Chapter 20
http://www.brainpop.com/science/space/solarsystem/
Section 1-Observing the Solar
System
Earth at the centerCenturies ago, the sun and stars moved across
the sky while Earth seemed to remain stationary
(still).
Greek Observations-several points of light
seemed to wander across the sky among the
stars. They called these PLANETS.
Mercury, Venus, Mars, Jupiter, Saturn
They thought that Earth was in a rotating dome
called a celestial sphere.
Geocentric- an Earth
centered model of
the solar system
“geo” -Earth
Geocentric SystemEarth is at the center
of the revolving
planets and stars.
Ptolemy’s Model
A.D. 140- Greek astronomer Ptolemy
developed the geocentric model
Astronomer- a scientist who studies
the universe beyond Earth.
His model had the Earth at the center with other
planets moving on smaller circles that move on
bigger circles.
This model was incorrect but showed how
motions of planets are observed.
This geocentric model was accepted for over
1,500 years!
Sun at the Center
Not everyone believed the Earth being at the
center.
Heliocentric was developed as the sun being the
center of the solar system
“helios” – sun
In the heliocentric system, the Earth and other
planets revolved around the sun.
People did not want to believe this system
because it went against Earth being the center
of the universe.
In a heliocentric system, Earth
and the other planets revolve
around the sun.
http://www.astro.utoronto.ca/~zhu/ast210/both.html
Copernican Revolution
1543- Nicolaus Copernicus further
developed the heliocentric model
Copernicus was able to work out
the arrangement of the known
planets and how they move around
the sun.
Because this was against the church
and the belief of the time, and
Copernicus did not have enough
evidence to support this idea, he
did not publish his theories until after
his death.
Galileo’s Evidence
1610- Galileo Galilei used newly
invented telescope to make discoveries
that supported the heliocentric model.
He saw 4 moons revolving around Jupiter
(proved not everything revolved around the
Earth)
He also saw that Venus goes through phases
similar to Earth’s moon which it would not have if
it circled around the Earth.
The Heliocentric Model must be correct!
Tycho Brahe’s
Observations
Copernicus correctly placed the sun as the
center of the universe but incorrectly assumed
the planets travel in orbits that are perfect
circles.
Late 1500’s- Tycho Brahe and assistants studied
and recorded the positions of the planets for 20
years without telescopes!
After Brahe died in 1601, his assistant Johannes
Kepler continued analyzing observations.
Kepler’s Calculations
By studying Mars, Kepler found
that Mar’s orbit was an ellipse
instead of a circle.
Ellipse- oval shape that is
closely circular
Using the evidence gathered by
Brahe, Kepler found that the
orbit of each planet is an
ellipse.
Modern Discoveries
Since Galileo’s time, our knowledge of the solar system
has increase dramatically.
We have discovered 3 more planets- Uranus, Neptune,
and Pluto
Astronomers have discovered other objects in the solar
system like comets and asteroids.
Today we know that the solar system consists of the
sun, nine planets and their moon, and several kinds of
smaller objects that revolve around the sun.
Galileo used a telescope to make observations as we
do today but we have more technology and have
placed telescopes in space as well as space probes to
explore further into the far reaches of our solar system.
Section 2
https://www.youtube.com/watch?v=HEheh1BH34Q
The Sun’s Interior
The sun does not have a solid surface, but is a ball of glowing gas
¾ mass is hydrogen, ¼ helium
Like the Earth, has an interior and atmosphere
The sun’s interior consists of the core, the radiation zone, and convection
zone.
https://www.youtube.com/watch?v=gS1dpowPlE8 (how does the sun work?)
3 parts of the sun
The core- or ‘central region’
Energy comes from nuclear fission
Nuclear fission- a process where hydrogen
atoms join together to form helium.
-this only occurs under extremely high pressure
and temperature
-temperature in the core- 15 million degrees
Celsius (27 mill. F)
Energy slowly moves out from the core into
space.
The radiation zone- ‘middle layer’ a region of
very tightly packed gas where energy is
transferred mainly in the form of
electromagnetic radiation.
Energy can take 100,000 years to move
through this layer.
The convection zone- ‘outer most layer’ hot
gases rise to the top from the bottom, cool,
then sink forming loops of gas that move
energy to the surface.
