The Pleiades cluster has an apparent magnitude of 1.6 and lies at an average distance of 444 light years from Earth. The cluster is also known as Melotte 22. It does not have an NGC designation.
Messier 45 contains a number of hot, blue, extremely luminous B-type stars and is one of the nearest star clusters to Earth. It is the easiest object of its kind to see without binoculars. M45 has a core radius of 8 light years and its tidal radius extends to about 43 light years. The cluster is home to more than 1,000 confirmed members, but only a handful of these stars are visible to the naked eye. The total mass of M45 is estimated at about 800 solar masses.

The Pleiades cluster occupies an area of 110 arc minutes, about four times the apparent diameter of the full Moon. Up to 14 stars are visible without binoculars in good conditions, with clear skies and no light pollution. The best time of year to observe M45 from northern latitudes is during the winter months, when Taurus constellation rises high in the sky. Because of the cluster's apparent size, the best way to see it is through binoculars and small or wide field telescopes. Higher magnification is only recommended for studying individual stars.

The names of the nine brightest stars in M45 are taken from Greek mythology and they represent the Pleiades, the Seven Sisters. The name of the Pleiades comes from Ancient Greek. It probably derives from plein ("to sail") because of the cluster's importance in delimiting the sailing season in the Mediterranean Sea: "the season of navigation began with their heliacal rising". However, in mythology the name was used for the Pleiades, seven divine sisters, the name supposedly deriving from that of their mother Pleione and effectively meaning "daughters of Pleione". In reality, the name of the star cluster almost certainly came first, and Pleione was invented to explain it.

The Pleiades Πλειάδες companions of Artemis, the seven daughters of the titan Atlas and the sea-nymph Pleione born on Mount Cyllene. They were 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 Dionysus. They were thought to have been translated to the night sky as a cluster of stars, the Pleiades, and were associated with rain.

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 their children.

• Maia (Μαῖα), eldest of the seven Pleiades, was mother of Hermes by Zeus.
• Electra (Ἠλέκτρα) was mother of Dardanus and Iasion, by Zeus.
• Taygete (Ταϋγέτη) was mother of Lacedaemon, also by Zeus.
• Alcyone (Ἀλκυόνη) was mother of Hyrieus, Hyperenor and Aethusa by Poseidon.
• Celaeno (Κελαινώ) was mother of Lycus and Nycteus by Poseidon; and of Eurypylus also by Poseidon, and of Lycus and Chimaereus by Prometheus.
• Sterope (Στερόπη) (also Asterope) was mother of Oenomaus by Ares.
• Merope (Μερόπη), youngest of the seven Pleiades, was wooed by Orion. In other mythic contexts she married Sisyphusand, becoming mortal, faded away. She bore Sisyphus several sons.
• Sometimes they are related to the Hesperides, nymphs of the morning star.

Version 1

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.

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 star cluster 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 Orionand plunge into the misty deepand all the gusty winds are raging,then do not keep your ship on the wine-dark seabut, 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."

The loss of one of the sisters, Merope, in some myths may reflect an astronomical event wherein one of the stars in the Pleiades star cluster disappeared from view by the naked eye.

Alternate version

In the account of Diodorus, the Pleiades were called Atlantides after their father Atlas and Hesperides from their mother Hesperis, daughter of Hesperus, brother of Atlas (making him the uncle of his bride). These sisters excelled in beauty and chastity and thus, Busiris, the king of the Egyptians, was seized with desire to get the maidens into his power; and consequently he dispatched pirates by sea with orders to seize the girls and deliver them into his hands. Later on, Heracles conquered this prince when the latter attempted to sacrifice the hero.

Meanwhile the pirates who had seized the girls while they were playing in a certain garden and carried them off, and fleeing swiftly to their ships had sailed away with them. Heracles came upon these pirates as they were taking their meal on a certain strand, and learning from the maidens what had taken place he slew the pirates to a man and brought the girls back to Atlas. In return, the father was so grateful to Heracles for his kindly deed that he not only gladly gave him such assistance as his Labour called for, but he also instructed him quite freely in the knowledge of astrology. A scholia also added that after this events, the Pleiades were then persecuted by Orion.

