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Chapter 29 – Our Solar System
"The earth is the cradle of humankind, but one cannot
live in the cradle forever." -- Konstantin Tsiolkovsky, 1895
29.1 Overview of our solar system
OBJECTIVES
Describe early models of our solar system.
Examine the modern heliocentric model of our solar system.
Relate gravity to the motions of celestial bodies.
Early Ideas
Geocentric ,meaning “Earth Centered”
In the early 1500s, Nicholas Copernicus formulated the heliocentric model of the solar system.
Copernicus
Nicolaus Copernicus found that in a heliocentric model of the solar system, • the inner planets move faster in their orbits than the outer planets, • giving the appearance from Earth that some planets move in a retrograde motion.
(http://imagine.gsfc.nasa.gov/Images/people/
Copernicus.gif )
Retrograde Motion
Retrograde motion is the movement of a planet in an opposing direction across the sky.
Galileo
Galileo’s discovery of Jupiter’s moons proved that not all celestial bodies orbit Earth; therefore, Earth is not necessarily the center of the solar system.
Kepler’s First Law
Kepler’s first law demonstrates that each planet has an elliptical orbit of unique size and shape with the Sun at one focus.
AU
Earth’s average distance from the Sun: 1.496 x 108 km or 1 astronomical unit.
Planets’ Orbits
All of the planets (& former planets) and their satellites orbit the Sun in the same direction, and all their orbits, except Pluto's lie near the same plane.
Eccentricity
When a planet is closest to the sun in its orbit, it is at ____________ and when it is farthest from the sun, it is at _________.
perihelionaphelion
Ellipses Terms to be familiar with.
•Major axis•Foci•Semi-major axis•Perihelion•Sun•Aphelion
Eccentricity
e =
Distance between fociMajor axis length
Kepler’s Second Law
Kepler’s second law is an imaginary line between the Sun and a planet that sweeps out equal amounts of area in equal amounts of time.
Closer Faster
Farther slower
Center of Mass
Isaac Newton determined that each planet does not orbit the Sun but instead orbits a center of mass between it and the Sun.
29.1 Overview of our Solar System Quiz
29.2 The Terrestrial Planets
OBJECTIVES
Describe the properties of the terrestrial planets.
Compare Earth with the other terrestrial planets.
Precession
The wobble of the Earth’s rotational axis is called precession.
The Moon’s gravitational force on Earth causes the sideways push that is responsible for precession.
Mercuryhas the largest day-night
temperature difference of all the planets in the solar system.
Mariner 10 image of Mercury
Venusis the planet most similar to
Earth in physical properties, such as diameter, mass, and density.
Venus - Computer Simulated Global View
Centered at 180 Degrees East Longitude
Venus (more)
The high concentration of carbon dioxide (CO2) in the atmosphere of Venus inhibits infrared radiation from escaping and keeps the surface extremely hot.
Earthis the only known planet in
our solar system where H2O is present in three states, solid, liquid & gas.
Image by Reto Stöckli (land surface, shallow
water, clouds).
Terrestrial planets are close to the size of Earth and have solid and rocky surfaces, while the gas giant planets are larger, more gaseous, and lack solid surface.
29.2 The Terrestrial Planets
Planet Rotation Period &
Size
Atmosphere &
Temperature
Surface Features
Interior & Magnetic Field
Additional Features
Mercury
1407.6 Hrs,
1/3 Earth-size
Atmosphere almost non-existent.
Mostly O2 and Na, Day 429◦C to -173◦C at
night
Craters and plains
High-density extensive
nickel-iron core, molten zone present- magnetic field detectable.
No moons
Venus
243R days, 95% of Earths-size
Primarily CO2 & N2,clouds of sulfuric acid, Average temperature is 464◦C
Smoothed by lava flows few impact-craters
Theorized that it is similar to earth, no
data to back this up.
No moons, highest albedo of any planet,
spin is retrograde, extreme
greenhouse effect
Earth
24 hrs, Exactly Earth-sized
(wink!)
78% - N2 21% - O2 Average
temperature is 15◦C
Effects of impacts erased
by erosion
Crust,mantle, inner and outer core, presence of magnetic field.
1 moon,
presence of liquid
water, mild greenhouse
effect
Mars
24 hrs 37 minutes,
½ of Earth’s size
Thin and consistent wind,
composition similar Venus’s.
Average temperature is -
60◦C
Plains & volcanoes
Theorized core of Fe &
Ni, no magnetic field.
2 moons, red color due to high Fe in
soil
Atmospheric conditions of the four terrestrial planets
Mercury
• almost non-existent
• mostly oxygen and sodium
Venus
• thick clouds• primarily of
carbon dioxide and nitrogen
• Include sulfuric acid
Earth Mars
• moderately dense
• composed of 78% nitrogen and 21% oxygen
• thin and there is consistent wind.