The Sun’s Atmosphere
Includes the photosphere, chromosphere,
and the corona
The Photosphere- (inner layer) (‘photos’ –
light) the sphere that gives off visible
light. Considered the sun’s surface layer
The Chromosphere- (middle layer)
(‘chroma’ – color) the sphere of color
The Corona- (outer layer) (‘corona’ –
crown) extends into space and thins into
streams of electrically charged particles
called solar wind.
Features on the Sun
Features on or just above the sun’s surface include sunspots, prominences,
and solar flares.
https://www.youtube.com/watch?v=HFT7ATLQQx8
Sunspots- areas of gas on the sun’s surface that are cooler than the gases
around them. Cool areas don’t give off much light and are darker.
Prominenceshuge reddish loops of gas (sunspots) extending over the edge of the sun
Solar flareswhen loops connect releasing magnetic energy, erupting into space.
Solar wind
Solar flares increase solar wind from the
corona, which reach Earth’s upper most
part of the atmosphere.
Normally blocked from Earth’s magnetic
field and atmosphere, at the North and
South poles, particles create powerful
electric currents causing gas molecules to
glow
Aurora- rippling sheet of light caused by
solar flares
Solar wind particles effect Earth’s
magnetic field creating magnetic storms,
disrupting radio, tv, phone, and electrical
power problems.
https://www.youtube.com/watch?v=Ip2ZGND1I9Q (aurora)
https://www.youtube.com/watch?v=2zOlkIyg3iE (solar wind)
https://www.youtube.com/watch?v=3JdWlSF195Y (song-why does the
sun shine?)
Section 3
4 inner planets
Mercury, Venus, Earth, and Mars
The 4 inner planets are small and have
rocky surfaces
Inner planets are also called terrestrial
planets
Earth
Characteristics:
Water: Liquid water on the
surface
70% covered
Exists in all three forms: solid,
liquid, and gas
Atmosphere:
Has enough gravity to hold gases
Nitrogen- 78% Oxygen- 20% and
other gases such as Argon and
Carbon Dioxide and water vapor.
Mercury
The smallest terrestrial
planet and closest to the sun
Characteristics:
A single probe called
Mariner 10 in the mid 1970’s
showed the surface with
craters and plains
The surface has changed
little over time.
http://www.space.com/20086-mercury-map-nasa-messenger.html
https://www.yout
ube.com/watch?v
=6KY-oB2i9lo
Mercury’s Atmosphere:
Almost NONE!
Small mass of the planet- weak gravity
Extreme temperatures- Greatest out of all planets
During the day the surface reaches 430°C, at night
(because of lack of atmosphere heat escapes to space)
temp goes to -170°C
Venus
Size and mass similar to
Earth and referred to as
Earth’s twin or Sister planet
Density and internal
structure similar to Earth’s.
Takes 7.5 Earth months to
rotate around the sun and 8
months to rotate around on
its axis. A day on Venus is
longer than a Venus year!
Rotates East to West
https://www.youtube.com/watch?v=HqFVx
WfVtoo
http://www.youtube.com/watch?v=hsgrTn
TTPpc (space school)
Venus’s Atmosphere:
Super thick and always cloudy
Made mostly of sulfuric acid.
Atmosphere is 90 times greater than Earths and would
crush you if you stood on Venus’s surface.
Carbon Dioxide traps heat in through the greenhouse
effect
Temperature average: 460°C- hot enough to melt lead.
Venus Continued
Probes have visited Venus.
Venera- 1970, Magellan- 1990 mapped entire surface
Covered with rock with volcanoes and plains formed by lava flows
Mars
“Red Planet”- iron rich rocks
Atmosphere:
More than 95% Carbon Dioxidesimilar to Venus but thinner
You could walk on Mars but would
need a tank of oxygen
Few clouds and temperatures
range from -140°C to 20°C
https://www.youtube.com/wa
tch?v=XmxaPKt94jI
(how mars lost its atmos)
https://www.youtube.com/watch
?v=i5D8e71c75U (living on mars)
Mars’s Water:
Scientist think large amounts of water flowed on Mars’s surface in
the distant past.
The atmosphere is so thin that any water will turn to gas.
