Lessico
Pleiadi
Ammasso aperto nella costellazione del Toro, ca. 15º a NW di Aldebaran. A occhio nudo sono visibili solo le sei stelle di magnitudine superiore a 5m, o le nove di magnitudine superiore a 6m (Atlante, il padre, Pleione, la madre, e le sette sorelle), ma in realtà fanno parte dell'ammasso un altro centinaio di stelle, distribuite su un'area di alcuni gradi quadrati. La distanza delle Pleiadi dalla Terra è di circa 400 anni luce, per cui le dimensioni reali dell'ammasso vengono a raggiungere i 30 anni luce.
Note fin
dalla più remota antichità con le denominazioni popolari di Gallinelle,
Chioccia coi pulcini, Colomba, le sette stelle più brillanti
vennero designate con i loro nomi mitologici dal poeta greco Arato di Soli
(III sec.
aC).
Il termine Pleiadi viene dal greco Pleiádes - le Pleiadi - vocabolo a sua volta derivato da péleia,as - equivalente a peleiás,ádos - che significano colomba; questo sostantivo a sua volta deriva dall’aggettivo peliòs, che significa livido, fosco, scuro (vedi Columba livia, il Piccione selvatico, per il quale però in greco si usava peristerà).
Johannes Hevelius
- 1690
Nella mitologia le Pleiadi erano le sette figlie di Atlante e dell'oceanina
Pleione che, secondo la mitologia greca, furono trasformate nell'omonima
costellazione. Questa è la lista più nota dei loro nomi: Taigete, Elettra,
Alcione, Asterope, Celeno, Maia,
Merope.
Erano variamente associate a divinità o a eroi come progenitrici di
stirpi regali, ma concepite anche come ninfe della dea Artemide (la romana
Diana); secondo
questa versione Zeus le strappò alla persecuzione del mitico cacciatore
Orione, trasformandole dapprima in colombe (peleiádes) e quindi in
stelle. Mentre le altre Pleiadi si erano unite a un dio, la sola Merope aveva
sposato un mortale, Sisifo, e per questo splende meno brillante in cielo.
Pleiadi
The Pleiades – 1885
Elihu Vedder (New York 1836 - Roma 1923)
Metropolitan Museum of Art - New York City
Le Pleiadi sono un ammasso aperto nella costellazione del Toro, conosciuto anche come M45 dal catalogo di Charles Messier. Questo ammasso piuttosto vicino (399 anni luce), è anche conosciuto come Le sette sorelle, anche se dagli ambienti cittadini solo cinque o sei delle stelle più brillanti sono visibili, mentre da un luogo più scuro se ne possono contare fino a dieci. Le stelle sono circondate da leggere nebulose a riflessione, osservabili solo in fotografie a lunga esposizione prese con telescopi di dimensione ragguardevole.
I membri visibili delle Pleiadi sono stelle blu o bianche, molto luminose. L'ammasso conta centinaia di altre stelle troppo deboli per essere visibili a occhio nudo. Le Pleiadi sono un ammasso giovane, con un'età stimata di circa 100 milioni di anni, e una vita prevista di soli altri 250 milioni di anni, a causa della bassa densità dell'ammasso.
Storia osservativa
La prominenza delle Pleiadi nel cielo notturno (nel cielo invernale nell'emisfero boreale e nel cielo estivo nell'emisfero australe) le ha rese importanti in molte culture:
- Tra i Maori della Nuova Zelanda le Pleiadi sono chiamate Mataariki e il loro sorgere a oriente significa l'inizio del nuovo anno (in giugno).
- Si dice che gli Indiani d'America misurassero la vista col numero di stelle che riuscivano a distinguere nelle Pleiadi. Anche nell'antichità europea, specialmente tra i Greci, le Pleiadi erano considerate un test della vista.
- Gli australiani aborigeni credevano che le Pleiadi fossero una donna che era stata quasi violentata da Kidili, l'uomo della Luna. Alternativamente, erano sette sorelle chiamate Makara.
- Nella mitologia greca Le sette sorelle erano tradizionalmente chiamate:
Asterope
Dryope o Merope o Aero
Elettra
Maia
Taygeta
Celaeno
Alcyone
Questi nomi sono oggi assegnati a singole stelle dell'ammasso. Erano ninfe
delle montagne (Oreadi), le figlie di Atlante e Pleione, anch'essi
rappresentati da stelle nell'ammasso; erano anche nipoti di Giapeto e
Climene, e sorelle delle Iadi, di Calipso e Dione. Si suicidarono dopo la
morte delle loro sorelle, le Iadi. Erano anche conosciute come le Atlantidi.
- In Giappone le Pleiadi sono conosciute come Subaru (parola conosciuta anche in Occidente, ma di cui molti ignorano il significato).
- Nella mitologia indù le Pleiadi (Krittika) sono le sei madri del dio della guerra Skanda, che per ognuna di loro ha sviluppato sei facce.
