Presentation on theme: "Introduction to Constellations Backyard Astronomy."— Presentation transcript:
Introduction to Constellations Backyard Astronomy
The Night Sky People have watched the night skies for millions of years. Some just out of curiosity. Some out of boredom. Some looking for portents, either good or bad. However, the one thing that they all saw was that there was a pattern in the way the stars revolved around the heavens.
The Night Sky You need only to look up for a few hours to begin to see these same patterns yourself. Like the Sun, stars rise in the east and set later in the west. Planets follow this same pattern unless they are in a retrograde period, though these periods are not especially common.
What You Need for Stargazing You don’t really need anything, but some things are handy, like… Complete darkness-Don’t laugh, it’s not that easy to find. Rural area are slowly being urbanized, bringing their lights with them. Light pollution is a real problem.
What You Need: Darkness Darkness means keeping up with the phases of the moon, too. When the moon is waxing past half full, it’s quite hard to see.
What You Need: Star Map/ Planesphere It is handy to have a star map to help get you oriented. Star Maps are also called planespheres. You can find them in hobby stores for a couple of bucks.
Finding Polaris and Why Polaris (or the North Star) is where you want to start. Because Polaris is aligned with the Earth’s axis of rotation, it remains fixed, with all the other planets and stars appearing to move around it. It is the one star that remains fixed at all times.
Getting Oriented or Where the Heck is North? Yea, you have to find north. It’s where Polaris (or North Star) is. You’ll need a compass or major highway to orient yourself. Highway 17 is good because it runs due north and south. You can make a compass with a needle, magnet and a cup of water. Just rub the needle across a magnet (see your refrigerator) or leave it attached overnight. Then rub the needle across your nose and place it in the cup very gently. It will float. It will turn north.
Figuring the Angle Once you’ve decided where north is (right ascension), face in that direction. Next you have to figure declination (up and down). Extend your arm and make a fist. Put the bottom of your fist on the horizon. The top of your fist is about 8 0 higher. Place your other fist on top of your first. You’ve now measured 16 0 up from the horizon. Polaris is located between 25 0 and 30 0 above the horizon. Polaris is faint, so look carefully!
Another Way to Find Polaris If all that compass making and angle junk is just too complicated, there is another way to find Polaris. Find the Big Dipper (part of a constellation). Most people recognize this asterism. The two stars that form the front of the cup of the dipper define a line pointing to Polaris.
Now That You’re Oriented, It’s Time to Explore. You’re pointed in the right direction, but what now. Stars and constellations move constantly and seasonally. What am I looking for? What you need is a star map.
Ursa Minor Once you’ve located Polaris, you’re ready to identify your first constellation. Polaris is the last star located in the handle of the asterism, the Little Dipper. The name of the constellation that contains the Little Dipper is Ursa Minor or Little Bear.
Ursa Minor Ursa Minor, also called the Little Dipper, is a circumpolar constellation. This means it never sets in the northern sky. The true figure represented by the stars is the Little Bear. There are several mythological stories behind these famous constellations. In Greek myth, Zeus was having an affair with the lovely Callisto. When his wife, Hera, found out she changed Callisto into a bear. Zeus put the bear in the sky along with the Little Bear, which is Callisto's son, Arcas.
Ursa Major Ursa Major is probably the most famous constellation, with the exception of Orion. Also known as the Great Bear, it has a companion called Ursa Minor, or Little Bear. Everyone living in the Northern Hemisphere has probably spotted the easily recognized portion of this huge constellation. The body and tail of the bear make up what is known as the Big Dipper. Several different cultures saw a big bear in the sky. The ancient Greeks had a few different stories to explain how the animal ended up there. In one story, Hera discovered Zeus was having an affair with Callisto and turned her into a bear. Zeus put her in the sky along with her son, Arcas, who became the Little Bear.
Draco Draco the dragon, is only present in the Northern Hemisphere, so those living in the Southern Hemisphere will never see this long constellation. The easiest way to spot Draco is by finding his head. It consists of four stars in a trapezoid, burning brightly just north of Hercules. From there, the tail slithers through the sky, eventually ending between the Big and Little Dippers. It can be difficult to trace Draco in the night sky. From the head, follow the body north towards Cepheus. It suddenly shifts south and west, ending up between the two dippers. The end of the constellation is held by Thuban, which was the pole star over 4,000 years ago.
