vendredi 12 septembre 2008
Some references name a certain "Arion" as the inspiration for the constellation.
There were two Arions in antiquity. One was a (mythic?) poet who may have lived in the eighth century BC. This Arion, travelling from Sicily to Corinth, was thrown overboard by the ship's crew, eager for the valuables he was carrying. A dolphin is said to have rescued the poet. But this dolphin probably isn't the constellation's origin.
The second Arion was a son of Poseidon and Demeter, and was in fact a horse (like his half-brother Pegasus). Instead of hooves, he had feet on his right side. And, unlike most horses, he could talk. But this Arion also has nothing to do with the constellation.
It is most likely however that the constellation is associated with Poseidon. It was probably his way of thanking one of his messengers for a job well done.
As God of the Sea, Poseidon had fifty sea-nymphs at his court. These were all born of Nereus and known therefore as the Nereids.
While Poseidon had many casual love affairs, when he set out to find a wife he was concerned that she be accustomed to life in the sea. His first choice was Thetis, one of the fifty Nereids. But he learned that any son born of Thetis would grow to become greater than his father. Clearly Poseidon couldn't accept that prophecy.
As a side note, Thetis married Peleus, a mortal, and they had a famous son named Achilles. Thetis dipped Achilles in the river Styx to make him invulnerable to his enemies. As most people now knows, since his mother grasped him by the heels, they were the only part of Achilles which were vulnerable. Wouldn't you know, the day would come when he'd get a poisoned arrow in his heel and die from it.
Poseidon's next choice in marriage was a sister of Thetis, called Amphitrite. But when Poseidon pressed Amphitrite to marry him, she was quite disgusted by the thought and fled to the far-off Atlas Mountains. Poseidon sent a number of messengers to persuade her to return, as his wife, to his underwater realm.
The messenger who succeeded in this task was the dolphin Delphinus. Amphitrite was so beguiled by Delphinus' pleadings she relented and returned to Poseidon and became the Queen of the Sea. They had many children.
Delphinus was later put in the heavens as a constellation by a grateful Poseidon.
The constellation's Bayer stars are not complete, and are mostly in the fourth and fifth magnitude range.
Delphinus has several fine binaries, a Mira-type variable, and a very remote globular cluster.
Beta Delphini is a very close visual binary with orbit of 26.7 years. Epoch 2000 values: 4.0, 4.9; PA 343º, separation 0.5".
Gamma1 and gamma2 Del form a fine binary with (perhaps) subtle colour change (observers argue over this; some find them both yellow, others that the companion is greenish or bluish): 4.5, 5.5; PA 268º, 9.6"
Struve 2725 is a wonderful sight in the same field as gamma Del (to the SW): 7.3, 8.0; PA 9º, separation 5.7".
What is the Dolphin?The Dolphin is either the dolphin who won the Sea God Poseidon a wife, or the dolphin that saved the life of the famous poet and musician Arion, a real person who lived about 600 B.C.E.
The Dolphin MatchmakerPoseidon began to seek a wife in the aftermath of the great war in which the elder gods were overthrown to put Poseidon and his fellows of the generation of the younger gods in power. The Sea God courted the sea nymph Amphitrite, but she was repelled by his rough manners, and fled from him. Poseidon sent the dolphin after her. The gentle dolphin pled Poseidon's case with the nymph, speaking of the god in the most glowing terms, and eventually Amphitrite agreed to become wife to Poseidon. In gratitude, the god set an image of the dolphin among the stars to be remembered forever.
The Homesick MusicianAnother story tells of the poet and musician Arion who had earned a fortune in the court of King Periander of Corinth. Arion spent many years in Corinth, but he had not been born there. And later in his life he became homesick for his native land. He begged the king for permission to make a visit home again.
How the Dolphin Saved the MusicianOn the journey home, Arion was set upon by the sailors of his ship, who proposed to throw him overboard and divide his possessions among themselves. Arion tried to delay his demise by singing a beautiful hymn to Apollo. The god Apollo was so pleased that he sent a dolphin to carry Arion off to safety.
Apollo Carries the Dolphin into the StarsWhen the crew of the ship returned to Corinth, they were arrested. Arion recovered his possessions, and the crew was executed. In gratitude to Apollo, Arion had a small dolphin made and set up in the Temple of Apollo at Corinth. Apollo later translated the dolphin statue up to the stars so that humankind might honor the brave and friendly little dolphin forever.