Da tempo si è supposto che le Pleiadi dovessero essere un gruppo di stelle relazionate l'una all'altra, piuttosto che derivanti da un allineamento visuale. Nel 1767 il reverendo John Michell calcolò che la probabilità di un tale allineamento fortuito di un numero così numeroso di stelle brillanti fosse di 1 su 500.000 e così concluse che le Pleiadi, e altri analoghi ammassi stellari, dovessero essere fisicamente correlate. Quando furono condotti studi osservativi sul moto proprio posseduto dalle stelle dell'ammasso, fu scoperto che si muovevano tutte nella stessa direzione attraverso il cielo, alla stessa velocità, dimostrando ulteriormente l'esistenza di una qualche relazione fra loro. Charles Messier misurò la posizione dell'ammasso e lo inserì come M45 nel suo catalogo, pubblicato nel 1774.
Distanza
La distanza delle Pleiadi è un importante elemento di riferimento nella scala delle distanze cosmiche. Poiché l'ammasso è relativamente vicino alla Terra, la sua distanza è relativamente semplice da misurare. Una volta noto il diagramma di Hertzsprung-Russell per l'ammasso, una conoscenza accurata della sua distanza permette agli astronomi, con un confronto, di stimare la distanza di altri ammassi. Altri metodi possono quindi essere utilizzati per determinare in cascata le distanze di galassie e ammassi di galassie da quelle dei singoli ammassi stellari e così è possibile stabilire una scala cosmica delle distanze.
I risultati di misurazioni precedenti al lancio del satellite Hipparcos (ESA, 1980) indicavano generalmente che le Pleiadi fossero a 135 parsec - da par(allax), parallasse, e sec(ond), secondo - dalla Terra. Il valore misurato invece dal satellite fu di soli 118 parsec, utilizzando il fenomeno della parallasse stellare. Lavori successivi dimostrarono che la misura indicata da Hipparcos per le Pleiadi era un errore, sebbene non se ne fosse individuata l'origine. In seguito alla revisione dell'elaborazione dei dati del satellite Hipparcos, avvenuta nel 2008, è stata proposta quale distanza dell'ammasso dalla Terra quella di 122 parsec, corrispondente a 399 anni luce. Altre misure, universalmente accettate, hanno indicato per la distanza delle Pleiadi dalla Terra il valore di 135 parsec, corrispondente a circa 440 anni luce. La diatriba su quale dei due valori sia da considerarsi corretto è in atto. Si noti che il valore di 135 parsec è stato fornito dal Telescopio spaziale Hubble, generalmente molto affidabile, che ha misurato la distanza di un'unica stella dell'ammasso. Hipparcos, invece, ha misurato le distanze di 54 stelle dell'ammasso, per il quale è stata stimata una distanza media.
Composizione
L'ammasso, il cui nucleo ha un diametro di circa 8 anni luce e il cui raggio mareale è di circa 43 anni luce, contiene più di 1000 membri, statisticamente confermati. È dominato da stelle blu calde e giovani, 14 delle quali possono essere potenzialmente viste a occhio nudo, a seconda delle condizioni osservative. La disposizione delle stelle più luminose ricorda la forma dell'Orsa maggiore e dell'Orsa minore. Si stima che l'ammasso contenga 800 masse solari.
L'ammasso contiene numerose nane brune, oggetti con meno dell'8% circa della massa del Sole, non abbastanza massicci da innescare reazioni di fusione nucleare nei loro nuclei e diventare stelle luminose. Esse possono rappresentare fino al 25% della popolazione totale dell'ammasso, anche se contribuiscono meno del 2% della massa totale. Gli astronomi hanno compiuto grandi sforzi per trovare e poter analizzare nane brune nelle Pleiadi e in altri giovani ammassi, perché in questi ambienti sono ancora relativamente brillanti e osservabili, mentre le nane brune degli ammassi più vecchi sono ormai affievolite e molto più difficili da studiare.
Nell'ammasso delle Pleiadi sono presenti anche alcune nane bianche. Data la giovane età dell'ammasso, ci si aspetta che le stelle della sequenza principale non abbiano avuto il tempo di evolvere in nane bianche, processo che richiede diversi miliardi di anni. Si ritiene che le progenitrici delle nane bianche siano state stelle massicce in sistemi binari. I trasferimenti di massa dalla stella di massa superiore, durante la sua rapida evoluzione, alla compagna, sarebbero risultati in un percorso più rapido per la formazione di una nana bianca, sebbene i dettagli di tale trasferimento da un pozzo gravitazionale più forte a uno più debole non siano stati chiariti.
Età e futura evoluzione
L'età di un ammasso stellare può essere stimata per confronto tra il diagramma HR misurato per l'ammasso e quello derivante da modelli teorici di evoluzione stellare. Utilizzando queste tecniche, per le Pleiadi è stata stimata un età compresa tra i 75 e i 150 milioni di anni, dove lo scarto è dovuto alle incertezze nei modelli di evoluzione stellare. In particolare, modelli che includono un fenomeno noto come sovra-avanzamento convettivo (convective overshoot), in cui materiale proveniente da una zona convettiva irrompe in una zona non-convettiva, forniscono per la stella un'età apparente maggiore.
