Structure

1
Structure Formation of the Solar System

• What is the Solar System?
• The Sun and everything gravitationally bound to
  it.
• There is a certain order to the Solar System.
• This gives us information on its formation.

The planets to scale with a portion of the Sun
visible in the background.
2
Part 1 Structure of the Solar System

• All the planets orbit the Sun in the same
  direction.
• All the planets orbit within nearly the same
  plane. Like a disk.
• Two type of planets
• Solid, rocky, small planets close to the Sun
  (like Earth)
• Gaseous, large planets far from the Sun (like
  Jupiter)

3
The Sun

• The Sun is a star.
• It is completely gaseous.
• It emits light and heat through nuclear fusion in
  its core.
• It is by far the largest object in the Solar
  System. 700 times more massive than all of the
  other objects in the Solar System put together.
• It is composed mostly of Hydrogen and Helium gas
  and traces of many other elements.
• The Sun spins on its axis counter-clockwise.

4
The Planets

• In order of increasing distance from the Sun
• Mercury
• Venus
• Earth
• Mars
• Jupiter
• Saturn
• Uranus
• Neptune
• Pluto

5
The Planets

• All the planets orbit in the same direction
  counter-clockwise as seen from above Earths
  North Pole.
• All the planets spin counter-clockwise too except
  for Venus, Uranus and Pluto.

6
The Inner or Terrestrial Planets

• Mercury, Venus, Earth and Mars share certain
  characteristics
• All are rocky bodies.
• All have solid surfaces.
• Except for Mercury all have at least a thin
  atmosphere
• They are called Terrestrial planets because of
  their resemblance to Earth.

7
The Outer or Jovian Planets

• Jupiter, Saturn, Uranus and Neptune share certain
  characteristics
• All are large, gaseous bodies.
• All have very thick atmospheres, with possibly
  liquid interiors and solid cores
• All have rings
• They are called Jovian planets because of their
  resemblance to Jupiter.

8
Pluto

• Pluto is unlike any of the terrestrial or jovian
  planets.
• much farther from the Sun than the terrestrial
  planets.
• much smaller than any jovian planet.
• composition is thought to be a mixture of ice and
  rock
• It is similar to some of the satellites of the
  jovian planets and similar to some asteroids.

9
Satellites (Moons)

• Most of the planets have satellites.
• Most of the satellites orbit in the equatorial
  plane of the planet.
• Most satellites orbit counter-clockwise.
• The jovian planets have more than a dozen
  satellites each.

Ganymede, Callisto, Io, and Europa. Four of
Jupiters largest satellites. These were
discovered by Galileo Galilei and together are
called the Galilean satellites of Jupiter.
10
Comets and Asteroids

• The Solar System is filled with millions of
  smaller bodies.
• Comets - composed of ice and rock
• Asteroids - composed of rock and/or metal
• There is also dust in space which can be seen in
  meteor showers

11
Part 2 Solar System Formation

• Our Milky Way Galaxy is filled with cold, dark
  clouds of gas and dust.
• These clouds are mostly hydrogen and helium with
  dust containing mostly iron, rock, and ice.
• The Solar System is thought to have formed from a
  huge, slowly rotating cloud about 4.5 billion
  years ago
• A nearby passing star or stellar explosion may
  have caused the cloud to collapse

12
Collapsing Gas Clouds

• As the cloud collapsed the original slow spin
  began to speed up. This caused the cloud to
  flatten into a disk shape.
• The gravitational pull of the cloud caused it to
  shrink further and caused most of the material to
  fall towards the core forming a large bulge.

13
Collapsing Gas Clouds?

• In the Great Nebula of the constellation Orion
  are huge clouds of gas and dust.
• Among these clouds the Hubble Space Telescope
  observed lumps and knots that appear to be new
  stars and planets being formed.

14
Planets in Formation?

• Around the star Beta Pictoris a large disk of
  dust and gas has been observed.
• The light from the star is much brighter than the
  disk so it had to be blocked for the disk to
  appear clearly.
• Disks have been seen around other stars too
  including Vega.

15
Birth of the Sun

• As material falls into towards the disk it
  collides with other material and heats up and
  melts.
• The increasing mass of the core also increases
  the gravitational pull and causes more material
  to be pulled in.
• When the mass is large enough and temperatures
  high enough nuclear fusion reactions begin in the
  core and a star is born!

16
Heating and Condensation of the Solar Nebula

• The heat from the Sun prevents ices from
  reforming on the dust grains in the region near
  the Sun.
• Ices condensed only in the outer parts of the
  Solar nebula.
• In the inner portion of the disk only materials
  like iron and silicates (rock) can condense into
  solids. Slowly they form clumps of material.
• In the outer portion of the disk much more
  material can condense as solids including ice.
  This extra material allows clumps to grow larger
  and faster.

17
Gravity does the job

• Within the disk, material is constantly colliding
  with one another. If the collisions are not too
  violent material may stick together.
• In the outer parts of the Solar Nebula the
  planets become large enough to have a significant
  gravitational pull and collect gas around them.
• Planets in the inner nebula can not grow enough
  to collect much gas.
• Eventually most but not all of the material was
  swept up by the planets.

18
The Last of the Planetesimals

• The remaining material exists today as
• comets which were flung out to a region far
  beyond Pluto called the Oort cloud and
• asteroids mostly between Mars and Jupiter (the
  Asteroid Belt) and beyond Pluto (the Kuiper Belt)