Ultimate Visual Dictionary (DK)

ULTIMATE




Zygomorphic
flower shape


Green striped
markings Upper sepal













Column
(fused male Anther cap
and female
parts)
Pollinium
(pockets of
pollen)
Spreading
petal
Spreading
petal VISUAL











Rostellum
Stigma



Lateral (side)
Labellum sepal
(slipper-
shaped petal)
Flower stalk



REVISED AND UPDA TED
GLFWLRQDU\



VISUAL








dictionary












Glabella



Eye



Thoracic
pleurae












Tail area
Tail shield


PREHISTORIC TRILOBITE

DIGITAL VIDEO CAMERA OVERHEAD VIEW OF OUR GALAXY
Liquid crystal
display (LCD) Location of
solar system
Viewfinder




Power switch



Cassette
compartment
lid
Battery


First
electron Nucleus
shell Second
electron
shell

Nucleus Windshield

Steering
Fault plane wheel
Dip of
fault plane
ANATOMY OF A
FLUORINE-19 ATOM
Radiator
Hade of
Headlight
fault
plane



STRUCTURE OF A FAULT
Exhaust
port





Floral
design







VELOCETTE OHV ENGINE MOSAIC DESIGN MODEL T FORD

VISUAL









dictionary









Pedicel
(flower stalk)

Sepal





Achene
(one-seeded
dry fruit)





Remains
of stigma
and style



STRAWBERRY










DK PUBLISHING

LONDON, NEW YORK, MUNICH, MELBOURNE, AND DELHI

THIS EDITION
DK LONDON DK DELHI
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Publishing Director Jonathan Metcalf
Anatomical And Botanical Models Supplied By Somso Modelle, Coburg, Germany





ORIGINAL EDITION (Ultimate Visual Dictionary)
Project Art Editors Heather McCarry, Johnny Pau, Chris Walker, Kevin Williams
Designer Simon Murrell
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Editor Jo Evans
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FIRST AMERICAN EDITION PUBLISHED UNDER THE TITLE
ULTIMATE VISUAL DICTIONARY, 1994
THIS REVISED EDITION PUBLISHED IN 2011 BY
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Discover more at www.dk.com

4

Canopy Fin
Spinneret
Prosoma
(cephalothorax)



Heat shield
Main landing
gear

SIDE VIEW OF ARV SUPER 2 AIRPLANE
Leg


CONTENTS
EXTERNAL FEATURES
OF A SPIDER

Third
Barrel
INTRODUCTION 6 stage
motor
THE UNIVERSE 8
Permanent
black ink Delta II
PREHISTORIC EARTH 54 launch
vehicle
PLANTS 110 second
stage
FOUNTAIN PEN AND INK ANIMALS 164
MARS PATHFINDER
THE HUMAN BODY 208
Face light Low pressure
emitting GEOLOGY, GEOGRAPHY, gases
diodes
Movable (LEDs) AND METEOROLOGY 262
tail
PHYSICS AND CHEMISTRY 304
RAIL AND ROAD 322

SEA AND AIR 370 Central
electrode
THE VISUAL ARTS 428
BALL CONTAINING HIGH
TEMPERATURE GAS (PLASMA)
SONY AIBO ARCHITECTURE 456
ROBOT DOG
MUSIC 500 Nonbreakable
plastic
Parallel SPORTS 522
bands
THE MODERN WORLD 564

APPENDIX 616 Shock
absorber

FOOTBALL HELMET
ONYX INDEX 624



5

Introduction



HE VISUAL DICTIONARY is a annotated, color photographs showing the skin,
Tcompletely new kind of reference muscles, and bones of the human hand. In this entry
you will quickly find that the bone you are searching
book. It provides a link between pictures
for is called the distal phalanx, and for good measure
and words in a way that no ordinary you will discover that it is attached to the middle
dictionary ever has. Most dictionaries phalanx by the distal interphalangeal joint.
simply tell you what a word means, but
Perhaps you want to know what a catalytic converter
the VISUAL DICTIONARY shows you—through looks like. If you look up “catalytic converter” in an
a combination of detailed annotations, ordinary dictionary, you will be told what it is and
possibly what it does—but you will not be able to tell
explicit photographs, and illustrations.
what shape it is or what it is made of. However, if
In the VISUAL DICTIONARY, pictures define you look up “catalytic converter” in the index of the
the annotations around them. You do not VISUAL DICTIONARY, you will be directed to the Modern
engines entry on page 344—where the introduction
read definitions of the annotated words,
gives you basic information about what a catalytic
you see them. The highly accessible converter is—and to page 350—where there is a
format of the VISUAL DICTIONARY, the spectacular exploded-view photograph of the
mechanics of a Renault Clio. From these pages you
thoroughness of its annotations, and
will find out not only what a catalytic converter looks
the range of its subject matter make like, but also that it is attached at one end to an
it a unique and helpful reference tool. exhaust pipe and at the other to a muffler.
Whatever it is that you want to find a name for, or
whatever name you want to find a picture for, you
How to use the VISUAL DICTIONARY will find it quickly and easily in the VISUAL DICTIONARY.
You will find the VISUAL DICTIONARY simple to use. Perhaps you need to know where the vamp on a
Instead of being organized alphabetically, it is
shoe is; or how to tell obovate and lanceolate leaves
divided by subject into 14 sections—THE UNIVERSE, apart; or what a spiral galaxy looks like; or whether
PREHISTORIC EARTH, PLANTS, ANIMALS, THE HUMAN BODY, birds have nostrils. With the VISUAL DICTIONARY at
etc. Each section begins with a table of contents hand, the answers to each of these questions, and
listing the major entries within that section. For thousands more, are readily available.
example, The Visual Arts section has entries on
Drawing, Tempera, Fresco, Oils, Watercolor, Pastels, The VISUAL DICTIONARY does not just tell you what the
Acrylics, Calligraphy, Printmaking, Mosaic, and names of the different parts of an object are. The
Sculpture. Every entry has a short introduction photographs, illustrations, and annotations are all
explaining the purpose of the photographs and specially arranged to help you understand which
illustrations, and the significance of the annotations.
parts relate to one another and how objects function.
If you know what something looks like, but don’t With the VISUAL DICTIONARY you can find in seconds
know its name, find the term you need by turning the words or pictures that you are looking for; or
to the annotations surrounding the pictures; if you you can simply browse through the pages of the
know a word, but don’t know what it refers to, use book for your own pleasure. The VISUAL DICTIONARY
the comprehensive index to direct you to the is not intended to replace a standard dictionary
appropriate page.
or conventional encyclopedia, but is instead a
stimulating and valuable companion to ordinary
Suppose that you want to know what the bone reference volumes. Giving you instant access to the
at the end of your little finger is called. With a language that is used by astronomers and architects,
standard dictionary, you wouldn’t know where musicians and mechanics, scientists and
to begin. But with the VISUAL DICTIONARY you simply
sportspeople, it is the ideal reference book for
turn to the entry called Hands—within THE HUMAN specialists and generalists of all ages.
BODY section—where you will find four fully





6

Sections of the VISUAL DICTIONARY •PHYSICS AND CHEMISTRY is a visual journey
The 14 sections of the VISUAL DICTIONARY contain a through the fundamental principles underlying
total of more than 30,000 terms, encompassing the physical universe, and provides the essential
a wide range of topics: vocabulary of these sciences.

•In the first section, THE UNIVERSE, spectacular •In RAIL AND ROAD, a wide range of trains, trams
photographs and illustrations are used to show and buses, cars, bicycles, and motorcycles are
the names of the stars and planets and to described. Exploded-view photographs show
explain the structure of solar systems, galaxies, mechanical details with striking clarity.
nebulae, comets, and black holes.
•SEA AND AIR gives the names for hundreds
•PREHISTORIC EARTH tells the story in annotations of parts of ships and airplanes. The section
of how our own planet has evolved since its includes civil and fighting craft, both
formation. It includes examples of prehistoric historical and modern.
flora and fauna, and fascinating dinosaur
models—some with parts of the body stripped •THE VISUAL ARTS shows the equipment and
away to show anatomical sections. materials used by painters, sculptors, printers,
and other artists. Well-known compositions
•PLANTS covers a huge range of species— have been chosen to illustrate specific artistic
from the familiar to the exotic. In addition techniques and effects.
to the color photographs of plants included in
this section, there is a series of micrographic •ARCHITECTURE includes photographs of
photographs illustrating plant details—such exemplary architectural models and illustrates
as pollen grains, spores, and cross-sections of dozens of additional features such as columns,
stems and roots—in close-up. domes, and arches.

•In the ANIMALS section, skeletons, anatomical •MUSIC provides a visual introduction to
diagrams, and different parts of animals’ bodies the special language of music and musical
have been meticulously annotated. This section instruments. It includes clearly annotated
provides a comprehensive guide to the photographs of each of the major groups of
vocabulary of zoological classification and traditional instruments—brass, woodwind,
animal physiology. strings, and percussion—together with modern
electronic instruments.
•The structure of the human body, its parts, and
its systems are presented in THE HUMAN BODY. •The SPORTS section is a guide to the playing
The section includes lifelike, three-dimensional areas, formations, equipment, and techniques
models and the latest false-color images. Clear needed for many of today’s most popular sports.
and authoritative annotations indicate the
correct anatomical terms. •In THE MODERN WORLD, items that are a
familiar part of our daily lives are taken apart
• GEOLOGY, GEOGRAPHY, AND METEOROLOGY to reveal their inner workings and give access to
describes the structure of the Earth—from the the language used by their manufacturers. It
inner core to the exosphere—and the physical also includes systems and concepts, such as
phenomena—such as volcanoes, rivers, glaciers, the internet, that increasingly influence our
and climate—that shape its surface. 21st century world.









