Download Earth is between the Sun and the Moon.

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Chapter 26:
THE SOLAR SYSTEM
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley
This lecture will help you
understand:
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The Solar System and Its Formation
The Sun
The Inner Planets
The Outer Planets
Earth’s Moon
Failed Planet Formation
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley
The Solar System and Its
Formation
The solar system consists of:
• Sun
• System of planets
• Asteroids
• Comets
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The Solar System and Its
Formation
Planets are divided into two classes:
• Inner planets:
Mercury
Venus
Earth
Mars
• Outer planets:
Jupiter
Saturn
Uranus
Neptune
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The Solar System and Its
Formation
The Nebular theory:
Theory that the Sun and planets formed
together from a cloud of gas and dust—a
nebula.
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The Solar System and Its
Formation
Nebular theory formation:
• Gravitation between materials in the cloud pulled it inward.
• When pulled inward, spin increased in accord with the
conservation of angular momentum.
• The spinning cloud conformed to the shape of a spinning
disk.
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The Solar System and Its
Formation
Nebular theory formation:
• The center of the disk is the protosun.
• Away from the center, planetesimals formed.
• Planetesimals accreted more matter to become planets.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley
The Solar System and Its Formation
CHECK YOUR NEIGHBOR
Which of the following orbits around the Sun?
A.
B.
C.
D.
Planets.
Comets.
Asteroids.
All of the above.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley
The Solar System and Its Formation
CHECK YOUR ANSWER
Which of the following orbits around the Sun?
A.
B.
C.
D.
Planets.
Comets.
Asteroids.
All of the above.
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The Solar System and Its Formation
CHECK YOUR NEIGHBOR
As a nebula shrinks under the influence of gravity, it
A.
B.
C.
D.
spins slower.
spins faster.
loses its spin.
spins into a protosun.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley
The Solar System and Its Formation
CHECK YOUR ANSWER
As a nebula shrinks under the influence of gravity, it
A.
B.
C.
D.
spins slower.
spins faster.
loses its spin.
spins into a protosun.
Explanation:
In accordance with the conservation of angular momentum, as the
radius of the nebula decreases, its spin rate increases (like a
skater who pulls her arms inward in a spin).
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The Sun
Sun:
• nearest star to Earth
• composed of mostly hydrogen in the plasma
phase
• hydrogen is fused to helium by thermonuclear
fusion in its core
• 4.5 million tons of mass are converted to energy
each second
• a tiny fraction of this energy reaches and
sustains Earth
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The Sun
CHECK YOUR NEIGHBOR
Strictly speaking, in every second that passes, the mass of
the Sun
A.
B.
C.
D.
decreases.
remains constant.
increases.
reinvents itself.
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The Sun
CHECK YOUR ANSWER
Strictly speaking, in every second that passes, the mass of
the Sun
A.
B.
C.
D.
decreases.
remains constant.
increases.
reinvents itself.
Explanation:
It is this decrease that bathes the solar system with radiant energy. Solar
mass is converted to energy via the celebrated equation, E = mc2.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley
The Inner Planets
The inner planets—four nearest to the Sun
composed of high-density solid rock:
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Mercury
Venus
Earth
Mars
Orbital speeds of planets around the Sun decrease with
increasing distance from the Sun.
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The Inner Planets
Mercury:
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closest to the Sun
slightly larger than our Moon
almost no atmosphere due to small size
daytime is long and hot (up to 430C)
nighttime is long and cold (about -170C)
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The Inner Planets
Venus:
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next closest to the Sun
diameter about 0.95 that of Earth
very dense atmosphere, mostly carbon dioxide
volcanically active
very harsh place
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The Inner Planets
Earth:
• third planet from the Sun—our home
• at a distance where most of its water is
neither solid nor gas, but liquid
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The Inner Planets
Mars:
• fourth planet from the Sun—a potential away-from-home
habitat
• little more than half Earth’s size
• thin atmosphere—95% carbon dioxide and 0.15%
oxygen
(A planet with a thin atmosphere is ineffective in reducing the
temperature difference between day and night!)