Un'altra metodologia per stimare l'età di un ammasso è di guardare agli oggetti di massa minore. In una stella della sequenza principale, il litio è rapidamente distrutto nelle reazioni di fusione nucleare che avvengono nel nucleo; una nana bruna, invece, può conservarne parte della quantità iniziale. La temperatura di ignizione per il litio è molto bassa - 2,5 milioni di gradi kelvin - e ciò significa che le nane brune di massa maggiore riusciranno infine a bruciarlo. Determinando il limite massimo della massa delle nane brune (dell'ammasso) ancora contenenti litio, è possibile avere un'idea dell'età dell'ammasso stesso. Applicando questa tecnica alle Pleiadi si è stimata un'età di 115 milioni di anni.
Il moto proprio dell'ammasso lo condurrà fra molti millenni nel futuro a mutare posizione rispetto a un osservatore a Terra, che lo vedrà transitare al di sotto del piede di quella che oggi è la costellazione di Orione. Inoltre, come la maggior parte degli ammassi aperti, le Pleiadi non resteranno gravitazionalmente vincolate in eterno, ma alcuni membri dell'ammasso saranno espulsi dopo incontri ravvicinati, mentre altri saranno spogliati di materia da campi gravitazionali mareali. Simulazioni suggeriscono che occorreranno circa 250 milioni di anni perché l'ammasso si disperda e che le interazioni gravitazionali con nubi molecolari giganti e i bracci della Galassia accelereranno il processo.
Nebulosità a riflessione
In condizioni osservative ideali, alcune tracce di nebulosità compaiono in fotografie a lunga esposizione e possono essere viste attorno all'ammasso. È chiamata nebulosa a riflessione ed è causata dalla riflessione della luce di una stella blu e calda da parte della polvere presente nella nebulosa.
Era stato inizialmente pensato che la polvere potesse essere un rimasuglio del processo di formazione dell'ammasso, ma all'età di 100 milioni di anni generalmente accettata per le Pleiadi, quasi tutta la polvere originariamente presente sarebbe stata dispersa dalla pressione di radiazione. Sembra, piuttosto, che l'ammasso stia transitando attraverso una regione di mezzo interstellare particolarmente polverosa.
Alcuni studi mostrano che la polvere responsabile della nebulosità non è uniformemente distribuita, ma è concentrata in due strati lungo la linea di vista dalla Terra. Questi strati potrebbero essere stati formati dalla decelerazione, nel moto della polvere verso le stelle, dovuta alla pressione di radiazione.
Pleiades
mythology
The Pleiades (in Greek, Pleiádes), companions of Artemis, were the seven daughters of the titan Atlas and the sea-nymph Pleione born on Mount Cyllene. They are the sisters of Calypso, Hyas, the Hyades, and the Hesperides. The Pleiades were nymphs in the train of Artemis, and together with the seven Hyades were called the Atlantides, Dodonides, or Nysiades, nursemaids and teachers to the infant Bacchus.
There is some debate as to the origin of the name Pleiades. Previously, it was accepted the name is derived from the name of their mother, Pleione. However, the name Pleiades is more likely to come from pléø (to sail), because the Pleiades star cluster is visible in the Mediterranean at night during the summer, from the middle of May until the beginning of November, which coincided with the sailing season in antiquity. This derivation was recognized by the ancients, including Virgil (Georgics 1.136-138).
The Seven Sisters
Several of the most prominent male Olympian gods (including Zeus, Poseidon, and Ares) engaged in affairs with the seven heavenly sisters. These relationships resulted in the birth of children.
Maia, eldest of the seven Pleiades, was mother of Hermes by Zeus.
Electra was mother of Dardanus and Iasion by Zeus.
Taygete was mother of Lacedaemon, also by Zeus.
Alcyone was mother of Hyrieus by Poseidon.
Celaeno was mother of Lycus and Eurypylus by Poseidon.
Sterope (also Asterope) was mother of Oenomaus by Ares.
Merope, youngest of the seven Pleiades, was wooed by Orion.
In other mythic contexts Merope married Sisyphus and, becoming mortal, faded away. She bore to Sisyphus several sons. All of the Pleiades except Merope consorted with gods.
Mythology
After Atlas was forced to carry the heavens on his shoulders, Orion began to pursue all of the Pleiades, and Zeus transformed them first into doves, and then into stars to comfort their father. The constellation of Orion is said to still pursue them across the night sky. In the Pleiades star cluster only six of the stars shine brightly, the seventh, Merope, shines dully because she is shamed for eternity for having an affair with a mortal. Some myths also say that the star that doesn't shine is Electra; she is said to have left her place so that she will not have to look down upon the ruin of Troy, because the city was founded by her son Dardanus.
One of the most memorable myths involving the Pleiades is the story of how these sisters literally became stars, their catasterism. According to some versions of the tale, all seven sisters committed suicide because they were so saddened by either the fate of their father, Atlas, or the loss of their siblings, the Hyades. In turn Zeus, the ruler of the Greek gods, immortalized the sisters by placing them in the sky. There these seven stars formed the constellation known thereafter as the Pleiades.