7



THE UNIVERSE




ANATOMY OF THE UNIVERSE .................................... 10
GALAXIES ................................................................. 12
THE MILKY WAY .................................................... 14
NEBULAE AND STAR CLUSTERS ................................ 16
STARS OF NORTHERN SKIES ...................................... 18
STARS OF SOUTHERN SKIES ...................................... 20
STARS ....................................................................... 22
SMALL STARS ........................................................... 24
MASSIVE STARS ........................................................ 26
NEUTRON STARS AND BLACK HOLES ........................ 28
THE SOLAR SYSTEM ................................................. 30
THE SUN .................................................................. 32
MERCURY ................................................................. 34
VENUS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
THE EARTH .............................................................. 38
THE MOON .............................................................. 40
MARS ....................................................................... 42
JUPITER .................................................................... 44
SATURN .................................................................... 46
URANUS ................................................................... 48
NEPTUNE AND PLUTO .............................................. 50
ASTEROIDS, COMETS, AND METEOROIDS .................. 52

THE UNIVERSE

Anatomy of the universe Fireball of rapidly
expanding, extremely
hot gas lasting about
one million years
THE UNIVERSE CONTAINS EVERYTHING that exists, from the tiniest subatomic particles
to galactic superclusters (the largest structures known). No one knows how big
the universe is, but astronomers estimate that it contains at least 125 billion
galaxies, each comprising an average of 100 billion stars. The most widely
accepted theory about the origin of the universe is the Big Bang
theory, which states that the universe came into being in a huge
explosion—the Big Bang—that took place between 10 and 20
billion years ago. The universe initially consisted of a very
hot, dense fireball of expanding, cooling gas. After about
one million years, the gas began to condense into
localized clumps called protogalaxies. During the
next five billion years, the protogalaxies continued
condensing, forming galaxies in which stars were
being born. Today, billions of years later, the
universe as a whole is still expanding, although
there are localized areas in which objects are
held together by gravity; for example, many
galaxies are found in clusters. The Big Bang
theory is supported by the discovery of faint,
cool background radiation coming evenly from
all directions. This radiation is believed to be
the remnant of the radiation produced by the
Big Bang. Small “ripples” in the temperature of
the cosmic background radiation are thought
to be evidence of slight fluctuations in the
density of the early universe, which resulted
in the formation of galaxies. Astronomers do
not yet know if the universe is “closed,” which
means it will eventually stop expanding and
begin to contract, or if it is “open,” which
means it will continue expanding forever.

FALSE-COLOR MICROWAVE MAP OF
COSMIC BACKGROUND RADIATION
Pale blue indicates
“cool ripples” in
Pink indicates “warm
ripples” in background background radiation
radiation






Low-energy
microwave radiation
corresponding to -454°F (-270°C)

Red and pink band High-energy gamma
Deep blue indicates indicates radiation radiation corresponding
background radiation corresponding to -454°F from our galaxy to 5,400°F (3,000°C)
(-270°C); (remnant of the Big Bang)

10

ANATOMY OF THE UNIVERSE

ORIGIN AND EXPANSION OF THE UNIVERSE OBJECTS IN THE UNIVERSE

Quasar (probably the center
of a galaxy containing a
massive black hole)

Universe about five
billion years after
Big Bang

CLUSTER OF FALSE-COLOR IMAGE
Protogalaxy GALAXIES IN VIRGO
(condensing gas cloud) OF 3C273 (QUASAR)




Galaxy spinning and
flattening to become
spiral shaped


NGC 4406 NGC 5236
(ELLIPTICAL GALAXY) (BARRED SPIRAL GALAXY)
Dark cloud
(dust and gas
condensing
to form a
protogalaxy)



Elliptical
galaxy in
which stars
form rapidly
NGC 6822 THE ROSETTE NEBULA
(IRREGULAR GALAXY) (EMISSION NEBULA)






Universe today
(13–17 billion years
after Big Bang)

THE JEWEL BOX THE SUN
Cluster of (STAR CLUSTER) (MAIN SEQUENCE STAR)
galaxies held
together by gravity

Elliptical galaxy
containing old stars
and little gas and dust
Irregular galaxy
Spiral galaxy
containing gas,
dust, and young stars
EARTH THE MOON


11

THE UNIVERSE
Galaxies

OPTICAL IMAGE OF NGC 4486
(ELLIPTICAL GALAXY) Globular cluster
containing very
A GALAXY IS A HUGE MASS OF STARS, nebulae, old red giants
and interstellar material. The smallest
Central region
galaxies contain about 100,000 stars, while
containing old
the largest contain up to 3 trillion stars. red giants
There are three main types of galaxy,
Less densely
classified according to their shape: elliptical,
populated region
which are oval shaped; spiral,
SOMBRERO,
A SPIRAL GALAXY which have arms spiraling Neighbouring galaxy
outward from a central bulge (those whose arms OPTICAL IMAGE OF LARGE MAGELLANIC
CLOUD (IRREGULAR GALAXY)
spiral from a bar-shaped bulge are called spirals);
and irregular, which have no obvious shape.
Sometimes, the shape of a galaxy is distorted by
a collision with another galaxy. Quasars (quasi- Tarantula Nebula
stellar objects) are thought to be galactic nuclei
but are so far away that their exact nature is still
uncertain. They are compact, highly luminous
objects in the outer reaches of the known
universe: while the farthest known “ordinary” Dust cloud obscuring
light from stars
galaxies are about 12 billion light-years away, the
farthest known quasar is about 13 billion light-
years away. Active galaxies, such as Seyfert Emission nebula
galaxies and radio galaxies, emit intense radiation.
In a Seyfert galaxy, this radiation comes from the
galactic nucleus; in a radio galaxy, it also comes
from huge lobes on either side of the galaxy. The Light from stars
radiation from active galaxies and quasars is
thought to be caused by material falling into
central black holes (see pp. 28-29).


OPTICAL IMAGE OF NGC 2997 (SPIRAL GALAXY)



Glowing nebula Dust in spiral
in spiral arm arm reflecting
blue light from
hot young stars

Spiral arm Hot, ionized
containing hydrogen gas
young stars emitting red light





Galactic nucleus Dust lane
containing
old stars




12

GALAXIES


OPTICAL IMAGE OF CENTAURUS A FALSE-COLOR RADIO
(RADIO GALAXY) IMAGE OF CENTAURUS A
Dust lane crossing
elliptical galaxy Red indicates
high-intensity
radio waves
Galactic nucleus Radio
containing lobe Blue indicates
powerful source low-intensity
of radiation radio waves
Radiation from
galactic nucleus

Light from Outline of
old stars optical image
Radio of Centaurus A
lobe
Yellow indicates
medium-intensity
radio waves

FALSE-COLOR RADIO IMAGE OF 3C 273 (QUASAR)
Radiation from jet Quasar nucleus
of high-energy
particles moving
away from quasar
White indicates high-
intensity radio waves
Blue indicates
low-intensity
radio waves



OPTICAL IMAGE OF NGC 1566 FALSE-COLOR OPTICAL IMAGE OF NGC 5754
(SEYFERT GALAXY) (TWO COLLIDING GALAXIES)
Blue indicates low-
intensity radiation
Red indicates
Nebula in medium-intensity
spiral arm radiation
Spiral arm
distorted by
gravitational
influence of
smaller galaxy
Compact nucleus
emitting intense Large spiral
radiation galaxy


Smaller galaxy
colliding with
Spiral arm large galaxy
Yellow indicates
high-intensity
radiation


13

THE UNIVERSE

The Milky Way



THE MILKY WAY IS THE NAME GIVEN TO THE FAINT BAND OF LIGHT that stretches
across the night sky. This light comes from stars and nebulae in our galaxy, known as
the Milky Way Galaxy or simply as “the Galaxy.” The Galaxy is believed to be a barred
spiral, with a dense central bar of stars encircled by four arms spiraling outward and
surrounded by a less dense halo. We cannot see the spiral shape because the solar system
is in one of the spiral arms, the Orion Arm (also called the Local Arm). From our
VIEW TOWARD position, the center of the Galaxy is completely obscured by dust clouds; as a result, optical
GALACTIC CENTER
maps give only a limited view of the Galaxy. However, a more complete picture can be
obtained by studying radio, infrared, and other radiation. The central part of the Galaxy is relatively small
and dense and contains mainly older red and yellow stars. The halo is a less dense region in which the oldest
stars are situated; some of these stars are as old as the Galaxy itself (possibly 13 billion years). The spiral
arms contain main sequence stars and hot, young, blue stars, as well as nebulae (clouds of dust and
gas inside which stars are born). The Galaxy is vast, about 100,000 light-years across (a light-year is about
5,870 billion miles/9,460 billion km); in comparison, the solar system seems small, at about 12 light-hours
across (about 8 billion miles/13 billion km). The entire Galaxy is rotating in space, although
the inner stars travel faster than those farther out. The Sun, which is
about two-thirds out from the center, completes one lap of the Galaxy PANORAMIC OPTICAL MAP OF OUR
about every 220 million years. GALAXY AND NEARBY GALAXIES
SIDE VIEW OF OUR GALAXY Polaris (the North
Star), a blue-green
Disk of spiral arms
Central bulge containing variable binary star
containing mainly mainly older stars
young stars
Light from stars
and nebulae in the
Perseus Arm
Halo containing Nucleus
oldest stars Galactic
plane
100,000 light-years Milky Way
(the band of light
OVERHEAD VIEW OF OUR GALAXY that stretches across
the night sky)
Central bulge

Nucleus Emission
nebula
Perseus Arm
Sagittarius
Crux-Centaurus Arm
Arm
Pleiades
(the Seven Sisters),
an open star cluster
Dust in spiral
arm reflecting Andromeda Galaxy, a spiral
blue light from galaxy 2.2 million light-years
hot young stars away; the most distant object
Orion Arm visible to the naked eye
(Local Arm)
Location of
solar system
Patch of dust clouds

14

THE MILKY WAY

PANORAMIC RADIO MAP OF OUR GALAXY PANORAMIC INFRARED MAP OF OUR GALAXY
North Galactic spur North Galactic Red indicates North Galactic Low-intensity infrared
(possibly radio emission Pole high-intensity Pole radiation from interstellar
from a supernova remnant) radio-wave emission gas and dust
Galactic Galactic
plane plane
Galactic
plane


Galactic
plane

High-intensity
Blue indicates Yellow and green infrared
low-intensity indicate medium-intensity South Galactic Pole radiation
radio-wave emission South radio-wave emission from region
Galactic Pole High-intensity infrared of starbirth
radiation from interstellar
gas and dust
Vega, a white main Dark clouds of dust and gas
sequence star; the fifth North Galactic Pole obscuring light from part of the
brightest star in the sky Sagittarius Arm
Light from stars and nebulae in the
part of the Sagittarius Arm between
the Sun and Galactic center
Light from stars
and nebulae in the
Perseus Arm


Galactic
plane















Orion’s belt,
a row of
three bright
stars
Orion Nebula
Sirius, a white main
sequence star; the
brightest star in the sky
Canopus, a white supergiant;
Dust clouds South Galactic Pole the second brightest star in the sky
obscuring
Galactic center Small Magellanic Cloud, an irregular Large Magellanic Cloud, an irregular galaxy 170,000 light-years
galaxy 190,000 light-years away away; one of the nearest galaxies to the Milky Way