Another story, given by Hyginus and Ovid, says that this is the dolphin that saved the life of Arion, a real-life poet and musician of the seventh century BC. Arion was born on the island of Lesbos, but his reputation spread throughout Greece for he was said to be unequalled in his skill with the lyre. While Arion was returning to Greece by ship from a concert tour of Sicily and southern Italy, the sailors plotted to kill him and steal the small fortune that he had earned.
When the sailors surrounded him with swords drawn, Arion asked to be allowed to sing one last song. His music attracted a school of dolphins which swam alongside the ship, leaping playfully. Placing his faith in the gods, Arion leaped overboard – and one of the dolphins carried him on its back to Greece, where Arion later confronted his attackers and had them sentenced to death. Apollo, god of music and poetry, placed the dolphin among the constellations, along with the lyre of Arion which is represented by the constellation Lyra.
Two stars in Delphinus bear the peculiar names Sualocin and Rotanev, which first appeared in the Palermo Catalogue of 1814 compiled by the Italian astronomer Giuseppe Piazzi. Read backwards, these names spell out Nicolaus Venator, the Latinized form of Niccolò Cacciatore, who was Piazzi’s assistant and eventual successor at Palermo Observatory. It is usually said that Cacciatore was responsible for the naming, which would make him the only person to have named a star after himself and got away with it. However, it is equally possible that the names were applied by Piazzi to honour his heir apparent, or “dauphin” (dolphin).
The constellation was once popularly called Job’s Coffin, presumably from its elongated box-like shape, although sometimes this name is restricted to the diamond formed by the four stars Alpha, Beta, Gamma, and Delta Delphini. Who originated the name Job’s Coffin, or when, is not known.
Cette constellation fut également connue sous le nom du Chameau chez les astronomes arabes et de la Baleine de Jonas chez les Hébreux.
Les deux étoiles les plus brillantes de cette constellation portent des noms traditionnels étranges, Sualocin (α Delphini) et Rotanev (l'étoile β). Ils ont une origine peu commune : apparaissant pour la première fois sur une catalogue d'étoiles publié par l'observatoire de Palerme en 1814, ils viennent en fait de Nicolaus Venator écrit à l'envers, le nom latinisé de Niccolo Cacciatore (Cacciatore et Venator signifiant chasseur), l'assistant directeur de l'observatoire à la publication du catalogue.
According to the first one, Greek god Poseidon wanted to marry Amphitrite, a nereid. She, however, wanting to protect her virginity, fled to the Atlas mountains. Her suitor then sent out several searchers, among them a certain Delphinus. Delphinus accidentally stumbled upon her and was able to persuade Amphitrite to accept Poseidon's wooing. Out of gratitude the god placed the image of a dolphin among the stars.
The second story tells of the Greek poet Arion of Lesbos (7th century BC), a court musician at the palace of Periander, ruler of Corinth. Arion had amassed a fortune during his travels to Sicily and Italy. On his way home from Tarentum his wealth caused the crew of his ship to conspire against him. Threatened with death, Arion asked to be granted a last wish which the crew granted: he wanted to sing a dirge. This he did and while doing so flung himself into the Sea from where he was rescued by a dolphin which had been charmed by Arion's music. The dolphin carried Arion to the coast of Greece and left.
The version of the tale that goes back to Eratosthenes says that Zeus one day took a fancy to the nymph Nemesis, who lived at Rhamnus, some way north-east of Athens. To escape his unwelcome advances she assumed the form of various animals, first jumping into a river, then fleeing across land before finally taking flight as a goose. Not to be outdone, Zeus pursued her through all these transformations, at each step turning himself into a larger and swifter animal, until he finally became a swan in which form he caught and raped her. Hyginus tells a similar story, but does not mention the metamorphoses of Nemesis. Rather, he says that Zeus pretended to be a swan escaping from an eagle and that Nemesis gave the swan sanctuary. Only after she had gone to sleep with the swan in her lap did she discover her mistake.
In both versions the outcome was that Nemesis produced an egg which was then given to Queen Leda of Sparta, some say by Hermes and others say by a passing shepherd who found the egg in a wood. Out of the egg hatched the beautiful Helen, later to become famous as Helen of Troy.
A simpler alternative says that Zeus seduced Leda in the form of a swan by the banks of the river Eurotas; with this story in mind, Germanicus Caesar refers to the swan as the ‘winged adulterer’. Leda was the wife of King Tyndareus of Sparta, which considerably complicated the outcome because she also slept with her husband later the same night.