The Greek poet Hesiod mentions the Pleiades several times in his Works and Days. As the Pleiades are primarily winter stars, they feature prominently in the ancient agricultural calendar. Here is a bit of advice from Hesiod:
"And if longing seizes you for sailing the stormy seas,
when the Pleiades flee mighty Orion
and plunge into the misty deep
and all the gusty winds are raging,
then do not keep your ship on the wine-dark sea
but, as I bid you, remember to work the land."
(Works and Days 618-23)
The Pleiades would "flee mighty Orion and plunge into the misty deep" as they set in the West, which they would begin to do just before dawn during October-November, a good time of the year to lay up your ship after the fine summer weather and "remember to work the land"; in Mediterranean agriculture autumn is the time to plough and sow.
The poet Lord Tennyson mentions the Pleiades in his poem Locksley Hall:
"Many a night I saw the Pleiads, rising through the mellow shade,
Glitter like a swarm of fire-flies tangled in a silver braid."
Pleiades
A map of the Pleiades
The Pleiades, also known as M45, the Seven Sisters, SED, Matariki or (in Japan) Subaru, is an open cluster in the constellation of Taurus. It is among the nearest star clusters, and is probably the best known, and is certainly the most obvious to the naked eye. It is sometimes referred to as the Maia Nebula, perhaps erroneously considering that the reflection nebulosity surrounding Maia is intrinsic (see below).
The cluster is dominated by hot blue stars which have formed within the last 100 million years. Dust that forms a faint reflection nebulosity around the brightest stars was thought at first to be left over from the formation of the cluster, but is now known to be an unrelated dust cloud that the stars are currently passing through. Astronomers estimate that the cluster will survive for about another 250 million years, after which it will have dispersed due to gravitational interactions with its galactic neighborhood.
Observational history
The Pleiades are a prominent sight in winter in the Northern Hemisphere and in summer in the Southern Hemisphere, and have been known since antiquity to cultures all around the world, including the Maori and Australian Aborigines, the Chinese, the Maya (who called them Tzab-ek), the Aztec and the Sioux of North America. Some Greek astronomers considered them to be a distinct constellation, and they are mentioned by Hesiod, and in Homer's Iliad and Odyssey. They are also mentioned three times in the Bible (Job 9:9, 38:31; Amos 5:8). The Pleiades (Krittika) are particularly revered in Hindu mythology as the six mothers of the war god Skanda, who developed six faces, one for each of them. Some scholars of Islam suggested that the Pleiades (At-thuraiya) are the Star in Najm which is mentioned in the Quran.
They have long been known to be a physically related group of stars rather than any chance alignment. The Reverend John Michell calculated in 1767 that the probability of a chance alignment of so many bright stars was only 1 in 500,000, and so correctly surmised that the Pleiades and many other clusters of stars must be physically related. When studies were first made of the stars' proper motions, it was found that they are all moving in the same direction across the sky, at the same rate, further demonstrating that they were related.
Charles Messier measured the position of the cluster and included it as M45 in his catalogue of comet-like objects, published in 1771. Along with the Orion Nebula and the Praesepe cluster, Messier's inclusion of the Pleiades has been noted as curious, as most of Messier's objects were much fainter and more easily confused with comets — something which seems scarcely possible for the Pleiades. One possibility is that Messier simply wanted to have a larger catalogue than his scientific rival Lacaille, whose 1755 catalogue contained 42 objects, and so he added some bright, well-known objects to boost his list.
Distance
The distance to the Pleiades is an important first step in the so-called cosmic distance ladder, a sequence of distance scales for the whole universe. The size of this first step calibrates the whole ladder, and the scale of this first step has been estimated by many methods. As the cluster is so close to the Earth, its distance is relatively easy to measure. Accurate knowledge of the distance allows astronomers to plot a Hertzsprung-Russell diagram for the cluster which, when compared to those plotted for clusters whose distance is not known, allows their distances to be estimated. Other methods can then extend the distance scale from open clusters to galaxies and clusters of galaxies, and a cosmic distance ladder can be constructed. Ultimately astronomers' understanding of the age and future evolution of the universe is influenced by their knowledge of the distance to the Pleiades.
Results prior to the launch of the Hipparcos satellite generally found that the Pleiades were about 135 parsecs away from Earth. Hipparcos caused consternation among astronomers by finding a distance of only 118 parsecs by measuring the parallax of stars in the cluster — a technique which should yield the most direct and accurate results. Later work has consistently found that the Hipparcos distance measurement for the Pleiades was in error, but it is not yet known why the error occurred. The distance to the Pleiades is currently thought to be the higher value of about 135 parsecs (roughly 440 light years).
Composition
The cluster core radius is about 8 light-years and tidal radius is about 43 light years. The cluster contains over 1000 statistically confirmed members, although this figure excludes unresolved binary stars. It is dominated by young, hot blue stars, up to 14 of which can be seen with the naked eye depending on local observing conditions. The arrangement of the brightest stars is somewhat similar to Ursa Major and Ursa Minor. The total mass contained in the cluster is estimated to be about 800 solar masses.
The cluster contains many brown dwarfs, which are objects with less than about 8% of the Sun's mass, not heavy enough for nuclear fusion reactions to start in their cores and become proper stars. They may constitute up to 25% of the total population of the cluster, although they contribute less than 2% of the total mass. Astronomers have made great efforts to find and analyse brown dwarfs in the Pleiades and other young clusters, because they are still relatively bright and observable, while brown dwarfs in older clusters have faded and are much more difficult to study.