Aquarius: The Water Bearer In Greek mythology Aquarius was Ganymede, "cup-bearer to the gods". Alpha Aquarii ("Sadalmelik") and beta Aquarii ("Sadalsuud") are twin supergiants with nearly identical names. The names mean, respectively, "The Lucky One of the King" and "The Luckiest of the Lucky". Gamma Aquarii shares in the good fortune: "Sadachbia": "The Lucky Star of Hidden Things" Incidentally, if the "Age of Aquarius" was celebrated in the 1960s, the real event is still some 600 years off: at that time Aquarius will contain the vernal equinox, marking the return of the Sun into the northern celestial hemisphere.
Aries: the Ram Aries, "The Ram", is an ancient constellation which was of considerable importance since the sun passed through it at the vernal equinox. This point has now moved into Pisces, but the vernal equinox is still known as the First Point of Aries. In another six hundred years the point will have moved into Aquarius. The Ram in question may have been the one whose golden fleece was the object of Jason's quest. There is some reason to believe that the Greeks just took over a much older horned animal at this time of the year; the horn being a symbol for fecundity, renewal, and so on. As the Sun came into this constellation, at the vernal equinox, the year itself was being renewed.
30 Capricornus the Sea-Goat The Sea Goat or Goat-Fish, as a creature with the head and body of a goat and the tail of a fish, may well have originated from Assyro-Babylonian depictions of their god of wisdom Oannes, who was half-man, half-fish.
Gemini The Twins Gemini, the Twins, are really only half-brothers. They share the same mother (Leda) but have different fathers. Castor's father was a king of Sparta, Tyndareus - who would be chased from his throne but later rescued by Heracles (who nevertheless wound up killing him). The father of Pollux was none other than Zeus, or Jupiter. Zeus visited Leda on her wedding night in the guise of a swan. Thus the twins would be born. (In fact two twins came from this double union, but let's not complicate the matter even more...)
Leo: The Lion The first on the list of Heracles' labors was the task of killing the Nemean Lion, a giant beast that roamed the hills and the streets of the Peloponnesian villages, devouring whomever it met. The animal's skin was impervious to iron, bronze, and stone. Heracles' arrows harmlessly bounced off the lion; his sword bent in two; his wooden club smashed to pieces. So Heracles wrestled with the beast, finally choking it to death. He then wrapped the lion's pelt about him; it would protect him from the next labor: killing the poisonous Hydra.
Libra: The Scales Libra means "The Scales" or "Balance", so named because when the zodiac was still in its infancy, some four thousand years ago, the sun passed through this constellation at the autumnal equinox (21 September). At the two equinoxes (Spring and Autumn) the hours of daylight and darkness are equal. As a symbol for equality, the constellation came to represent Justice in several middle Eastern cultures. However, the Greeks had a different perspective; at one time Scorpius, which lies just to the east, was much larger, and the stars that make up Libra were then known as the Claws of the Scorpion.
Pisces: The Fish Pisces is an ancient constellation derived, some say, from the story of the terrible Greek god Typhon. (This is not the Chinese word for "big wind", which - in English - is of course spelled "typhoon". The French, however, spell this word "typhon", which adds to the confusion. It is possible that the Chinese borrowed the word from the Greek. The modern Greek equivalent is spelled "tau upsilon phi omega nu" and means "cyclone".)
Sagittarius It was the Romans who named the constellation Sagittarius ("sagitta" is Latin for `arrow'), although several stars carry Arabic names which identify just which portion of the constellation they represent. Sagittarius has a muddled history. In ancient times the asterism of three bright stars in a curved line was seen as a bow to some, leading both Greek and Roman writers to confuse the constellation with Centaurus.
Scorpius: The Scorpion As mentioned regarding Orion, Gaia may have sent the scorpion to kill the mighty hunter, as he had vowed to rid the earth of all wild animals. Or Apollo might have told Gaia of Orion's boast, fearful that Orion had designs on Apollo's sister Artemis. In any case it was Gaia who sent the scorpion to kill Orion. Later the animal would chase Orion across the heavens, but it could never catch him, for the scorpion was so placed that it would rise in the east only after Orion had safely disappeared over the western horizon.
Taurus: The Bull Is Taurus attacking Orion, the Hunter, or are the Horns of the Bull the real story? The horn was a symbol of fertility and bountiful riches in many cultures for thousands of years, and it is probably the case here, for the constellation would have announced the Vernal Equinox at around 4000 BC.
Virgo: The Virgin Virgo is the second largest constellation (after Hydra). As a member of the Zodiac, Virgo has a number of ancient myths and tales. The Sun passes through Virgo in mid-September, and is therefore the constellation that announces the harvest. Virgo is often represented as a "maiden" (as its name indicates). In antiquity, she may have been Isis, the Egyptian protectress of the living and the dead and the principal mother goddess.
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