CHAPTER 1 - Lincoln High School

CHAPTER 1:
Discovering
the Night Sky
WHAT DO YOU THINK?
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Is the North Star—Polaris—the brightest star in
the night sky?
Do astronomers regard constellations as the
familiar patterns of stars in the sky?
What causes the seasons?
When is the Earth closest to the Sun?
How many zodiac constellations are there?
Does the Moon have a dark side that we never
see from Earth?
Is the Moon ever visible during the daytime?
In You
will discover…
• how astronomers organize the night sky to help them
locate objects
• that the Earth’s spin on its axis causes day and night
• how the tilt of the Earth’s axis of rotation and the
Earth’s motion around the Sun combine to create the
seasons
• that the Moon’s orbit around the Earth creates the
phases of the Moon and lunar and solar eclipses
• how the year is defined and how the calendar was
developed
Seasons are caused because the Earth’s axis is tilted and as the Earth
revolves around the Sun, different parts of the Earth receive more direct
sunlight (summer), while other parts of the Earth receive sunlight which is
more spread out (winter).
The universe is huge, and the sizes and distances of
objects in the universe vary greatly. Therefore we use
scientific notation, which involves powers of ten notation to
describe numbers much smaller or much greater than 1.
Some common examples of powers of ten:
POWER
DECIMAL
NAME
METRIC PREFIX
103
1000
one thousand
Kilo
109
1,000,000,000
one billion
Giga
10-6
0.000001
one millionth
micro
THE SCALES OF
THE UNIVERSE
The range of objects
we study are from
the extremely small
subatomic particles,
to objects which are
gigantic, such as a
galaxy or the size of
the known universe
itself.
Each division up the
line indicates an
increase in size by
100,000.
What Have Astronomers Discovered in Our Universe?
PLANETS
ASTEROIDS
STARS
GALAXIES
COMETS
NEBULA
CLUSTERS OF GALAXIES
INTERGALACTIC GAS
In order to more easily locate objects in the sky, we
divide the sky into regions named after familiar
patterns of stars called constellations.
Ancient constellations were
imaginary pictures outlined
by familiar patterns of stars.
Modern astronomers divide the sky into
88 official constellations or regions of
space, many of which contain the
ancient star patterns.
Some Common Guides to Finding Constellations
Using the “Big Dipper” as a guide
The “Winter Triangle”
The “Summer Triangle”
Astronomers describe the universe as an imaginary
sphere surrounding the earth on which all objects in the
sky can be located, called the CELESTIAL SPHERE.
 As viewed from Earth, the
celestial sphere appears to rotate
around two axis points, the north
and south celestial poles, which
are located directly above the
Earth’s poles.
Between these is the celestial
equator, which divides the
celestial sphere into northern and
southern hemispheres.
We define the position of an
object on the celestial sphere
using two coordinates, right
ascension and declination.
Cyclic motions of the Sun and stars in our sky
are due to motions of the Earth
1. ROTATION=the spin of the Earth on its axis. It takes one
day for the Earth to complete one rotation.
2. REVOLUTION=the movement of the Earth in orbit around
the sun. It takes one year for the Earth to complete one
revolution.
3. PRECESSION=the slow conical (top-like) motion of the
Earth’s axis of rotation. It takes 26,000 years for the Earth
to complete one cycle of precession.
The apparent westward motion of the Sun,
Moon, and stars across our sky each day is
caused by Earth’s rotation.
At middle latitudes, we see the Sun, Moon, and many of the stars
first come into view moving upward, rising at some point along the
eastern horizon. Then, they appear to arc across the sky. Finally,
they disappear somewhere along the western horizon.
We generalize this motion to make statements such as, “The Sun
rises in the east and sets in the west.”
However, not all stars in our sky rise and set, and different latitudes
view the movements of the stars differently.
The stars near the poles of the celestial
sphere (shown here) move in trails that
circle the pole and never set. They are
called circumpolar.
The view of the stars movement
depends on our latitude.
NORTH
POLE
EQUATOR
MIDDLE
LATITUDES
Different parts of the world experience different times of day as the Earth
rotates.
TIME ZONES which can be used to calculate the time of day in any given
part of the world.
The Earth also revolves around the Sun, which changes our view of the stars.
From our perspective, the Sun
appears to move through the
stars along a special path
called the ecliptic.
From an outside view, we see the
Earth revolve around the Sun.
We define the plane of the
Earth’s orbit as the ecliptic plane.
