Download The Beginning of Our Solar System

Ch 27
Questions??
 What are some theories about how our solar system
began?
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.
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
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
Diagram of Nebular Hypothesis
Nebular Hypothesis
 Step 1:
 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
Nebular Hypothesis
 Step 4:
 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!
The Planets
 The Inner 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
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.
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
Earth’s Layers
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.
Formation of Earth
Outgassing
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.
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.
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.
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.
Chapter 27
Multiple Choice
1. 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
Chapter 27
Multiple Choice, continued
1. 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
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.
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.
Chapter 27
Multiple Choice, continued
3. The original atmosphere of Earth consisted of
A.
B.
C.
D.
nitrogen and oxygen gases
helium and hydrogen gases
ozone and ammonia gases
oxygen and carbon dioxide gases
Chapter 27
Multiple Choice, continued
3. The original atmosphere of Earth consisted of
A.
B.
C.
D.
nitrogen and oxygen gases
helium and hydrogen gases
ozone and ammonia gases
oxygen and carbon dioxide gases
Chapter 27
Multiple Choice, continued
4. Scientists think that the core of Earth is made of
molten
F.
G.
H.
I.
iron and nickel
nickel and magnesium
silicon and nickel
iron and silicon
Chapter 27
Multiple Choice, continued
4. Scientists think that the core of Earth is made of
molten
F.
G.
H.
I.
iron and nickel
nickel and magnesium
silicon and nickel
iron and silicon
Chapter 27
Short Response
6. What four planets make up the group known as the
inner planets?
Early Models of the Solar
System
 Geocentric = ?
 Earth centered solar system


Aristotle proposed this idea
Sun, stars and planets
revolved around the Earth
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
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.
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.
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.
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.
Law of Equal Areas
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
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
Example:
 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
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.
Law of Inertia:
QUIZ!!!!!
1.
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
QUIZ!!!
1.
Kepler’s first law states that each planet orbits the
sun, not in a circle, but in an ellipse.
True or False??
True
QUIZ!!!
1.
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