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Chapter 16
Formation of the Solar System
Necessary Materials
•
Atoms, all of them, but
mostly hydrogen, are
scattered throughout
space. With little pressure,
these atoms exist as gases
(even though space is very
cold). As pressure
increases, heat increases
and atoms can be forced to
become liquids, then
solids.
Forces
1. Gravity pulls on all
objects, drawing them
closer together
2. Friction creates heat as
atoms are forced into
close contact
3. Pressure is created by
particles bouncing off
each other, pushing out.
Formation of the solar system
1. Gravity causes the
atoms in the nebula
to begin to collapse
inward.
2. As matter falls in,
friction between
atoms creates heat.
Collapsing matter
also begins to spin
(rotate).
3. Clumps begin to form
(snow-ball effect) as
particles collide. Clumps
sweep up more matter,
becoming larger.
- called planetessimals
4. The smaller clumps
continue to orbit the
center of gravity (the
largest clump), now called
a protostar.
5. At the center of gravity,
the densest part of the
cloud is also the hottest.
- Heat makes it start to
glow (protostar).
6. At 10 million degrees
celcius the cloud begins
to fuse atoms ( a star
turns on).
• Fusion- the process by
which smaller atoms are
fused into larger ones
– Two hydrogen atoms get
squeezed together forming
a helium atom.
– This releases a huge
amount of energy.
5. At the center of gravity,
the densest part of the
cloud is also the hottest.
- Heat makes it start to
glow.
6. At 10 million degrees
celcius the cloud begins
to fuse atoms ( a star
turns on).
• Fusion- the process by
which smaller atoms are
fused into larger ones
– Two hydrogen atoms get
squeezed together forming
a helium atom.
– This releases a huge
amount of energy.
7. The fusion process
stops the collapse of
the nebula as the
protostar becomes a
star. The flow of
energy out from the
star creates a solar
wind, clearing out the
loose gas and dust,
leaving only the
clumps that remain to
become planets.
M V
Stars verses Planets
• A star produces its
own light and
generates power by
E Mthe process
J
of fusion
• A planet cannot
produce its own light
(it shines only
S reflected light)
U
and itN
orbits another object.
Planets are much smaller
than stars. The main
difference between them
is their size. Bigger
means
Sunhotter.
P
Structure of the Sun
• The sun is our local
star which forms the
heart of our solar
system.
• It is a medium sized,
medium-bright yellow
star.
PhotosphereCorehottest, the
densestsurface
visible
part ofof
the
sun,sun
the
where fusion
occurs
ChromosphereRadiative
Zonelower atmosphere
heat
and
light
of the
sun,
can
slowly
their
only bework
seen
way
outa solar
during
eclipse.
Corona- upper
atmosphere
of the heat
sun,
Convective Zoneonly
visible
during
and light
make
theiranway
eclipse.
out as hot gases rise and
cooler gases fall
Core
Radiative
Zone
Convective Zone
Other parts of the sun
• Solar flares- eruptions or
storms on the surface of
the sun.
• Sun spots- cooler, dark
spots on the sun
– caused by disturbances in
the sun’s magnetic field.
– Follows an eleven year
cycle. More sunspots
mean higher average
temperatures on Earth.
• Aurora- an Earth
phenomena caused by
solar particles colliding
with the Earth’s magnetic
field. (also called the
Northern/ Southern
Lights)
The Inner Planets
•
•
•
•
Mercury
Venus
Earth
Mars
• Terrestrial
– Rocky surfaces
Mercury
Fastest Planet
• Rotation
– 58 days, 16 hours
• Revolution
– 88 days
• Diameter
– 4,878 km (smaller than
the Earth)
• Surface details
–
–
–
–
Looks a lot like our moon
No moons orbiting
No atmosphere
Very hot during the day,
very cold at night
– Hard to study because it is
so close to the sun. It has
been visited by one Earth
satellite in the 1970’s. A
new satellite is currently on
its way to orbit the planet in
2011.
Venus
• Rotation
Earth’s Twin
• Surface details
– 243 days
– Retrograde (sun rises
in the west)
• Revolution
– 224 days
• Diameter
– 12,104 km (only
slightly smaller than
the Earth)
– No moons orbiting
– Dense atmosphere
keeps it very hot day
and night.
• High winds, sulfuric acid
rain
– It has been visited by
several Earth satellites
and landers.
