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Origin of the Solar System

The Solar Nebula Hypothesis

Differentiation

Atmospheres

Oceans

Life

What observations were used to

formulate a hypothesis?

Formation of the solar system…

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1. All of the planets orbit the sun in the same direction, in the same plane, and in nearly circular orbits

Pluto is the exception – and it’s not a planet!!

2. Most* of the planets spin on their axes in the same direction

*except Venus and Uranus

3. Planets can be put into two groups:

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4. We have an asteroid belt, a Kuiper Belt, and comets

These observations lead

us to assume a common

origin for the planets in

the solar system

The prevailing hypothesis

is called the Solar Nebula

Hypothesis

Implication

The Eagle Nebula ~ a site of active

star formation

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Question The diagram below shows the solar system during the

time that planets were forming. Where does the solar nebula hypothesis predict that large, Jovian planets would form?

temperatures

too hot for

water to be

solid

temperatures

cold enough for

water to be

solid

outer regions

of disk – not

much material

here

Practice

• In groups, complete the “Solar System Formation” worksheet (handed out).

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Question

Which statement best describes the solar nebula hypothesis?

1. The solar system formed from the remnants of a collision between two stars.

2. The solar system formed from the collapse of a large spinning cloud.

3. The solar system formed from a giant explosion.

4. The solar system formed from material that was thrown off when the Sun started to spin too fast.

Question

Would you expect a Jupiter-like planet to form in the region of Venus?

1. Yes, because gas was distributed evenly throughout the solar system during planet formation.

2. No, because the solar wind blew gases away from that region during planet formation.

3. No, because there was no ice available in that region during planet formation.

4. No, because protoplanets in that region were spinning too fast to gather gases during planet formation.

Question

This plot shows the temperature gradient during the formation of another solar system (red line; our solar system is the black line). What type of planet would you expect to find at 1 AU?

1. A terrestrial planet.

2. A jovian planet.

3. It is impossible to say.

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Does the nebular hypothesis explain the observations?

1. Most of the planets orbit the sun in the

same direction, in the same plane, and in

nearly circular orbits

2. Most of the planets spin on their axis in

the same direction

3. The planets can be put into two groups

4. We have an asteroid belt, a Kuiper Belt, and

comets

Early planets were HOT!

Differentiation

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Comparison of Interiors

3.8 to 4.28 billion years old

Earth’s oldest rock has its own

facebook page!!

Primary atmosphere: collected during planet formation

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Secondary atmosphere: from outgassing during differentiation and comet impacts

Tertiary atmosphere: when a secondary atmosphere undergoes significant modification

Earth’s evolving

atmosphere

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right temp

= oceans

?

Development of plants & animals

“Age of

Invertebrates”

“Age of Fishes”

“Age of

Reptiles”

“Age of

Mammals”

Humans develop Extinction of

dinosaurs and

many other

species 1st flowering plants

Extinction of

trilobites and

many other

marine animals First reptiles

First fishes

Trilobites dominant

1st shelled organisms

First insect fossils

First land plants

Dinosaurs dominant

1st birds

1st multicelled organisms

“Age of

Amphibians”

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Questions you should be able to answer.

• What observations led to the Solar Nebula Hypothesis?

• Describe the Solar Nebula Hypothesis.

• Why did some planets develop into terrestrial planets and some into Jovian planets?

• Why were early planets hot?

• How old is the oldest rock on Earth?

• What is differentiation?

• What is the difference between a primary, secondary, and tertiary atmosphere? Where in the solar system can I find examples of each?