According to one interpretation, she gave birth to a single egg from which hatched the twins Castor and Polydeuces as well as Helen. The shell of this egg was said to have been put on display at a temple in Sparta, hanging by ribbons from the ceiling. A rival account says that Leda produced two eggs, from one of which emerged Castor and Polydeuces while from the other came Helen and her sister Clytemnestra. To add to the confusion, Polydeuces and Helen were reputedly the children of Zeus, while Castor and Clytemnestra were fathered by Tyndareus. Castor and Polydeuces are commemorated by the constellation Gemini, where Polydeuces is better known to astronomers by his Latin name, Pollux.
Cygnus’s brightest star, Deneb, marks the tail of the swan; its name comes from dhanab, the Arabic word for ‘tail’. The Greeks had no name for this prominent star. Deneb is a highly luminous supergiant, over 3000 light years away, the most distant of all first-magnitude stars. It forms one corner of the so-called Summer Triangle of stars completed by Vega in the constellation Lyra and Altair in Aquila.
The beak of the swan is marked by a star named Albireo, revealed by small telescopes to be a beautiful coloured double star of green and amber, like a celestial traffic light. The German historian Paul Kunitzsch has traced the tortuous history of the name Albireo. It started with an Arabic translation of the Greek word for ‘bird’, ornis, the name by which both Aratus and Ptolemy knew the constellation. In the Middle Ages this Arabic name was mistranslated back into Latin, where it was described as ab ireo, meaning that it was thought to come from the name of a certain herb. This phrase was itself mistaken for an Arabic name and was rewritten as albireo. Hence the name Albireo, although it looks Arabic, is completely meaningless.
Cygnus lies in the Milky Way and hence contains many attractive star fields for sweeping with binoculars. Its most celebrated object cannot be seen by optical means at all: a black hole, called Cygnus X-1 because it is a strong source of X-rays, which lies halfway along the swan’s neck.
Son nom provient de l'arabe ذنب Al Dhanab, la queue. Le même nom fut donné à d'autres étoiles, notamment Deneb Kaitos, l'étoile la plus brillante de la constellation de la Baleine.
Deneb, Alpha Lyrae (Véga) et Alpha Aquilae (Altaïr), trois étoiles très brillantes, sont très visibles en été dans le ciel nocturne et forment ce qu'on appelle le triangle d'été.
La distance exacte de la Terre à Deneb est mal connue ; la plupart des étoiles situées à des distances similaires ne sont pas visibles à l'œil nu et ne peuvent être identifiées que sur des catalogues d'étoiles quand elles sont connues. Différentes sources donnent des distances variant entre 1600 et 3200 années-lumière (500-1000 parsec). La détermination de telles distances est très difficile : la parallaxe ne pouvant être utilisée (le satellite Hipparcos donne une parallaxe de 0,001 arcsec, ce qui correspond à une distance de 1000 parsec ; mais l'erreur estimée est 60%).
Sa luminosité est environ 60 000 fois plus élevée que celle du Soleil : si Deneb était une source ponctuelle de lumière située à la même distance que le Soleil, sa lumière serait plus intense que la plupart des lasers industriels.
Sans surprise, Deneb est une supergéante bleue, 200 fois plus grande que le Soleil (placée à sa place, elle s'étendrait bien au-delà de l'orbite terrestre), l'une des plus grande que l'on connaisse et une masse de 25 fois celle du Soleil. Elle finira vraisemblablement en supernova d'ici un million d'années.
Cette étoile est encerclée par une nébuleuse diffuse appelée IC 1316, ou la Région de Gamma Cygni. Sadr représente également une ville d'Irak.
Epsilon Cygni is a cool orange giant star that is, as many visible stars tend to be, well along in terms of its stellar evolution. While young in comparison to the Sun its larger mass gives it a much shorter lifespan, and the star is in the beginning stages of its death. It's 72 light-years from the earth.
The name "Gienah" derives from the Arabic word for wing, جناح janāħ.
Un autre nom est Al Fawaris (الفوارس), signifiant "Les cavaliers" ; nommée d'après un ancien astérisme arabe du Cygne qui comprenait Delta Cygni.
Swans occur throughout the Greek myths; often one of the principal gods has occasion to transform himself into a swan, usually to seduce some attractive nymph or even a queen. Zeus, for example, felt he had a better chance with Leda, the King of Sparta's wife, should he turn himself briefly into a swan, just on her wedding night. The result was Pollux, half-brother of Castor.
The swan commemorated in the night skies, at least as far as the Greeks are concerned, isn't precisely known. It may be Cycnus, son of Poseidon.
Zeus had two brothers, Hades and Poseidon. When the three of them overthrew their father Cronus, they drew lots for their realm. Hades won the Underworld, Zeus the Heavens, and Poseidon the Seas.