We can see how different stars appear at different times of day by looking at
the position of the Sun against the backdrop of stars. The side of the Earth
facing the Sun is experiencing “day,” while the side of the Earth turned away
from the Sun is experiencing “night.”
SEPTEMBER
MARCH
The seasons we experience are linked to the motion of the Sun along the
celestial sphere.
The point of the Sun’s path
farthest north on the celestial
sphere is called the summer
solstice (JUN 21), while the point
of the ecliptic farthest south is
called the winter solstice (DEC
21).
The two points on the ecliptic
where the Sun crosses the
celestial equator are called
equinoxes. During the vernal
equinox (MAR 21), the Sun is
moving north, while during the
autumnal equinox (SEPT 21), the
Sun is moving south.
Remember that the seasonal
names of the equinoxes and the
solstices refer to seasons in the
NORTHERN hemisphere. The
seasons occurring in the
SOUTHERN hemisphere are
exactly opposite.
The Sun rises at different points along the horizon at different times of the year
and also peaks at different heights.
Gravitational forces of the Sun and the Moon pulling on the Earth as it
rotates causes the Earth to undergo a top-like motion called precession.
Over a period of 26,000 years, the Earth’s rotation axis slowly moves in a
circular motion.
This precession causes the position of the North Celestial Pole to slowly
change over time. Today, the North Celestial Pole is near the star
Polaris, which we call the “North Star.” However, in 3000 BC, Thuban
was close to the North Celestial Pole and in 14,000AD, Vega will be in
this location.
One effect of this motion is to change the location in the Earth’s orbit at
which summer and winter occur, and thus change the time of year
when the Sun appears in certain constellations.
Aries is the first of the twelve zodiacs. It represents the beginning of all things and
usually displays a strong desire to lead. Aries is adventurous, energetic,
pioneering, and courageous. Arians always want to be on top. They tend to be
frank and open but also self-centered and willful. Arians love adventure and
almost has no fear. All is done with great enthusiasm which affects the people
around them. Aries is loyal to family and friends. Aries is ruled by the forceful
Mars. Arians are good athletes, doctors, explorers, soldiers, and leaders.
Sometimes they like physical, emotional and mental extremes but Arians should
be careful not to go too far with their extremism.
Aries attractions:
Aries colors:
Aries stones:
Aries plants:
Aries celebrities:
Gemini, Leo, Libra, Scorpio
All shades of red
diamond, ruby, emerald, amethyst
fern, poppy
Leonardo da Vinci, Raphael, Marlon Brando, Charlie Chaplin,
Bach, Adolf Hitler, Al Gore, Aretha Franklin, Camille Paglia, Celine
Dion, Diana Ross, Elton John, Warren Beatty, Francis Ford
Coppola, Gloria Steinem, Harry Houdini, Johann Sebastian Bach,
Joseph Campbell, Kareem Abdul-Jabbar, Leonard Nimoy, Rosie
O'Donnell, Tennessee Williams, Thomas Jefferson, Vincent Van
Gogh.
Taurus Characteristics
Taurus is the second sign of the zodiac, representing growth and development.
Taurus is patient, reliable, warmhearted, loving, persistent, and determined. It
likes few changes which determines its reserved and practical nature. Taurueans
show a great interest in all physical matters. Taurus is faithful to friends and
lovers. However, when insulted Taurueans remember it forever. No other sign in
the zodiac is closer to earth then Taurus. Taurus is ruled by Venus and seeks
harmony with its surroundings. Taureans like being part of a team. However, they
have reputation for stubbornness. Taureans are good teachers, scientists,
designers, and chefs.
Taurus
attractions:
Taurus colors:
Taurus stones:
Taurus plants:
Taurus
celebrities:
Libra, Scorpio, Capricorn
All shades of blue, green
rose quartz, emerald
daisy, lily
Immanuel Kant, Karl Marx, Jack Nicholson, Barbra Streisand, Benjamin
Spock, Billy Joel, Bing Crosby, Bono, Candice Bergen, Charlotte Bronte,
Cher, Audrey Hepburn, Frank Capra, Jerry Seinfeld, Katharine Hepburn,
Michelle Pfeiffer, Queen Elizabeth II, Sigmund Freud, Stevie Wonder,
William Shakespeare.
