Chapter 15.1 (pages 394-397)

Solar System is born!

Review from Yesterday:

• Gravity:– What two things effect gravity?

• Mass and weight:– What are they?– How are they measured?– What are their units?

• How are they all connected?

Key concepts:

• Explain the relationship between gravity and pressure in a nebula

• Describe how the solar system formed

Key Vocabulary:

• Nebula• Solar Nebula

Our world revealed: Hubble telescope images

Solar Nebulas:

• Where does the materials come from that make up our solar systems???– Clouds in the universe called nebulas

• Nebulas: clouds that are mixtures of gases (hydrogen and helium) and dust made of elements

• Review time:– Element– Mixture

The universe…how did it all begin?

Remember these terms!

Formation of planets and stars?

• Two forces that interact in nebulas:– GRAVITY– PRESSURE

• Gravity holds the particles of matter in a nebula together– a lot of space between matter in

nebulas, so the gravitational force is just enough to keep the nebula from drifting apart

Gravity begins the process…

Formation of planets and stars?

• Why don’t nebulas collapse due to gravity?– Temperature causes the particle to move around

(temperature is low = little movement, etc.)– When the particles collide due to movement, the

particles move away due to PRESSURE– Pressure keeps the nebula from collapsing on

itself

Solar system formation:• From Planetesimals to Planets• As bits of dust circled the center of the

solar nebula, some collided and stuck together to form golf ball–sized bodies.

• These bodies eventually drifted into the solar nebula, where further collisions caused them to grow to kilometer-wide bodies.

• As more collisions happened, some of these bodies grew to hundreds of kilometers wide.

• The largest of these bodies are called planetesimals, or small planets.

How does it form?

How long does it take?

Why is gravity and pressure so important?

Formation of planets and stars? The Birth of a Star

• As the planets were forming, other matter in the solar nebula was traveling toward the center.

• The center became so dense and hot that hydrogen atoms began to fuse, or join, to form helium.

• Fusion released huge of energy and created enough outward pressure to balance the inward pull of gravity.

• When the gas stopped collapsing, our sun was born and the new solar system was complete!

Review: the important stuff:

Review:

• The solar system formed out of a vast cloud of gas and dust called the nebula.

• Gravity and pressure were balanced until something upset the balance. Then, the nebula began to collapse.

• Collapse of the solar nebula caused heating at the center, while planetesimals formed in surrounding space.

• The central mass of the nebula became the sun. Planets formed from the surrounding materials.

Homework:

• Workbook: Chapter 15.1-– Pages 190-192`