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LAB - Reading Activity on the Constellations of the Zodiac
Observation - The Night Sky
The night sky is full of objects to view. A telescope is not necessary to view some of the more prominent
objects, but first it is important to introduce the most important feature: the stars.
The stars appear to form a sphere surrounding the Earth, so it is not by accident that it is named the
Celestial Sphere. However, in reality there is no sphere, and the stars are actually in a variety of distances
from the Earth. It is also important to understand that all of the stars visible in the night sky are a part of our
galaxy - the Milky Way. The most distant stars make up a faint band of our galaxy that is viewable from
the darkest locations.
In order to help find our way around the night sky, various groupings of stars are identified as
constellations. These constellations make up mythic characters like Pegasus, Andromeda, and Orion for the
northern hemisphere, and objects like Telescopium, Tucana and Crux for the southern hemisphere.
In total, there are 88 constellations. With the exception of the constellations of the Zodiac, there are no
specific arrangements to the constellations. For more information on the Zodiac, click here.
Because the Earth is tilted by 23.45º, the northern hemisphere (United States, Canada, Europe, Asia, and
Russia) can see some of the southern hemisphere (Australia, New Zealand, South America, Antarctica and
the southern parts of Africa) stars and visa versa, it can be difficult to differentiate what can and cannot be
seen from your exact location so please consult your local almanac. Of course, nothing takes the place of
actually stepping outside and looking for yourself!
The Constellations of the Zodiac
The Zodiac is the name of the virtual belt in which the planets, Sun, and Moon appear to move about the
sky. In reality, the planets and their respective moons (most of them anyway) orbit the Sun about the same
plane. Because the orbits of the planets are not on a perfect plane, the Zodiac band is 16° wide - 8° on
either side of the ecliptic.
When mentioning the Zodiac, the subject of Astrology also comes to mind. Astronomy and Astrology are
not the same thing. Astronomy is a science while Astrology is not. The pseudo-science of Astrology plot
the positions of the Sun and planets about 12 constellations that constitute the Zodiac. The result of these
positions is the effect the given planet, Sun or Moon on your birth sign. There are two problems regarding
this plot: there are 13 constellations in the Zodiac and the position of the Sun within the Zodiac was plotted
2000 years ago. Because the Earth in inclined by 23.45 degrees, it rotates like a top. This is called
precession.
Precession is the act of a planet spinning like a top. Click on the image to view a demonstration of
precession.
Because our planet Earth is tilted by 23.45 degrees, it also precesses. The result will be a shift in the
position of the constellations relative to us on Earth (video care of Swinburne Astronomy Online).
The result is shifting of the constellations. This means that the Astrological plots and predictions based on
your birth sign are really off by one month. For example, I was born in early March so my Astrological
birth sign is Pisces. In reality however my birth sign is Aquarius since the Sun was in this constellation
when I was born.
Of course, I do not believe in the predictions of Astrology simply because the other eight planets have no
affect on life here on Earth. If this were so, then the orbital speed of the Earth will gradually decrease since
the more massive planets orbit the Sun slower than the Earth. This is simply not the case. However, it
should be noted that the Sun and Moon do in fact influence Earth in a number of ways to include weather
and tidal changes. As far as personality, wealth, health and relationships, there is no scientific evidence to
prove these effects.
The following table introduces the 13 constellations that make up the Zodiac - the large bright object in
each of the images is our Sun.
Name
Aquarius
Image
Mythology
Water Carrier
Babylonian Name.
In Greek mythology, Aquarius (also known as Ganymede in Roman myth) was a
beautiful young boy whom Zeus brought to Olympus to be the cup bearer of the
Gods. It is suggested that Zeus fell in love with Aquarius.
Aries
Ram or Golden Fleece.
In Greek mythology, the ram carried Athamas's son Phrixux and daughter Helle to
Colchis to escape Ino. When the ram reached Colchis, Phrixux sacrificed the ram
and hung its fleece in the Grove or Ares. This fleece turned to gold and later was
the quest of Jason and the Argonauts.