• composition is similar to Venus’s
Mercury
Venus Earth Mars
29.3 The Gas Giant Planets
OBJECTIVES
Describe the properties of the gas giant planet.
Identify the unique nature of the object “formerly-known-as-the-Planet-Pluto”.
29.3 The Gas Giant Planets
Planet Rotation Period & Size
Atmosphere Surface Features
Interior & Magnetic Field
Additional Features
Jupiter
9.925 hrs, 11 X
Earth’s size
90% - H2 10% - He,
Liquid metallic hydrogen present
Belts are low, warm, dark-
colored clouds that sink. Zones are high, cool , light-colored
clouds that rise.
Earth-sized solid core of heavier
material, magnetic field generated by electric currents in liquid metallic
hydrogen.
63 moons, accounts for 70% of mass of our solar system’s
planets
Saturn
10 hrs 39 minutes, almost 10 X Earth’s
size
75% - H2 25% - He,
Liquid metallic hydrogen present
Structure similar to Jupiter.
Earth-sized solid core of heavier
material, magnetic field 1000 times stronger than
earth’s.
Prominent feature is the rings, 61 named moons, second largest in our solar system, least dense , less than that
of water
Uranus
17.24R hrs, 3.95 X Earth’s size
83% - H2 15% - He
2% - Methane, this gives it
the blue-green color
No distinct zones or belts.
Structure similar to Jupiter and
Saturn.
Very small solid core, Strong
magnetic field.
Rings present, at least 27
moons, axis is tipped to almost
90 degrees (rolls around the sun?)
Neptune
16 hrs 11 minutes, 3.87 X Earth’s size
Similar to Uranus
Distinct zones & belts present.
Structure similar to Jupiter and
Saturn.
Similar to Uranus.
Rings present, 13 moons, blue-green
color
29.3 the object “formerly-known-as-the-Planet-Pluto”.
Planet Rotation Period Atmosphere
Surface Features Interior
Additional Features
Pluto
6.38R days, 17 % of Earth’s
size
98% N2, Methane and traces of
CO
More similar to a moon of the gas
giants.
50% to 75% rock mixed with ices
Largest difference between
Aphelion (50 AU) and perihelion
(30 AU)
Composition
The gas giants are composed primarily of lightweight elements, such as hydrogen, helium & methane.
Jupiter Saturn Uranus
Neptune
Rapid RotationThe rapid rotation of the largest gas giant
Jupiter, causes its clouds to flow in alternating cloud types called belts and zones.
Jupiter
Belts are low, warm, dark-colored clouds that sink. Zones are high, cool , light-colored clouds that rise.
Blue Color
Neptune and Uranus , the two gas giants appear blue because of the methane in their atmosphere.
Uranus
Neptune
NeptuneNeptune has clouds and atmospheric belts
and zones similar to those of Saturn and Jupiter.
Neptune
Pluto’s EccentricityPluto’s orbit is so eccentric that while at
perihelion, Pluto is closer to the Sun than Neptune is.
The eccentric orbit of Pluto is 50 AU from the Sun at aphelion and almost 30 AU from the Sun at perihelion.
Pluto's orbit seen from the plane of the ecliptic, showing its high inclination compared to the other planets
Terrestrial and the Gas giant planets
Terrestrial planets
• four planets close to the Sun
• Mercury, Venus, Earth, and Mars
• solid, rocky surfaces • smaller
Gas giant planets
• farther from the Sun• Jupiter, Saturn, Uranus,
and Neptune• more gaseous• lack a solid surface• larger
Both are categories of the planets of our solar system
29.2 & 29.3 Quiz (8pts)Riddle me this .
29.4 Formation of Our Solar System
OBJECTIVES
Describe how the planets formed from a disk surrounding the young sun.
Explore remnants of solar system formation.
Interstellar Cloud
Interstellar cloud, a cloud of gas and dust from which stars and planets are formed.
Solar Nebula TheoryInterstellar cloud can condense and become concentrated enough to form a star and possibly planets.
The dense concentration of gas at the center of the solar nebula eventually became the Sun.
PlanetismalsPlanetismals are tiny grains of condensed material that accumulate and merge together to form these large bodies possibly growing until they reach hundreds of kilometers in diameter.
Asteroids
Bodies of interplanetary debris that orbit the Sun with most in the area between Mars and Jupiter are called asteroids.
CometsComets are small, icy body made of ice and rock that has a highly eccentric orbit around the Sun.
The Oort cloud and the Kuiper belt are two cluster of comets.
Haley 's comet seen here in 1986. It will appear again in 2062.
Meteor
The result when Earth intersects a cometary orbit is a meteor shower.
Meteor
Meteor is interplanetary material that burns up and becomes a bright, glowing streak of light in Earth’s atmosphere.
Two examples are the Perseids (August) & Leonid (November).
Meteorite
Is interplanetary material that enter’s Earth’s atmosphere and collides with the ground rather than burning up.
29.4 Quiz