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Space Science
Formation of the Solar System
and Other Planetary
Systems
Space Science Key Terms
Astronomy: study of the universe (do not
confuse with astrology)
 Galaxy: a large collection of stars, dust
and gas bound together by________.
 We measure distance in space using
Astronomical units (AU)
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1AU is the average distance from the Earth to
the sun (about 150 million km)
Key terms cont.
Solar system: sun and all the planets and
dwarf planets that revolve around the sun.
 Planets: major bodies that revolve around
the sun.
 Solar nebula: the rotating cloud of dust
and gas from which the sun and planets
are formed.
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You will discover…
•how the solar system formed
•why the environment of the early solar system was
much more violent than it is today
•how the planets are grouped
•how astronomers characterize each planet’s
“personality”
•how the moons throughout the solar system formed
•what the debris of the solar system is made of
•that planets have been observed around a growing
number of stars
•that newly forming star and planet systems are being
observed
Video

https://www.youtube.com/watch?v=-x8KMR0nx8
The lightest and simplest elements, hydrogen and helium, are
abundant in the universe. Heavier elements, such as iron and
silicon, are created by thermonuclear reactions in the interiors of
stars, and then ejected into space by those stars.
Ejection of Matter from Stars
FORMATION OF
PLANETARY
NEBULA
SUPERNOVA
EXPLOSIONS
Great clouds of gas and dust
ejected from old stars are
gathered into regions from
which new stars can be
made.
This region in the
constellation of Orion shows
new stars still surrounded by
the nebula from which they
were formed.
Solar System Formation
The Formation of a Solar System
A solar system begins as a gas cloud
that collapses toward the center under
the influence of gravity.
A condensation forms at the center,
which is called a protostar. This forms
the sun of the solar system from
fusion (contains 99% of matter from
the nebula)
A flattened disk of matter surrounds
the protostar, which begins to shine.
The Formation of a Solar System
The rising temperature from the sun
removes the gas from the inner regions,
leaving dust and larger debris.
The planets establish dominance in
their regions of the solar system.
After almost all of the remaining gas, dust,
and small debris has been collected by the
larger objects, the solar system takes on the
form we recognize today.
PLANET FORMATION
Within the disk that surrounds
the protosun, solid grains
collide and clump together into
planetesimals.
The terrestrial planets are built up
by collisions and the accretion of
planetesimals by gravitational
attraction.
The jovian planets are formed by
gas accretion.
COMPUTER SIMULATION OF THE
FORMATION OF THE SOLAR SYSTEM
Planets and moons which
have no appreciable
atmosphere will show
scars from impacts with
planetary debris, called
craters.
Our Moon still has
numerous craters,
providing evidence of
many impacts in its history.
Debris in Our Solar System Today
Asteroids—rocky bodies several kilometers
across which orbit the sun—are found mainly in
the asteroid belt located between the orbits of
Mars and Jupiter.
Even smaller rocky objects, called meteoroids,
are scattered throughout the solar system.
Billions of chunks of rock and ice called
comets are located beyond the orbit of
Neptune. Occasionally, one of these will be
pulled toward the inner solar system and form
the familiar “tails” as it orbits close to the Sun.
Comparative Planetology
ORBITS
•The planets nearest to the Sun (Mercury, Venus, Earth, and Mars) are
relatively close together, while those farther away (Jupiter, Saturn, Uranus,
Neptune, and Pluto) are more spread out.
•Most of the planets are in nearly circular orbits.
•SIZE=the physical volume of the planet
•MASS=the amount of matter in an object
•DENSITY=the amount of mass per unit volume
Density depends on the composition of an object
and not just the size. The objects shown here all
have the same mass but different densities.
Two Basic Groups of Planets
TERRESTRIAL
JOVIAN
Small size
Large size
Low Mass
Massive
Higher density
Low density
Mostly rock, heavy
elements (iron, nickel)
Mostly gas (did not
lose lighter
elements); colder
Mercury, Venus, Earth,
Mars
Jupiter, Saturn,
Uranus, Neptune
Pluto: The first Dwarf Planet
Best described as an ice ball made of
frozen gases and rock.
 Very tilted orbit, unlike the other planets.
 2006 classified as a dwarf planet, not a
“real” planet.

Formation of Solid Earth
Young Earth was very hot (high temp from
becoming a new planet), which was hot
enough to melt iron.
 Iron sank to the middle of the earth (core)
and less dense materials forced up to the
surface.
 This led to the differentiation of the distinct
layers of the geosphere.

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What are these layers?
Formation of Earth’s
Atmosphere
During the differentiation process, lighter
elements (hydrogen, helium) made their
way to the surface of Earth.
 The high concentrations of these elements
did not stay in the atmosphere

Earth’s gravity was top weak to hold them in
the atmosphere.
 Blown away by solar wind

Formation of Earth’s
Atmosphere


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Outgassing: volcanic eruptions very frequent,
leading to the release of new elements into the
atmosphere (water vapor, carbon dioxide,
nitrogen, sulfur dioxide, methane, ammonia)
The radiation from the sun caused the ammonia
and water vapor to break down. Also, oxygen
combined to form ozone.
Early life on Earth consisted of plants, which
converted CO2 to O2 by photosynthesis

Oxygen levels in the atmosphere increased.
Formation of Earth’s Oceans

Some of Earths water may have come
from space


Ice bodies (comets) collided with Earth, water
became part of the atmosphere and cooled to
form rain.
First ocean was probably first fresh water.

Over millions of years rainwater fell to Earth.
Overtime, more dissolved materials were
carried to the oceans. Some of these
chemicals combined to form salts.
WHAT DO YOU THINK?
How many stars are there in the solar
system?
 Was the solar system created as a direct
result of the formation of the universe?
 How long has the Earth existed?
 Is Pluto always the farthest planet from the
Sun?
 What typical shapes do moons have?
 Have any Earth-like planets been
discovered orbiting Sun-like stars?

WHAT DID YOU KNOW?
How many stars are there in the solar
system?
 Only one star, the Sun.
 Was the solar system created as a direct
result of the formation of the universe?
 No. All matter and energy were created by
the Big Bang, but the solar system formed
billions of years after the Big Bang.
 How long has the Earth existed?
 4.6 billion years.
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WHAT DID YOU KNOW?
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Is Pluto always the farthest planet from the Sun?
No. Pluto’s orbit is highly eccentric, bringing the
planet inside Neptune’s orbit for about 20 years
every 250 years.
What typical shapes do moons have?
Most look roughly like potatoes.
Have any Earth-like planets been discovered
orbiting Sun-like stars?
No. Nearly all the planets orbiting Sun-like stars
are Jupiter-like gas giants.