Poseidon soon wished to dominate the earth as well, and contested Athene for the right. All the gods cast their vote, and Athene won by a single vote.
Cycnus, Poseidon's son, had been exposed at birth, lain out on the seashore to die. However, a swan took pity and flew down to care for the newborn.
Cycnus became the king of Colonae, a city north of Troy, but he wasn't a particularly good king. He set his own children adrift on the sea when his new wife fell in love with one of his sons (Tenes). He then killed his wife when he found she had lied to him.
Cycnus defended Troy when Achilles' onslaught. However in their individual struggle, Achilles proved too strong, as he choked the life out of Cycnus. Poseidon grieved for his son and turned him into a swan.
There are another three obscure Greek gods named Cycnus, all of which have something to do with swans. The Greeks always linked names with their like-sounding counterparts. The Greek word for swan is "kuknos" which was close enough to "cycnus" to explain its etymology.
Despite the myths, this constellation was known simply as "Ornis" (Bird) to the Greeks. It was the Romans who named it Cygnus and who adopted the Greek myths to explain its name.
The Arabs (and other cultures since then) saw the constellation as a hen.
Alpha Cygni is known as Deneb, from Al Dhanab al Dajajah (the Hen's Tail). It marks the tail of the swan.
This is a supergiant (more than a hundred times the diameter of the Sun) with a very high luminosity. Since it is so far away (3200 light years) its real brilliance is lost in space.
Beta Cygni is called Albireo, which is really a mistake. The words written in a sixteen-century edition of Ptolemy's Almagest, had been "ab ireo" (the meaning of which rests a mystery). The Arabs called it "Al Minhar al Dajajah", the Hen's Beak.
This is a magnificent binary with a nice colour contrast (see below).
Gamma Cygni is "Sadr", from Al Sadr al Dajajah, "The Hen's Breast". Between gamma and beta Cygni is the Cygnus Star Cloud, a vast region of exceptional beauty.
Epsilon Cygni is "Gienah", from Al Janah, "The Wing".
Beta1 and beta2 form an extraordinary binary: gold and blue (or perhaps yellow and blue-green).
The component is quite wide, making it a popular object for binoculars.
AB: 3.1, 5.1; PA 54 degrees, separation 34.3".
Delta Cygni is a visual binary with an orbit of 828 years. Presently the values are: 2.9, 6.3; 224º, 2.5".
Mu Cygni is another visual binary (4.8, 6.1) with a long orbit, 789 years. For the next fifty years the orbit will continue to appear to approach the primary (as seen from the earth). The 2000.0 values are: 309º, 1.85".
Tau Cygni is a visual binary with a 49.9 year orbit: 3.9, 6.8. The 2000.0 year values are PA 328º, separation 0.8".
30 Cygni and 31 Cygni [omicron1] form a wonderful triple, suitable for binoculars:
AB: 4.0, 5.0; 333º and separation 338" (orange and turquoise). C: 7.0; 173º, separation 107" (blue).
61 Cygni is another fine binary of two orange stars: 5.2, 6.0. The 2000.0 values are PA 150º, and separation 30.3".
61 Cygni also holds the distinction of being the first star to have its parallax measured. This occurred in 1838, by Friedrich Wilhelm Bessel, a German astronomer.
Distance (Light Years) 386 ± 26
Visual Magnitude 3.05
Color (B-V) 1.13
Names For This Star
The name of this star looks Arabic, but it isn't. Actually the name of this seems to derive from the Latin phrase ab ireo applied to the constellation of Cygnus in the 1515 edition of Ptolemy's Almagest.
Description of the Star
Burnham describes Albireo as one of the most beautiful double stars in the sky, consisting of a bright "golden yellow" primary with a blue or "sapphire" companion.
The brighter star Albireo A is a K3II bright giant. This type of star is cooler than the sun, with an effective temperature of approximately 4100 K. It is probably about 20 times larger in radius than the sun and 100 times as luminous.
The The Bright Star Catalog suggests additional components at separations from A well under one sec of arc. The Hipparcos Catalog lists a C component at a separation of 0.389 seconds of arc (46 AU separation at the distance of the star). The C component is some 2 magnitudes dimmer than A.
Distance (Light Years) 3200 ± 1800
Visual Magnitude 1.25
Color (B-V) 0.09
Names For This Star
Other names for this star are Deneb el Adige, Arided, Aridif, Gallina, or Arrioph.
The commonly recognized name Deneb is derived from the Arabic phrase Al Dhanab al Dajajah meaning "The Hen's Tail."
