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Proficiency Step #5---Constellations This proficiency step will address the constellations and asterisms that have made the night sky both more familiar and somewhat confusing. As in the previous step, we will discuss the history and lore of the constellations as a whole—as well as a few of the more “recognized” individual constellations. There are 88 official constellations—too many to cover in great detail here. This proficiency step will serve as a “door opener” to the night sky. It is hoped that interested people will take advantage of the many resources available on the subject to become familiar with at least a dozen of the many interesting constellations. In fact, proficiency in the subject of constellations and asterisms will require at least a basic knowledge of 12 constellations. The choice of which 12 constellations one must learn is entirely up to each individual. The 88 modern Constellations Andromeda • Antlia • Apus • Aquarius • Aquila • Ara • Aries • Auriga • Boötes • Caelum • Camelopardalis • Cancer • Canes Venatici • Canis Major • Canis Minor • Capricornus • Carina • Cassiopeia • Centaurus • Cepheus • Cetus • Chamaeleon • Circinus • Columba • Coma Berenices • Corona Australis • Corona Borealis • Corvus • Crater • Crux • Cygnus • Delphinus • Dorado • Draco • Equuleus • Eridanus • Fornax • Gemini • Grus • Hercules • Horologium • Hydra • Hydrus • Indus • Lacerta • Leo • Leo Minor • Lepus • Libra • Lupus • Lynx • Lyra • Mensa • Microscopium • Monoceros • Musca • Norma • Octans • Ophiuchus • Orion • Pavo • Pegasus • Perseus • Phoenix • Pictor • Pisces • Piscis Austrinus • Puppis • Pyxis • Reticulum • Sagitta • Sagittarius • Scorpius • Sculptor • Scutum • Serpens • Sextans • Taurus • Telescopium • Triangulum • Triangulum Australe • Tucana • Ursa Major • Ursa Minor • Vela • Virgo • Volans • Vulpecula Any discussion of astronomical objects necessarily must include a definition of the “celestial sphere”. Imagine that a small marble was placed in the exact center of a basketball. If we call the marble “Earth” and the inside of the basketball—as seen from the marble—the celestial sphere, we can imagine all of the stars and visible objects in space as being “projected” onto the inside of the basketball. In reality every object in space is a different distance from the earth, but for the purposes of “remembering” and locating them all, it is handy to imagine them on an imagined plane around the earth. We can then divide this inside view of the sphere into sectors for the purpose of locating objects. What is a constellation, anyway? The International Astronomical Union divides the entire sky into 88 sections of varying size and shape—and which correspond to particular groupings of stars that represent certain shapes. Some well-known constellations contain instantly recognizable patterns of stars—while others have patterns that are less than obvious--and in some cases quite dim. Most of the 44 northern constellations are based on Greek traditions and are named after characters in Greek mythology. The constellation boundaries were drawn up by Eugene Delporte in 1930—and to this day are used to designate the location of objects on the celestial sphere. It is important to understand that the constellation is not the pattern defined by a group of stars, but rather, the section of the sky (established by Delporte) that contains the pattern—although many people refer to the patterns, themselves, as constellations. What is an asterism? Asterisms are simply groupings of stars that form recognizable shapes—but that are not representative of the constellation area, though they may (or may not) be part of a constellation figure. The best example of this is the Big Dipper which is instantly recognizable as a dipper, but is actually the hind quarters of Ursa Major (the big bear). The summer triangle is an easily found asterism in the summer sky and is made up of three of the brightest stars in the sky—each of which is actually in three separate constellation areas (Vega in Lyra, Deneb in Cygnus, and Altair in Aquilla). The Coathanger asterism (officially called Brocchi’s cluster) is very small and not at all noticeable with the naked eye—but easily viewed through binoculars. It is located about 1/3 of the way from Altair to Vega in the summer triangle in the constellation Vulpecula. There are many other asterisms in the northern hemisphere—and one can also