15

THE UNIVERSE

Nebulae and star clusters



A NEBULA IS A CLOUD OF DUST AND GAS inside a galaxy. Nebulae become visible if the
gas glows, or if the cloud reflects starlight or obscures light from more distant objects.
Emission nebulae shine because their gas emits light when it is stimulated by radiation
from hot young stars. Reflection nebulae shine because their dust reflects light from stars
in or around the nebula. Dark nebulae appear as silhouettes because they block out light
from shining nebulae or stars behind them. Two types of nebula are associated with dying
stars: planetary nebulae and supernova remnants. Both consist of expanding shells of gas
HODGE 11, A
that were once the outer layers of a star. A planetary nebula is a gas shell drifting away
GLOBULAR CLUSTER
from a dying stellar core. A supernova
TRIFID NEBULA (EMISSION NEBULA)
remnant is a gas shell moving away from a stellar
core at great speed following a violent explosion
called a supernova (see pp. 26-27). Stars are often Reflection
found in groups known as clusters. Open clusters nebula
are loose groups of a few thousand young stars
that were born from the same cloud and are
drifting apart. Globular clusters are densely
Emission
packed, roughly spherical groups of hundreds nebula
of thousands of older stars.
PLEIADES (OPEN STAR CLUSTER)
WITH A REFLECTION NEBULA
Wisps of dust and Dust lane
hydrogen gas. The
cluster is passing
through a region of
interstellar
material Starbirth region
(area in which
Young star in an dust and gas
open cluster of more clump together
than 1,000 stars to form stars)
Reflection nebula


HORSEHEAD NEBULA (DARK NEBULA)

Glowing filament
of hot, ionized Star near southern
hydrogen gas end of Orion’s belt


Emission nebula
Alnitak (star in
Orion’s belt)
Horsehead Nebula

Dust lane
Reflection nebula

Dark nebula
obscuring light
Emission nebula from distant stars



16

NEBULAE AND STAR CLUSTERS



ORION NEBULA (DIFFUSE EMISSION NEBULA)
Glowing
cloud of dust Gas cloud
and hydrogen emitting
gas forming light due to
part of Orion ultraviolet
Nebula radiation from
the four young
Trapezium stars
Dust cloud


Trapezium
(group of four
young stars)
Green light
from hot,
ionized
oxygen gas
Glowing
Red light filament of
from hot, hot, ionized
ionized hydrogen gas
hydrogen gas










VELA SUPERNOVA REMNANT
Supernova
remnant (gas
shell consisting
of outer layers
HELIX NEBULA (PLANETARY NEBULA)
of star thrown
off in
supernova
Planetary nebula
(gas shell expanding explosion)
outward from dying
stellar core)
Hydrogen gas
emitting red
Core remnant with light due to
surface temperature being heated
of about 180,000°F by supernova
(100,000°C) explosion
Red light from
hot, ionized
hydrogen gas

Blue-green light from Glowing
hot, ionized oxygen filament of
and nitrogen gases hot, ionized
hydrogen gas


17

THE UNIVERSE

Stars of northern skies


L U P U S
WHEN YOU LOOK AT THE NORTHERN SKY, you look away from the densely
populated Galactic center, so the northern sky generally appears less
Antares
bright than the southern sky (see pp. 20-21). Among the best-known
sights in the northern sky are the constellations Ursa Major S L I B R A
(the Great Bear) and Orion. Some ancient civilizations believed U P U T
that the stars were fixed to a celestial sphere surrounding the U R Zubenelgenubi
Earth, and modern maps of the sky are based on a similar A Zubeneschamali C A
idea. The North and South Poles of this imaginary N T N S
celestial sphere are directly above the North and South E
Poles of the Earth, at the points where the Earth’s axis C O R P E
of rotation intersects the sphere. The celestial North Spica R G E
Pole is at the center of the map shown here, and I S
V Arcturus Alphecca
Polaris (the North Star) lies very close to it. The
celestial equator marks a projection of the CORONA BOREALIS
Earth’s equator on the sphere. The ecliptic C O R V U S B O Ö T E S
marks the path of the Sun across the sky C O M A B E R EN I C E S
as the Earth orbits the Sun. The Moon and H Cor
planets move against the background of Y CANES Caroli U Alkaid
the stars because the stars are much more D E R Denebola V E N AT I C I R
distant; the nearest star outside the solar R C R A T S Alioth Kochab
system (Proxima Centauri) is more A L A U R
than 50,000 times farther away than A S E L E O M M I
N A S A
O
the planet Jupiter. Algieba J Dubhe N
N
X T A M I N O R O O
T
R
ORION L E Regulus R
Chi Orionis S
I
Chi 2 Orionis 1 V A Ecliptic
Nu Orionis E C A N C E R L
Xi Orionis L S Alphard Y N X
I Praesepe
Heka A X Equator Castor G G A
Y Ce lestial Pollux E Capella
Mu Orionis P R I
Bellatrix M
U
Betelgeuse M O Precyon I N I A
C A N I S
El Nath
N
Alhena
O
M i l k y
C M I N O R
Orion’s belt Gamma P W a y C E R Betelgeuse Aldebaran
Omicron Velorum U A O
Orionis N S N
O
P
Strius I
I S
Alnitak Orionis
P
Pi 2 I R
Wezen Mirzam
Orionis S Adhara M A J O R O
Pi 3
Rigel
Pi Orionis
4
Orionis
Pi 5
C L E P U S
Saiph Pi 6 Orionis
O
Mintaka L U M B A C A E L U M
Eta Orionis
Tau Orionis
Orion
VISIBLE STARS IN THE NORTHERN SKY
Nebula Rigel
Alnilam
18

STARS OF NOR THERN SKIES


THE BIG DIPPER, PART OF URSA MAJOR (THE GREAT BEAR)
Alcor
S C O R P I U S Mizar Dubhe
Shaula


Kaus A U S T Alkaid
C O R O N A
Australis R A L I S
Nunki
S
C
S
U
T
S E RPE N S
Alioth
U
O P H I U C H U
Megrez
M
S
A G I T T A R I U S
A
Ras C A U D A Q Ecliptic Merak
Alhague
Phekda
U
I
L
H E R C U L E S
A C A P R I C
Altair
L Y R A O
DE L PHI N U S U Enif Pegasi
Vega V U L P E C U L A S RN U PEGASUS AND ANDROMEDA
Theta
Eltanin C Y G N UL E S
U A Lambda Pegasi
D R A
S E Q U Deneb
C
Deneb Enif Q Algedi
Al Kappa Pegasi
O
U S
Nair
U
P H E U S Alderamin S A S N Pi Pegasi Hamal
R
Polaris U I I C R I G Iota Pegasi
U
E L A C E R T A S S S T R
C Scheat A Markab P I S U U Mu Pegasi
A S S I O P E I A Schedar E G Fomalhaut S Matar Xi Pegasi
A

C Alpheratz P
A S Scheat
D Algenib P T O R
A N D R O M E E L
Mirach
Mirfak Almach C U
Algol S C Omicron Markab
P E R S E U S TRIANGU LU M Celestial Equator S Andromedae
I
Hamal
P
A R I E S Deneb Nair Al
Zaurak
Pleiades Kaitos X Lambda Algenib
T A
U R U S
Mira N I Andromedae
E Theta
Menkar O Andromedae
C E T U S H
P
Andromeda Alpheratz
Galaxy
N U S
A
D Nu Andromedae
R I
E F O R N A X Delta
Acamar Phi Andromedae Andromedae
51 Andromedae
Mirach
Mu Andromedae
Almach
19

THE UNIVERSE

Stars of southern skies

H E R C U L E S
WHEN YOU LOOK AT THE SOUTHERN SKY, you look toward the Galactic
center, which has a huge population of stars. As a result, the Milky
Way appears brighter in the southern sky than in the northern sky
Vega
(see pp. 18-19). The southern sky is rich in nebulae and star
clusters. It contains the Large and Small Magellanic Clouds, R A Ras Alhague Ras Algethi
which are two of the nearest galaxies to our own. Stars make L Y
fixed patterns in the sky called constellations. However, O P H I U C H
the constellations are only apparent groupings of stars, S Albireo U
U S
since the distances to the stars in a constellation may N
G S E R P E N S C A U D A
vary enormously. The shapes of constellations may Y S A G I T T A
C A Q U I L A Sabik
change over many thousands of years due to the
Altair S
relative motions of stars. The movement of the Kaus
Deneb R I U S Borealis R P I U
constellations across the sky is due to the Earth’s Nunki Shanta
motion in space. The daily rotation of the Earth D E L P H I N U S T A S C O
causes the constellations to move across the W a y Equ ator Algedi C A I T A R A
sky from east to west, and the orbit of the Celestial P R I G
Earth around the Sun causes different areas y E Q U U L E U S C A S
k O
of sky to be visible in different seasons. The l S R
visibility of areas of sky also depends on M i I U N P A V O
Enif U
the location of the observer. For instance, R Deneb S I N D U S Peacock
A Algedi U S
stars near the celestial equator may be U C I S
seen from either hemisphere at some P Q S T R I N G Al Nair
time during the year, whereas stars L A C E R T A E A P I U S R U S T Small H Y
close to the celestial poles (the celestial G A Fomalhaut U C A N A Cloud
South Pole is at the center of the map A S
Magellanic D RU S
shown here) can never be seen from Scheat S Markab C U Nair AI
Zaurak
the opposite hemisphere. U L P T
E
Deneb O R P H O E N I X Achernar R E T I C U L U M
S
Kaitos R
HYDRUS (THE WATER SNAKE) AND
MENSA (THE TABLE) I
Algenib
Small Alpheratz D
Magellanic Cloud F O R N A X A
Beta Hydri C N
E
Mira U
T
U
Mirach S S
P I S C E S
Menkar
Gamma T Hamal
Hydri A R I E S
A N D R O M E D A
Almach R I A N G U L U M Ecliptic T A U
Alcyone
Gamma Mensae R
Pleiades U
Alpha Mensae Algol S
Alpha Eta Mensae P E R S E U S
Hydri Mirfak
Beta Mensae
Delta Hydri
Large Magellanic
Epsilon Hydri
Cloud VISIBLE STARS IN THE SOUTHERN SKY
20