Arided derives from an earlier Arabic designation of the constellation. Its meaning is unclear.
Aridif and Arrioph derive from the Arabic name Al Ridf, meaning "The Hindmost", which certainly describes the star as it lies in the tail of the Swan of Cygnus.
The name "Gallina" is Latin and means "hen." It was sometimes used in the past to name the constellation, but later appeared as a name for the brightest star in the constellation.
Description of the Star
Deneb is a white A2Ia supergiant star. Assuming a distance of 1600 ly, Burnham estimates the luminosity of Deneb to be 60,000 times that of the sun. At 3200 ly, the luminosity would be nearer to 250,000 times that of the sun. Burnham estimates the mass at 20 times that of the sun.
Distance (Light Years) 72.06 ± 0.84
Visual Magnitude 2.48
Color (B-V) 1.03
Names For This Star
Gienah derives from the Arabic Al Janah meaning "The Wing." The star should probably be called "Gienah Cygni" to distinguish it from the Gienah in Corvus.
Description of the Star
Gienah Cygni is a cool, orange K0-III giant star 40 times as luminous as the sun. The spectral type implies a temperature of perhaps 4500 K, a mass more than 4 times that of the sun and a radius maybe 16 times greater.
Gienah has a dim 13th magnitude companion designated Gienah C lying 78 seconds of arc from the A component, corresponding to a projected distance of 1700 AU. (The B component seems not to be physically associated with the system; it is merely a background star that appears at a small angular separation from A.)
Distance (Light Years) 1520 ± 360
Visual Magnitude 2.23
Color (B-V) 0.68
Names For This Star
Sadr, alternatively Sador or Sadir, derives from the Arabic name for the star Al Sadr al Dajajah, "The Hen's Breast."
The name of the star reflects the Arabic idea of the constellation of Cygnus, that is, as a hen rather than a swan.
Description of the Star
Sadr is a yellowish F8Ib supergiant star having a luminosity of perhaps 20,000 times that of the sun. The spectal type implies a mass about 10 times that of the sun and a diameter maybe 100 times that of the sun.
The Brighter Stars of Cygnus
ZeusThe Swan is the god Zeus in disguise flying off to seduce a woman. Exactly which woman is in some question.
NemesisIn some stories the target of Zeus' affections is the nymph Nemesis, and the outcome of Zeus' conquest is an egg, which was given to Queen Leda of Sparta. From the egg hatched the beautiful child who was to become Helen of Troy.
Queen LedaIn other versions of the story, it was Queen Leda herself, who was seduced by Zeus, but nevertheless slept with her husband King Tyndareus on the very seem evening. There was still an egg produced as the result of the coupling - or even two eggs. After all Zeus had taken the form of a bird. From the egg - or eggs, came the Twins Castor and Polydeuces (known to the Romans as Pollux). We see the Twins in the sky as the Gemini.
Helen and ClytemnestraSome say that there were two girls born from the eggs as well, Helen and her sister Clytemnestra.
Helen and Polydeuces were the children of Zeus and immortal. Castor and Clytemnestra were the children of Leda's mortal husband Tyndareus and were therefore mortal.
Orpheus was transformed into a swan after his murder, and was said to have been placed in the sky next to his lyre (Lyra).
Finally, it is said that a king named Cycnus was a relative or lover of the ill-fated Phaëthon. The son of Apollo, Phaethon tricked his father into allowing him to ride the chariot of the Sun, but lost control and was struck down by Zeus. Grief-stricken after Phaëthon's death, and determined to give his remains a proper burial, Cycnus dove to the bottom of the river Eridanus to find him. He dove so many times into the river that he was transformed into the swan Cygnus, and is visible in the sky today.
Cygnus, together with other constellations in the Zodiac sign of Sagittarius (specifically Lyra and Aquila, together with Sagittarius itself), may be a significant part of the origin of the myth of the Stymphalian Birds, one of The Twelve Labours of Heracles.
In Chinese mythology, the constellation Cygnus is the site of the once-a-year magpie bridge (鹊桥, Que Qiao) which connects the lovers Niu Lang and Zhi Nu (see Qi Xi).
In Ovid's Metamorphoses, there are three people named Cygnus, all of whom are transformed into swans. The first is the relative of Phaethon mentioned above, who is the son of Sthenelus and king of Liguria. The second is a boy from Tempe, to whom Phyllius gives several tamed animals as gifts. When Phyllius refuses to give Cygnus a tamed bull that the boy demands, Cygnus throws himself off a cliff in a fit of spite. Instead of falling to his death, Cygnus is transformed into a swan and flies away. The third person named Cygnus is a son of Neptune. He is a warrior in the Trojan War who is invulnerable to all stabbing weapons, much to the frustration of his enemy, Achilles. Achilles finally kills him by smashing his face in with his shield, but Neptune saves Cygnus by transforming him into a swan.