Although most accounts are uniform as to the number, names, and main myths concerning the Pleiades, the mythological information recorded by a scholiast on Theocritus' Idylls with reference to Callimachus has nothing in common with the traditional version. According to it, the Pleiades were daughters of an Amazonian queen; their names were Maia, Coccymo, Glaucia, Protis, Parthenia, Stonychia, and Lampado. They were credited with inventing ritual dances and nighttime festivals.

Genealogy

The Pleiades are the seven daughters of Atlas and Pleione, and half-sisters of the Hyades, whose mother was Æthra (`bright sky'; a different Æthra than the mother of Theseus). They were perhaps also half-sisters of the Hesperides, who were daughters of either Night alone, or Atlas and Hesperis (`evening'), or Ceto and Phorcys. Both Pleione and Æthra were Oceanids, daughters of Oceanus and Tethys, the titans who ruled the outer seas before being replaced by Poseidon. Atlas (`he who dares' or `suffers'; from the Indo-European tel-, tla-, `to lift, support, bear'), another titan, led their war against the gods, and was afterward condemned by Zeus to hold up the heavens on his shoulders. The Pleiades were also nymphs in the train of Artemis, and together with the seven Hyades (`rainmakers' or `piglets'; individual Hyad names are not fully agreed upon) were called the Atlantides, Dodonides, or Nysiades, nursemaids and teachers to the infant Bacchus. The Hesperides (`nymphs of the west'), apparently not counted in this, were only three, and dwelled in an orchard of Hera's, from which Heracles fetched golden apples in his eleventh labor.

Individual Sisters

• Alcyone or Halcyone - `queen who wards off evil [storms]' -

  Seduced by Poseidon and gave birth to either Hyrieus (the name of Orion's father, but perhaps not the same Hyrieus) or Anthas, founder of Anthæa, Hyperea, and Halicarnassus.

  Another Alcyone, daughter of Æolus (guardian of the winds) and Ægiale, married Ceyx of Trachis; the two jokingly called each other Hera and Zeus, vexing those gods, who drowned Ceyx in a storm at sea; Alcyone threw herself into the sea at the news, and was transformed into a halcyon (kingfisher). Legend has it the halcyon hen buries her dead mate in the winter before laying her eggs in a compact nest and setting it adrift on the sea; Æolus forbids the nest to be disturbed, so the water is calm for 14 days centered on the winter solstice, called the Halcyon Days. The actual bird does not build nests however; instead the story probably derives from an old pagan observance of the turning season, with the moon-goddess conveying a dead symbolic king of the old year to his resting place. Though this Alcyone and the Pleiad Alcyone appear to be separate individuals, they may be related: in 2000 BC, a vigorous period of ancient astronomy, the Pleiades rose nearly four hours earlier than they do today for the same time of year, and were overhead at nightfall on the winter solstice, when the Halcyon supposedly nested; their conjunction with the sun during spring equinoxes at that time may have something to do with the association of the cluster with birds, which are often used as symbols of life and renewal.

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• Asterope or Sterope - `lightning', `twinkling', `sun-face', `stubborn-face' (Indo-European ster-, `star', `stellar', `asterisk', etc.) -

  In some accounts, ravished by Ares and gave birth to Oenomaus, king of Pisa. In others, Oenomaus was her husband, and they had a beautiful daughter, Hippodaima, and three sons, Leucippus, Hippodamus, and Dysponteus, founder of Dyspontium; or, Oenomaus may instead have had these children with Euarete, daughter of Acrisius.

  Another Asterope was daughter of the river Cebren. Still another was daughter of Porthaön, and may have been the mother of the Sirens, who lured sailors to their deaths with their enchanting singing. A possible alternate name is Asterië (`of the starry sky' or `of the sun'), which may also be a name for the creatrix of the universe, Eurynome, in the Pelasgian myth. Graves mentions her as a Pleiad only in passing, with no other mention in the other references. Perhaps she was at one time a Pleiad when different names were used, or an earlier version of Sterope, whose name is similar; or perhaps Graves is incorrect. He also in passing calls the titan or oak-goddess Dione a Pleiad, without explanation or corroboration. Does the term have a broader meaning in some contexts?