• Radar maps show
surface details similar to
the Earth without water
Earth
• Rotation
– 23 hours, 56 minutes
• Revolution
– 365 days, 6 hours
• Diameter
– 12,756 km
• Surface details
– One moon, Luna
– Complex atmosphere
keeps it from getting too
hot during the day or too
cool at night.
• Large amount of liquid
water
– Only place in the
universe known that is
capable of sustaining
life
Mars
The Red Planet
• Rotation
– 24 hours, 37 minutes
• Revolution
1 year, 322 days
• Diameter
– 6,794 km (about 1/3 the
size of the Earth)
• Surface details
– 2 moons, Phobos, Deimos
• Small moons, probably
captured asteroids
– Thin atmosphere
• Large dust storms and other
weather patterns seen
– It has been visited by several
Earth satellites and landers.
• Detailed photos show
surface details similar to the
Earth with evidence of past
water
The Asteroid Belt
The Planet that never was
• Around 2,000 asteroids have been
discovered orbiting the sun between Mars
and Jupiter. Most are small only a few
miles across. There may be 1 million such
objects orbiting inside this area.
The asteroid belt is found between the orbits of Mars and
Jupiter. It holds most of the asteroids found orbiting the sun. It
is believed they might have been a small planet that was
prevented from forming by the gravity of Jupiter.
The first 4 asteroids discovered
• Ceres (also the largest)
– Discovered 1/1/1801 by Giuseppe Piazzi
– 1/3 the mass of all asteroids combined
• Pallas
– Discovered 3/28/1802 by Heinrich Olbers
– 1/12 the mass of all asteroids combined
• Juno
– 9/1/1804 by Karl Harding
– 1/100 the mass of all asteroids
• Vesta
– Discovered 3/29/1807 (Olbers)
– 1/10th the mass of all asteroids
The Outer Planets
•
•
•
•
Jupiter
Saturn
Uranus
Neptune
• Gas Giants (no rocky
surfaces)
– Consist of layers of
gases that blend
smoothly into the
denser layers in their
interiors
– All have systems of
rings (made up of dust
and small rocks)
– All have many moons
Jupiter
• Rotation
King of the Planets
• Surface details
– 9 hours, 50 minutes
• Revolution
– 11.3 years
• Diameter
– 142,984 km (largest of
all planets, heavier
than all of the planets
together)
• Jupiter’s gravity makes
it very important to the
solar system.
– 60-100 moons
• 4 very large moons, the rest
are very small
– Gases are divided into
bands of different colors,
altitudes and temperatures
• Great red spot, a storm first
seen over 400 years ago
– Very thin ring system.
– It has been visited by
several Earth satellites
Saturn
Planet with Ears
• Rotation
– 10 hours, 20 minutes
• Revolution
– 29.5 years
• Diameter
– 120,536 km (least dense
planet, less dense than
water)
• Saturn bulges at the
equator because of its fast
rotation and low density.
• Surface details
– 40 - 60 moons
• The solar system’s largest moon,
Titan, has its own atmosphere
– Gases are divided into bands
similar but cooler than Jupiter’s
• Storms and aurora have been
seen
– Only ring system easily seen on
Earth.
– It has been visited by several
Earth satellites, including one
orbiting now
Uranus
A Planet on its Side
• Rotation
– 17 hours, 14 minutes
• Revolution
– 83.6 years
• Diameter
– 51,118 km
• Surface details
– 20-30 moons
- Some show evidence of violent
pasts, which might explain why
Uranus orbits sideways
– Less banding in the clouds (much
cooler) than Jupiter or Saturn
– Planet orbits on its side
• Each of its poles points at the sun
for part of the year
– It has been visited by one Earth
satellite, Voyager 2
– First planet to be “discovered” (the
closer ones can be seen by
everyone)
• Found by William Herschel in
1781.
Neptune
Ocean Planet
• Rotation
– 16 hours, 7 minutes
• Revolution
– 163.6 years
• Diameter
– 49,528 km
• Surface details
– 13+ moons
• One large moon, Triton, has a
thin atmosphere
– Seems to give off more heat and
light than it gets from the sun
• Great Dark Spot has been seen
until recently
– It has been visited by one Earth
satellite, Voyager 2
– Second planet “discovered”
• Found by in 1846 John Adams
and Urbain Le Verrier, who
predicted its location using
Kepler’s and Newton’s laws.
The Edge of the Solar System
The Kuiper Belt, home of the comets.
This is a region outside Neptune’s orbit,
on the edge of our solar system, that
holds many icy objects which may collide
and fall toward the sun and melt.