envision and create one’s own asterism since they are not officially recognized landmarks in the sky. They can, however, be quite helpful in learning to locate objects in what could otherwise be a real confusing mess of stars. The ability to find at least three asterisms should be considered part of becoming “proficient” in this proficiency step. A few other asterisms: The “teapot” in Sagittarius, the “belt” of Orion, the “fishhook” of Scorpius, the “great square” of Pegasus, the “seven sisters”, and the “W” of Cassiopeia. We tend to think of constellations as a group of related stars that form a pattern, when in fact, most of the constellations consist of stars that are not related—that is, they are varying distances from Earth and their relative positions are simply a coincidence. It might be convenient to note here that the science of astronomy has existed for many centuries—much longer than the invention of telescopes. Ancient peoples found that dividing up the sky into “sectors” made things more manageable and easier to remember. The earliest references to the constellations were from the Middle-eastern Sky Myths of the 8th century BC, but the most complete early references can be found in the writings of the ancient Greek astronomer Eratosthanes and the Roman writer Hyginus. They were adapted to Greek culture from prior Sumerian and Babylonian cultures. Many other cultures had their own versions of constellations, including the Chinese, which had an elaborate and well-established set of “different” constellations. Many of the stars have Arabic names—a testament to the advanced astronomical “science” practiced by middle-eastern “astronomers” of centuries past. This proficiency step will deal primarily with constellations of the northern hemisphere since it is impossible to view many of the southern constellations from our Wisconsin location. Information about the southern constellations is abundant on the internet and in all public libraries. Most of the currently recognized northern constellations are variations of “star groupings” that were established by the ancient Greeks. Although the groupings have changed over the centuries with the influences of various cultures and prominent astronomers, the basic shapes and the lore accompanying the shapes has survived the ages and to this day are used to remember where things are in the night sky. The stories are many and varied—and while they are not required to remember the location of celestial objects, they can make the pursuit of astronomy more interesting and fun. The basis for most of the stories are from Greek Mythology. The Zodiac: Imagine, for a moment, that we are on that marble (the Earth) inside the basketball (the celestial sphere). The apparent path that the sun takes as the earth turns is called the Ecliptic. This is actually the path that the Earth takes as it orbits the sun, but from our point of view on Earth it appears that the sun is moving across the sky. The line it traces on the inside of the basketball as it goes all the way around the marble is the ecliptic. As it happens, there are 13 constellations that are along this line. As in many things in life, someone decided that one of them doesn’t count, but the other 12 comprise the constellations of the Zodiac. It might be a good idea at this point to describe the difference between Astronomy and Astrology. Astronomy is the study of the universe and everything in it (often generalized to the study of the night sky). Astrology is a “science” devoted to the belief that certain constellations along the ecliptic have an affect on the lives of humans. In astronomical circles, the zodiac is simply 12 (or 13) constellations that happen to lie along the line of the ecliptic. The 12 zodiacal constellations are: Aries, the ram; Cancer, the crab; Capricorn, the goat; Gemini, the twins; Leo, the lion; Libra, the scales; Pisces, the fish; Sagittarius, the archer; Scorpius, the scorpion; Taurus, the bull; and Virgo, the virgin. General Constellation Lore: Most ancient cultures saw pictures in the stars of the night sky. The earliest known efforts to catalog the stars date to cuneiform texts and artifacts dating back roughly 6000 years. These remnants, found in the valley of the Euphrates River, suggest that the ancients observing the heavens saw the lion, the bull, and the scorpion in the stars. The constellations as we know them today are undoubtedly very different from those first few--our night