STARS OF SOUTHERN SKIES

CENTAURUS (THE
Alpha Centauri Epsilon CENTAUR) AND
Centauri CRUX (THE
Hadar Zeta SOUTHERN CROSS)
Centauri
Mimosa
C O R O N A
B O R E A L I S
Eta Centauri
Acrux
Alphecca
Omega Menkent
B
Epsilon
S E RP E N S Unukalhai O Ö Crucis Centauri
CA P UT
Arcturus
Delta
T
E
Crucis
S Iota Centauri
B E R E N I C E S Gamma Centauri
Zubeneschamali C O M A Cor Caroli Gacrux
Graffias L
I C A N E S
Zubenelgenubi V E N A T I C I CANIS MAJOR (THE GREAT DOG) Furud
B
Antares R A V
Adhara
I
Sigma Canis Majoris
R U
Spica
G R
Omicron Canis Majoris
1
S
Porrima O
Denebola A Mirzam
C E N T A U
Alpha M
Centauri R U S A
C O RVU S
Sirius
C RU X R O
Hadar C
J
TRIANGULUM
Acrux L L R
Muliphen
H
E
A USTRALE
Y
O
EO
Miaplacidus V E L A D M I Pi Canis Majoris
A T E R S E X T A N S
V O L A N S R Wezen
A Markeb A N T L I A Regulus N O R Omicron 2 Canis Majoris
N Aludra
I A
MENSA
Large R
Magellanic A
Cloud C Gamma Alphard SAGITTARIUS (THE ARCHER)
Velorum
DORADO PICTOR Canopus Ec liptic Pi Sagittarii Omicron Sagittarii
Xi 2 Sagittarii
Beta
Pictoris P U P P I S Upsilon Sagittarii
C A N I S Celestial Psi Sagittarii
Adhara M A J O R Equator
Phaet Rho 1 Sagittarii
C O L U M B A
C A N C E R X
Sirius Procyon N Nunki M22
Mirzam Y (NGC 6656)
globular
M O N O C E R OS CA N I S L Tau cluster
MI N O R
LE P US
Rigel Pollux
Sagittarii
Betelgeuse Castor Lagoon
M I N I Nebula
O R I O N E 62 Sagittarii
G Zeta
Aldebaran Sagittarii
El Nath
Kaus
Borealis
Theta 1 Sagittarii
A U R I G A Menkalinan Kaus
Meridionalis
Iota Sagittarii
Capella Nash
Alrami
Eta
Arkab Prior Kaus Australis Sagittarii
21

THE UNIVERSE

Stars



STARS ARE BODIES of hot,
glowing gas that are born in
nebulae (see pp. 24-27). They STAR SIZES
vary enormously in size, mass, and
Red giant from 10 to
temperature: diameters range from
100 million miles (15 to
about 450 times smaller to over 1,000 times 150 million km) wide
bigger than that of the Sun; masses range
OPEN STAR CLUSTER The Sun
AND DUST CLOUD from about a twentieth to over 50 solar masses; (main sequence star;
and surface temperatures range from about 5,500ºF diameter 870,000
(3,000ºC) to over 90,000ºF (50,000ºC). The color of a star is determined miles/1.4 million km)
by its temperature: the hottest stars are blue and the coolest are red.
White dwarf
The Sun, with a surface temperature of 10,000ºF (5,500ºC), is
(diameter of 2,000 to
between these extremes and appears yellow. The 30,000 miles/3,000 to
energy emitted by a shining star is usually produced ENERGY EMISSION FROM THE SUN 50,000 km)
by nuclear fusion in the star’s core. The brightness Nuclear fusion Neutrinos travel to Earth
of a star is measured in magnitudes—the brighter in core produces directly from Sun’s core
gamma rays in about 8 minutes
the star, the lower its magnitude. There are two
and neutrinos
types of magnitude: apparent magnitude, which
Lower-energy
is the brightness seen from Earth, and absolute
radiation travels
magnitude, which is the brightness that would be to Earth in about
seen from a standard distance of 10 parsecs (32.6 8 minutes
light-years). The light emitted by a star may be split
to form a spectrum containing a series of dark lines
(absorption lines). The patterns of lines indicate the
presence of particular chemical elements, enabling Earth
astronomers to deduce the composition of the star’s
atmosphere. The magnitude and spectral type (color) Lower-energy radiation
of stars may be plotted on a graph called a Sun (mainly ultraviolet, infrared,
and light rays) leaves surface
Hertzsprung-Russell diagram, which shows that
High-energy radiation
stars tend to fall into several well-defined groups.
(gamma rays) loses energy while traveling
The principal groups are main sequence stars (those to surface over 2 million years
which are fusing hydrogen to form helium), giants,
supergiants, and white dwarfs.
NUCLEAR FUSION IN MAIN
SEQUENCE STARS LIKE THE SUN
STAR MAGNITUDES
Positron Deuterium Proton
APPARENT MAGNITUDE ABSOLUTE MAGNITUDE
nucleus
Brighter stars
-9 Rigel: absolute Neutron
magnitude of -7.1
Sirius: apparent
magnitude of -1.46
Rigel: apparent 0 Sirius: absolute
magnitude of +0.12
magnitude of +1.4
Proton Helium-4
(hydrogen nucleus
Objects of magnitude Neutrino
higher than about +9 nucleus)
+6.0 cannot be seen Helium-3
by the naked eye Gamma rays nucleus
Fainter stars

22

STARS










HERTZSPRUNG-RUSSELL DIAGRAM
Hotter stars TEMPERATURE (°F) Cooler stars
65,000 18,000 9,000 6,500 4,500
More luminous stars -7
-6
-5
Deneb (blue supergiant) -4 S U PERG IA NT S Betelgeuse (red supergiant)
-3
-2
-1 GIANTS
0 Arcturus (red giant)
Sirius A (massive
main sequence star) +1
+2
+3 M A I N S E Q U E N C E S TA R S
+4
ABSOLUTE +5 The Sun (yellow main
VISUAL sequence dwarf)
+6
MAGNITUDE
+7
+8
+9
+10
Sirius B (white dwarf) +11
+12
+13 W R IT E DWA RF S Barnard’s Star (main
+14 sequence red dwarf)
+15
Less luminous stars +16
O5 B0 A0 F0 G0 K0 M0 M5
SPECTRAL TYPE

STELLAR SPECTRAL ABSORPTION LINES
Hydrogen Hydrogen Sodium Hydrogen
Calcium line gamma line beta line Helium line lines alpha line




STAR OF SPECTRAL
TYPE A (e.g., SIRIUS)




STAR OF SPECTRAL
TYPE G (e.g., THE SUN)



Hydrogen Magnesium Sodium Hydrogen
beta line lines lines alpha line


23

THE UNIVERSE

Small stars
STRUCTURE OF A
MAIN SEQUENCE STAR
SMALL STARS HAVE A MASS of up to about one and a half Core containing hydrogen
times that of the Sun. They begin to form when a region of fusing to form helium
higher density in a nebula condenses into a huge globule of Radiative
gas and dust that contracts under its own gravity. Within zone
a globule, regions of condensing matter heat up and
Convective
begin to glow, forming protostars. If a protostar
zone
contains enough matter, the central temperature
reaches about 27 million °F (8 million °C). At this
temperature, nuclear reactions in which hydrogen
fuses to form helium can start. This process releases
REGION OF energy, which prevents the star from contracting
STAR FORMATION
more and also causes it to shine; it is now a main
IN ORION
sequence star. A star of about one solar mass remains
on the main sequence for about 10 billion years, until much of the hydrogen in Surface temperature
the star’s core has been converted into helium. The helium core then contracts, 10,000°F (5,500°C)
and nuclear reactions continue in a shell around the core. The core becomes hot Core: 27 million °F
enough for helium to fuse to form carbon, while the outer (15 million °C)
layers of the star expand and cool. The expanding
star is known as a red giant. When the
STRUCTURE OF A NEBULA
helium in the core runs out, the outer
layers of the star may be blown
away as an expanding gas shell
called a planetary nebula. The
remaining core (about 80 Young main
sequence star
percent of the original
star) is now in its final
Dense region of dust and
stages. It becomes
gas (mainly hydrogen)
a white dwarf star condensing under gravity
that gradually cools to form globules
and dims. When it
finally stops shining
Hot, ionized hydrogen
altogether, the dead gas emitting red light
star will become due to being stimulated
by radiation from hot
a black dwarf.
young stars
Dark globule of dust and
gas (mainly hydrogen)
contracting to form protostars
LIFE OF A SMALL STAR OF ABOUT ONE SOLAR MASS
About 1.4 million km
Cool cloud of
gas (mainly Natal cocoon
hydrogen) Star
(shell of dust
and dust Glowing blown away by producing
ball of gas energy by
(mainly radiation from
Dense globule hydrogen) protostar) nuclear fusion
condensing to in core
form protostars
NEBULA PROTOSTAR MAIN SEQUENCE STAR
Duration: 50 million years Duration: 10 billion years
24

SMALL STARS


Outer envelope consisting
STRUCTURE OF A RED GIANT mainly of hydrogen
Shell where hydrogen is
fusing to form helium
Cooling, expanding Intermediate layer
outer layers glow red
consisting mainly
of helium
Shell where
Surface temperature helium is fusing
6,300°F (3,500°C) to form carbon

Carbon core
temperature
180 million °F
(100 million °C)




































Outer layers form Very dense core (one
40 million miles (70 million km) expanding teaspoonful weighs Cooling core
gas shell about five tons) glows red
Dense,
contracting
core

Cooling, About 8,000 Cold,
expanding miles (13,000 km) dead core
outer layers COOLING
RED GIANT PLANETARY NEBULA WHITE DWARF WHITE DWARF BLACK DWARF
Duration: 100 million years Duration: 35,000 years


25

THE UNIVERSE

Massive stars SUPERNOVA



MASSIVE STARS HAVE A MASS AT LEAST THREE TIMES that of the Sun, and some
stars are as massive as about 50 Suns. A massive star evolves in a similar way to a
small star until it reaches the main sequence stage (see pp. 24-25). During its life
as a main sequence star, it shines steadily until the hydrogen in its core has fused
to form helium. This process takes billions of years in a small star, but only millions
of years in a massive star. A massive star then becomes a red supergiant, which
initially consists of a helium core surrounded by outer layers of cooling, expanding TARANTULA NEBULA BEFORE
gas. Over the next few million years, a series of nuclear reactions form different SUPERNOVA
elements in shells around an iron core. The core eventually collapses in less than
a second, causing a massive explosion called a STRUCTURE
supernova, in which a shock wave blows OF A RED SUPERGIANT
away the outer layers of the star.
Outer envelope consisting
Supernovae shine brighter than an mainly of hydrogen
entire galaxy for a short time. Layer consisting
Sometimes, the core survives mainly of helium
the supernova explosion. If
Layer consisting
the surviving core is mainly of carbon
between about one and a
Layer consisting
half and three solar
mainly of oxygen
masses, it contracts to
become a tiny, dense Layer consisting
mainly of silicon
neutron star. If the
core is greater than
three solar masses, Shell of hydrogen
it contracts to fusing to form
helium
become a black hole
(see pp. 28-29).
Shell of helium
fusing to form
carbon
Shell of carbon
Surface temperature fusing to form
5,500°F (3,000°C) oxygen
Cooling, expanding Shell of oxygen fusing
outer layers glow red to form silicon