• equatorial temperatures range from 30C in day to
–130C at night
• presently the focus of planetary exploration
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley
The Inner Planets
Mars:
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The Outer Planets
Outer planets:
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gaseous, low-density worlds
appreciably larger than Earth
more widely spaced than the inner planets
in order of distance from Sun—
Jupiter
Saturn
Uranus
Neptune
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The Outer Planets
Jupiter:
• first of the outer planets, beyond Mars
• more than 11 times Earth’s diameter—
giant of the solar system
• composition more liquid than gaseous or
solid
• atmospheric pressure more than a million
times that of Earth’s
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The Outer Planets
Jupiter:
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The Outer Planets
Jupiter:
• atmosphere is 82% hydrogen, 17% helium, 1%
methane, ammonia, and other molecules—
cough!
• no definite surface as occurs on the inner rocky
planets
• solid core of iron, nickel, and other minerals
Because of its thick atmospheric blanket, daytime and
nighttime temperatures are about the same for equal
altitudes above its “surface.”
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The Outer Planets
Jupiter’s four largest moons
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The Outer Planets
Jupiter’s moon Europa has an ice-capped
ocean, which may hold extraterrestrial life
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The Outer Planets
Saturn:
• most remarkable for its easily
seen rings
• twice as far from Earth as
Jupiter
• diameter about ten times that
of Earth, excluding the rings
• lowest density of all
planets—could float in giant
bathtub (density is less than
that of water)
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The Outer Planets
Saturn:
• surrounded by rings—
hypothesized to be bits of a moon never formed,
or remnants of a moon torn apart by tidal forces
— inner part of rings, like any satellite, travels
faster than outer part of the ring system
Rocks that make up the rings orbit
independently of other rocks.
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The Outer Planets
Saturn’s largest moon, Titan, was visited by the
Cassini spacecraft.
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The Outer Planets
Uranus:
• twice as far from Earth as
Saturn is
• diameter about four times that
of Earth
• 98 tilt to the orbital plane—a
most unusual feature
• faint ring system
• methane atmosphere
• very cold place
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley
The Outer Planets
Neptune:
• lies beyond Uranus
• diameter almost four times
that of Earth, somewhat
smaller than Uranus
• atmosphere mainly
hydrogen and helium
• highly elongated elliptical
path about the Sun
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The Outer Planets
Pluto:
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since 2006, classified as a dwarf planet
very unlike other planets in composition, size, and orbit
highly elliptical orbit, like comets
spends most of its orbital time well beyond Neptune, in
the Kuiper Belt
• composition like that of Kuiper-Belt objects
• look-alike neighbors not classified as planets
• former planetary status was more historical than
astronomical
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The Outer Planets
CHECK YOUR NEIGHBOR
Which planet is more dense than water?
A.
B.
C.
D.
Mars.
Venus.
Neptune.
All of the above.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley
The Outer Planets
CHECK YOUR ANSWER
Which planet is more dense than water?
A.
B.
C.
D.
Mars.
Venus.
Neptune.
All of the above.
Comment:
Saturn is the only planet with a density less than that of water.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley
Earth’s Moon
Earth’s Moon:
• more is known about the Moon than any other celestial
body
• diameter about one quarter that of Earth
• no atmosphere—no weather and erosion to conceal past
scarring of its surface (wears no “makeup”)\
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Earth’s Moon
Twelve people have stood on the Moon.
Here we see Buzz Aldrin, one of the three
Apollo 11 astronauts.
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Earth’s Moon
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Earth’s Moon
Phases of the Moon:
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Earth’s Moon
The Moon spins about its polar axis as it
revolves around Earth.
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Earth’s Moon
CHECK YOUR NEIGHBOR
During the time of a new Moon, the
A.
B.
C.
D.
Sun is between Earth and the Moon.
Moon is between the Sun and Earth.
Earth is between the Sun and the Moon.
None of the above.
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Earth’s Moon
CHECK YOUR ANSWER
During the time of a new moon, the
A.
B.
