists hypothesize that Earth’s first oceans were made of fresh water. How did oceans obtain fresh water?
A. Water vapor in the early atmosphere cooled and fell to Earth as rain.
B. Frozen comets that fell to Earth melted as they traveled through the atmosphere.
C. As soon as icecaps formed, they melted because Earth was still very hot.
D. Early terrestrial organisms exhaled water vapor, which condensed to form fresh water.

25. Multiple Choice, continued
Chapter 27
Multiple Choice, continued
The original atmosphere of Earth consisted of
A. nitrogen and oxygen gases
B. helium and hydrogen gases
C. ozone and ammonia gases
D. oxygen and carbon dioxide gases

26. Multiple Choice, continued
Chapter 27
Multiple Choice, continued
The original atmosphere of Earth consisted of
A. nitrogen and oxygen gases
B. helium and hydrogen gases
C. ozone and ammonia gases
D. oxygen and carbon dioxide gases

27. Multiple Choice, continued
Chapter 27
Multiple Choice, continued
Scientists think that the core of Earth is made of molten
F. iron and nickel
G. nickel and magnesium
H. silicon and nickel
I. iron and silicon

28. Multiple Choice, continued
Chapter 27
Multiple Choice, continued
Scientists think that the core of Earth is made of molten
F. iron and nickel
G. nickel and magnesium
H. silicon and nickel
I. iron and silicon

29. Short Response Chapter 27
6. What four planets make up the group known as the inner planets?

30. Early Models of the Solar System
Geocentric = ?
Earth centered solar system
Aristotle proposed this idea
Sun, stars and planets
revolved around the Earth

31. Claudius Ptolemy Proposed changes to Aristotle’s model
Thought that planets moved in small circles, called epicycles, as they revolved around the Earth.
Explained why some planets seemed to move backwards at times: retrograde motion.
The word ”retrograde” derives from the Latin words “retro” meaning backwards, and “gradus”, meaning step

32. A circular orbit in a circular orbit.
This satisfied the Greek’s idea
of an Earth centered Universe
and the idea that the motion of
the heavenly bodies moved in
perfect circles.

33. Early Models of the Solar System
Heliocentric = ?
Sun centered solar system
Copernicus proposed this idea
Planets revolved around the
sun but at different speeds
and distances from the sun.

34. Kepler’s Laws Law of Ellipses
eccentricity - the degree of elongation of an elliptical orbit
(symbol, e)
The law of ellipses states that each planet orbits the sun in a path called an ellipse, not in a circle.

35. Kepler’s Laws Law of Equal Areas
The law of equal areas describes the speed at which objects travel at different points in their orbit. It states that equal areas are covered in equal amounts of time as an object orbits the sun.
When the object is near the sun, it moves relatively rapidly. When the object is far from the sun, it moves relatively slowly.

36. Law of Equal Areas

37. Kepler’s Laws Law of Periods
orbital period - the time required for a body to complete a single orbit
The law of periods describes the relationship between the average distance of a planet from the sun and the orbital period of the planet

38. Kepler’s Third Law
The mathematical equation, K x a3 = p2, where K is a constant, describes this relationship.
When distance is measured in astronomical units (AU) and the period is measured in Earth years,
K = 1 and a3 = p2.
a = average distance from the sun
p = period

39. Example: a³ = (11.9)² a³ = 142 a = 5.2 AU a³ = p²
Jupiter has an orbital period of 11.9 Earth years.
Find the average distance.
a³ = p²
a³ = (11.9)²
a³ = 142
a = 5.2 AU

40. Kepler’s Laws explained by Newton:
inertia the tendency of an object to resist being moved or, if the object is moving, to resist a change in speed or direction until an outside force acts on the object
Who discovered gravity?
Newton
Gravity - an attractive force that exists between any two objects in the universe.
While gravity pulls an object towards the sun, inertia keeps the object moving forward in a straight line. This forms the ellipse of a stable orbit.
The gravitational pull is strongest closer to the sun, and weakest further from the sun.

41. Law of Inertia:

42. QUIZ!!!!!
A planet moves relatively slower when it is farther from the sun than it does when it is closer to the sun.
True or False?
True

43. QUIZ!!!
Kepler’s first law states that each planet orbits the sun, not in a circle, but in an ellipse.
True or False??
True

44. QUIZ!!! True of False False
Kepler’s third law states that the square of the average distance of a planet from the sun is proportional to the cube of the orbital period.
True of False
False