Pleiades

The Pleiades, also known as Seven Sisters and Messier 45, is an asterism of an open star cluster containing young B-type stars in the northwest of the constellation Taurus. At a distance of about 444 light-years, it is among the nearest star clusters to Earth and the nearest Messier object to Earth, being the most obvious star cluster to the naked eye in the night sky. It contains the reflection nebulae NGC 1432, an HII region, and NGC 1435, known as the Merope Nebula. Around 2330 BC the Pleiades marked the vernal point. Due to the brightness of its stars, the Pleiades is viewable from most areas on Earth, even in locations with significant light pollution.
The cluster is dominated by hot blue luminous stars that have formed within the last 100 million years. Reflection nebulae around the brightest stars were once thought to be leftover material from their formation, but are now considered likely to be an unrelated dust cloud in the interstellar medium through which the stars are currently passing. This dust cloud is estimated to be moving at a speed of approximately relative to the stars in the cluster.
Computer simulations have shown that the Pleiades were probably formed from a compact configuration that once resembled the Orion Nebula. Astronomers estimate that the cluster will survive for approximately another 250 million years, after which the clustering will be lost due to gravitational interactions with the galactic neighborhood.
Together with the open star cluster of the Hyades, the Pleiades form the Golden Gate of the Ecliptic. The Pleiades have been said to "resemble a tiny dipper," and should not be confused with the "Little Dipper," or Ursa Minor.

Origin of name

The name, Pleiades, comes from. It probably derives from because of the cluster's importance in delimiting the sailing season in the Mediterranean Sea: "the season of navigation began with their heliacal rising". In Classical Greek mythology the name was used for seven divine sisters called the Pleiades. In time, the name was said to be derived from that of a mythical mother, Pleione, effectively meaning "daughters of Pleione". In reality, the ancient name of the star cluster related to sailing almost certainly came first in the culture, naming of a relationship to the sister deities followed, and eventually appearing in later myths, to interpret the group name, a mother, Pleione.

Astronomical role of M45 in antiquity

The M45 group played an important role in ancient times for the establishment of many calendars thanks to the combination of two remarkable elements. The first, which is still valid, is its unique and easily identifiable appearance on the celestial vault near the ecliptic. The second, essential for the ancients, is that in the middle of the third millennium BC, this asterism marked the vernal point.
The importance of this asterism is also evident in northern Europe. The Pleiades cluster is displayed on the Nebra sky disc that was found in Germany and is dated to around 1600 BC. On the disk the cluster is represented in a high position between the Sun and the Moon.
This asterism also marks the beginning of several ancient calendars:

In ancient India, it constitutes, in the Atharvaveda, compiled around 1200-1000 BC, the first , which is called , a revealing name since it literally means 'the Cuttings', i.e. "Those that mark the break of the year". This is so before the classic list lowers this to third place, henceforth giving the first to the star couple β Arietis and γ Arietis, which, notably in Hipparchus, at that time, marks the equinox.
In Mesopotamia, the MUL.APIN compendium, the first known Mesopotamian astronomy treatise, discovered at Nineveh in the library of Assurbanipal and dating from no later than 627 BC, presents a list of deities who stand on "the path of the Moon", a list which begins with mul.MUL.
In Greece, the are a group whose name is probably functional before having a mythological meaning, as André Lebœuffle points out, who has his preference for the explanation by the Indo-European root *pe/ol-/pl- that expresses the idea of 'multiplicity, crowd, assembly'.
Similarly, the Ancient Arabs begin their old parapegma type calendar, that of the, with M45 under the name of . And this before their classic calendar, that of the manāzil al-qamar or 'lunar stations', also begins with the star couple β Arietis and γ Arietis whose name, , is literally "the Two Marks " Although M45 is no longer at the vernal point, the asterism still remains important, both functionally and symbolically. In addition to the changes in the calendars based on the lunar stations among the Indians and the Arabs, consider the case of an ancient Yemeni calendar in which the months are designated according to an astronomical criterion that caused it to be named Calendar of the Pleiades: the month of, literally 'five', is that during which the Sun and, i.e. the Pleiades, deviate from each other by five movements of the Moon, i.e. five times the path that the Moon travels on average in one day and one night, to use the terminology of.
Nomenclature and mythology

