Rubaiyat de Omar Khayyam

Description

The origin of the name “Pleiads” comes from the Greek Mythologie: the Pléiades are seven sisters, girls of Atlas and Pléioné: Astérope, Mérope (or Dryope, or Aéro), Electra, Maïa, Taygète, Célaéno (or Sélène) and Alcyone.

One counts today approximately 1400 star S composing this cluster, of which a dozen are visible with the naked eye. It extends on 2°, that is to say the equivalent of 4 times the apparent diameter of the the Moon. Its density is thus relatively low compared to the other open clusters. The age of the cluster is estimated at 100 million years, but it should not live a long time since it should separate in 250 million years, partly because of its weak density. It is well here about the life of the cluster and not of stars the component.

The 9 most brilliant stars of the cluster draw their name from the 7 sisters and their parents. Their magnitudes lies between 2,86 and 5,44, therefore accessible to the naked eye. Astérope with the characteristic to be a double star.

History of their discovery

As of Prehistory

As Wolfhard Schlosser underlines it, professor of astronomy at the University of the Ruhr (Bochum), the priests and Chaman S of the Neolithic attached an extreme importance to this constellation, since its appearance marked in all the Northern hemisphere, the beginning of the harvests.

a pictorial representation of this cluster is also found on the Disque of Nebra dated from the beginning of the Bronze Age (1600 av. J. - C.).

the “constellation” of the Pleiads is also quoted in many cultures and religions. It also appears in the Odyssey of Homère, like with three recoveries in the Bible.

In traditional Antiquity

If the Pleiads are known since highest Antiquity, the oldest written reference of this object goes back to the poet Hésiode (700 av. J. - C.). At the time of Hésiode, one believed in his influence on agriculture (a little like the Moon nowadays).

At the time modern

the March 4th 1769, Charles Messier adds this cluster to its catalogs astronomical.
In 1846, the German astronomer Johann Heinrich von Mädler note that the stars do not have of measurable movement, one compared to the other.

It from of deduced that they form the center of a stellar system broader good whose Alcyone would be more close to the center. The assumption was refuted by the other astronomers. It is retained however that they move well in group.

the first photographs of the cluster reveal a cloud of dust around stars.

This Nébuleuse reflects the light of these stars, located in the vicinity or inside.

The most brilliant part is discovered the October 19th 1859 by Ernst Wilhelm Tempel, around Mérope; nebula indexed as a NGC 1435. In 1875, an extension of the cloud is discovered around Maïa and is classified with NGC 1432. Other extensions are observed around Alcyone, Electra, Célaéno and Taygète in 1880. The complex structure of the cloud is finally revealed by the brothers Henry and Isaac Roberts between 1885 and 1888.

This nebula is not a remainder of the original cloud of dust which gave rise to the Pleiads. Indeed, the two objects do not have same apparent speed. The cluster will have crossed this cloud on its way.

Anecdote in connection with the Pleiads: the Japanese name of the cluster is Subaru , which means “unit”.

In 1953, 5 Japanese companies amalgamated to form “Fuji Heavy Industries Ltd”. This new group adopted the cluster Subaru as a name and logo of the well-known make of car.

How to observe it

Thanks to strong the magnitude S of stars the component, this cluster is visible with the naked eye in the sky of Automne. It is located in the constellation of the Bull near the axis formed by the étoiles : Sirius (Large Dog) - Belt of Orion (Orion) - Aldébaran (Bull).

In addition to being a beautiful object, it is also an excellent test of vision! 5 stars quickly are distinguished, then, as the eye adapts, other stars appear. Thus, up to 10-11 stars are visible if the conditions weather are good.

With a pair of binoculars, or a Telescope with a broad field, one will obtain much more stars. It is in this manner that the cluster will give the most satisfaction. With more powerful telescopes or a narrower field, only part of the cluster will be visible.

Nebula is revealed truly only in Photographie.

See too

List of stars of the cluster of the Pleiads

Simple: Pleiads (star cluster) Zh-yue: 七姊妹星團

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