The constellation name was common in Greek, Babylonian and Egyptian cultures.
Cancer
Crab
Juno sent a crab to defeat Hercules while fighting Hydra. The crab was crushed by
Hercules.
Capricorn
Sea Goat
Also known as Amalthea who provided for baby Zeus after Rhea saved him from
Cronos.
The word "cornucopia" comes from the broken horn of Capricorn - or the "horn of
plenty."
Gemini
Twin Brothers
The two bright stars - Castor and Pollux - are also the brothers' names. They were
the brothers of Helen of Troy.
They are also the protectors of ships and sailors.
Leo
Lion
Prehistoric constellation associated with royalty. In Egyptian mythology, it
represents the life giving floods since the Sun was in this constellation during the
heavy rains.
In Greek mythology, Leo represents the Nemean Lion which was killed by
Hercules.
Libra
Scales
The only "non-living" object in the Zodiac.
Romans chopped claws from Scorpio during Autumn Equinox to make Libra.
In Greek mythology, Libra is the scaled held by Astraea that represents justice.
Ophiuchus
Serpent Holder
While not an Astrological sign, Sun spends longer time here than in Scorpio.
In Greek mythology, Ophiuchus is a legendary physician who tried to become
immortal to avoid death. Zeus killed him with a bolt of lightening, but honored
him because of good works.
Pisces
Two Fish
Venus and her son Cupid escaped Typhon as two fish tied together.
In Greek mythology, they are Aphrodite and Eros.
Sagittarius
The Archer
A Chiron, half-man half-horse, sent to kill the scorpion (Scorpio).
In Babylonian mythology, this represents the demon Pabilsaq.
Scorpio
The Scorpion
Sent by Gaia to kill Orion when he said he would kill all animals.
It is also said that Apollo sent the scorpion to kill Orion.
Orion and Scorpio are on opposite sides of the sky.
Taurus
The Bull
Babylonian constellation.
Jupiter turns into bull to carry off Europa - daughter of King of Crete.
It is also said that Zeus brought the ram to try and win the heart of Europa.
Virgo
The Virgin
Goddess of farms and harvest. Virgo could also represent Ishtar, Isis, Demeter,
Cybele, and Athena.
Also thought to represent Astraea, the daughter of Zeus representing justice.
It is also suggested that Virgo represents Persephone, queen of the underworld.
Astrology and Astronomy constellation comparison:
Constellation
Astrology Date
True Astronomical Date
Aries
March 21 - April 20
April 19 - May 13
Taurus
April 21 - May 21
May 14 - June 19
Gemini
May 22 - June 21
June 20 - July 20
Cancer
June 22 - July 22
July 21 - August 9
Leo
July 23 - August 21
August 10 - September 15
Virgo
August 22 - September 23
September 16 - October 30
Libra
September 24 - October 23
October 31 - November 22
Scorpio
October 24 - November 22
November 23 - November 29
Ophiuchus
Not Included
November 30 - December 17
Sagittarius
November 23 - December 22
December 18 - January 18
Capricorn
December 23 - January 20
January 19 - February 15
Aquarius
January 21 - February 19
February 16 - March 11
Pisces
February 20 to March 20
March 12 - April 18
Notice how the Sun spends more time in Ophiuchus than in Scorpio yet Ophiuchus is not included in the
Astrology charts.
http://astronomyonline.org/observation/zodiac.asp
Discussion Questions - Answer the following based on the passage above from
AstronomyOnline.org on the constellations of the zodiac and from what you’ve learned
in class. Use information directly from the reading to support your answers.
1. Are stars found in a sphere surrounding Earth? Explain your answer.
2. What is a constellation, and how many are there?
3. Can you see all the constellations? Why or why not?
4. How many constellations does the Sun pass through?
5. Why is your astrological (horoscope) sign wrong by one month? Explain your
answer.
6. What is your astrological sign, what does it mean, and what is the mythology of
your sign?
7. What is your true astronomy sign and is it different than your astrological sign?
Explain your answer.