Core of mainly iron at 5.4-9
billion °F (3-5 billion °C) Shell of silicon fusing
to form iron core
LIFE OF A MASSIVE STAR OF
ABOUT 10 SOLAR MASSES Star producing
About 2 million
Glowing miles (3 million km) energy by nuclear
fusion in
ball of gas
Dense globule (mainly hydrogen) core
condensing to
form protostars
Natal cocoon (shell
of dust blown away
Cool cloud of gas by radiation from
(mainly hydrogen) protostar)
and dust
NEBULA PROTOSTAR MAIN SEQUENCE STAR
Duration: a few hundred Duration: 10 million years
thousand years
26

MASSIVE STARS



FEATURES OF A SUPERNOVA

Shock wave travels outward
Ejecta (outer layers of star from core at 20,000 miles/sec
thrown off during explosion) (30,000 km/sec)
travels at 6,000 miles/sec
(10,000 km/sec)


TARANTULA NEBULA SHOWING
SUPERNOVA IN 1987
Reverse shock wave
moves inward and
heats ejecta, causing
it to shine
Chemical elements
heavier than iron
are produced in
the explosion and
scattered into space
















Central
temperature:
Contracting 18 billion ºF
core consisting
(10 billion ºC)
mainly of neutrons
remains after explosion



Extremely dense core
Light energy
of a billion Suns 6 miles (4 km) (one teaspoonful
emitted during explosion weighs about a
Core mass of billion tons)
less than three
solar masses
60 million miles
(100 million km) Outer layers of
star blown off NEUTRON STAR
in explosion Core of mass greater
Contracting than three solar masses
stellar core may continues contracting
Cooling, remain after to become black hole
expanding supernova
outer layers
Accretion
SUPERNOVA disk
RED SUPERGIANT Duration of
Duration: 4 million years visibility: 1–2 years BLACK HOLE

27

THE UNIVERSE

Neutron stars


and black holes



NEUTRON STARS AND BLACK HOLES form from the stellar cores that remain after
stars have exploded as supernovae (see pp. 26-27). If the remaining core is
between about one and a half and three solar masses, it contracts to form a
neutron star. If the remaining core is greater than about three solar masses,
it contracts to form a black hole. Neutron stars are typically only about
6 miles (10 km) in diameter and consist almost entirely of subatomic
particles called neutrons. Such stars are so dense that a teaspoonful
would weigh about a billion tons. Neutron stars are observed as Nebula of gas
pulsars, so-called because they rotate rapidly and emit two beams and dust
surrounds pulsar
of radio waves, which sweep across the sky and are detected as
short pulses. Black holes are characterized by their extremely Rapidly
strong gravity, which is so powerful that not even light can escape; rotating pulsar
as a result, black holes are invisible. However, they can be
detected if they have a close companion star. The gravity of the Beam of
radiation X-RAY IMAGE OF PULSAR
black hole pulls gas from the other star, forming an accretion from pulsar AND CENTRAL REGION
disk that spirals around the black hole at high speed, heating up OF CRAB NEBULA
and emitting radiation. Eventually, the matter spirals in to cross (SUPERNOVA REMNANT)
the event horizon (the boundary of the black hole),
thereby disappearing from the visible universe.
Rotational axis
of neutron star
PULSAR (ROTATING NEUTRON STAR)

Beam of radio waves Path of beam
possibly produced by of radio waves
rapid rotation of
magnetic field
Magnetic axis
North Pole
North magnetic
polar region
Solid, crystalline
external crust Magnetic
field line
Solid, neutron-rich
internal crust

Layer of
superfluid neutrons
Magnetic axis
Solid core
Beam of radio waves
possibly produced by
rapid rotation of
magnetic field
South Pole South magnetic
polar region


28

NEUTRON STARS AND BLACK HOLES

STELLAR BLACK HOLE
Blue supergiant star
Gas current (outer layers of nearby blue supergiant
pulled toward black hole by gravity)
Singularity (theoretical region in which the physics of
the material is unknown)
Hot spot (region of intense friction
where gas current joins accretion disk)

Gas in outer part of
accretion disk emitting
Event horizon low-energy radiation
(boundary of
black hole)
























Hot gas in inner part of
Accretion disk (matter accretion disk emitting
spiraling around black hole) high-energy X-rays
Black hole Gas at temperatures of millions °F
FORMATION OF A BLACK HOLE spiraling at close to the speed of light
Stellar core remains
after supernova Light rays increasingly
explosion bent by gravity as core
collapses Core shrinks beyond Light rays cannot
its event horizon to escape because
become a black hole gravity is so strong






Density, pressure,
and temperature of
Core greater core increase as core Event
than three solar collapses horizon
masses collapses Singularity
Outer layers under its own gravity (theoretical region in which the
of massive star
physics of the material is unknown)
thrown off in explosion
SUPERNOVA COLLAPSING STELLAR CORE BLACK HOLE

29

THE UNIVERSE
The solar system PLANETARY ORBIT

(EXAGGERATED)
Perihelion (orbital
THE SOLAR SYSTEM consists of a central star (the
point closest to Sun)
Sun) and the bodies that orbit it. These bodies
include eight planets and their more than 160
Sun
known moons; dwarf planets; Kuiper Belt objects;
asteroids; comets; and meteoroids. The solar
Elliptical
system also contains interplanetary gas and dust. orbit
The planets fall into two groups: four small rocky Planet
orbiting Sun Direction of
planets near the Sun (Mercury, Venus, Earth, and
planetary
Mars); and four planets farther out, the giants (Jupiter, Saturn, rotation
Uranus, and Neptune). Between the rocky planets and giants is the
asteroid belt, which contains thousands of chunks of rock orbiting the
Aphelion (orbital
Sun. Beyond Neptune is the Kuiper Belt and, more distant, the Oort Cloud.
point farthest
Most of the bodies in the planetary part of the solar system move around the Sun from Sun)
in elliptical orbits located in a thin disk around the Sun’s equator. All the planets
orbit the Sun in the same direction (counterclockwise when viewed from above)
and all but Venus and Uranus also spin about their axes in this direction. Moons Aphelion of Neptune:
2.8 billion miles
also spin as they, in turn, orbit their planets. The entire solar system orbits the
center of our galaxy, the Milky Way (see pp. 14-15).
Perihelion of
Perihelion of Venus: 66.7 million miles
ORBITS OF INNER PLANETS Mercury
Perihelion of Earth: 91.4 million miles
Average orbital speed of Venus: 21.8 miles/sec
Average orbital speed of Mercury: 29.8 million miles/sec
Average orbital speed of Earth: 18.5 miles/sec
Average orbital speed of Mars: 15 miles/sec

Mars Perihelion of Mars:
128.4 million miles
Earth
Venus
Sun
Aphelion of Mercury: 43.3 million miles
Aphelion of Venus: 67.7 million miles
Asteroid Aphelion of Pluto:
belt Aphelion of Earth: 94.5 million miles 4,583 million miles
MERCURY
Year: 87.97 Earth days Aphelion of Mars: 154.8 million miles
Mass: 0.06 Earth masses
Diameter: 3.051 miles











VENUS EARTH MARS JUPITER
Year: 224.7 Earth days Year: 365.26 days Year: 1.88 Earth years Year: 11.87 Earth years
Mass: 0.81 Earth masses Mass: 1 Earth mass Mass: 0.11 Earth masses Mass: 317.83 Earth masses
Diameter: 7,521 miles Diameter: 7,926 miles Diameter: 4,217 miles Diameter: 88,850 miles

30

Perihelion of Uranus:
ORBITS OF 1,700 million miles
OUTER PLANETS
Inner planetary orbits
AND PLUTO
Sun Perihelion of Saturn:
837 million miles

Saturn

Perihelion of Jupiter:
Aphelion of Saturn: 460 million miles
936 million miles

Jupiter Uranus
Aphelion of Jupiter:
507 million miles
Average orbital speed of
Jupiter: 8.1 miles/sec
Average orbital speed
Aphelion of Uranus: of Saturn: 6 miles/sec
1,867 million miles
Average orbital
speed of Uranus:
4.2 miles/sec


Pluto
Direction of
Neptune orbital motion
Average orbital speed
of Neptune: 3.4 miles/sec
INCLINATION OF ORBITS
TO THE ECLIPTIC
Average orbital speed
of Pluto: 2.9 miles/sec
Pluto: 17.2°
Mercury: 7°
Venus: 3.39°
Saturn: 2.49°
Mars: 1.85°
Neptune: 1.77°
Jupiter: 1.3°
Uranus: 0.77°
Ecliptic (Earth’s orbital plane) Earth: 0°













SATURN URANUS NEPTUNE PLUTO
Year: 29.66 Earth years Year: 84.13 Earth years Year: 164.70 Earth years Year: 248.09 Earth years
Mass: 95.16 Earth masses Mass: 14.54 Earth masses Mass: 17.14 Earth masses Mass: 0.0022 Earth masses
Diameter: 74,901 miles Diameter: 31,765 miles Diameter: 30,777 miles Diameter: 1,429 miles

31

THE UNIVERSE

The Sun HOW A SOLAR ECLIPSE OCCURS



THE SUN IS THE STAR AT THE CENTER of the solar system.
Sun
It is about five billion years old and will continue to shine
as it does now for about another five billion years. The
Sun is a yellow main sequence star (see pp. 22-23) about
870,000 miles (1.4 million km) in diameter. It consists
almost entirely of hydrogen and helium. In the Sun’s Moon passes
core, hydrogen is converted to helium by nuclear between Sun
SOLAR
and Earth
PHOTOSPHERE fusion, releasing energy in the process. The energy Umbra
(inner, total
travels from the core, through the radiative and convective zones, to shadow) of
the photosphere (visible surface), where it leaves the Sun in the form Region of Moon
Earth from
of heat and light. On the photosphere there are often dark, relatively which total
cool areas called sunspots, which usually appear in pairs or groups and eclipse is visible Penumbra
are caused by the cooling effect of the magnetic field. Other types of (outer,
Region of Earth partial
solar activity are flares, which are usually associated with sunspots,
from which partial shadow)
and prominences. Flares are sudden discharges of high-energy eclipse is visible of Moon
radiation and atomic particles. Prominences are huge loops or
Umbra (inner, total Earth
filaments of gas extending into the solar atmosphere; some last for shadow) of Earth
hours, others for months. Beyond the photosphere is the
Penumbra (outer,
chromosphere (inner atmosphere) and the extremely rarified corona partial shadow)
(outer atmosphere), which extends millions of miles into space. Tiny of Earth
particles that escape from the corona give rise to the solar wind,
which streams through space at hundreds of miles per second. The
chromosphere and corona can be seen from Earth when the Sun
TOTAL SOLAR ECLIPSE
is totally eclipsed by the Moon.
SURFACE FEATURES
Corona (outer
Gas loop (looped Prominence (jet of gas at atmosphere
prominence) edge of Sun’s disk up to of extremely
hundreds of thousands of hot, diffuse gas)
miles high)
Spicule Moon covers
(vertical Sun’s disk
jet of gas)