Gemini Characteristics
Gemini is the third sign of the zodiac, representing quickness of thought. Geminis
are good communicators. They are active and clever. Geminis are adaptable,
versatile, communicative, witty, intellectual, and eloquent. Sometime they can be
pessimistic which is caused by their dualistic nature. Geminis like being part of a
group. They always follow the rules of the game. Understanding and tolerant, they
can be helpful in any situation. They usually liven up any social gathering with their
ideas and verbal facility. Gemini is ruled by Mercury. Geminis can adapt to any
situation, however they still try to keep their independence. Geminis like to travel
and socialize. Geminis are good lawyers, politicians and public speakers.
Gemini attractions:
Gemini colors:
Gemini stones:
Gemini plants:
Gemini celebrities:
Virgo, Libra, Sagittarius
yellow, light green
citrine, amber, tourmaline
tansy, yarrow, privet
John Wayne, Paul Gauguin, Sir Arthur Conan Doyle, Alanis Morissette,
Allen Ginsburg, Anne Frank, Bill Moyers, Bob Dylan, Bob Hope, Che
Guevara, Clint Eastwood, Frank Lloyd Wright, Joe Namath, John F.
Kennedy, Marilyn Monroe, Michael J. Fox, Miles Davis, Norman Vincent
Peale, Queen Victoria, Sandra Bernhard, Thomas Hardy, William Butler
Yeats.
Cancer Characteristics
Cancers are protective, traditional, and emotional. Cancer is probably the most
emotional of all the signs. This makes Cancers romantic and shy. Sometimes
Cancers can be aggressive in getting what they want. They like extremes: they
can be joyful and melancholic in a short period of time. The heart of their
personality is sensitivity. They take everything very personally. Cancers will find
their security in their families. They give high value to their homes which should be
luxurious. Cancers do not like to be criticized or insulted. Cancer is ruled by the
moon. Cancers like to give away things. They are good lawyers, architects,
designers, and painters.
Cancer attractions:
Cancer colors:
Cancer stones:
Cancer plants:
Cancer celebrities:
Pisces, Scorpio, Aquarius
while, pale colors
moonstone, pearl, peridot
water lilies, rushes
Mike Tyson, Antoine de Saint-Exupery, Bill Cosby, Courtney Love,
Ernest Hemingway, Harrison Ford, Henry David Thoreau, Henry VIII,
John Glen, Julius Caesar, Kevin Bacon, Louis Armstrong, Meryl
Streep, OJ Simpson, Princess Diana, Rembrandt van Rijn, Robin
Williams, Sylvester Stallone, The Dalai Lama, Tom Cruise, Tom
Hanks, Twyla Tharp.
Leo Characteristics
Leos are like lions: energetic, free, and independent. Leos likes to get things done.
They are excellent leaders because of their authoritative and confident character.
They are very loyal to other people, even to their enemies. They like to socialize
and give away presents. They like to buy fancy items. Leos like to get the attention
of others. They can do many different jobs and learn easily. They always follow their
principles so it is very unlikely to be surprised by a Leo. They also like children and
are good entertainers. Leo is ruled by the Sun. Leos are optimist because of their
strong confidence in themselves. Leos are good leaders, managers, performers and
negotiators.
Leo attractions:
Leo colors:
Leo stones:
Leo plants:
Leo celebrities:
Scorpio, Capricorn, Leo
ocher, golden
yellow topaz, ruby, tiger's eye
sunflower, lavender
Carlos Santana, Alfred Hitchcock, Amelia Earhart, Andy Warhol, Arnold
Scharzenegger, Bill Clinton, Carl Jung, Dustin Hoffman, Emily Bronte,
Fidel Castro, George Bernard Shaw, Herman Melville, Jacqueline
Kennedy Onassis, Madonna, Mae West, Monica Lewinsky, Napoleon,
Peter O'Toole, Robert De Niro, Robert Redford, Stanley Kubrick, Tipper
Gore, Whitney Houston.
Virgo Characteristics
Virgo likes to attack back when confronted. Virgos need to receive a lot attention,
adoration and gratitude. Virgos are accurate, competent and effective. They like
rationality. Virgos like to help and solve problems quickly. They do not do it for
compliments. Virgos are not wasteful. Being perfectionists, they like order and
cleanness in their home. Virgos change friends often. They have only a few real
friends because they give very special values to friendship to which other people
cannot commit. Virgo is ruled by Mercury. Virgos are very bright and educated. They
are good scientists, teachers, analysts and planners.