α CrB is an eclipsing binary system similar to Algol (β Per). Its period is 17.36 days, with magnitude varying from +2.21 to +2.32, which is hardly noticeable to the unaided eye.
α CrB is believed to be a stream star member of the Ursa Major Moving Group.
A large disc of dust and material has been shown to exist around Alphecca, prompting speculation of a similar planetary/proto-planetary system to that currently assumed around Vega. How the binary-star dynamic would affect such a system is the subject of intense debate.
The name Gemma is Latin for "jewel". The other traditional name comes from Arabic al-fakkah, "the broken" (ring of stars), from فكّ fakk "unsealed"). الفكه
β Coronae Borealis was first announced to be a binary star in 1907, based on spectroscopic observations at Lick Observatory; J. B. Cannon published an orbit in 1914, finding a period of 40.9 days. Later spectroscopic investigations by F. J. Neubauer at Lick, published in 1944, found a period of 10.5 years, with no evidence for the 41-day periodicity. Antoine Labeyrie and his coworkers resolved the pair by speckle interferometry in 1973 and found that the two stars were separated by about 0.25 arcseconds; this work was published in 1974. The pair was also observed visually by Coteau in 1973. A number of orbits were subsequently published using visual and speckle-interferometric observations, both alone and in conjunction with spectroscopic data. In 1999, Söderhjelm published an orbit using speckle-interferometric data together with Hipparcos observations.
Neubauer's 1944 work found a small variation in the radial velocity of β Coronae Borealis with a periodicity of 320 days, suggesting the presence of a third, lighter, body in the system. A 1999 study of the system by long-baseline infrared interferometry performed at Palomar Observatory found no evidence for this, and showed that any tertiary companion with this period must have mass 10 Jupiter masses or below. This study also found very weak evidence for the presence of a companion with a shorter, 21-day, period, but the data was insufficient to draw a positive conclusion.
The story is connected to a more notable myth, of the Minotaur and of Theseus, who was destined to kill it. To do so, he needed Ariadne's help. This beautiful young maiden was the daughter of Minos, king of Crete. She was also the half-sister to the Minotaur, the half-man half-bull which lived at the centre of a labyrinth.
Every year Minos ordered seven young men and seven maidens from Athens to be served up to the Minotaur. The current hero in Athens was Theseus, son of Poseidon, and heir to the Athenian throne. Only a young man, Theseus had already proved himself by a variety of heroic deeds. Then time came for the yearly tribute to Crete. Theseus volunteered to be one of the seven young men.
As he arrived in Crete, Theseus was met by Minos, who challenged the young man to prove he was indeed the son of Poseidon. Minos threw a gold ring into the sea, and told Theseus to fetch it.
Theseus dove into the deep, and was met by dolphins which escorted him to the palace of the Nereids. Thetis, one of the Nereid sisters (or sea nymphs), gave Theseus a jewelled crown that Hephaestus had made. With the gold ring and the crown, Theseus swam back to Crete. This feat received the loving admiration of Ariadne.
Ariadne had a magic ball of twine that could roll out by itself and follow the path to the centre of the labyrinth, where the Minotaur was kept. She promised to help Theseus kill the Minotaur if he would marry her and take her back to Athens. Theseus agreed, so she gave him the ball of twine. Theseus followed the rolling twine to the centre of the labyrinth and promptly killed the Minotaur.
Unfortunately he forgot his promise. Or, some say, he did marry Ariadne, giving her the jewelled crown as a wedding present. And then he later abandoned her on the isle of Naxos, on the way to Athens.
Others have it that Theseus sailed off, leaving a sleeping Ariadne to pine for her loss. She implored her father, Zeus, to make amends. Zeus took pity and sent Dionysus to comfort his daughter.
Another version has Dionysus visiting Naxos and falling in love with Ariadne, so he cast a spell on Theseus. Theseus then forgot all about Ariadne and sailed off for Athens. In any case, Dionysus took her for his bride and placed the jewelled crown of Hephaestus on her head.
They raised four sons and `lived happily ever after'. When Ariadne died Dionysus took the wedding crown and placed it in the heavens between Hercules and Bootes.
The seven stars that make up the crown are not terribly bright, except for Gemma, or Alphecca (alpha Coronae Borealis), which is a 2.2 magnitude star 75 light years away.
