Ch 19.1 Part 1 A solar system is born

1
Ch 19.1 Part 1A solar system is born

• Lesson objectives
• Explain the basic process of planet formation.
• Compare the inner planets with the outer planets
• Describe the difference between rotation and
  revolution
• Describe the shape of orbits of the planets and
  explain what keeps them in their orbits

2
The Solar Nebula

• The solar system is composed of the sun (a star)
  and the planets and other bodies that travel
  around the sun.
• But how did our solar system come to be?
• All the ingredients for building planets are
  found in the vast, seemingly empty regions
  between the stars. But these regions are not
  really empty- they contain a mixture of gas and
  dust.

3

• The gas is mostly hydrogen and helium, while the
  dust is made up of tiny grains of elements such
  as carbon and iron.
• The dust and gas clump together in huge
  interstellar clouds called nebulas.

4
Gravity and pressure finding a balance

• Gas and dust have mass therefore it must have
  gravity.
• The amount of mass determines the amount of
  gravity an object has.
• Because the matter in a nebula is so spread out,
  the attraction between gas particles is very
  small.
• If a nebulas density were great enough, then the
  attraction between the particles might be strong
  enough to pull everything together into the
  center of the cloud.
• But even large clouds dont necessarily collapse
  toward the center because there is another effect
  or force that pushes in the opposite direction of
  gravity. Pressure.

5
(See figure 19.1 in text for drawings)

• Because of gravity, the particles in a nebula are
  attracted to one another
• As the nebulas molecules get closer together,
  pressure increases and works in the opposite
  direction.
• The inward force of gravity is finally balanced
  by the outward pressure, and the nebula becomes
  stable
• The opposing forces of gravity and pressure reach
  a balance in a nebula.
• When something happens to upset this balance. (ex
  two nebulas crashing into each other) it can
  cause the gravity to overtake the pressure and
  start the formation of a star.

6
The Solar Nebula Forms

• (Key term) Planetesimal the tiny building blocks
  that make a planet
• 1. The young solar nebula begins to collapse due
  to gravity

7

• 2.The solar nebula begins to rotate, flatten, and
  get warmer near its center
• 3.Planetesimal begin to form within the swirling
  disk

8

• 4. Because of their greater gravitational
  attraction, the largest Planetesimal begin to
  collect more and more of the dust and gas of the
  solar nebula
• 5. Smaller Planetesimal collide with the larger
  ones, and planets begin to grow

9

• 6. The remaining dust and gas are gradually
  removed from the solar nebula leaving planets
  around the sun
• A new solar system.

10

• Asteroids, comets and meteoroids are left-over
  debris from the original Nebula

11
Birth of a star

• But what was happening at the middle of the solar
  nebula?
• The central part of the nebula contained so much
  mass and had become so hot that hydrogen fusion
  began.
• This created so much pressure at the center of
  the solar nebula that outward pressure balanced
  the inward force of gravity
• At this point the gas stop collapsing and the sun
  was born
• This caused the remaining gas and dust to be
  blown into deep space by a strong solar wind.

12

• From the time the nebula first started to
  collapse, it took 10 million years for the solar
  system to form.
• How do we know this?
• By studying distant nebulas with telescopes like
  the Hubble Space Telescope which are now able to
  show us some of the fine details inside distant
  nebulas

13
Formation of the solar systemThe Big Picture
14
Home Work

• Read Pages 510 to 514
• Do questions 1 3 Pg 514

15
Home work

• Read pages 515 to 518
• Do questions 1 -3 pg 518