sky is a compendium of images from a number of different societies, both ancient and modern. By far, though, we owe the greatest debt to the mythology of the ancient Greeks and Romans. In Homer’s The Iliad, he describes the making of Achilles’ shield which had pictures of “the earth, and sky, and sea, the weariless sun and the moon waxing full, and all the constellations that crown the heavens, Pleiades and Hyades, the mighty Orion and the Bear, which men also call by the name of Wain: she wheels round in the same place and watches for Orion, and is the only one not to bathe in Ocean.” (Iliad XVIII 486-490) At the time of Homer, however, most of the constellations were not associated with any particular myth, hero, or god. They were instead known simply as the objects or animals which they represented--the Lyre, for instance, or the Ram. By the 5th century B.C., though, most of the constellations had come to be associated with myths, and the Catasterismi of Eratosthenes completed the mythologization of the stars. Despite the many mentions of the stars in Greek and early Roman texts, by far the most thorough star catalog from ancient times belongs to the Roman Ptolemy of Alexandria, who grouped 1022 stars into 48 constellations during the 2nd century A.D. Although Ptolemy's Almagest does not include the constellations which may only be seen from the southern hemisphere, it forms the basis for the modern list of 88 constellations officially designated by the International Astronomical Union. The influence of both the Greek and Roman cultures may be plainly seen; the myths behind the constellations date back to ancient Greece, but we use their Latin names. Mythology, of course, influenced the naming of many objects in the night sky, not just the constellations. The planets all bear names from Roman mythology. A Few Notable Constellations: One of the oldest constellations, Ursa Major (ER-suh MAY-jer), The Great Bear is also one of the best known. In particular are the seven stars which make up what is commonly known as the Big Dipper or the Plough. In Cherokee legend, the handle of the Big Dipper represents a team of hunters pursuing the bear. The Iroquois of Canada and the Micmac's of Nova Scotia believe that each spring the hunt begins when the bear leaves Corona Borealis, its den. Hunted by seven warriors, the bear isn't killed until autumn when it disappears from the sky. A new bear then emerges from Corona Borealis and the hunt begins again. The early Britons interpreted the Big Dipper as King Arthur's chariot. The Romans viewed it as a team of seven oxen, harnessed to the pole and driven by Arcturus. In Greek legend, Zeus and Callisto, a mortal, had a son called Arcas. Hera, Zeus's jealous wife turned Callisto into a bear. One day, while Callisto's son was out hunting he almost killed his mother. Rescued by Zeus, Callisto was placed in the heavens with her son, whom Zeus also transformed into a bear. Callisto is Ursa Major and Arcas is Ursa Minor. Ursa Major is full of unique celestial objects. The two outer edge stars that make up the "bowl" of the dipper are Merak, the top one, and Dubhe. Connect a line between the two, and extend it north a distance about five times the distance between them. It will connect with the North Star, Polaris. If you extend the handle of the dipper with a line, it will lead to the star, Arcturus, in the constellation, Bootes. In one Greek myth, the star represented the guardian, Arcturus, who kept the bears from straying from their path. Above the head of the bear are two galaxies, M81 and M82. Both are 12 million light years away, but M81 is one of the brightest galaxies in the sky. Finally, the Owl Nebula is located to the lower left of Dubhe. It is so named because some photographs reveal what looks like a pair of eyes. Most of the constellation is circumpolar, which means it can be viewed all year long. However, parts of the legs will disappear from the sky in the fall and reappear in the winter. Brightest Stars Magnitudes Galaxies Alioth 1.77 NGC 3031 (M81) Dubhe 1.79 NGC 3034 (M82) Alkaid 1.86 NGC 3077 Mizar 2.09 NGC 3079 Phad 2.44 NGC 3184 Psi 3.01 NGC 3198 Tanian Australis 3.05 NGC 3310 Talita 3.14 NGC 3556 (M108) Theta 3.17 NGC 3992 (M109) Megrez 3.31 NGC 5457 (M101) NGC 5475 NGC 3587 (M97--Owl Nebula) Winnecke4 (M40—Double Star) Orion (oh-RYE-un), the Hunter has been recognized for thousands of years. The Chaldeans knew this group of stars as Tammuz, named