Photosphere
(visible surface)
SUNSPOTS
Granulated surface
of Sun
Chromosphere
(inner atmosphere)
Penumbra
(lighter, outer region)
containing radial fibrils
Umbra (darker, inner
region) temperature
about 7,200°F (2,700°C)
Photosphere
temperature
9,900°F (5,500°C)

THE SUN

EXTERNAL FEATURES AND
INTERNAL STRUCTURE OF THE SUN Radiative zone 230,000
miles (380,000 km) thick
Convective zone 90,000
Chromosphere miles (140,000 km) thick Chromosphere
(inner atmosphere)
temperature
up to 6,000 miles 18,000°F (10,000°C) Photosphere
(2,000 km) thick temperature 9,900°F
Corona (5,500°C)
(outer atmosphere)
Corona temperature 3.6
million °F (2 million °C)
Photosphere
(visible surface)
Core temperature 27
million °F (15 million °C)



































Supergranule
Filament (convection cell)
(prominence visible
against photosphere)

Granulated
Prominence surface
(jet of gas at edge of
Sun’s disk up to hundreds of
thousands of miles high) Macrospicule: vertical jet
of gas 25,000 miles
(40,000 km) high
Spicule: vertical jet of gas
6,000 miles (10,000 km) high
Gas loop
Sunspot Solar flare (looped prominence)
(cool region) (sudden release
of energy associated
with sunspots)

33

THE UNIVERSE

Mercury TILT AND ROTATION OF MERCURY
Axis of
to orbital plane
rotation Perpendicular
MERCURY IS THE NEAREST PLANET to the Sun, orbiting at an Axial tilt of 2°
average distance of about 36 million miles (58 million km). North
Pole
Because Mercury is the closest planet to the Sun, it moves
faster than any other planet, travelling at an average speed Orbital
of nearly 30 miles (48 km) per second and completing an plane
orbit in just under 88 days. Mercury is very small (only
40 percent bigger than the Moon) and rocky. Most of the
MERCURY
surface has been heavily cratered by the impact of meteorites,
although there are also smooth, sparsely cratered lava-covered plains. The Caloris
Basin is the largest crater, measuring about 800 miles (1,300 km) across. One rotation
It is thought to have been formed when a 38-mile- (60-km-) diameter takes 58 days South Pole
and 16 hours
asteroid hit the planet, and is surrounded by concentric rings of
mountains thrown up by the impact. The surface also has many clifflike DEGAS AND BRONTË (RAY CRATERS)
ridges (called rupes) that are thought to have been formed when the
hot core of the young planet cooled and shrank about four billion years Bright
ago, buckling the planet’s surface in the process. The planet rotates ray of
ejecta
about its axis very slowly, taking nearly 59 Earth days to complete (ejected
one rotation. As a result, a solar day (sunrise to sunrise) on Mercury material)
is about 176 Earth days—twice as long as the 88-day Mercurian year.
Mercury has extreme surface temperatures, ranging from a Brontë
maximum of 800°F (430°C) on the sunlit side to -270°F (-170°C)
Unmapped
on the dark side. At nightfall, the temperature drops very quickly
region
because the planet’s atmosphere is almost nonexistent. It
consists only of minute amounts of helium and hydrogen
captured from the solar wind, plus traces of other gases.
Degas with
FORMATION OF A RAY CRATER Path of rocky ejecta central peak
Path of meteorite
Debris thrown colliding with planet (ejected material)
out by impact Ejecta forms
secondary craters
Wall of rock
thrown up
around crater
Impact forms
saucer-shaped Loose debris
crater on crater floor
Fractured rock
SECONDARY CRATERING
METEORITE IMPACT
Wall of rock forms Ray of ejecta
ring of mountains (ejected material)
Small secondary
crater
Loose ejected rock


Central mountain Falling debris
rings form if floor forms ridges on
of large crater side of wall
recoils from
meteorite impact

RAY CRATER

34

MERCUR Y


COMPOSITION OF ATMOSPHERE
Principal constituents EXTERNAL FEATURES AND INTERNAL
helium and hydrogen STRUCTURE OF MERCURY
Minor constituents
sodium and oxygen
Traces of neon, argon,
and potassium Monteverdi
Thin crust Rubens
Vyãsa
CRATERS AND PLAINS NEAR
MERCURY’S NORTH POLE Mantle 375 miles B OR E AL I S Unmapped region
(600 km) thick P LAN ITIA
Praxiteles
Borealis Planitia
(smooth plain with a
few young craters)
Kuan
Han-
ch’ing
Terrain with
many old craters

Chong
Heine Ch’ol
Strindberg
Maximum sunlit surface
temperature 800°F (430°C)
Van Eyck
Polygnotus
Vivaldi
CALORIS BASIN Iron core 2,250 miles

PLANITLA
Caloris Montes SOBKOU (3,600 km) in
diameter, with 80%
Balzac of Mercury’s mass
Phidias
BUDH
Tyagaraja PLANITIA
Mantle of
Philoxenus
silicate rock
Zeami
Goya Crust of
silicate rock
Sophocles
Tolstoj Renoir
Vãlmiki
Minimum dark-side
Milton surface temperature
-270°F (-170°C)
Liang K’ai
Chekhov

Beethoven Schubert
Bello Bramante
Discovery Rupes
Shelley
Coleridge
Hawthorne Fram Rupes
Michelangelo Wagner Bach

35

THE UNIVERSE

Venus TILT AND ROTATION OF VENUS
Axis of
rotation Perpendicular
to orbital plane
VENUS IS A ROCKY PLANET and the second planet from
Axial tilt of 2°
the Sun. Venus spins slowly backwards as it orbits the Sun, North
Pole
causing its rotational period to be the longest in the solar
system, at about 243 Earth days. It is slightly smaller Orbital
than Earth and probably has a similar internal structure, plane
consisting of a semisolid metal core, surrounded by a
rocky mantle and crust. Venus is the brightest object in
RADAR IMAGE OF
VENUS the sky after the Sun and Moon because its clouds reflect
sunlight strongly. The main component of the atmosphere is carbon
dioxide, which traps heat in a greenhouse effect far stronger than that on  One rotation
takes 243 days South Pole
Earth. As a result, Venus is the hottest planet, with a maximum surface
and 14 minutes
temperature of about 900°F (480°C). The thick cloud layers contain droplets
of sulfuric acid and are driven around the planet by winds at speeds of up to
220 miles (360 km) per hour. Although the planet takes 243 Earth days to
CLOUD FEATURES
rotate once, the high-speed winds cause the clouds to circle the planet in
only four Earth days. The high temperature, acidic clouds, and enormous Polar hood Dark, mid-latitude
atmospheric pressure (about 90 times greater at the surface than that on band
Earth) make the environment extremely hostile. However, space probes
have managed to land on Venus and photograph its dry, dusty surface.
The Venusian surface has also been mapped by probes with radar
equipment that can “see” through the cloud layers. Such radar maps
reveal a terrain with craters, mountains, volcanoes, and areas where
craters have been covered by plains of solidified volcanic lava. There
are two large highland regions called Aphrodite Terra and Ishtar Terra.

VENUSIAN CRATERS
Danilova
Cloud features swept
Ejecta (ejected around planet by
material) winds of up to 220
miles (360 km/h)
Central peak
Howe Dirty yellow hue
due to sulfuric acid Bright
in atmosphere polar band
FALSE-COLOR RADAR MAP Metis Regio Maxwell Montes Bell Regio Tethus Regio
OF THE SURFACE OF VENUS
Atalanta Planitia
Sedna Planitia Leda Planitia
ISHTAR TERRA
Eisila Regio Tellus Regio

Guinevere Planitia Niobe Planitia
Phoebe Regio
Ovda Regio
Alpha Regio
Thetis Regio
APHRODITE TERRA
Themis Regio
Lavinia Planitia Aino Planitia
Helen Planitia Lada Terra


36

VENUS

EXTERNAL FEATURES AND Maxwell Dekla Tessera
INTERNAL STRUCTURE OF VENUS Cleopatra Montes
Patera Nefertiti Corona
T E R R A
Akna Montes I S H T A R
Colette N I O B E P L A N I T I A
L A K S H M I
Sacajawea P L A N U M L Tellus Tessera
E T E L L U S
P L
Vesta Rupes A N D A R E G I O
B E L L I
S E D N A T Pavlova
R E G I O I
Gula Mons P L A N I T I A A
O V D A R E G I O
Sif Mons
Hestia
Sappho
Patera G U I N E V E R E Rupes
E I S I L A R E G I O



P L A N I T I A

Semisolid core of iron
and nickel 3,750 miles
N AV K A
A L P H A
P L A N I T I A R E G I O (6,000 km) in diameter
Hathor
Mons L A V I N I A Rocky mantle
P L A N I T I A

Eve Crust of silicate rock


ATMOSPHERE
STRUCTURE
Haze containing
Thermosphere droplets of
sulfuric acid
A P H R O D I T E
T E R R A
Thick cloud layers
containing droplets
of sulfuric acid P T I
N
L
A
A
I
A T
Lower haze of dust I I N T
N
and sulfuric acid Mantle 1,900 miles T A I N O
Troposphere aerosol (extremely (3,000 km) thick I A P L A N I
small droplets)
Clear atmosphere T E R R A
of mainly carbon Crust 30 miles L A D A
dioxide (50 km) thick Maximum surface
temperature 900°F
COMPOSITION (480°C)
Carbon dioxide about 96%
Nitrogen about 3.5%
Carbon monoxide, argon, sulfur
dioxide, and water vapor about 0.5%
37