Also present in the cluster are several white dwarfs. Given the young age of the cluster normal stars are not expected to have had time to evolve into white dwarfs, a process which normally takes several billion years. It is believed that, rather than being individual low- to intermediate-mass stars, the progenitors of the white dwarfs must have been high-mass stars in binary systems. Transfer of mass from the higher-mass star to its companion during its rapid evolution would result in a much quicker route to the formation of a white dwarf, although the details of this supposed transfer from a deeper gravity well to a lesser are unexplained.
Age and future evolution
Ages for star clusters can be estimated by comparing the Hertzsprung-Russell diagram for the cluster with theoretical models of stellar evolution, and using this technique, ages for the Pleiades of between 75 and 150 million years have been estimated. The spread in estimated ages is a result of uncertainties in stellar evolution models. In particular, models including a phenomenon known as convective overshoot, in which a convective zone within a star penetrates an otherwise non-convective zone, result in higher apparent ages.
Another way of estimating the age of the cluster is by looking at the lowest-mass objects. In normal main sequence stars, lithium is rapidly destroyed in nuclear fusion reactions, but brown dwarfs can retain their lithium. Due to lithium's very low ignition temperature of 2.5 million kelvins, the highest-mass brown dwarfs will burn it eventually, and so determining the highest mass of brown dwarfs still containing lithium in the cluster can give an idea of its age. Applying this technique to the Pleiades gives an age of about 115 million years.
The cluster's relative motion will eventually lead it to be located, as seen from Earth many millennia in the future, passing below the feet of what is currently the constellation of Orion. Also, like most open clusters, the Pleiades will not stay gravitationally bound forever, as some component stars will be ejected after close encounters and others will be stripped by tidal gravitational fields. Calculations suggest that the cluster will take about 250 million years to disperse, with gravitational interactions with giant molecular clouds and the spiral arms of the galaxy also hastening its demise.
Reflection nebulosity
Under ideal observing conditions, some hint of nebulosity may be seen around the cluster, and this shows up in long-exposure photographs. It is a reflection nebula, caused by dust reflecting the blue light of the hot, young stars.
It was formerly thought that the dust was left over from the formation of the cluster, but at the age of about 100 million years generally accepted for the cluster, almost all the dust originally present would have been dispersed by radiation pressure. Instead, it seems that the cluster is simply passing through a particularly dusty region of the interstellar medium.
Studies show that the dust responsible for the nebulosity is not uniformly distributed, but is concentrated mainly in two layers along the line of sight to the cluster. These layers may have been formed by deceleration due to radiation pressure as the dust has moved towards the stars.
Names and technical information
The nine brightest stars of the Pleiades are named for the Seven Sisters of Greek mythology: Sterope, Merope, Electra, Maia, Taygete, Celaeno and Alcyone, along with their parents Atlas and Pleione. As daughters of Atlas, the Hyades were sisters of the Pleiades. The English name of the cluster itself is of Greek origin, though of uncertain etymology. Suggested derivations include: from plein, to sail, making the Pleiades the "sailing ones"; from pleos, full or many; or from peleiades, flock of doves.
In folklore and literature
The
Moon is set,
And the Pleiades.
Night's half gone,
Time's passing.
I sleep alone now. ”
Sappho
“ Can
you bind the beautiful Pleiades?
Can you loose the cords of Orion? ”
Job 38:31
“
Many a night I saw the Pleiads, rising thro' the mellow shade,
Glitter like a swarm of fireflies tangled in a silver braid. ”
Alfred Tennyson, Locksley Hall
The Pleiades' high visibility in the night sky has guaranteed it a special place in many cultures, both ancient and modern. In Greek mythology, they represented the Seven Sisters, while to the Vikings, they were Freyja's hens, and their name in many old European languages compares them to a hen with chicks.
To the Bronze Age people of Europe, such as the Celts (and probably considerably earlier), the Pleiades were associated with mourning and with funerals, since at that time in history, on the cross-quarter day between the autumn equinox and the winter solstice (see Samhain, also Halloween or All Souls Day), which was a festival devoted to the remembrance of the dead, the cluster rose in the eastern sky as the sun's light faded in the evening. It was from this acronychal rising that the Pleiades became associated with tears and mourning. As a result of precession over the centuries, the Pleiades no longer marked the festival, but the association has nevertheless persisted, and accounts for the significance of the Pleiades astrologically.
The early Monte Alto Culture and others in Guatemala such as Ujuxte and Takalik Abaj, made its early observatories, using the Pleiades and Eta Draconnis as reference, they were called the seven sisters, and thought to be their original land.
Heliacal risings very often mark important calendar points for ancient peoples. The heliacal rising of the Pleiades (around June) also begins the new year for the Maori of New Zealand, who call the Pleiades Matariki. There is an analogous holiday in Hawai?i known as Makali?i. The ancient Aztecs of Mexico and Central America based their calendar upon the Pleiades. Their calendric year began when priests first remarked the asterism rising heliacally in the east, immediately before the sun's dawn light obliterated the view of the stars. Aztecs called the Pleiades Tianquiztli (meaning "marketplace").