after the month in which the stars that make Orion's 'belt' become visible before sunrise. The Syrians called it Al Jabbar, the Giant. The Egyptians called it Sahu, the soul of Osiris. In Greek mythology, Orion was a giant and a great hunter. One legend tells how Artemis, the goddess of the Moon and of the hunt, fell in love with Orion. Her twin brother, Apollo, saw Orion swimming far out to sea. He challenged his sister to hit the faint dot among the waves. Artemis shot an arrow, hitting and killing Orion. Inconsolable, she placed his body in the heavens together with his hunting dogs. With the three stars that make Orion's belt, Rigel and Betelgeuse make this one of the most attractive constellations in the Northern Hemisphere from December to April. For most observers Orion is the most impressive constellation of the sky. With its large number of bright stars and the distinct group given by the three belt stars it is easy to find in the winter sky. Orion offers a wealth of interesting and famous objects like the great Orion Nebula M 42/43 and the Horsehead Nebula (at IC 434). The brightest star is Rigel (Beta Orionis), visible in the lower right. Against the convention, that greek letters are given in order of intensity, the second bright star Betelgeuse is named Alpha Orionis (Orions left 'shoulder'). Brightest Star Magnitude Open Clusters Nebulae Rigel 0.12 NGC 1981 NGC 1976 (M42) Betelgeux 0.5 NGC 2175 NGC 1982 Bellatrix 1.64 NGC 2068 Alnilam 1.70 IC 434 Alnitak 1.77 Cassiopeia (kass-ee-oh-PEE-uh) was the mother of Andromeda and the wife of Cepheus, the Ethiopian King of Joppa. The Romans believed this striking W-shaped constellation was Cassiopeia, chained to her throne as a punishment for her vain boastfulness. Cassiopeia is an easily-seen constellation that is in the far northern sky. It circles the pole star (Polaris) throughout the year and also straddles the Milky Way. The five major stars of Cassiopeia (also known as "The Lady of the Chair") are shaped like a "W" (or an "M," depending on your orientation). All of the stars in Cassiopeia are all less than second magnitude brightness. The brightest star in Cassiopeia is Schedar (alpha CAS), which is a multiple star that is pale rose in color and varies in magnitude from 2.2 to 2.8 magnitudes. The second-brightest, called Caph (beta CAS), is a white star of magnitude 2.4. Cassiopeia contains two open clusters, M52 (magnitude 7.3) and M103 (magnitude 7.4). The strongest radio source, Cassiopeia A, emanates from Cassiopeia; it is the remnant of a supernova which ocurred about A.D. 1660, and is 10,000 light years from us. Brightest Stars Magnitude Open Clusters Nebulae Gamma 2.2 NGC 7654 (M52) NGC 7635 Shedir 2.23 NGC 7789 NGC 281 Chaph 2.27 NGC 129 Ruchbah 2.68 NGC 457 Seign 3.38 IC 1805 Achird 3.44 NGC 581 (M103) NGC 1027 NGC 654 NGC 659 NGC 663 The Swan is one of the more obvious constellations in the summer skies. Because of its shape it is sometimes called the Northern Cross. Cygnus (SIG-nus) is the northern hemisphere's answer to the Crux. Cygnus straddles the northern Milky Way. One story claims that Cygnus is Orpheus, the hero of Thrace who sang and played his lyre so beautifully that wild animals and even trees would come and hear him play. It is said that Orpheus was transported to the skies as a swan so that he could be near his lyre. Cygnus is sometimes called the Northern Cross. Deneb, visible as the tail of the swan, is the brightest star of Cygnus with 1.26 mag. Together Deneb and Vega (in Lyra) form the famous summer triangle with the star Altair in the more southern constellation Aquila. A number of galactic deep sky objects reside in Cygnus, most striking of which is the so called North America Nebula near the intersection of the “cross.” Brightest Stars Magnitude Open Clusters Planetary Nebula Nebulae Deneb 1.25 NGC 6811 NGC 6826 NGC 6888 Sadr 2.20 NGC 6819 NGC 6960 Gienah 2.46 NGC 6834 IC 5067/70 Delta 2.87 NGC 6866 NGC 6992/5 Albireo 3.08 NGC 6871 NGC 7000 Zeta 3.20 NGC 6910 IC 5146 Xi 3.72 NGC 6913 M29) Tau 3.72 NGC 6939 Kappa 3.77 NGC 7092 (M39) This is the fifth largest constellation, although it is not the most obvious. One of the most famous of all of the classical heroes, Hercules (HER-kyu-leez) was incredibly strong and was the half mortal son of Zeus. He was named after the greatest Greek goddess, Hera. Hercules means 'glory (or honour) of Hera,' and he became a favorite with the gods. Apollo made his bow and arrows, Athene