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Chapter 28 Lecture
Conceptual
Integrated Science
Second Edition
The Solar
System
© 2013 Pearson Education, Inc.
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
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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:
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Mercury
Venus
Earth
Mars
– Outer planets:
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Jupiter
Saturn
Uranus
Neptune
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The Solar System and Its Formation
• According to the nebular theory, 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 the cloud was pulled inward, its spin
increased in accordance 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 (continued)
– The center of the disk is the protosun.
– Away from the center, planetesimals formed.
– Planetesimals accreted more matter to
become planets.
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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
Explain your answer to your neighbor.
© 2013 Pearson Education, Inc.
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.
Explain your answer to your neighbor.
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The Sun
• The Sun is the nearest star to Earth.
• The Sun is composed of mostly hydrogen in the
plasma phase.
• Hydrogen is fused to helium by thermonuclear
fusion in the Sun's core.
• In the Sun 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.
Explain your answer to your neighbor.
© 2013 Pearson Education, Inc.
The Inner Planets
• The inner planets are the four nearest the Sun.
They are composed of high-density solid rock.
– Mercury
– Venus
– Earth
– Mars
• The orbital speeds of planets around the Sun
decrease with increasing distance from the Sun.
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The Inner Planets
• Mercury
– Mercury is the closest planet to the Sun.
– It is slightly larger than our Moon.
– Mercury has almost no atmosphere because of its
small size.
– Mercury's daytime is long and hot (up to 430C); its
nighttime is long and cold (about -170C).
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The Inner Planets
• Venus
– Venus is the next closest planet to the Sun.
– Its diameter about 0.95 that of Earth.
– Venus has a very dense atmosphere, made up of
mostly carbon dioxide.
– Venus is volcanically active and is a very harsh place.
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The Inner Planets
• Earth
– Earth is the third planet from the Sun—our
home.
– Earth is at a distance from the Sun where
most of its water is neither solid nor gas, but
liquid.
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The Inner Planets
• Mars
– Mars is the fourth planet from the Sun—a potential
away-from-home habitat.
– It is a little more than half Earth's size.
– Mars has a 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!
– On Mars, equatorial temperatures range from 30C
during the day to –130C at night.
– Mars is presently the focus of planetary exploration.
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The Inner Planets
• Mars
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The Outer Planets
• The outer planets are
– gaseous, low-density worlds.
– appreciably larger than Earth.
– more widely spaced than the inner planets.
– The outer planets in order of distance from
the Sun:
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Jupiter
Saturn
Uranus
Neptune
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The Outer Planets
• Jupiter
– Jupiter is the first of the outer planets, beyond
Mars.
– It is more than 11 times Earth's diameter—the
giant of the solar system.
– Jupiter's composition is more liquid than
gaseous or solid.
– Jupiter's atmospheric pressure is more than a
million times that of Earth.
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The Outer Planets
• Jupiter
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The Outer Planets
• Jupiter (continued)
– Jupiter's atmosphere is 82% hydrogen, 17% helium,
and 1% methane, ammonia, and other molecules—
cough!
– There is no definite surface on Jupiter, as occurs on
the inner rocky planets.
– Jupiter's solid core is made up of iron, nickel, and
other minerals.
– Because of Jupiter's thick atmospheric blanket, its
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
– Saturn is most remarkable
for its easily seen rings.
– Saturn is twice as far from
Earth as Jupiter is.
– Saturn's diameter, excluding
the rings, is about ten times
that of Earth.
– Saturn has the lowest
density of all planets—it
could float in a giant bathtub
(density is less than that of
water).
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The Outer Planets
• Saturn (continued)
– Saturn is surrounded by rings.
• The rings are hypothesized to be bits of a moon
never formed, or remnants of a moon torn apart by
tidal forces.
• The inner part of the rings, like any satellite, travels
faster than the outer part of the ring system.
• The 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
– Uranus is twice as far from
Earth as Saturn is.
– Uranus's diameter is about four
times that of Earth.
– Uranus is tilted 98 to the
orbital plane—a most unusual
feature.
– Uranus has a faint ring system.
– Uranus has a methane
atmosphere and is a very cold
place.
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The Outer Planets
• Neptune
– Neptune lies beyond Uranus.
– Neptune's diameter is almost
four times that of Earth,
somewhat smaller than Uranus.
– Its atmosphere is mainly
hydrogen and helium.
– Neptune has a highly elongated
elliptical path about the Sun.
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The Outer Planets
• Pluto
– Since 2006, Pluto has been classified as a
dwarf planet.
– It is very unlike the other planets in composition, size,
and orbit.
– Pluto has a highly elliptical orbit, like comets.
– It spends most of its orbital time well beyond
Neptune, in the Kuiper belt.
– Pluto's composition is like that of Kuiper belt objects.
– Its look-alike neighbors are not classified as planets.
– The 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
Explain your answer to your neighbor.
© 2013 Pearson Education, Inc.
Earth's Moon
• More is known about the Moon than any other
celestial body.
• The Moon's diameter is about one—quarter that
of Earth.
• The Moon has 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
Explain your answer to your neighbor.
© 2013 Pearson Education, Inc.
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
Explain your answer to your neighbor.
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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
• 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
– Asteroids are small rocky
bodies that orbit the Sun.
– Most are located between
Mars and Jupiter.
– Some asteroids encounter
Earth.
– Unnoticed on the ground,
asteroids are conspicuous
on ice (the reason many are
found in Antarctica).
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Failed Planet Formation
• Comets
– Comets differ from asteroids in chemical
composition.
– Comets are masses of water, methane, and
ice—dirty snowballs.
– Most are located in the Kuiper belt and Oort
cloud.
– Comets have highly elliptical (highly
eccentric) orbital paths.
– The tails of comets are swept outward
from the Sun by solar wind.
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Failed Planet Formation
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Failed Planet Formation
CHECK YOUR NEIGHBOR
Asteroids are small rocky bodies that
A.
B.
C.
D.
orbit the Sun.
reside mainly between Mars and Jupiter.
are smaller than Earth's Moon.
all of the above
Explain your answer to your neighbor.
© 2013 Pearson Education, Inc.
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
Explain your answer to your neighbor.
© 2013 Pearson Education, Inc.
Failed Planet Formation
• Meteoroids are relatively
small (sand-grain to boulder
size) pieces of debris chipped
off asteroids or comets.
• A meteor is
– a meteoroid that strikes
Earth's atmosphere.
– often called a "falling star."
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Failed Planet Formation
• A meteorite is 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
Explain your answer to your neighbor.
© 2013 Pearson Education, Inc.