THE UNIVERSE

The Earth TILT AND ROTATION OF THE EARTH
Axis of Axial tilt
rotation of 23.4°
THE EARTH IS THE THIRD of the eight planets that orbit
the Sun. It is the largest and densest rocky planet, and the
only one known to support life. About 70 percent of the North Orbital
Pole plane
Earth’s surface is covered by water, which is not found in
liquid form on the surface of any other planet. There are
four main layers: the inner core, the outer core, the mantle,
and the crust. At the heart of the planet the solid inner core
THE EARTH
has a temperature of about 11,900°F (6,600°C). The heat
from this inner core causes material in the molten outer core and mantle to South Pole
circulate in convection currents. It is thought that these convection currents
generate the Earth’s magnetic field, which extends into space as the
One rotation takes
magnetosphere. The Earth’s atmosphere helps screen out some of the Perpendicular to
23 hours and
orbital plane
harmful radiation from the Sun, stops most meteoroids from reaching the planet’s 56 minutes
surface, and traps enough heat to prevent extremes of cold. The Earth has one
natural satellite, the Moon, which is thought to have formed when a huge asteroid
impacted Earth in the distant past.
Microorganisms began
THE FORMATION OF THE EARTH to photosynthesize,
creating a build
up of oxygen
The heat of the collisions
caused the planet to
glow red

The cloud formed
a disk of material
around the young
Sun’s equator.
The disk material
stuck together to
form planets
4.6 BILLION YEARS THE EARTH WAS 4.5 BILLION YEARS THE CONTINENTS BROKE
AGO, THE SOLAR FORMED FROM AGO THE SURFACE UP AND REFORMED,
SYSTEM FORMED COLLIDING COOLED TO FORM GRADUALLY MOVING
FROM A CLOUD OF ROCKS THE CRUST TO THEIR PRESENT
ROCK, ICE, AND GAS POSITIONS
Solar wind enters atmosphere and produces aurora Magnetosphere (region affected
by magnetic field)





Solar wind (stream of
electrically charged
particles)





THE EARTH’S
MAGNETOSPHERE
Axis of geographic poles
Van Allen radiation belt Earth Axis of magnetic poles

38

THE EAR TH

EXTERNAL FEATURES AND COMPOSITION OF THE EARTH
INTERNAL STRUCTURE
OF THE EARTH
Atmosphere 300 Other elements less than 1 %
miles (500 km) deep
Greenland
Aluminum 0.4% Calcium 0.6%
Crust 4–25 miles Nickel 2.7%
(6–40 km) thick Sulfur 2.7%
Magnesium 17%
Silicon 13%
Mantle about Oxygen 28%
1,740 miles (2,800
km) thick
N O R T H A T L A N T I C Iron 35%
O C E A N


Outer core
1,430 miles
(2,300 km) thick

Surface temperature
between -126°F and
136°F (-88°C and 58°C)
Cyclonic
storm
Core temperature 11,900 °F (6,600 °C)
Molten core of Solid inner core
iron and nickel of iron and nickel E U R O P E
1,500 miles (2,400
Gutenberg discontinuity km) in diameter
(boundary between outer Atlas Mountains
core and mantle)
Sahara (desert
Mantle of mostly solid region)
silicate material A F R I C A

Mohorovicic
discontinuity Congo Basin
(boundary (tropical rain
between mantle forest)
and crust)
S O U T H S O U T H
PA C I F I C A M E R I C A S O U T H A T L A N T I C
O C E A N
Crust of silicate rock O C E A N

Land forms about
30% of surface
Amazon Basin (tropical
rain-forest region)
Cloud typically covers about
Andes (mountain range 70% of surface
near crustal plate
boundary)
Oceans cover about
70% of surface
Earthquake region along
crustal plate boundary
39

THE UNIVERSE

The Moon TILT AND ROTATION OF THE MOON

Axis of Perpendicular to
rotation orbital plane
THE MOON IS THE EARTH’S only natural satellite.
It is relatively large for a moon, with a diameter Axial tilt
North of 6.7°
of about 2,155 miles (3,470 km)—just over a
Pole
quarter that of the Earth. The Moon takes the same
time to rotate on its axis as it takes to orbit the Orbital
plane
Earth (27.3 days), and so the same side (the near
THE MOON FROM side) always faces us. However, the amount of the
EARTH surface we can see—the phase of the Moon—
One
depends on how much of the near side is in sunlight. The Moon is dry rotation
and barren, with negligible atmosphere and water. It consists mainly takes 27 Earth
days and 8 hours South Pole
of solid rock, although its core may contain molten rock or iron. The
surface is dusty, with highlands covered in craters caused by meteorite
CRATERS ON OCEANUS PROCELLARUM
impacts, and lowlands in which large craters have been filled by
solidified lava to form dark areas called maria or “seas.” Maria occur
mainly on the near side, which has a thinner crust than the far side. Aristarchus
Many of the craters are rimmed by mountain ranges that form the
Cobra Head
crater walls and can be thousands of feet high.
(head of
Schröter’s
Valley)
De la Rue
NEAR SIDE OF THE MOON Aristoteles Herodotus
Hercules
Aristillus
Plato Atlas
Montes Apenninus
M A R E F R I G O R I S
Archimedes
Montes Jura Cleomedes
Sinus Iridum
Macrobius
Bright rays of Julius Caesar
ejected material M A R E I M B R I U M M A R E M A R E
S E R E N I T A T I S C R I S I U M
Copernicus
M A R E
Aristarchus
V A P O R U M M A R E M A R E
T R A N Q U I L L I TAT I S F E C U N D I T A T I S
O C E A N U S Langrenus
P R O C E L L A R U M
Kepler
Vendelinus
M A R E
N E C T A R I S
Encke
Cyrillus
Flamsteed
Petavius
Fra Mauro N U B I U M Fracastorius
M A R E
Furnerius
Grimaldi
Catharina
Letronne
M A R E
Rupes Altai
H U M O R U M
Gassendi
Albategnius
Mersenius
Ptolemaeus
Arzachel
Walter
Pitatus
Stöfler
Schickard Deslandres
Alphonsus Bailly Tycho Clavius Maginus
40

THE MOON


PHASES OF THE MOON Last quarter Waning
gibbous Line of sight
Waning crescent

Full Moon
Earth
Sunlight
New Moon Waxing gibbous
Waxing
Orbital path of Moon Dust on surface 6 in (15 cm) thick
crescent First quarter
Surface cratered
due to impact of
FAR SIDE OF THE MOON Rocky crust covered with loose regolith (soil) large meteorites

Mantle 600 miles (1,000 km)
thick Mach
Region where moonquakes originate

Semisolid outer core

D’Alembert Avogadro
Campbell
Compton
Wiener
Fabry


Seyfert
Joliot
Hertzsprung
Fleming Korolev
M A R E
Crust of near side
M O S C O V I E N S E
Mendeleev 100 miles (60 km) thick
Small inner core
Keeler
with a central
temperature of
M A R E 2,700°F (800°C)
S M I T H I I
Pasteur Crust of far side
60 miles (100 km) thick
Hilbert
Galois
Doppler
M A R E
M A R E
I N G E N I I
Tsiolkovsky
O R I E N T A L E
Montes Rook
Milne
Montes Cordillera
Gagarin
Jules Verne Mendel
Roche Apollo
Van de Graaff
Planck
Schrodinger Zeeman
Von Kármàn Leibnitz Antoniadi
41

THE UNIVERSE

Mars TILT AND ROTATION OF MARS
Axial tilt
Perpendicular
Axis of of 24° to orbital plane
MARS, KNOWN AS THE RED PLANET, is the fourth planet rotation
from the Sun and the outermost rocky planet. In the
North Pole
19th century, astronomers first observed what were
thought to be signs of life on Mars. These signs Orbital
plane
included apparent canal-like lines on the surface, and
dark patches that were thought to be vegetation. It is
now known that the “canals” are an optical illusion,
MARS
and the dark patches are areas where the red dust that
covers most of the planet has been blown away. The fine dust particles are
often whipped up by winds into dust storms that occasionally obscure One rotation South Pole
takes 24 hours
almost all the surface. Residual fine dust in the atmosphere gives the
and 37 minutes
Martian sky a pinkish hue. The northern hemisphere
of Mars has many large plains formed of solidified SURFACE FEATURES OF MARS
volcanic lava, whereas the southern hemisphere has
Bright
many craters and large impact basins. There are also
water-ice fog
several huge, extinct volcanoes, including
Olympus Mons, which, at 370 miles (600 km)
across and 15 miles (25 km) high, is the largest Fog in canyon 12 miles
(20 km) wide at end of
known volcano in the solar system. The surface Valles Marineris
also has many canyons and branching channels.
The canyons were formed by movements of the
surface crust, but the channels are thought to have
Syria Planum
been formed by flowing water that has now dried
up. The Martian atmosphere is much thinner than
Earth’s, with only a few clouds and morning mists.
NOCTIS LABYRINTHUS (CANYON SYSTEM)
Mars has two tiny, irregularly shaped moons called
Phobos and Deimos. Their small size indicates that
Summit caldera
they may be asteroids that have been captured by  consisting of
the gravity of Mars. overlapping
collapsed
volcanic craters
THE SURFACE
OF MARS
Gentle slope
produced by
lava flow

Cloud formation
OLYMPUS MONS (EXTINCT SHIELD VOLCANO)
MOONS OF MARS






Dark area where
dust has been
blown away by
wind South Surface covered PHOBOS DEIMOS
polar ice with red-colored Average diameter: 14 miles Average diameter: 8 miles
cap iron oxide dust Average distance from Average distance from
planet: 5,800 miles planet: 14,600 miles

42

MARS
North polar ice cap of
frozen carbon dioxide EXTERNAL FEATURES AND
and water ice INTERNAL STRUCTURE OF MARS
Tempe Fossae
Cirrus-type condensation
Mareotis Fossae
Uranius Tholus VA S T I TA S clouds of water ice
Tantalus Fossae B O R E A L I S P L A N I T I A Dust storm
A C I D A L I A
Alba Fossae Branching channels, possibly
formed by water flow
Alba Patera
Milankovic Valles Marineris (canyon
system 2,500 miles/
A R C A D I A P L A N I T I A P L A N U M C H R I S E P L A N Y T I A depth is 3.5 miles/6 km)
4,000 km long; average
L U N A E
Coprates Chasma
Ceraunius Tholus
Tharsis Tholus Average surface
temperature
M A R G A R I T I F E R -40°F (-40°C)
Solid, rocky crust S I N U S Holden
containing water-ice
permafrost (permanently
frozen subsoil) Ritchey
Metallic, possibly A R G Y R E
molten, core 1,600 miles P L A N I T I A
(2,500 km) in diameter Darwin
Cloud formation
Mantle of
silicate rock
Lampland
Thaumasia
Fossae
Pavonis Mons Slipher
Olympus Ascraeus Mons Lowell ATMOSPHERE
Mons
STRUCTURE
South polar ice cap
of frozen carbon
dioxide and Thermosphere
water ice
Mantle 1,200 miles
(2,000 km) thick
Stratosphere Thin clouds of frozen
carbon dioxide
A M A Z O N I S
Crust 25–30 miles (40 –50 km) thick
P L A N I T I A
Isolated clouds
and fog of icy
Thin atmosphere
S U R I A of mainly carbon water vapor
P L A N U M dioxide
Troposphere
Red, iron-rich dust
Noctis Labryrinthus
COMPOSITION
Cyclonic Carbon dioxide about 95%
storm
system Nitrogen about 2.7%
Arsia Mons
Argon about 1.6%
Oxygen, carbon monoxide,
and water vapor about 0.7%

