Planetarium, Fifth Grade, Lesson IV "What's Your Sign?" (The Ecliptic and the Zodiac) I. Lesson Overview. There is much more here than you can possibly cover in just 45 minutes. Feel free to omit things and substitute other things to make the session your own. A. Last week, we talked about why the North Star is important, how it compared to other stars, and how the Earth rotates on its axis. We also talked about what would happen if the Earth suddenly stopped rotating. B. This week, we'll be talking about the constellations that make up the Zodiac constellations. We'll also learn about the ecliptic and learn about other constellations that are within the ecliptic but are not recognized as Zodiac constellations. It is important to note we teach this lesson in a scientific manner. We are not here to promote Astrology and the Zodiac signs, but to demonstrate their important historical perspective relating to seasonal constellations and navigational tools. C. Dome In Fifth grade, we are providing planispheres to each student. Take 5-10 minutes before each dome lesson, and teach students how to find one constellation. For instance, they could be broken up into groups to find one constellation in the North, East, South or West. Then have each group point out their constellation under the dome. For graduation, they will each receive their own planisphere. 1. Practice for 5-10 minutes with the planisphere before going under the Dome. 2. Review constellations from last month’s lesson. 3. Quickly review the ecliptic, celestial sphere and horizon, zenith, celestial north pole, celestial meridian, declination and right ascension. 4. Point out the zodiac constellations. Have students point out constellations under the Dome.
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II. The Ecliptic. The apparent path the Sun appears to take through the sky as a result of the Earth's revolution around it. 1 This is the imaginary strip of sky that the Sun, Moon and planets appear to wander in.2 Our solar system can be thought of as somewhat flat, with most of the planets (the exception being Pluto) moving in very nearly the same plane.3 III. The Zodiac Usually the Moon and planets are not positioned exactly on the ecliptic line (because they're not located exactly in the same orbital plane as Earth), but lie within several degrees of it and form a sort of narrow strip encompassing the entire sky. We call this strip the Zodiac.4 A. The ecliptic runs exactly along the middle of the Zodiac. The Zodiac is usually considered to be 8 or 9 degrees to either side of the ecliptic line. B. Why do we call it "Zodiac" rather than "ecliptic strip"? Twelve constellations through which the ecliptic passes form the Zodiac. The name is derived from the Greek, meaning "animal circle," also related to the word "zoo," and it comes from the fact that most of these constellations are named for animals, such as Leo, the Lion, Taurus, the Bull and Cancer, the Crab. These names, readily identifiable on sky charts, are familiar to millions of skywatchers. 5 It is also sometimes called the "Road of the Sun."6 C. What can you find in the Zodiac? At night, you can see the 12 Zodiac constellations. If we could see the stars in the daytime, we would see the Sun slowly wander from one constellation of the Zodiac to the next, making one complete circle around the sky in one year. We also see the visible planets in our solar system in the Zodiac.
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"Understanding the Ecliptic and the Zodiac,"Space, http://www.space.com/spacewatch/ecliptic_030228.html. 2 Hathaway, "The Friendly Guide to the Universe," p. 383. 3 "Understanding the Ecliptic and the Zodiac,"Space, http://www.space.com/spacewatch/ecliptic_030228.html. 4 "Understanding the Ecliptic and the Zodiac,"Space, http://www.space.com/spacewatch/ecliptic_030228.html. 5 "Understanding the Ecliptic and the Zodiac,"Space, http://www.space.com/spacewatch/ecliptic_030228.html. 6 Rao, "Celestial Balancing Act: Why the Scorpion Lost His Claw," Space, http://www.space.com/spacewatch/scorpion_scales_030620.html
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Ancient astrologers were able to figure out where the Sun was on the Zodiac by noting which is the last constellation of the Zodiac to rise ahead of the Sun, or the first to set after it. Obviously, the Sun had to be somewhere in between. As such, each month a specific constellation was conferred the title of "House of the Sun," and in this manner each month-long period of the year was given its "sign of the Zodiac." D. Non-Zodiac constellations in the Zodiac. The number most commonly given is 12: Sagittarius, Capricorn, Aquarius, Pisces, Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra and Scorpio. 1. Ophiuchus, the thirteenth Zodiac constellation. There is another constellation that lies smack dab in the Zodiac strip of sky: Ophiuchus. In fact, the Sun spends more time traversing through Ophiuchus than nearby Scorpius. During 2003, the Sun officially resides in Scorpius for less than a week: from Nov. 23-29. It then moves into Ophiuchus on Nov. 30 and remains within its boundaries for more than two weeks -- until Dec. 17. Yet the Serpent Holder is not considered a member of the Zodiac and so must defer to Scorpius. We'll discuss that more under the dome. 2. 24 "would-be" Zodiac constellations. The number of Zodiac constellations depends on how you define the Zodiac strip of sky. Say you decide to include all of the constellations that are within 8 degrees on either side of the ecliptic. (Venus is the only naked eye planet that reaches more than 8° away from the ecliptic. ) You can quickly see that there are not 12 constellations of the zodiac but 24! That will include familiar constellations like Cetus the Whale, Corvus the Crow, Orion, Auriga, Pegasus and Canis Minor.7 E. Astrology. A. What is astrology? The familiar "star sign", or more precisely the "sun sign", under which a person is born refers to the position of the sun in the signs on the tropical ecliptic at the time of his or her birth.
