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