Indigenous Australians and Mainland Asians
Depending on the tribe or clan, there are several stories regarding the origins of the Pleiades. Some Indigenous Australian peoples believed the Pleiades was a woman who had been nearly raped by Kidili, the man in the moon.
Another version, often painted by Gabriella Possum Nungurayyi as this is her dreaming (or creation story), daughter of the late Clifford Possum Tjapaltjarri from the Central desert art movement of Papunya, depicts the story of seven Napaltjarri sisters being chased by a man named Jilbi Tjakamarra. He tried to practice love magic to one of the sisters but the sister did not want to be with him and with her sisters, they ran away from him. They sat down at Uluru to search for honey ants but when they saw Jilbi, they went to Kurlunyalimpa and with the spirits of Uluru, transformed into stars. Jilbi transforms himself into what is commonly known as the Morning Star in Orion's belt[citation needed], thus continuing to chase the seven sisters across the sky.
Among the Ban Raji, who live in semi-nomadic settlements scattered throughout western Nepal and northern India, the Pleiades are called the "Seven sisters-in-law and one brother-in-law" (Hatai halyou daa salla). Ban Rajis note that when the Pleiades rises up over the mountain each night, they feel happy to see their ancient kin (Fortier 2008:in press). On a more practical note, Ban Rajis can tell that evening has arrived, indicating that it is about eight o’clock by local time standards when their star-kin rise above the Nepali mountains bordering the Kali River.
Native Americans
The Lakota Tribe of North America had a legend that linked the origin of the Pleiades to Devils Tower. According to the Seris (of northwestern Mexico), these stars are seven women who are giving birth. The constellation is known as Cmaamc, which is apparently an archaic plural of the noun cmaam "woman". It was common among the indigenous peoples of the Americas to measure keenness of vision by the number of stars the viewer could see in the Pleiades, a practice which was also used in historical Europe, especially in Greece.
The Native American tribe, the Kiowa, had a myth similar to the Lakota that explained the creation of the Pleiades. According to the Kiowa there were seven young maidens that went out to play and were spotted by several giant bears. The bears saw the young women and began to chase them. In an effort to escape the bears the women climbed on top of a rock and prayed to the spirit of the rock to save them. Hearing their prayers the rock began to rise from the ground towards the Heavens so that the bears couldn't reach the maidens. The seven women reached the sky and were then turned into the star constellation we know today. The bears in an effort to climb the rock left deep claw marks in the sides which had become too steep to climb. The rock later became known as Devil's Tower which is located in the state of Wyoming.
In the ancient Andes, the Pleiades were associated with abundance, because they return to the Southern Hemisphere sky each year at harvest-time. In Quechua they are called collca', or storehouse.
Paul Goble, Native American storyteller, tells a Blackfoot legend that he says is told by other tribes as well. In the story, the Pleides are orphans that were not cared for by the people, so they became stars. Sun Man is angered by the mistreatment of the children and punishes the people with a drought, until the dogs, the only friends of the orphans, intercede on behalf of the people.
The American Hopi Indians buit their underground Kivas for multiple utilitarian uses. The most important of which was their ceremonial meeting place. The access was a ladder through a small hole in the roof of the round hole in the ground. During certain ceremonies, the night passage of the Pleiades over the center of the opening of the entrance hole was a direct signal to begin a certain ceremony. Most of the cultures used the angle of the Pleiades in the night sky as a time telling device.
Ukrainian
In Ukrainian traditional folklore the Pleiades are known as Stozhary, Volosozhary), or Baby-Zvizdy. 'Stozhary' can be etymologically traced to stozharnya meaning a 'granary', 'storehouse for hay and crops', or can also be reduced to the root sto-zhar meaning 'hundredfold glowing'. 'Volosozhary' (the ones whose hair is glowing), or 'Baby-Zvizdy' (female-stars) refer to the female tribal deities. Accordingly to the legend, seven maids lived long ago. They used to dance the traditional round dances and sing the glorious songs to honor the gods. After their death the gods turned them into water nymphs, and, having taken them to the Heavens, settled them upon the seven stars, where they dance their round dances (symbolic for moving the time) to this day. In Ukraine this asterism was considered a female talisman until recent times.
Other cultures
The Subaru logo depicts the six stars of the Pleiades cluster that are usually visible from earth with the unaided eye. (However it is possible to see much more than six stars under favorable conditions)
In the Bible the Pleiades supposedly mentioned as Khima (Amos 5:8), Talmud (Berachot 58B) says that it has about 100 stars.
In the Arab, Persian, and Turkic worlds, the Pleiades are referred to Surayya and allegorically refer to something of beauty.
In Japan, the Pleiades are known as Subaru, and have given their name to the car manufacturer whose logo incorporates six stars to represent the five smaller companies that merged into one. Subaru Telescope, located in Mauna Kea Observatory on Hawaii, is named after the Pleiades also.
In Turkish they are known as Ülker. In Arabic the Pleiades are known as "Sureyya" and in Persian language they are known as "Pervin".