gave him a magnificent robe, Hermes provided him with a sword and Castor (the greatest warrior), taught him how to use it. Hephaestus, the smithy of the gods, made a golden breastplate for Hercules. Armed and protected, Hercules paraded through Greek mythology performing eight heroic acts and twelve labors. At the end of his life, as a reward for his bravery, Jupiter made him one of the gods, placing him in the sky. Hercules’ appearence is quite faint, but the central trapeze is not so hard to find. In Hercules is the brightest Globular Star Cluster of the northern hemisphere: M13. With a visual magnitude of 5.7 it can be seen by naked eye as a very faint object. A small amateur telescope will resolve individual stars in M13. The brightest star Alpha Herculis (3.1 mag) is Hercules’ left foot. Brightest Star Magnitude Globular Cluster Kornephoros 2.77 NGC 6341 (M92) Rutilicus 2.81 NGC 6205 (M13) Rasalgethi 3.0 Sarin 3.14 The Little Bear, also known as the Little Dipper, Ursa Minor (ER-suh MY-ner) looks like a spoon, or dipper, with the handle bent back. This collection of stars was recognised by the Greek astronomer, Thales in 600BC. According to Greek legend, Ursa Minor is Arcas, son of beautiful Callisto (Ursa Major, The Great Bear). Placed in the sky by Zeus, Ursa Minor and Ursa Major follow each other endlessly around the north celestial pole. This constellation is famous not only for being a “partner” to the ubiquitous “Big Dipper,” but it also has the honor of containing the conspicuous pole star, Polaris. The dipper, itself, is not particularly bright or important, but Polaris happens to approximately line up with the polar axis of the earth—that is, if a line were drawn from the south pole, through the Earth, through the north pole and out into space, it would point approximately at Polaris. Since the Earth spins on it’s axis, the entire sky appears to revolve around Polaris—one complete “spin” every day. There are no significant deep sky objects in Ursa Minor. Brightest Star Magnitude Polaris (North Star) 1.99 Kocab 2.08 Pherkad Major 3.05 Sagittarius (sadge-ih-TAIR-ee-us) is located on the Milky Way. It is one of the twelve constellations that make up the Zodiac, the most distinctive aspect of Sagittarius is the group of stars (asterism) within it, which look like a teapot, complete with spout and handle. Sagittarius is often thought to represent a centaur, half man, half horse, and is usually considered to be Chiron, identified with the constellation of Centaurus. However, Sagittarius holds a drawn bow which is aimed at Scorpius, not in character with Chiron who was known for his kindness and wisdom. Some say that Chiron was created to guide Jason and the Argonauts as they sailed on the Argo. Many deep sky objects reside in Sagittarius, including 15 Messier objects and the Milky Way’s brightest star clouds—and the center of our galaxy. There are open and globular clusters, nebulae, variable stars, double stars and galaxies—much to see—even with binoculars. It lies low in the northern summer sky, however, and is best observed during the summer months. The complex radio source Sagittarius A also eminates from this area. Astronomers believe that it is associated with a supermassive black hole at the center of the galaxy. Brightest Stars Magnitude Open Clusters Globular Clusters Planetary Nebula Nebulae Kaus Australis 1.85 NGC 6494 (M23) NGC 6626 (M28) NGC 6818 (M17) NGC 6514 (M20) Nunki 2.02 NGC 6520 Ascella 2.59 NGC 6531 (M21) NGC 6656 (M22) Kaus Meridionalis 2.70 NGC 6530 NGC 6637 (M69) NGC 6715 (M54) Kaus Borealis 2.81 NGC 6613 (M18) NGC 6681 (M70) Albaldah 2.89 IC 4725 (M25) NGC 6809 (M55) Alnasr 2.99 NGC 6716 NGC 6864 (M75) NGC 6523 (M8) NGC 6618 The Constellation Seasons: Learning the constellations can be a daunting task since many of the star groupings are faint and mostly do not really look at all like the “pictures” they represent. One way to keep the task manageable is to learn a few at a time. Since only a few of the constellations are circumpolar from our location (visible all year long as they rotate around the north star), it can be helpful to study the constellations by dividing them up according to the seasons that they are visible. After all, it is much easier to become familiar with Virgo in the late winter and spring months when it is visible in the night sky than it would be if it could not be seen at all—such as in the summer or fall. There are many sources of information