Two frozen polar ice caps
Water may be frozen underground.
Mars’s Seasons:
Axis is tilted – has seasons like Earth
Northern and southern poles have different season so one ice cap
grows and the other shrinks.
Windstorms cause dust to blow around
Exploring Mars
Many space probes have visited
Mars.
NASA’s Spirit and Opportunity
rovers have explored and
examined rocks and soil samples,
finding strong evidence of liquid
water.
Several volcanoes flowed in
Mars’s past but are inactive now.
Olympus Mons is the largest
volcano in the solar system.
https://www.youtube.com/watch?v=nQ
fJ7j2UGGk (planet rap)
https://www.youtube.com/watch?v=
B8OUL9QYNpI (curiosity)
Section 4
The first 4 outer planets- Jupiter, Saturn, Uranus, and Neptuneare much larger and more massive than Earth.
They do not have a solid surface and often called Gas Giants.
The 5th planet, Pluto, is small and rocky like the terrestrial planets.
Gas GiantsComposed of hydrogen and helium in liquid form
Strong gravitational force compared to terrestrial planets
Outer layers are extremely cold, inner layers temperatures
increase
Have many moons
All have rings-small particles of ice and rock
Jupiter
The largest and most
massive planet
Atmosphere:
Made of hydrogen and
helium
The Great Red Spot- a
storm larger than Earth,
similar to a hurricane, and
first observed in the mid1600’s.
Structure:
Dense core of rock and iron
Thick mantle made of liquid hydrogen
and helium
Crushing weight of atmosphere- 30
million times stronger than Earth.
Jupiter’s Moons:
Galileo discovered Jupiter’s 4 largest
moons- Io (has active volcanoes), Europa
(icy crust covers liquid oceans),
Ganymede (largest moon in solar system;
larger than Mercury), and Callisto
(covered with craters).
Dozens of others orbit around Jupiter
Saturn
Second largest planet in solar system.
Only planet that is less dense than
water (it will float)
Atmosphere:
Mainly hydrogen and helium
Clouds and storms (hurricane discovered recently at the north pole)
Rings: (chunks of rock and ice)
Has most spectacular than any other planet
Broad and thin like a compact disc
Moons: Largest-Titan
First, let’s get something
straight-
Comparison
Uranus: Gas Giant, planet
near the end of our solar
system.
Your Anus: Human biologyorgan near the end of the
digestive system.
Uranus Atmosphere:
Looks blue-green because of methane in atmosphere
Has rings
Discovering Uranus:
1781-William Herschel opened up the door
for active solar system study
Exploring Uranus:
Voyager 2 arrived and sent back close-ups showing only a few clouds
Uranus rotates in 17hrs
Uranus’s axis is tilted at 90 degrees from its vertical. (rotates top to
bottom instead of side to side)
Believed a large object hit into Uranus and knocked it on its side.
Uranus Moons:
5 largest have icy, cratered surfaces
Some have lava flows
Total of about 27 moons.
Neptune
Cold, blue planet with visible
clouds
Could be slowly shrinking,
heating up interior, producing
clouds and storms in
atmosphere.
Discovery:
First as a mathematical
prediction based on Uranus’s
orbit.
Thought gravity of an unseen
planet was affecting Uranus
and discovered in 1846.
Exploring Neptune:
Voyager 2 discovered a Great Dark Spot, like Jupiter’s
Great Red Spot, but did not last long. Spots seem to come
and go.
Moons:
13 moons- largest Triton(thin atmosphere and south pole
covered with nitrogen ice)
Pluto
Very different than gas giants
Pluto has a solid surface, much
smaller and dense than outer
planets.
Has a single moon: Charon which
is more than half the size of Pluto
and sometimes called a double
planet.
Pluto’s orbit:
Takes 248 Earth years to revolve
around the sun!
Very elliptical, brings it closer to
the sun than Neptune
Is Pluto a planet?
Pluto is very small
Pluto may only be slightly larger than some of the other
pieces of ice, rock, and dust that orbit in our solar system.
If astronomers had discovered these other objects, it may
not have been called a planet.
Recently astronomers have discovered a larger body
beyond Pluto but have not classified or named this as a
planet yet.