In Chinese constellations, they are mao, the Hairy Head of the white tiger of the West, while the name of the Hindu God Kartikeya means him of the Pleiades.
In the Swahili language of East Africa they are called "kilimia" (Proto-Bantu *ki-dimida in Bantu areas E, F, G, J, L, and S) which comes from the verb -lima meaning "dig" or "cultivate" as their visibility was taken as a sign to prepare digging as the onset of the rain was near.
In the closely related Sesotho language of the Southern Africa's Basotho people the Pleiades are called "Seleme se setshehadi" ("the female planter"). Its disappearance in April (the 10th month) and the appearance of the star Achernar signals the beginning of the cold season. Like many other Southern African cultures, Basotho associate its visibility with agriculture and plenty.
In Western astrology they represent coping with sorrow[19] and were considered a single one of the medieval fixed stars. As such, they are associated with quartz and fennel.
In Indian astrology the Pleiades were known as the asterism (nakshatra) K?ttika (which in Sanskrit is translated as "the cutters.")[20] The Pleiades are called the star of fire, and their ruling deity is the Vedic god Agni, the god of the sacred fire. It is one of the most prominent of the nakshatras, and is associated with anger and stubbornness.
The word has acquired a meaning of "multitude", inspiring the name of the French literary movement La Pléiade and an earlier group of Alexandrian poets, the Alexandrian Pleiad.
Jehovah's Witnesses, during their first 60 years, believed the Pleiades cluster was the physical location of Jehovah God's throne.
Nebra sky disk
The Nebra sky disk is a bronze disk of around 30 cm diameter, patinated blue-green and inlaid with gold symbols. These are interpreted generally as a sun or full moon, a lunar crescent, and stars (including a cluster interpreted as the Pleiades). Two golden arcs along the sides, marking the angle between the solstices, were added later. A final addition was another arc at the bottom surrounded with multiple strokes (of uncertain meaning, variously interpreted as a Solar Barge with numerous oars, as the Milky Way or as a rainbow).
The disk is attributed to a site near Nebra, Saxony-Anhalt in Germany, and associatively dated to c. 1600 BC. It has been associated with the Bronze Age Unetice culture. The disk is unlike any known artistic style from the period, and had initially been suspected of being a forgery, but is now widely accepted as authentic.
Discovery
The disk appeared as if from nowhere on the international antiquities market in 2001. Its seller claimed that it had been looted by illegal treasure hunters with a metal detector in 1999. Archaeological artefacts are the property of the state in Saxony-Anhalt and following a police sting operation in Basel, Switzerland, the disk was acquired by the state archaeologist, Dr Harald Meller. As part of a plea bargain, the illicit owners led police and archaeologists to the site where they had found it together with other remains (two bronze swords, two hatchets, a chisel and fragments of spiral bracelets). Though no witnesses were present at the first discovery, archaeologists have opened a dig at the site and have uncovered evidence that support the looters' claim (in the form of traces of bronze artefacts in the ground, as well as matching earth samples found sticking to the artefacts). The disk and its accompanying finds are now in Halle in the Landesmuseum für Vorgeschichte (State Museum for Prehistory) of Saxony-Anhalt, Germany. The two looters received a four months and a ten months sentence by a Naumburg court in September 2003. An appeal court raised these to six and twelve months, respectively.
The discovery site identified by the arrested metal detectorists is a prehistoric enclosure encircling the top of a 252 m elevation in the Ziegelroda Forest, known as Mittelberg ("central hill"), some 60 km west of Leipzig. The surrounding area is known to have been settled since the Neolithic, and Ziegelroda Forest is said to contain around 1,000 barrows.
The enclosure is oriented in such a way that the sun seems to set every solstice behind the Brocken, the highest peak of the Harz mountains, some 80 km to the northwest. It was claimed by the treasure-hunters that the artefacts were discovered within a pit inside the bank-and-ditch enclosure.
Dating
The more precise dating of the Nebra skydisk, however, depended upon the dating of a number of Bronze Age weapons which were offered for sale with the disk and said to be from the same site. These axes and swords can be typologically dated to the mid 2nd millennium BC (Unetice culture). Radiocarbon dating of a birch bark particle found on one of the swords to between 1600 and 1560 BC confirmed this estimate. This corresponds to the date of burial, at which time the disk had likely been in existence for several generations.
According to an analysis of trace elements by x-ray fluorescence by E. Pernicka, University of Freiberg, the copper originated at the Mitterberg in Austria, while the gold is from the Carpathian Mountains. Copper from Bottendorf in the immediate vicinity of Nebra has definitely not been used. But few copper objects are found where they were originally smelted.
History
Initially the disk had thirty-two small round gold circles, a large circular plate, and a large crescent-shaped plate attached. The circular plate is interpreted as either the Sun or the full Moon, the crescent shape as the crescent Moon (or either the Sun or the Moon undergoing eclipse), and the dots as stars, with the cluster of seven dots likely representing the Pleiades.