C.
D.
Sun is between Earth and the Moon.
Moon is between the Sun and Earth.
Earth is between the Sun and Moon.
None of the above.
Explanation:
A new Moon is mainly in the daytime sky, between Earth and the
Sun. When it is exactly between them, we have a solar eclipse.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley
Earth’s Moon
CHECK YOUR NEIGHBOR
During the time of a full Moon, the
A.
B.
C.
D.
Sun is between Earth and the Moon.
Moon is between the Sun and Earth.
Earth is between the Sun and the Moon.
None of the above.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley
Earth’s Moon
CHECK YOUR ANSWER
During the time of a full Moon, the
A.
B.
C.
D.
Sun is between Earth and the Moon.
Moon is between the Sun and Earth.
Earth is between the Sun and the Moon.
None of the above.
Explanation:
A full Moon occurs when Earth is between the Sun and Moon,
while in Earth’s view, the hemisphere of the Moon is fully in
sunshine. When Earth is exactly between the Sun and the Moon,
we have a lunar eclipse.
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Earth’s Moon
A magnetic compass
aligns with a
magnetic field.
Like a compass in a
magnetic field, the
Moon aligns with
Earth’s gravitational
field.
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Earth’s Moon
Eclipses occur when the Moon’s shadow
falls on part of Earth.
This is a solar eclipse.
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Earth’s Moon
A lunar eclipse occurs when Earth’s
shadow falls on the Moon.
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Earth’s Moon
Eclipse:
The red light of sunrises and sunsets all
around Earth is refracted onto the Moon’s
surface during a lunar eclipse.
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Failed Planet Formation
Asteroids:
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small rocky bodies that orbit the Sun
most are located between Mars and Jupiter
some encounter Earth
unnoticed on ground—conspicuous on ice (the reason
many are found
in Antarctica)
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Failed Planet Formation
Comets:
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differ from asteroids in chemical composition
are masses of water, methane, and ice—dirty snowballs
most located in Kuiper Belt and Oort Cloud
highly elliptical (highly
eccentric) orbital paths
• tail of comets swept outward
from Sun by solar wind
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Failed Planet Formation
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley
Failed Planet Formation
CHECK YOUR NEIGHBOR
Asteroids are small rocky bodies that
A.
B.
C.
D.
orbit the Sun.
mainly reside between Mars and Jupiter.
are smaller than Earth’s Moon.
All of the above.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley
Failed Planet Formation
CHECK YOUR ANSWER
Asteroids are small rocky bodies that
A.
B.
C.
D.
orbit the Sun.
mainly reside between Mars and Jupiter.
are smaller than Earth’s Moon.
All of the above.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley
Failed Planet Formation
CHECK YOUR NEIGHBOR
The tails of comets point in a direction
A.
B.
C.
D.
toward the Sun.
away from the Sun.
at nearly right angles to the Sun.
None of the above.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley
Failed Planet Formation
CHECK YOUR ANSWER
The tails of comets point in a direction
A.
B.
C.
D.
toward the Sun.
away from the Sun.
at nearly right angles to the Sun.
None of the above.
Explanation:
The solar wind blows the tails in a direction away from the Sun.
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Failed Planet Formation
Meteoroids
are relatively small (sand-grain
to boulder size) pieces of debris
chipped off asteroids or comets
Meteor:
• a meteoroid that strikes Earth’s
atmosphere
• often called a “falling star”
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Failed Planet Formation
Meteorite
a meteoroid that survives the trip through
the atmosphere and reaches Earth’s
surface
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Failed Planet Formation
CHECK YOUR NEIGHBOR
Which of these makes contact with Earth’s surface?
A.
B.
C.
D.
Meteor.
Meteorite.
Meteoroid.
None of the above.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley
Failed Planet Formation
CHECK YOUR ANSWER
Which of these makes contact with Earth’s surface?
A.
B.
C.
D.
Meteor.
Meteorite.
Meteoroid.
None of the above.
Comment:
A meteorite has changed its status from meteoroid to meteor to
meteorite.
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