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• Celæno - `swarthy' -

  Had sons Lycus (``wolf'') and Chimærus (``he-goat'') by Prometheus. No other data.

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• Electra or Eleckra - `amber', `shining', `bright' (Indo-European wleik-, `to flow, run', as a liquid); electrum is an alloy of silver and gold, and means amber in Latin, as does the Greek elektron; Thales of Miletus noted in 600 BC that a rubbed piece of amber will attract bits of straw, a manifestation of the effects of static electricity (outer charge stripping via friction), and perhaps the origin of the modern term -

  Wife of Corythus; seduced by Zeus and gave birth to Dardanus, founder of Troy, ancestor of Priam and his house. Called Atlantis by Ovid, personifying the family. May also, by Thaumas, be the mother of the Harpies, foul bird-women who lived in a Cretan cave and harried criminals, but this could be a different ocean-nymph of the same name. Another Electra was a daughter of Oedipus, though this may not be the same Oedipus who killed his father and married his mother. She is said to be mother of Dardanus and Iason.

  Yet another Electra was a daughter of Agamemnon and Clytæmnestra, with an alternate name of Laodice, and with brother Orestes and sisters Chrysothemis and Iphigeneia (or Iphianassa), though the latter sister may have been Clytæmnestra's niece, adopted from Theseus and Helen. Agamemnon was king of Mycenæ and led the Greeks against Troy; he was murdered at his return by Clytæmnestra and her lover Ægisthus, both of whom Orestes and Electra killed in revenge, whence the psychological term `Electra complex'. This Electra was also wife to the peasant Pylades, and bore him Medon and Strophius the Second.

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• Maia - `grandmother', `mother', `nurse'; `the great one' (Latin) -

  Eldest and most beautiful of the sisters; a mountain nymph in Arcadia. Seduced by Zeus and gave birth to Hermes. Later became foster-mother to Arcas, son of Zeus and Callisto, during the period while Callisto was a bear, and before she and Arcas were placed in the heavens by Zeus (she as Ursa Major, he as either Boötes or Ursa Minor).

  Another Maia was the Roman goddess of spring, daughter of Faunus and wife of Vulcan (his Greek counterpart, Hephæstus, married Aphrodite instead). Farmers were cautioned not to sow grain before the time of her setting, or conjunction with the sun. The month of May is named after her, and is coincidentally(?) the month in which the solar conjunction happens. By our modern calendar, the conjunction occurred in April in early Roman times, with the shift since then due to the precession of the Earth's axis; but calendars too have changed over time, especially before the time of Julius Caesar, so the month and the cluster's solar conjunction may have lined up then as well.

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• Merope - `eloquent', `bee-eater', `mortal' -

  Married Sisyphus (se-sophos, `very wise'), son of Æolus, grandson of Deucalion (the Greek Noah), and great-grandson of Prometheus. She bore Sisyphus sons Glaucus, Ornytion, and Sinon; she is sometimes also said to be mother of Dædalus, though others in the running are Alcippe and Iphinoë. Sisyphus founded the city of Ephyre (Corinth) and later revealed Zeus's rape of Ægina to her father Asopus (a river), for which Zeus condemned Sisyphus to roll a huge stone up a hill in Hades, only to have it roll back down each time the task was nearly done. Glaucus (or Glaukos) was father of Bellerophon, and in one story was killed by horses maddened by Aphrodite because he would not let them breed. He also led Lycian troops in the Trojan War, and in the Iliad was tricked by the Greek hero Diomedes into exchanging his gold armor for Diomedes' brass, the origin of the term `Diomedian swap'. Another Glaucus was a fisherman of Boeotia who became a sea-god gifted with prophecy and instructed Apollo in soothsaying. Still another Glaucus was a son of Minos who drowned in a vat of honey and was revived by the seer Polyidos, who instructed Glaucus in divination, but, angry at being made a prisoner, caused the boy to forget everything when Polyidos finally left Crete. The word glaukos means gleaming, bluish green or gray, perhaps describing the appearance of a blind eye if glaucoma (cataract) derives from it. Is the name Glaucus a reference to sight, or blindness, physical or otherwise? It is also curious that meropia is a condition of partial blindness.

