Right ascension:3h 47m 24s
Distance:390–460 ly (120–140 pc)
Other designations:M45, Seven Sisters, Melotte 22
In astronomy, the Pleiades or Seven Sisters (Messier object 45 or M45), is an open star cluster containing middle-aged hot B-type stars located in the large constellation of Taurus (Latin for bull, ). Taurus is one of the constellations of the zodiac, which means it is crossed by the plane of the ecliptic. It came to symbolize the bull in the mythologies of Ancient Babylon, Egypt and Greece. Taurus hosts two of the nearest open clusters to Earth, the Pleiades and the Hyades, both of which are visible to the naked eye.
The Pleiades is among the nearest star clusters to Earth and is the cluster most obvious to the naked eye in the night sky. The name Pleiades comes from Greek mythology; the celestial entity has several meanings in different cultures and traditions.
The cluster is dominated by hot blue and extremely luminous stars that 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 (hence the alternate name Maia Nebula after the star Maia), but is now known to be an unrelated dust cloud in the interstellar medium that the stars are currently passing through.
Computer simulations have shown that the Pleiades was probably formed from a compact configuration that resembled the Orion Nebula. Astronomers estimate that the cluster will survive for about another 250 million years, after which it will disperse due to gravitational interactions with its galactic neighborhood.
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.
In Tamil culture this star cluster is attributed to Lord Murugan (Lord Murugan raised by the six sisters known as the Kārththikai Pengal and thus came to be known as Kārtikeyan). In Sanskrit he is known as Skanda. The Pleiades (Krittika) are particularly revered in Hindu mythology as the six mothers of the war god Murugan, who developed six faces, one for each of them.
In Japan, the constellation is mentioned under the name Mutsuraboshi (“six stars”) in the 8th century Kojiki and Manyosyu documents. The constellation is also known in Japan as Subaru (“unite”) and is depicted in the logo and name of the Subaru automobile company. The Persian equivalent is Parvin (pronounced Parveen).
They have long been known to be a physically related group of stars rather than any chance alignment.
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.
The nine brightest stars of the Pleiades are named for the Seven Sisters of Greek mythology: Sterope, Merope, Electra, Maia, Taygeta, Celaeno, and Alcyone, along with their parents Atlas and Pleione. As daughters of Atlas, the Hyades were sisters of the Pleiades.
The following table gives details of the brightest stars in the cluster:
|Name||Pronunciation (IPA & respelling)||Designation||Apparent magnitude||Stellar classification|
|Alcyone||/ælˈsaɪ.əniː/ al-SY-ə-nee||Eta (25) Tauri||2.86||B7IIIe|
|Atlas||/ˈætləs/ AT-ləs||27 Tauri||3.62||B8III|
|Electra||/ɨˈlɛktrə/ i-LEK-trə||17 Tauri||3.70||B6IIIe|
|Maia||/ˈmeɪə/, /ˈmaɪə/ MAY-ə, MY-ə||20 Tauri||3.86||B7III|
|Merope||/ˈmɛrəpiː/ MERR-ə-pee||23 Tauri||4.17||B6IVev|
|Taygeta||/teɪˈɪdʒɨtə/ tay-IJ-i-tə||19 Tauri||4.29||B6V|
|Pleione||/ˈplaɪ.əniː/ PLY-ə-nee||28 (BU) Tauri||5.09 (var.)||B8IVpe|
|Celaeno||/sɨˈliːnoʊ/ sə-LEE-noh||16 Tauri||5.44||B7IV|
|Sterope, Asterope||/ˈstɛrɵpiː/, /əˈstɛrɵpiː/ (ə)-STERR-ə-pee||21 and 22 Tauri||5.64;6.41||B8Ve/B9V|