43

THE UNIVERSE

Jupiter TILT AND ROTATION OF JUPITER


Axis of rotation Axial tilt of 3.1°
JUPITER IS THE FIFTH PLANET from the Sun and
the innermost of the four giant planets. It is the North Pole Perpendicular
to orbital plane
largest and the most massive planet, with a
diameter about 11 times that of the Earth and a
mass about 2.5 times the combined mass of the
seven other planets. Jupiter is thought to have a
small rocky core surrounded by an inner mantle
JUPITER
of metallic hydrogen (liquid hydrogen that acts
like a metal). Outside the inner mantle is an outer mantle of liquid Orbital plane
hydrogen and helium that merges into the gaseous atmosphere.
One rotation takes South Pole
Jupiter’s rapid rate of rotation causes the clouds in its atmosphere
9 hours and 55 minutes
to form belts and zones that encircle the planet parallel to the
equator. Belts are dark, low-lying, relatively warm cloud layers, GREAT RED SPOT AND WHITE OVAL
and zones are bright, high-altitude, cooler cloud layers.
Within the belts and zones, turbulence causes the
Great Red Spot
formation of cloud features such as white ovals
(anticyclonic
and red spots, both of which are huge storm systems. storm system)
The most prominent cloud feature is a storm called
the Great Red Spot, which consists of a spiraling
Red color
column of clouds three times wider than the Earth probably due
that rises about five miles (8 km) above the upper to phosphorus
cloud layer. Jupiter has a thin, faint, main ring, inside
White oval
which is a tenuous halo ring of tiny particles. Beyond
(temporary
the main ring’s outer edge is a broad and faint anticyclonic
two-part gossamer ring. There are 63 known Jovian storm system)
moons. The four largest moons (called the
Galileans) are Ganymede, Callisto, Io, and
Europa. Ganymede and Callisto are cratered and GALILEAN MOONS OF JUPITER
icy. Europa is smooth and icy and is thought to
have a subsurface water ocean. Io is covered
in bright red, orange, and yellow splotches.
This coloring is caused by sulfurous
material from active volcanoes that shoot
plumes of lava hundreds of miles above
the surface.

EUROPA CALLISTO
INNER RINGS OF JUPITER
Diameter: 1,950 miles Diameter: 2,983 miles
Main ring Average distance from Average distance from
planet: 416,900 miles planet: 1,168,200 miles

Halo ring






GANYMEDE IO
Diameter: 3,270 miles Diameter: 2,263 miles
Average distance from Average distance from
planet: 664,900 miles planet: 262,100 miles

JUPITER
ATMOSPHERE EXTERNAL FEATURES AND INTERNAL STRUCTURE OF JUPITER
STRUCTURE
Zone (high-pressure
region of rising gases)
Atmosphere of mainly
hydrogen and helium
Red-colored
Stratosphere storm
White clouds of
ammonia crystals Outer mantle
merging into
atmosphere
Dark orange
clouds of ammonium
Troposphere hydrosulfide crystals
Bluish clouds of water
ice and water droplets

Inner mantle 18,500
COMPOSITION miles (30,000 km) thick
Hydrogen about 90%
Helium about 10%
Plume
Traces of ammonia, (trailing
methane, and water cloud)
vapor
High-altitude
North polar white cloud
aurora
Outer mantle of liquid
North Temperate Zone
hydrogen and helium
Inner mantle of
North Temperate Belt
metallic hydrogen
Rocky core 17,500 miles
North Tropical (28,000 km) in diameter Core temperature
Zone
54,000°F (30,000°C)
North Equatorial
Belt




Equatorial Zone




South Belt (low-pressure
Equatorial Belt region of sinking
gases)
South
Tropical Zone
South
Temperate Belt
White oval
South (temporary
Temperate Zone
anticyclonic
Cloudtop
storm system)
Flash of lightning Great Red Spot temperature
(anticyclonic -180°F (-120°C)
storm system)
45

THE UNIVERSE

Saturn TILT AND ROTATION OF SATURN

Axial tilt of 26.7° One rotation
takes 10 hours
SATURN IS THE SIXTH PLANET from the Sun. It is a and 40 minutes
gas giant almost as big as Jupiter, with an equatorial
North
diameter of about 75,000 miles (120,500 km). Saturn
Pole
is thought to consist of a small core of rock and ice Orbital
plane
surrounded by an inner mantle of metallic hydrogen
(liquid hydrogen that acts like a metal). Outside the
inner mantle is an outer mantle of liquid hydrogen
FALSE-COLOR
IMAGE OF SATURN that merges into a gaseous atmosphere. Saturn’s
South Pole
clouds form belts and zones similar to those on
Jupiter, but obscured by overlying haze. Storms and eddies, seen as Perpendicular Axis of
rotation
red or white ovals, occur in the clouds. Saturn has an extremely thin to orbital plane
but wide system of rings that is about half a mile (1 km) thick but
extends outward to about 260,000 miles (420,000 km) from the
FALSE-COLOR IMAGE OF SATURN’S
planet’s surface. The main rings comprise thousands of narrow
CLOUD FEATURES
ringlets, each made of icy rock lumps that range in size from tiny
particles to chunks several yards across. The D, E, and G rings are Ribbon-shaped
striation caused
very faint, the F ring is brighter, and the A, B, and C rings are by winds of 335
bright enough to be seen from Earth with binoculars. In 2009, mph (540 km/h)
a huge dust ring was discovered 4 million miles (6 million km)
beyond the main system. Saturn has more than 60 known moons,
Oval (rotating
some of which orbit inside the rings and are thought to exert a storm system)
gravitational influence on the shapes of the rings. Unusually, seven
of the moons are co-orbital—they share an orbit with another
moon. Astronomers believe that such co-orbital moons may have
originated from a single satellite that broke up.

INNER RINGS OF SATURN MOONS OF SATURN
D ring
C ring (“crepe ring”)
B ring
Cassini Division
A ring
Encke
Division ENCELADUS TETHYS
Diameter: 509 miles Diameter: 652 miles
F ring Average distance from Average distance from
planet: 148,000 miles planet: 183,000 miles










DIONE MIMAS
Diameter: 695 miles Diameter: 247 miles
Average distance from Average distance from
planet: 254,000 miles planet: 115,600 miles

SATURN

ATMOSPHERE
COMPOSITION STRUCTURE
EXTERNAL FEATURES AND Hydrogen about 96.3%
INTERNAL STRUCTURE
OF SATURN Helium about 3.3%
Haze of
Traces of ammonia, methane, Stratosphere ammonia crystals
and water vapor
Clouds form belts (dark,
low-altitude layers) and White clouds of
zones (bright, high- ammonia crystals
altitude layers) Atmosphere of mainly
hydrogen and helium
Dark orange clouds
Troposphere of ammonium
hydrosulfide
crystals
Outer mantle merging
into atmosphere
Blue clouds of water
ice and water vapor

F ring
A ring (broad ring
comprising many ringlets)
Inner mantle 9,000
miles (15,000 km) thick B ring (broad ring
comprising many ringlets)
C ring (“crepe ring”; broad ring
comprising many ringlets)

D ring

Outer mantle of
liquid hydrogen
Inner mantle of
liquid metallic hydrogen

Rock and ice core
18,500 miles (30,000
km) in diameter

Core temperature Cassini Division
27,000°F (15,000°C) (apparent gap
containing at least
100 ringlets)
Encke Division (gap
Equator swept by in which the moon
winds of 1,100 mph Pan orbits)
(1,800 km/h)










Cloud-top temperature
about -290°F (-180°C)
Radial spoke
(probably dust particles Anne’s Spot
above plane of rings) (anticyclonic storm system)

47

THE UNIVERSE

Uranus TILT AND ROTATION OF URANUS
Axial tilt
of 97.9° Perpendicular to
orbital plane
URANUS IS THE SEVENTH PLANET from the Sun
and the third largest, with a diameter of about
32,000 miles (51,000 km). It is thought to Orbital
consist of a dense mixture of different types of plane South Pole
ice and gas around a solid core. Its atmosphere
contains traces of methane, giving the planet a
blue-green hue, and the temperature at the cloud
FALSE-COLOR Axis of
IMAGE OF URANUS tops is about -350°F (-210°C). Uranus is the most
rotation
featureless planet to have been closely observed:
only a few icy clouds of methane have been seen so far. Uranus is
North One rotation
unique among the planets in that its axis of rotation lies close to its Pole takes 17 hours
orbital plane. As a result of its strongly tilted rotational axis, Uranus rolls and 14 minutes
on its side along its orbital path around the Sun, whereas other planets spin
more or less upright. Uranus is encircled by main rings that consist of rocks
interspersed with dust lanes and two distant outer rings made of dust. The
rings contain some of the darkest matter in the solar system and are extremely MAJOR MOONS
narrow, making them difficult to detect: most of them are less than 6 miles (10 km)
wide, whereas most of Saturn’s rings are thousands of miles in width. There are
27 known Uranian moons, all of which are icy and most of which are farther out
than the rings. The 13 inner moons are small and dark, with diameters of less
than 100 miles (160 km), and the five major moons are between about 290 and
1,000 miles (470 and 1,600 km) in diameter. The major moons have a wide variety
of surface features. Miranda has the most varied surface, with cratered areas
broken up by huge ridges and cliffs 12 miles (20 km) high. Beyond these are nine
MIRANDA
much more distant moons with diameters less than 90 miles (150 km). Diameter: 295 miles
Average distance from
planet: 80,700 miles
RINGS OF URANUS


Epsilon ring
Lambda ring

Delta ring
RINGS AND DUST LANES ARIEL TITANIA
Gamma ring Diameter: 720 miles Diameter: 981 miles
Average distance from Average distance from
planet: 118,800 miles planet: 270,900 miles
Eta ring
Beta ring

Alpha ring

Rings 4 and 5

Ring 6 UMBRIEL OBERON
Diameter: 726 miles Diameter: 946 miles
Average distance from Average distance from
Zeta ring
planet: 165,500 miles planet: 362,000 miles