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The Beginning of Our Solar System
Ch 27
Questions??What are some theories about how our solar
system began?
The Nebular Hypothesissolar 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 HypothesisThe 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 HypothesisSome 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 HypothesisStep 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 HypothesisStep 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 PlanetsThe Inner Planets:Mercury, Venus, Earth, Mars
Smaller, rockier, more dense than outer planetsContain 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 rocksScientist 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 nickelMantel: surrounds core, think layer of iron &
magnesium rich rockCrust: outermost layer, less dense, silica rich
rock
Earth’s Layers
Earth’s AtmosphereThe 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.
OutgassingOutgassing 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 AtmosphereThe 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 OceansWere 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.
Multiple Choice1. 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, continued1. 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, continued2. 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, continued2. 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, continued3. The original atmosphere of Earth consisted
of
A. nitrogen and oxygen gasesB. helium and hydrogen gasesC. ozone and ammonia gasesD. oxygen and carbon dioxide gases
Chapter 27
Multiple Choice, continued3. The original atmosphere of Earth consisted
of
A. nitrogen and oxygen gasesB. helium and hydrogen gasesC. ozone and ammonia gasesD. oxygen and carbon dioxide gases
Chapter 27
Multiple Choice, continued4. Scientists think that the core of Earth is
made of molten
F. iron and nickelG. nickel and magnesiumH. silicon and nickelI. iron and silicon
Chapter 27
Multiple Choice, continued4. Scientists think that the core of Earth is
made of molten
F. iron and nickelG. nickel and magnesiumH. silicon and nickelI. iron and silicon
Chapter 27
Short Response6. What four planets make up the group known
as the inner planets?
Chapter 27
Early Models of the Solar SystemGeocentric = ?
Earth centered solar system Aristotle proposed this idea Sun, stars and planets
revolved around the Earth
Claudius PtolemyProposed changes to Aristotle’s modelThought 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 SystemHeliocentric = ?Sun centered solar system
Copernicus proposed this ideaPlanets revolved around the sun but at different speeds and distances from the sun.
Kepler’s LawsLaw of Ellipseseccentricity - 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 LawsLaw 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 LawsLaw 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 LawThe 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 sunp = period
Example:Jupiter has an orbital period of 11.9 Earth
years.Find the average distance.
a³ = p²
a³ = (11.9)²a³ = 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