Virgo attractions:
Virgo colors:
Virgo stones:
Virgo plants:
Virgo celebrities:
Gemini, Pisces, Taurus
indigo, violet, silver
carnelian, amethyst, pyrite
sage, wintergreen
Agatha Christie, Mother Theresa, Mary Shelley, Bruno Bettleheim, D. H.
Lawrence, Dorothy Parker, Geraldine Ferraro, H G Wells, Ingrid Bergman,
Julio Iglesias, Leonard Bernstein, Marcia Clark , Michael Jackson, Oliver
Stone, Queen Elizabeth, Sean Connery, Sophia Loren, Stephen King.
Libra Characteristics
Libra is very sociable and likes being a part of a group. Libras have gentle and
refined personalities and like to be praised and pampered. Libras are
perfectionists. They like to give fair justice when they hear all disputing sides.
Libras are loyal, caring, nice, and adaptive. Libras are very trustworthy in
friendships and relationships. Sometimes this makes them unreasonably
possessive to other people. Libras like large, open spaces like halls and stadiums.
They like to be out in nature. The sign is ruled by Venus. Libras also are very
devoted to what they do and always try to get things done with excellence. Libras
are good judges, managers, writers and social workers.
Libra
attractions:
Libra colors:
Libra stones:
Libra plants:
Libra
celebrities:
Aquarius, Aries, Taurus
dark blue, pink
opal, jade
strawberry, violet, pansy
Luciano Pavarotti, Martina Navratiova, Margaret Thatcher, Harold Pinter,
Barbara Walters, Brigitte Bardot, Bruce Springsteen, Carrie Fisher,
Christopher Reeve, Dwight D. Eisenhower, Eugene O'Neill, F. Scott
Fitzgerald, George Gershwin, Gwyneth Paltrow, John Coltrane, John
Lennon, Johnny Cochran, Julie Andrews, Mahatma Gandhi, Mickey Mantle,
Oscar Wilde, Paul Simon, Susan Sarandon, Truman Capote, Will Smith.
Scorpio Characteristics
Scorpios have very complicated personality. They are clever, non-compromising,
calculating, and self protective. Money is very important for them. Sometimes they
have "a sixth sense": they can feel things by intuition that other people cannot. They
are very loyal and protective towards friends and loved ones. They can change
radically according to the situation. Scorpios could say something and have in mind
exactly the opposite. They are good actors. They can "poison" other people at any
time - a harm that may last for long time. They would do anything to accomplish
their goals. In relationships, they could be dangerously jealous. They are also
passionate and caring. Scorpio is ruled by Mars. Scorpios are good teachers,
actors, businessmen, accountants and sociologists.
Scorpio attractions: Capricorn, Leo, Pisces
Scorpio colors:
red, black, gray
Scorpio stones:
garbet, black pearl, ruby
Scorpio plants:
hemlock, poppy, roots
Scorpio celebrities: Whoopi Goldberg, Georgia O'Keefe, Maradona, Bill Gates, Billy Graham,
Bonnie Raitt, Calista Flockhart, Charles Manson, Dan Rather, Demi
Moore, George Eliot, Hillary Rodham Clinton, Jane Pauley, Jodie Foster,
Jonas Salk, KD Lang, Larry Flynt, Leonardo DiCaprio, Marie Curie, Martin
Luther, Pablo Picasso, Pablo Picasso, Price Charles, Richard Burton,
Roseanne, Ted Turner, Theodore Roosevelt.
Sagittarius Characteristics
Sagittarius has energetic and active personality. People carrying this sign what
to know everything and everyone. They are also like to travel and to be close to
nature. Sagittarians are optimistic, faithful, and honest. Other people often share
their problems with Sagittarians to seek help and understanding. Sagittarians
are not very emotional. They adjust quickly to any environment. Sagittarians are
good friends but still they keep their freedom and neutrality. Sagittarius is ruled
by Jupiter. Sagittarius are very curious by nature. Such curiosity makes them
well educated and intelligent people. Sometimes Sagittarians can be rebellious
but they can quickly calm down and return to their ordinary nature. Sagittarius
are good salesmen, scientists, researcher and analysts.
Sagittarius
attractions:
Sagittarius colors:
Sagittarius stones:
Sagittarius plants:
Sagittarius
celebrities:
Gemini, Aries, Taurus, Virgo
beige, blue, bronze
amethyst, turquoise, citrine
chestnuts, asparagus
Bruce Lee, William Blake, Beethoven, Brad Pitt, Emily Dickinson, Frank
Sinatra, Frank Zappa, Jane Austen, Jim Morrison, Jimi Hendrix, Joe
DiMaggio, Mark Twain, Noel Coward, Steven Spielberg, Tina Turner, Walt
Disney, Winston Churchill, Woody Allen.