At some later date, two arcs (constructed from gold of a different origin, as shown by its chemical impurities) were added at opposite edges of the disk. To make space for these arcs, one small circle was moved from the left side toward the center of the disk and two of the circles on the right were covered over, so that thirty remain visible. The two arcs span an angle of 82°, correctly indicating the angle between the positions of sunset at summer and winter solstice at the latitude of the Mittelberg (51° N). Given that the arcs relate to solar phenomena, it is likely the circular plate represents the Sun not the Moon.
The final addition was another arc at the bottom, the "sun boat", again made of gold from a different origin. By the time the disk was buried it also had thirty-nine or forty holes punched out around its perimeter, each approximately 3 mm in diameter.
Significance
Possibly an astronomical instrument as well as an item of religious significance, the disk is a beautiful object; the blue-green patina of the bronze may have been an intentional part of the original artifact. If authentic, the find reconfirms that the astronomical knowledge and abilities of the people of the European Bronze Age included close observation of the yearly course of the Sun, and the angle between its rising and setting points at summer and winter solstice. While Stonehenge and the Neolithic "circular ditches" such as the 5th millennium BC Goseck circle were used to mark the solstices, the disk is the oldest known "portable" instrument to allow such measurements.
Another view is that the Nebra disk can be linked to the solar calendar reconstructed by Alexander Thom from his analysis of standing stone alignments in Britain. MacKie has argued that several aspects of the disk support this view, following up the work of Prof. Wolfhard Schlosser. The first is that the Mittelberg – the hill on which the disk is supposed to have been found – is so situated that when the sun sets at two distant mountain peaks in the north-west, both midsummer and May Day are accurately marked (and therefore also the old Celtic harvest festival on Aug. 2nd); these are three important dates in the 16 'month' Thom solar calendar. The second feature is the two golden arcs on either side of the disk which subtend angles of about 82 degrees; this is the angular distance between sunrise and sunset at midsummer and midwinter at the latitude of Mittelberg. This surely implies a detailed knowledge of the yearly solar cycle on the part of the disk's designer. The third feature is the 32 golden 'star spots' on the disk. Although Thom found really clear evidence for only sixteen subdivisions of the solar year (of 21 or 22 days) in the standing stone alignments, there were some indications of a further subdivision into 32 parts of 10 or 11 days.
Authenticity
There were initial suspicions that the disk might be an archaeological forgery. Peter Schauer of the University of Regensburg, Germany, argues that the Nebra disk is a fake. He is quoted as saying: "If you urinate on a piece of bronze and then hide it in the ground for a few weeks you can produce the same patina as on the disk."
Richard Harrison, professor of European prehistory at the University of Bristol and an expert on the Beaker people allowed his initial reaction to be quoted in a BBC documentary: "When I first heard about the Nebra Disc I thought it was a joke, indeed I thought it was a forgery. Because it’s such an extraordinary piece that it wouldn’t surprise any of us that a clever forger had cooked this up in a backroom and sold it for a lot of money."
Though Harrison had not seen the skydisk when he was interviewed, it was a reasonable skepticism at that point, but the disk is now widely accepted as authentic and dated to roughly 1600 BC on grounds of typological classification of the associated finds. As the item was not excavated using archaeological methods, even its claimed provenance may be made up, hence authenticating it has depended on microphotography of the corrosion crystals, which produced images that could not be reproduced by a faker.
Dr Harald Meller, lecturing to the Society of Antiquaries of Scotland in April 2008, gave a list of reasons for the authenticity of the disc and for its find spot being on the Mittelberg. The most persuasive of the latter was the discovery by the archaeologists – in the pit in which the looters said they had found the metalwork – of a fragment of gold leaf which exactly fits the gap which existed in the gold leaf covering on the 'sun' symbol when it was originally recovered.
Exhibition
The disk was the center of an exhibition titled Der geschmiedete Himmel ("the smithied heavens"), showing 1,600 Bronze Age artifacts, including the Trundholm sun chariot, shown at Halle from 15 October 2004 to 22 May 2005, from 1 July to 22 October 2005 in Kopenhagen, from 9 November 2005 to 5 February 2006 in Vienna, from 10 March to 16 July 2006 in Mannheim and from 29 September 2006 to 25 February 2007 in Basel. On 20 June 2007 a multimedia visitor center was opened near the discovery site at Nebra.
Legal issues
The state of Saxony-Anhalt has registered the disk as a trademark, which has resulted in two lawsuits. In 2003, Saxony-Anhalt successfully sued the city of Querfurt for depicting the disk design on souvenirs. In an ongoing (as of 2006) lawsuit, Saxony-Anhalt is suing the publishing houses Piper and Heyne over an abstracted depiction of the disk on book covers. The Magdeburg court is required to assess the case's relevance according to German copyright law. The defenders argue that as a cultic object, the disk had already been "published" in the Bronze Age, and that consequently all protection of intellectual property associated with it has long expired. The plaintiff on the other hand argues that the editio princeps of the disk is recent, and according to German law protected for the next 25 years, or until 2027. Another argument concerns the question whether a notable work of art may be registered as a trademark in the first place.
Popular culture
The disk has begun to attract the kind of pseudoarchaeology, neopagan and paranormal speculation that is associated with Stonehenge and Arkaim. The Nebra Skydisk is also the name of an experimental band out of Binghamton, New York.
