Transcript Formation of the Solar System

Formation of the Solar System
Chapter 27 page 684-
The solar system
consists of the sun, the planets and all
of the other bodies that revolve
around the sun
The Nebular Hypothesis
1796 French mathematician Pierre-Simon,
marquise de Laplace
The sun and the planets condensed at about
the same time out of a rotating cloud of gas
and dust called a nebula
Solar Hypothesis
 Matter is spread throughout the universe
 Some of it accretes, or comes together, in clouds
of gas and dust
 About 5 billion years ago, one of these clouds
began to be drawn together by gravity after it
increased due to a nearby supernova or other
forces
 The rotating cloud of gas and dust is called a
solar nebula
Accretion-matter is drawn
together by gravity
The sun formed of gas in the middle of the
rotating cloud
Planetesimals form from the collision of
small bodies farther out
Planetesimals collide to form protoplanets
Eventually, protoplanets become large and
form planets and their moons
Formation of Inner Planets
 Were close to the sun with large percentages of
heavy elements
 Lost their gases because the gravity was not
strong enough to hold them
 When nuclear fusion began the remaining
lighter elements were blown away from the
blast
 As cooling progressed, the heavier elements sank
and layers formed
 Today the inner planets are small, rocky and
denser than outer planets
Formation of Outer Planets
 Formed in the colder regions
 Did not lose their lighter elements
 At first their centers were heavy elements with
ice exteriors
 Now because of intense pressure, they have
layers of liquid gases
 Called gas giants because
1. Composed mostly of gases
2. Low density
3. Are huge planets
Pluto—The First Dwarf Planet
Since 1930 until recently, Pluto has been
known as the 9th planet
However, it was unlike the gas giants
In 2006, astronomers changed the
definition of planet and changed Pluto’s
classification to a dwarf planet
The definition of a planet
recently changed
Planet qualifications
Must orbit the sun
Must have a basically round shape
(hydrostatic equilibrium)
Must have cleared its orbit of other
objects
– Pluto misses the third—the Kuiper Belt
My very excellent mother just
served us nine pizzas. nachos
Mercury, Venus, Earth, Mars, Jupiter, Saturn,
Uranus, Neptune, Pluto
Not shown to scale
Formation of Solid Earth
At first very hot
 3 reasons
1. Heat from collisions with planetesimals
2. Weight of layers compressed and heated
3. Radioactive elements
Layers Form
 Earth was hot enough
to melt iron
 Denser materials sank
 Process called
differentiation
Present Earth
 has a solid surface,
but the interior is still
hot enough to cause
change i.e. plate
tectonics
Formation of
Earth‘s Atmosphere
 The atmosphere
formed because of
differentiation
 Less dense gas
molecules like
hydrogen and helium
rose to the surface
 Early atmosphere was
H and He
These gases were so light they . .
Were not held by Earth’s gravity
Blown away by the solar wind
(There was not a fully developed magnetic
field )
– It protects our present atmosphere
Outgassing from Volcanoes
 Released large
amounts of water
vapor, carbon dioxide,
nitrogen, methane,
sulfur dioxide and
ammonia
 These gases reacted
with radiation from
the sun to form
ozone that protects
us from UV radiation
Present Atmosphere
 Cyanobacteria and
early green plants
changed carbon
dioxide into oxygen
 About 2 by years ago
the amount of oxygen
increased rapidly
78% nitrogen
21% oxygen
1% other gases
Formation of Earth’s Oceans
Earth’s water may have
come from space
 Collisions with
comets added water to
the atmosphere
 Other water came from
volcanoes
 When Earth cooled
enough for water to
condense, the oceans
formed