The Pleiades are a prominent sight in winter in the Northern Hemisphere, and are easily visible from mid-southern latitudes. They have been known since antiquity to cultures all around the world, including the Celts ; pre-colonial Filipinos, for whom it indicated the beginning of the year; Hawaiians, Māori ; Indigenous Australians ; the Achaemenid Empire, whence in Persians ; the Arabs ; the Chinese ; the Quechua ; the Japanese ; the Maya; the Aztec; the Sioux; the Kiowa; and the Cherokee. In Hinduism, the Pleiades are known as ; कृत्तिका and are scripturally associated with the war deity and are also identified or associated with the . Hindus celebrate the first day of the month of Kartik as Diwali, a festival of abundance and lamps. The Pleiades are also mentioned three times in the Bible, using the constellation's Hebrew name ; כִּימָה.
The earliest known depiction of the Pleiades is likely a Northern German Bronze Age artifact known as the Nebra sky disk, dated to approximately 1600 BC. The Babylonian star catalogues name the Pleiades , meaning 'stars', and they head the list of stars along the ecliptic, reflecting the fact that they were close to the point of the vernal equinox around the twenty-third century BC. The Ancient Egyptians may have used the names "Followers" and "Ennead" in the prognosis texts of the Calendar of Lucky and Unlucky Days of papyrus Cairo 86637. Some Greek astronomers considered them to be a distinct constellation, and they are mentioned by Hesiod's Works and Days, Homer's Iliad and Odyssey, and the Geoponica. The Pleiades was the most well-known "star" among pre-Islamic Arabs and so often referred to simply as "the Star". Some scholars of Islam suggested that the Pleiades are the "star" mentioned in in the Quran.
On numerous cylinder seals from the beginning of the first millennium BC, M45 is represented by seven points, while the Seven Gods appear, on low-reliefs of Neo-Assyrian royal palaces, wearing long open robes and large cylindrical headdresses surmounted by short feathers and adorned with three frontal rows of horns and a crown of feathers, while carrying both an ax and a knife, as well as a bow and a quiver.
As noted by scholar Stith Thompson, the constellation was "nearly always imagined" as a group of seven sisters, and their myths explain why there are only six. Some scientists suggest that these may come from observations as far back as 100,000 BC when Pleione was farther from Atlas and hence, more visible as a separate star to the unaided eye.

Subaru

In Japan, the cluster is mentioned under the name in the eighth-century Kojiki. The cluster is now known in Japan as Subaru, from the intransitive verb subaru, meaning "to cluster together".
The Subaru Telescope, the flagship telescope of the National Astronomical Observatory of Japan, located at the Mauna Kea Observatory on the island of Hawaii, was named after the cluster. It had the largest monolithic primary mirror in the world from its commissioning in 1998 until 2005.
It was also chosen as the brand name of Subaru automobiles to reflect the origins of the firm as the joining of five companies, and is depicted in the firm's six-star logo.

Tolkien's Legendarium

In J. R. R. Tolkien's legendarium, where The Lord of the Rings is set, Pleiades is referred to as Remmirath, the netted stars, as are several other celestial bodies, such as the constellation Orion as Menelvagor, swordsman of the Sky.

Observational history

was the first astronomer to view the Pleiades through a telescope. He thereby discovered that the cluster contains many stars too dim to be seen with the naked eye. He published his observations, including a sketch of the Pleiades showing 36 stars, in his treatise Sidereus Nuncius in March 1610.
The Pleiades have long been known to be a physically related group of stars rather than any chance alignment. 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 surmised that the Pleiades and many other clusters must consist of physically related stars. When studies were first made of the proper motions of the stars, 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 that 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 the number on his list.
Edme-Sébastien Jeaurat then drew in 1782 a map of 64 stars of the Pleiades from his observations in 1779, which he published in 1786.