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Shapiro, "The Real Constellations of the Zodiac," The list of 24 is: Aquarius, Cetus, Libra, Scorpio, Aries, Corvus, Ophiuchus, Scutum, Auriga, Crater, Orion, Serpens, Cancer, Gemini, Pegasus, Sextans, Canis Minor, Hydra, Pisces, Taurus, Capricorn, Leo, Sagittarius and Virgo.
http://www.griffithobs.org/IPSRealConst.html.
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B. Astrology and precession. Because of the precession of the equinoxes over the last three thousand years or so, the signs are out of phase with the astronomical constellations for which they are named by about a month.8 See Chart B following lesson. C. Example. Let's say you are a "Cancer." This means that you were born between June 21 and July 21. Theoretically, this means you have something in common with everyone else who is a "Cancer:" the Sun was "in" the constellation Cancer in that one-month period. This means that when you looked up in the daytime on your birthday, Cancer will be up, only you won't be able to see it because of the light of the Sun. On the evening of your birthday, you wouldn't be able to see the constellation Cancer because by that time, the Earth will have rotated such that the Sun is on the other side of the world, and Cancer with it. The trouble with this is that, due to prececession – the slight wobble of the Earth's axis in space – the Sun passes through the constellations nearly a month earlier than it did in Roman times. This throws all of the signs out of whack. So if you're a "Cancer," astronomically speaking you are probably a Gemini instead!9 IV. Dome: find the 12 Zodiac constellations; identify and reinforce ecliptic. 1. Spend 5-10 minutes teaching students how to use the planisphere. Break into groups and have each group find a seasonal zodiac constellation. 2. Have each child figure out his/her Zodiac sign. Hand out Chart A below to make this easier. 3. Point out the celestial sphere, ecliptic, celestial horizon, zenith, and celestial north pole. Point out the celestial meridian (beginning of spring) runs through Pisces. The celestial meridian is a longitude line (declination line). 4. Consider using the H.A. Rey cylinder to easily identify the 12 Zodiac constellations. 5. Switch to the starfield cylinder (or urban starfield) to find the Zodiac constellations. 6. Find Ophiuchus, the 13th Zodiac sign, and tell the story below.
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Wikipedia on-line encyclopedia, http://en.wikipedia.org/wiki/Zodiac. Kerrod, "The Book of Constellations," p. 23.
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OPHIUCHUS The Serpent Bearer Ophiuchus is a summer constellation visible in the East. There is some disagreement over the origin of the constellation Ophiuchus. Some Greek stories center around Heracles, who killed Draco. In Egypt, the constellation Ophiuchus is associated with a real person, Imhotep. Imhotep was a great philosopher, doctor and architect. Over 4,650 years ago, he designed and built the great step pyramid for Pharaoh Djoser at Saqqara on the Nile River (2650 B.C.E.). Most people who have studied this believe that Orphichus represents Asclepius, the Greek god of medicine. Asclepius was the son of Apollo and a nymph called "Coronis." He was taught medicine by the centaur Chiron. Asclepius became the Argonaut's surgeon and sailed with them on their ship. He managed to bring a number of people back to life, including the son of King Minos of Crete. Then Asclepius tried to revive Orion after he was bitten by the scorpion. Pluto, the god of the Underworld, learned of Asclepius' work and began to complain. He argued to Zeus that if Asclepius had his way, Pluto would soon be robbed of the entire population of Hades. Zeus agreed; men couldn't become immortal. So he sent a thunderbolt to end Asclepius' life. Asclepius was placed in the heavens with the Serpent, which is a symbol of renewed life. Ophichus is unusual: 1. It is the only constellation that lies on the ecliptic like the other 12 Zodiac constellations but isn't recognized as a Zodiac constellation. The reason Ophichus isn't recognized as a Zodiac constellation is that it wasn't always located in the ecliptic. Stars have "proper motion" because they are moving through space. Stars are so far away that it takes hundreds or thousands of years before we can discern their movement through space. (Like if you look at a highway close up, the cars seem to move fast, but if you look at a highway from far away, the cars seem not to move at all.) 2. It is very large – the eleventh largest in the sky. 3. It contains Barnard's Star, which is the fourth closest star to Earth, after Alpha, Beta and Proxima Centauri. It is only six lightyears away. It is a red star, but very hard to find without a telescope. Barnard's Star has the fastest proper motion of all of the stars, which means it is moving through space fastest. It changes position by the width of the full moon every 175 years.