  Another Merope was daughter of Dionysus's son Oenopion, king of Chios; Orion fell in love with her, and Oenopion refused to give her up, instead having him blinded. Orion regained his sight and sought vengeance, but was killed by Artemis, or by a scorpion, or by some other means (many versions).

  Yet another Merope and her sister Cleothera (with alternate names of Cameiro and Clytië for the two of them) were orphaned daughters of Pandareus.

  Still another was mother of Æpytus by Cresphontes, king of Messenia. Her husband was murdered by Polyphontes, who claimed both her and the throne, but was later killed by Æpytus to avenge his father's death.

  One last, more often known as Periboea, was wife of Polybus, king of Corinth. The two of them adopted the infant Oedipus after his father Laius left him to die, heeding a prophecy that his son would kill him, which, of course, he eventually did.

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• Taygete or Taygeta - ? tanygennetos, `long-necked' -

  Seduced by Zeus and gave birth to Lacedæmon, founder of Sparta, to which she was thus an important goddess. In some versions of the story, she was unwilling to yield to Zeus, and was disguised by Artemis as a hind (female red deer) to elude him; but he eventually caught her and begot on her Lacedæmon, whereupon she hanged herself.

  Another Taygete was niece to the first. She married Lacedæmon and bore Himerus, who drowned himself in a river after Aphrodite caused him to deflower his sister Cleodice. One of the Taygetes may have been mother to Tantalus, who was tormented in Hades with thirst and hunger for offending the gods; however his parentage is uncertain; his mother may instead be Pluto (not the Roman version of Hades), daughter of either Cronus and Rhea or Oceanus and Tethys, and his father Zeus or Tmolus.

Astromorphosis

One day the great hunter Orion saw the Pleiads (perhaps with their mother, or perhaps just one of them;) as they walked through the Boeotian countryside, and fancied them. He pursued them for seven years, until Zeus answered their prayers for delivery and transformed them into birds (doves or pidgeons), placing them among the stars. Later on, when Orion was killed (many conflicting stories as to how), he was placed in the heavens behind the Pleiades, immortalizing the chase.

Lost Pleiad

The `lost Pleiad' legend came about to explain why only six are easily visible to the unaided eye (I have my own thoughts on this). This sister is variously said to be Electra, who veiled her face at the burning of Troy, appearing to mortals afterwards only as a comet; or Merope, who was shamed for marrying a mortal; or Celæno, who was struck by a thunderbolt. Missing Pleiad myths also appear in other cultures, prompting Burnham to speculate stellar variability (Pleione?) as a physical basis. It is difficult to know if the modern naming pays attention to any of this. Celæno is the faintest at present, but the "star" Asterope is actually two stars, each of which is fainter than Celæno if considered separately.

Possible Planets

Analyzing deep-infrared images obtained by the Spitzer Space Telescope and Gemini North telescope, astronomers discovered that one of the cluster's stars - HD 23514, which has a mass and luminosity a bit greater than that of the Sun, is surrounded by an extraordinary number of hot dust particles. This could be evidence for planet formation around HD 23514.

Other Ancient Pleiades

The Wurundjeri people of the Kulin nation explain them in the Karatgurk story. Another story involves seven sisters, the Maya-Mayi who were so beautiful that a warrior, Warrumma, kidnaps two of them. They eventually escape by climbing a pine tree that continually grows up into the sky where they join their other sisters.

However, stars were commonly used to measure time and the seasons and to regulate daily activities before written culture, and long after in some cultures. The myths of the Australian Aboriginal people are, as around the world, to do with moral lessons and various reminders such as when to eat certain types of food, which is itself a cultural connection in the general form of the stories. Therefore, the study of the stars is probably the oldest knowledge on earth, such that it remains an intriguing possibility that aboriginal star knowledge does contain some fragments of a much older original culture. Aboriginal people came to Australia from Asia 50,000 years ago (well before Greek culture formed 3,000-4,000 years ago), and presumably the Aboriginal people originally came from Africa. While there is no hard evidence of a cultural connection, the possibility should not be written off, and the door is open to research to construct models of older human cultures, through the tracing of these narratives and other means such as linguistics.[8]