Download 20.1 A Solar System is Born

4/9/2014
20.1 A Solar System is Born
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1. Explain the relationship between gravity and
pressure in a nebula.
2. Describe how the solar system formed.
• Describe the basic structure and composition
of the sun.
• Explain how the sun generates energy.
• Describe the surface activity of the sun and
identify how this activity affects Earth.
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The Solar Nebula
The ingredients for building planets, moons, and
stars are found
• in the vast regions of space between the stars
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The Solar Nebula
Nebula – a large cloud of gas and dust in
interstellar space
• Where stars are born or explode at the end of
their lives
• Hydrogen, helium, carbon, iron
• Two forces that interact with nebulas to create
planets and stars
– Gravity & Pressure
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Gravity Pulls Matter Together
What holds the matter of nebulas together?
• The force of gravity
Compared to air, nebulas are
less dense than air.
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Pressure Pushes Matter Apart
“Temperature is a measure of the average kinetic
energy
or the energy of motion, of the particles in an
object.”
High temp = high movement = particles crash into
each other = pressure
Why doesn’t the nebula cloud collapse?
The outward pressure balances the inward gravity
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Pressure Pushes Matter Apart
Gravity and Pressure in a Nebula (figure 2)
1. Gravity causes the particles in a nebula to be
attracted to each other
2. As particles move closer together, collisions
cause pressure to increase and particles are
pushed apart.
3. If the inward force of gravity is balanced by
outward pressure, the nebula becomes
stable.
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Upsetting the Balance
What can upset the balance between gravity
and pressure in a nebula?
If two nebulas collide or a nearby star explodes
What are globules?
Small regions or gas clouds of a nebula that are
pushed together.
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Upsetting the Balance
“As the matter in a globule collapses…
inward the temperature…
increases and the stage is set for stars to form.”
Solar nebula – the cloud of gas and dust that
formed our solar system.
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How the Solar System Formed
1. The young solar nebula begins to collapse
2. The solar nebula rotates, flattens, and becomes warmer
near its center
3. Planetesimals begin to form within the swirling disk.
4. As the largest planetesimals grown in size, their gravity
attracts more gas and dust.
5. Smaller planetesimals collide with the larger ones, and
planets begin to grow
6. A star is born, and the remaining gas and dust are blown
out of the new solar system.
How long did it take our solar system to form?
10 million years
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From Planetesimals to Planets
Planetesimals – small planets
• Bits of dust stuck together
• Future collisions cause them to grow
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Gas Giant or Rocky planet?
What are the outer planets
of the solar system made of?
Nebula gases
Name the outer planets
made of this matter.
Jupiter, Saturn, Uranus,
Neptune
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Gas Giant or Rocky planet?
What are the inner planets of the solar system
made of?
Rocky material
Name the inner planets made of this matter.
Mercury, Venus, Earth, Mars
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Birth of a Star
How is a star created?
• Matter traveling towards the
center becomes so dense
and hot that hydrogen atoms
began to fuse, or join, to
form helium
• Fusion releases energy
• Outward and inward
pressure is balanced
• Gas stops collapsing
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