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Chart A -- What's My Sign? March 21 – April 20 April 21 – May 20 May 21 – June 20 June 21 – July 21 July 22 – August 21 August 22 – September 21 September 22 – October 22 October 23 – November 21 November 22 – December 20 December 21 – January 19 January 20 – February 18 February 19 – March 20 Aries, the Ram Taurus, the Bull Gemini, the Twins Cancer, the Crab Leo, the Lion Virgo, the Virgin Libra, the Scales Scorpio, the Scorpion Sagittarius, the Archer Capricorn, the Sea Goat Aquarius, the Water-Bearer Pisces, the Fishes
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Chart B – Actual Astronomical Dates The actual astronomical dates of the zodiac constellations no longer coincide with the dates commonly used in astrology.10 Birthdates Sign Symbol Tropical March 21 - April 19 Sidereal April 14 - May 14 Actual Astronomical Dates (as of AD 2000) April 19 - May 13 May 14 - June 19 June 20 - July 20 July 21 - August 9 August 10 September 15 September 16 October 30 October 31 November 22 November 23 November 29 November 30 December 17 archer goat water fish November 22 December 21 December 22 January 19 January 20 February 18 February 19 March 20 December 16 January 14 January 15 February 12 February 13 March 14 March 15 - April 13 December 18 January 18 January 19 February 15 February 16 March 11 March 12 - April 18
Aries Taurus Gemini Cancer Leo Virgo Libra Scorpio Ophiuchus Sagittarius Capricornus Aquarius Pisces
ram bull twins crab lion virgin scale scorpion
April 20 – May 20 May 15 - June 14 May 21 – June 20 June 15 - July 16 June 21 – July 22 July 23 - August 22 August 23 September 22 September 23 October 22 October 23 November 21 July 17 - August 16 August 17 – September 16 September 17 October 17 October 18 November 16 November 17 December 15
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Wikipedia on-line encyclopedia, http://en.wikipedia.org/wiki/Zodiac.
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EXTRA DOME ACTIVITIES
These are extra activities to expand the Fifth grade curriculum. Additional activities and explanation of the cylinders can be found in the “Astronomy & More” binder on the storage room desk. In addition, peruse the Meteor and Moon binder for activities or educational material.
1. By Fifth grade, the students should be able to point out numerous
constellations using H.A. Rey, Greek Mythology, the Urban Sky and Starfield cylinders. To add variety in the lesson plans, point out the same constellations using the two Chinese cylinders or the Native American cylinder. Stories, activities and descriptive directions are provided in the “Astronomy & More” three ring binder. This binder is located on the desk in the planetarium storage room.
2. We locate our stars near the 40th degree North Latitude. a. Point out what the stars would look like if we were at the equator (0 degrees) or at the North Pole (straight up at 90 degrees). b. Light up the meridian degree projector to point out the angle differences from Orion to North Star. c. Using hands and fingers, try and measure the degree variations. See if this applies under the Dome, and if not, why? 1 finger width – 1 degree Fist width – 10 degrees Baby finger to Thumb width – 20 degrees. 3. Each month, volunteer instructors receive a copy of the Sky calendar. Using the Starfield cylinder, place the Moon and planets in relation to the appropriate constellations. 4. Put up the eight phases of the Moon. Have the students identify each phase. Place all the planets up on the Ecliptic path. 5. For an extra dome session (June), break up the students in groups to create their own cylinders. Using the transparent cellophane and markers found in the storage room’s plastic containers, have each group create a new cylinder around a story (The Seven Brothers – Cheyenne story on Big Dipper) or a constellation (Ophiuchus, the Serpent Slayer). One class researched various parts of Ophiuchus’s life, wrote it up, drew on the clear cylinder and each group narrated their story. This took two sessions. A drawing was held to see which student in the group got to take the cylinder’s home.
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