Capricorn Characteristics
Capricorns never repeat their mistakes. They are very careful, slow, practical and
thrifty. Their reserved personality can cause problems in their relationships. They
are faithful to their family and loved ones. Their personality is also kind and
affectionate but is suppressed by shyness. Trying to be perfect in everything they
undertake, they often miss great opportunities because of insecurity in their
abilities. Careful planning and insuring against any negative outcome is a must for
all their deeds. Capricorn is ruled by Saturn. Capricorn's nature can be easily
changed when they are loved or respected by other people. Capricorns are good
brokers, politicians, economists and bankers.
Capricorn attractions:
Capricorn colors:
Capricorn stones:
Capricorn plants:
Capricorn celebrities:
Cancer, Leo, Taurus, Virgo
brown, gold, green, purple, white
amethyst, azurite, garnet, malachite, tiger eye, quartz
Chrysanthemum and Poinsettia
Albert Schweitzer, Benjamin Franklin, Carlos Casteneda, Cary
Grant, Clara Barton, David Bowie, Edgar Allen Poe, Elvis
Presley, Henri Matisse, Henry Miller, Humphrey Bogart, Isaac
Newton, Jim Carrey, Joan Baez, Joan of Arc, Louis Pasteur,
Mao Tse Tung, Martin Luther King Jr., Mary Tyler Moore,
Muhammad Ali, Nicholas Cage, Richard Nixon, Stephen
Hawking.
Aquarius Characteristics
Aquarians have a good sense of humor. They are gentle and caring and they are not
very sociable. They to prefer to be alone or with their closest friends. That's why
Aquarius chooses its friends carefully. They like to receive compliments and are
ready to forgive when harmed. They can easily entertain other people which makes
them charming and wanted. Usually they are calm and sincere. However, when they
get angry, they can be dangerous. Most of the times they overestimate the sincerity
and the promises of their partners for which they regret later on. Aquarius is ruled by
Saturn and Uranus. Aquarians are good workers and usually are paid well.
Aquarians usually have many different hobbies and are creative and skilful in many
areas. Aquarians are good computer scientists, doctors, pilots and writers.
Aquarius
attractions:
Aquarius colors:
Aquarius
stones:
Aquarius plants:
Aquarius
celebrities:
Aries, Gemini, Libra
gray, light blue
hematite, amber
resins, dandelion
Geena Davis, Anna Pavlova, Nastassja Kinsky, Oprah Winfrey, Placido
Domingo, Abraham Lincoln, Charles Darwin, Charles Dickens, Clark Gable,
Edouard Manet, Franklin D. Roosevelt, Galileo, George Burns, Jackie
Robinson, James Dean, James Joyce, John Travolta, Lord Byron, Michael
Jordan, Mozart, Norman Rockwell, Paul Newman, Ronald Reagan, Susan B
Anthony, Thomas Edison, Toni Morrison, Virginia Woolf, Wayne Gretsky.
Pisces Characteristics
Pisces are a little bit of everything. They are independent and mystical. They are
sensitive and loving. They can easily adapt and change according the situation.
Sometimes they are so colorful that they contradict their own rules and principles.
Pisces can handle many different tasks at once and be successful in all of them.
They can tolerate other people's behaviors. This makes very strong friends out of
them. They also learn easy and can change professions without concern. Although
trying to be independent, they like to have somebody above them to mange all the
tasks they perform. Pisces are ruled by Jupiter and Neptune. They are religious
and pay strong attention to family and relationship values. Pisces are good for any
profession as long as they are not the major players.
Pisces attractions:
Pisces colors:
Pisces stones:
Pisces plants:
Pisces celebrities:
Aquarius, Cancer, Scorpio
aquamarine, purple
jade, opal, amethyst
seaweed, mosses
Liza Minnelli, Nina Simone, Sandro Botticelli, Michail Gorbachov, Albert
Einstein, Anais Nin, Bobby Fischer, Cindy Crawford, Elizabeth Barret
Browning, Elizabeth Taylor, Frederic Chopin, Gabriel Garcia Marquez,
George Washington, Glenn Close, John Steinbeck, Kurt Cobain,
Michelangelo, Ralph Nader, Roger Daltry, Rudolf Nureyev, Victor Hugo,
Pierre Renoir.Albert Einstein, Anais Nin, Bobby Fischer, Cindy Crawford,
Elizabeth Barret Browning, Elizabeth Taylor, Frederic Chopin, Gabriel
Garcia Marquez, George Washington, Glen Close, John Steinbeck, Kurt
Cobain, Michelangelo, Ralph Nader, Roger Daltry, Rudolf Nureyev, Victor
Hugo, Pierre Renoir.