The rest of the Bayer stars vary from three to six magnitude. The constellation includes several fine binaries, an unusual variable, and an extremely faint cluster of galaxies.
Gamma CrB is also a spectroscopic binary (period uncertain) as well as a very close visual binary (see below).
Zeta CrB is actually two stars which form a splendid binary (see below). The two are approximately 220 light years away, given their parallax of 0.015".
Gamma CrB (Struve 1967) is a close binary with an orbit of 91 years. The PA is 265º and separation about 0.2".
Eta CrB (Struve 1937) is a fine binary with orbit of 41.5 years. Presently the companion can be found at PA 47º and separation 0.9".
Zeta2 and zeta1 CrB (Struve 1965): a pleasant pair of blue-white stars with 5.0 and 6.0 magnitudes; PA 305º, separation 6.3". Note that zeta2 is the primary.
Sigma CrB (Struve 2032) is a slow binary, with a period of a thousand years. Currently the companion is at PA 236º and separation 7.03"
Nu1 and nu2 CrB (Struve I 29) form a very wide (but only optical) pair of orange giants, quite suitable for binoculars: PA 166º, separation 372".
Alpha Coronae Borealis
Distance (Light Years) 74.7 ± 1.4
Visual Magnitude 2.22
Color (B-V) -0.02
Names For This Star
Other names for this star are Alphekka, Alphacca, Gemma, Gnosia, The Jewel, Gnosia Stella Coronae, or Ashtaroth.
Gemma is Latin, perhaps meaning a bud. This might be connected with the idea of Corona Borealis as a floral crown. Gnosia Stella Coronae is the Latin name applied to the star by the Roman poet Virgil in his Georgics composed in the first century C. E.
Ashtaroth was a middle-eastern goddess, also known as Astarte, who may be equated perhaps with the Greek love goddess Aphrodite. The names Alphecca, Alphekka, or Alphacca derive from the Arabic phrase Al Na`ir al Fakkah meaning "The Bright One of the Dish."
Description of the Star
Alphecca is an eclipsing binary. The brighter star of the pair is a white A0V main sequence star. This spectral type corresponds to an effective temperature of 9900 K. The star diameter must be about 2.5 times the sun's diameter. The star must be 50 times as luminous as the sun with maybe 3 times the mass.
The dimmer companion is a G5V main sequence dwarf having 90% of the sun's diameter, a slightly cooler temperature than the sun - 5500 K, 70% of the solar luminosity, and 90% of the solar mass.
The orbital period of the two stars about their common center of mass is 17.4 days. The apparent magnitude of the two stars dims by about 0.1 magnitude when the smaller star passes in front of the larger one.
Burnham gives the mean separation between the two stars as 17 million miles. Correcting this figure for the distance to the star system measured by Hipparcos Catalogue gives a mean separation of 40 million miles or about 0.4 AU. This is approximately the distance between the sun and planet Mercury.
The Northern Crown
The Brighter Stars of Corona Borealis
Ariadne's CrownThe Northern Crown belonged to Ariadne of Crete, the daughter of King Minos.
Tribute for the MinotaurCrete was well known in mythology as the site of the great Labyrinth in which lived the monstrous Minotaur, which was half-human and half-bull.. The Minotaur was slain by the Athenian hero Theseus, the son of King Ageus, who gave his name to the Agean Sea. The Athenians had been defeated by the Cretans in battle and were forced to pay tribute. The periodic tribute were Athenian youths, both young men and women, who were locked in the Labyrinth to provide fodder for the Minotaur.
Theseus Takes a HandTheseus decided to end the tribute and arranged that he should sail to Crete with the young men and women to be sacrificed to the Minotaur. Ariadne caught a glimpse of him and fell in love. She met with Theseus and promised to help him, if he would agree that she would sail off with him after he defeated the Minotaur. After extracting his promise, she gave him a ball of twine, which he could unwind behind himself as he walked into the Labyrinth underneath the Cretan Palace. The trail of string would show him the way out of the maze formed by the twists and turns of the Labyrinth.
Ariadne AbandonedTheseus found the Minotaur and slew it. Then Ariadne, Theseus, and the Athenian young people stole a Cretan ship and sailed off to Athens. They stopped at the island of Naxos, where Theseus abandoned Ariadne. There are many different accounts as to why he left her there. Some say that she was seen by the Wine God Dionysius, who fell in love with her on the spot and sent Theseus off.