that look at the constellations in this way—especially on the internet and in many notable books. The following constellations are listed by the season in which they are prominent in the northern hemisphere. Obviously, many will overlap seasons and will be visible somewhat longer. The Spring Constellations: Bootes Canes Venatici Coma Berenices Corvus Draco Hercules Libra Lupus Ophiuchus Scorpius Serpens Caput Serpens Cauda Ursa Major Ursa Minor Virgo Boo CVn Com Crv Dra Her Lib Lup Oph Sco Ser Ser UMA UMI Vir The Herdsman The Hunting Dogs Berenice's Hair The Crow The Dragon Hercules, the Hero The Scales The Wolf The Serpent Bearer The Scorpion The Serpent's Head The Serpent's Tail The Great Bear The Little Bear The Virgin The Summer Constellations: Aquarius Aquila Capricornus Cepheus Corona Australis Coronas Borealis Cygnus Delphinus Equuleus Lacerta Lyra Pegasus Piscis Austrinus Sagitta Sagittarius Scutum Vulpecula Aqr Aql Cap Cep CrA CrB Cyg Del Equ Lac Lyr Peg PsA Sge Sgr Sct Vul The Water Bearer The Eagle The Sea Goat Cepheus, a King of Ethiopia The Southern Crown The Northern Crown The Swan The Dolphin The Little Horse The Lizard The Harp The Flying Horse The Southern Fish The Arrow The Archer The Shield The Little Fox The Autumn Constellations: Andromeda Aries Auriga Camelopardalis Cassiopeia Cetus Eridanus Lepus Perseus Pisces Sculptor Taurus Triangulum And Ari Aur Cam Cas Cet Eri Lep Per Psc Scl Tau Tri Andromeda, daughter of Cepheus The Ram The Charioteer The Giraffe Cassiopeia, the Queen of Etheopia The Whale The River Eridanus The Hare The Hero The Fish The Sculptor The Bull The Triangle The Winter Constellations: Cancer Canis Major Canis Minor Crater Gemini Hydra Leo Leo Minor Lynx Monoceros Orion Sextans Cnc CMA CMi Crt Gem Hya Leo LMi Lyn Mon Ori Sex The Crab The Big Dog The Little Dog The Cup The Twins The Water Monster The Lion The Little Lion The Lynx The Unicorn The Hunter The Sextant A Word About Binoculars: For most of the history of humans on earth, astronomy was practiced using nothing more than the naked eye. It wasn’t until Galileo invented the telescope that we were able to “see” with considerably more depth and understanding the wonders of space. In these modern times, anyone with a few dollars can purchase a pair of binoculars that would absolutely amaze Galileo and his contemporaries. A simple pair of $20 binoculars and a desire to see a little more than you otherwise could without them—will bring a whole new universe into view. Find the constellation Vulpecula and look through the binoculars and the “Coathanger” asterism appears. Look at the Pleades in the constellation Taurus—you will see more than seven “sisters,” as well as some whispy nebulosity. Zero in on the dim “smudge” in the constellation Andromeda and a spectacular view of our nearest galaxy appears. In the early evening or pre-sunrise morning, the planet Venus can be a spectacular sight—as is distant Jupiter with it’s four easily-seen Galilean moons. There is a lifetime of surprises and wonder “up there” for anyone willing to look up through binoculars. …and if it leads to a more serious hobby or pastime, well…there are worse problems, to be sure. Proficiency: To show proficiency in this topic, it is suggested that one should demonstrate a general knowledge of the constellations; their history, lore, and reason for being. Familiarity with any 12 constellations from at least two seasons is considered adequate. A general description of the Zodiac and the definition of asterisms—along with at least 3 examples is required. And lastly, the ability to point out and identify the 12 constellations and 3 asterisms in the night sky to a fellow StarSplitter who has already passed this proficiency level. Suggested Sources to learn more: www.wyalusing.org (Click on “StarGazing” for lots of StarSplitters and Astronomy information) http://en.wikipedia.org/wiki/constellation (a very good discussion of the constellations—and some good links to other constellation related sites) http://en.wikipedia.org/wiki/List_of_constellations (a clickable list of links to all the 88 constellations) http://www.virtualcolony.com/sac/all-search-form.html (a large database with extensive deep sky information) http://www.astromax.com/con-page/con-88.htm (a complete list of the constellations with clickable links to each one—with star charts) Please watch the excellent Filippenko “lessons” on the VHS or DVD media in the StarSplitters library.