Pluto
• Rotation
Double Planet
– 6 days, 10 hours
(retrograde)
• Revolution
– 248 years
– Actually closer to the sun
than Neptune for part of its
orbit
• Diameter
– 2,320 km (smaller than our
moon)
• Surface details
– 1 confirmed moon, Charon
• Charon orbits locked in a very
tight orbit
• May be at least two other moons
recently found.
– Surface is likely mostly ice and
dust
• Not terrestrial nor gas
• Similar to the composition of a
comet
• Very small, very far away, very
hard to study
– It has not been visited yet, one
Earth satellite is on its way
– Discovered by Clyde Tombaugh
in 1930
Beyond Pluto
• Sedna
Comets are dirty snowballs that melt as they fall toward the sun. The gas and
dust left behind produce a tail that is always pushed away from the sun.
The most famous comet is named after
Edmond Halley. He was the first person
to realize that comets return in cycles.
He realized a series of comets that had
been seen many times since 240 B.C.
was actually a single comet. In the
1700’s he correctly predicted the return
of the comet that would bare his name.
It returned as predicted 16 years after he
died. Halley’s comet returns every 76
years.
Short period comets from the Kuiper Belt
have defined orbits within our solar
system and predictable returns.
Long period comets come from farther
away (the Oort Cloud) and swing far
away from the sun. They might never
return.
Ion tail
Dust tail
The tail consists of two parts. A dust tail made of pieces of the comet lit by
sunlight and an ion tail made of charged particles created by passing through
the solar wind. The tail is only visible
as the comet approaches the sun. It shrinks and disappears as the comet
orbits away. Studying comets lets us see what the early solar system was
like since the material in a comet has been frozen and unchanged since the
The Moon (Luna)
• Rotation
– 27 days, 7.7 hours
• Revolution
– 27 days, 7.7 hours
*
• Keeps the same side
always facing the
Earth
• Diameter
– 3,476 km
• No atmosphere (means
no weather)
• Made of the same rocks
as the Earth (probably a
piece broken off from the
Earth early in its history).
• This is the only place,
other than Earth, where
humans have walked.
Phases of the
Waning
Moon
crescent
Third
Quarter
Waning
gibbous
*
New
Moon
Full
moon
Waxing
crescent
First
Quarter
Waxing
gibbous
Eclipse
• A solar eclipse occurs when the moon
blocks the sun creating a shadow for some
observers on the Earth.
*
Only visible to those in the right place at the
right time, always during the day, always
during a new moon (but not every new moon).
• A lunar eclipse occurs when the
moon passes through the shadow created
by the Earth. Some light is bent by the
Earth’s atmosphere causing the moon to
change colors.
*
Visible to everyone who can see the moon, always
at night (or near sunrise or sunset), always during a
full moon (but not every full moon).
Our moon, Luna, was most likely formed
from pieces blown off of the Earth by a
massive collision. This is believed
because of the size of the moon, the
closeness of the it’s orbit as well as the
composition of rocks being very similar to
those found on Earth.
The dark patches are called maria
(meaning “seas”) because they were
believed to contain water. Now we know
they are darker colored rocks, probably
created when lava filled massive impact
craters.
The brighter spots are smaller impact
craters and rays produced by materials
thrown out by meteor collisions.
The moons of Mars were named after the children of the Greek god of
war, Mars.
• Phobos (Fear) orbits closer to
its planet than any other moon in the
solar system. It takes only 7 ½ hours
to orbit Mars and has a diameter of 23
km.
• Deimos (Hate) takes 30 hours to
orbit Mars and has a diameter of 12 km.
Ganymede is the
largest of the four
and the heaviest of
all moons.
Europa is covered
with a smooth ice
surface. It may
hide an ocean
below.
Io is badly beaten by
Jupiter’s magnetic
field. It is the most
volcanically active
place in the solar
system
Callisto has many
impact craters and
a two-tone surface
(one half is much
lighter than the
other).
Major Moons of Jupiter: The Galilean Satellites
Galileo used the first telescope to discover
these moons (the first moons seen besides
our own). By watching these moons orbit
their parent planet Galileo confirmed his
belief that the planets moved around the sun,
which was different than common belief.
Titan is the largest moon in
the solar system. It has an
atmosphere made of
methane. It is the only
moon we have landed on,
besides our own, with a
robot spacecraft.
Iapetus has two different
colored sides and a 20 mile
high ridge around its middle
making it look like a walnut.
Dione is made mostly of
water ice.
Major Moons of Saturn
Tethys has strange
deep ridges of ice.