Another familiar cycle is the lunar cycle. When the Moon orbits the Earth,
the amount of the side facing the Earth that is lit changes, creating the
Moon’s phases. This phase cycle is called the synodic period and is 29½
days long.
One common misconception is
that the Moon is only visible at
night. However, the time of
day in which the Moon is in our
sky varies depending on its
phase. This picture clearly
displays the Moon, visible
during the day.
A synodic month is the time it takes for the Moon to orbit the Earth with
respect to the Sun and is 29½ days long.
A sidereal month is the time it takes for the Moon to orbit the Earth with
respect to the stars and is 27.3 days long.
The two times
are different
because the
Earth moves in
its orbit around
the Sun as the
Moon moves in
its orbit around
the Earth.
During a new or full moon phase, when the Moon, Sun, and Earth are
aligned, the Moon may enter the shadow of the Earth, or the shadow of the
Moon may reach the Earth, creating eclipses. However, these eclipses do
not occur during every full or new moon because the Moon’s orbit is tilted
by 5 with respect to the Earth-Sun (ecliptic) plane.
THE THREE TYPES OF LUNAR ECLIPSES
PENUMBRAL = the
Moon appears dimmed.
PARTIAL = part of the
Moon enters the umbra of
the Earth’s shadow and is
darkened.
TOTAL = all of the Moon
enters the Earth’s
shadow and becomes a
reddish color, only lit from
light bending around the
Earth’s atmosphere.
During a total lunar eclipse, the Moon moves in and out
of the umbra of the Earth’s shadow.
SOLAR ECLIPSES occur when the moon’s shadow reaches the earth.
Unlike lunar
eclipses,
solar
eclipses
occur at
specific
places on
the Earth,
indicated by
the arrow.
1. If you are located where the umbra of the Moon’s
shadow reaches, you will see a total solar eclipse,
during which the entire disk of the Sun is covered by
the Moon, revealing the faint solar corona
surrounding the Sun.
2. Those just outside of this region where the
penumbra of the Moon’s shadow reaches will only
see a partial solar eclipse, during which only part of
the disk of the Sun is covered by the Moon.
3. Sometimes eclipses occur when the Moon is too far
away from the Earth to completely cover the Sun in
our sky. When this occurs, the Moon appears in the
center and a thin ring, or “annulus,” of light
surrounds it. These are called annular eclipses.
TOTAL ECLIPSE
ANNULAR ECLIPSE
WHAT DID YOU KNOW?
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Is the North Star—Polaris—the brightest star in
the night sky?
No. Polaris is of medium brightness.
Do astronomers regard constellations as the
familiar patterns of stars in the sky?
Sometimes. However, a constellation is formally
an entire region of the celestial sphere.
What causes the seasons?
The tilt of the Earth’s rotation axis with respect to
the ecliptic.
WHAT DID YOU KNOW?
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When is the Earth closest to the Sun?
January 3 of each year.
How many zodiac constellations are there?
13. There are 12 zodiac signs.
Does the Moon have a dark side that we never see from
Earth?
Half of the Moon is always dark, but when we see less
than a full Moon, we are seeing part of the dark side.
Is the Moon ever visible during the daytime?
The Moon is visible at some time during daylight hours
almost every day of the year.
Key Terms
angle
angular diameter
(angular size)
annular eclipse
arc angle
celestial equator
celestial pole
celestial sphere
circumpolar star
constellation
declination
degree
diurnal motion
eclipse path
ecliptic
equinox
gravitation
line of nodes
lunar eclipse
lunar phase
north celestial pole
partial eclipse
penumbra
penumbral eclipse
precession
precession of the
equinoxes
revolution
right ascension
rotation
scientific notation
sidereal month
sidereal period
solar corona
solar day
solar eclipse
south celestial pole
summer solstice
synodic month
terminator
time zone
total eclipse
umbra
vernal equinox
winter solstice
zenith
zodiac