A Gift for AriadneIn any case, The Northern Crown belongs to Ariadne. Some say that it was given to her as a wedding present by Aphrodite. Others say that the crown was given to Theseus by the sea nymph Thetis and that Theseus used the light of its sparkling gems to find his way through the Labyrinth. Theseus then probably then gave the crown to Ariadne.
Dionysius Tosses the CrownThe god Dionysius married Ariadne there in Naxos. Dionysius was so overcome by joy as he married his love that he tossed the crown high into the sky. As the crown rose above the earth, the jewels in it turned into stars, and the crown became one of the constellations.
Ariadne, daughter of King Minos of Crete, is famous in mythology for her part in helping Theseus to slay the Minotaur, the gruesome creature with the head of a bull on a human body. Ariadne was actually half-sister to the Minotaur, for her mother Pasiphae had given birth to the creature after copulating with a bull owned by King Minos. To hide the family’s shame, Minos imprisoned the Minotaur in a labyrinth designed by the master craftsman Daedalus. So complex was the maze of the labyrinth that neither the Minotaur nor anyone else who ventured in could ever find their way out.
He sailed off with Ariadne, but no sooner had they reached the island of Naxos than he abandoned her. As she sat there, cursing Theseus for his ingratitude, she was seen by Dionysus. The god’s heart melted at the sight of the forlorn girl and he married her on the spot.
Accounts differ about where Ariadne’s crown came from. One story says that it was given to her by Aphrodite as a wedding present. Others say that Theseus obtained it from the sea nymph Thetis, and that its sparkling light helped Theseus find his way through the labyrinth. Whatever the case, after their wedding Dionysus joyfully tossed the crown into the sky where its jewels changed into stars. Its brightest star is called Gemma, the Latin for ‘jewel’, although it is also known as Alphekka from the Arabic name for the constellation.
The constellation is quite old, and is said to represent the crown worn by the centaur Sagittarius (and sometimes known as "Corona Sagittarii").
Like a number of other constellations in the southern hemisphere, its Bayer stars are far from complete, and are rather faint as well.
Kappa2 and kappa1 Coronae Australis form a gorgeous fixed double, visible in most of North America (as far north as Vancouver and Winnipeg) but only part of Europe, generally south of Paris or Stuttgart, and not at all in the UK.
Kappa2 is the primary: 5.9, 6.6; 359º and separation 21.4".
h5014 is a close visual binary with an orbit of 191 years. These are two equal stars: 5.7, 5.7. Epoch 2000 values are PA 346º and separation 0.9".
Corona Australis has no long-period variables, but there are several irregular variables of considerable interest. Two of these, TY and R, are found in the nebulosity NGC 6726/27/29 (see below).
This tiny constellation has been recognized over the centuries by many cultures and has been known by an equal number of different names.
It has been called the Southern Wreath by the Greeks. It represents the crown worn by the centaur Sagittarius and sometimes known as Corona Sagittarii.
The Romans knew it as the Golden Crown of Sagittarius, as the Little Crown, the Southern Coil, and the Crown of Eternal Life.
The Arabs have called it the Tortoise, the Woman's Tent, the Ostrich's Nest, and the Dish.
The Chinese also called it the Tortoise, or Pee.
The Southern Crown
DionysiusThe Southern Crown is probably associated with the Wine God Dionysius, the Twice-Born.
DionysiusThe god Dionysius was the sired by Zeus in one of his many seductions of mortal women. Dionysius's mother was Semele, who like many of Zeus' paramours, suffered as the result of the jealousy of Zeus' spouse Hera.
Hera's PlotWhile Semele was pregnant with Dionysius, Hera approached her in the form of an old woman, the very nursemaid who had brought up Semele herself. She offered Semele advice and concern, but she pretended that she disbelieved that the child Semele carried was really the offspring of Zeus himself. She advised Semele to beg of her lover that he appear to her in his true divine form, the very same form in which he embraced his divine spouse Hera.
'Just a Hunk of Burnin' Love'The next time that Zeus approached, Semele asked that he embrace her in his divine form. Zeus was unable to resist her request, but he knew what would happen. And indeed, when the god embraced poor Semele she was burned to a crisp by his glory.
Zeus Plays MotherThe child Dionysius was ripped from Semele's womb and sewn into Zeus' thigh, where he grew to term. Because the child was first born from Semele's womb and then again from Zeus' thigh, he became known as The Twice-Born. After the birth of Dionysius, Zeus gave the boy to Semele's sister Ino to raise.
A Crown for SemeleLater Dionysius journeyed to the Underworld to retrieve his mother from the Realm of the Dead. He left a gift of myrtle there in exchange for Semele, and then set the Southern Crown among the stars in honor of this woman who had borne him.