Pleiades

Lore & Background

The name Pleiades comes from Ancient Greek: Πλειάδες, probably deriving from plein ('to sail') because of the cluster's importance in delimiting the sailing season in the Mediterranean Sea. In Classical Greek mythology the name was used for seven divine sisters called the Pleiades, later said to be derived from a mythical mother, Pleione. The ancient name of the star cluster related to sailing almost certainly came first, with the naming of sister deities following, and eventually appearing in later myths to interpret the group name. In ancient India, it constitutes the first nakṣatra in the Atharvaveda, called Kṛttikā, literally meaning 'the Cuttings', i.e. 'Those that mark the break of the year'. In Mesopotamia, the MUL.APIN compendium presents a list of deities on 'the path of the Moon' beginning with mul.MUL. The Ancient Arabs began their old parapegma calendar with M45 under the name al-Thurayyā.

Reader's Guide

The Pleiades cluster has played an important role in ancient times for the establishment of many calendars, thanks to its unique and easily identifiable appearance near the ecliptic and the fact that in the middle of the third millennium BC it marked the vernal point. 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, estimated to be moving at about 18 km/s relative to the stars. Together with the Hyades, the Pleiades form the Golden Gate of the Ecliptic. The cluster has been known since antiquity to cultures all around the world, including the Celts, pre-colonial Filipinos, Hawaiians, Māori, Indigenous Australians, Persians, Arabs, Chinese, Quechua, Japanese, Maya, Aztec, Sioux, Kiowa, and Cherokee. In Japan, the cluster is known as Subaru, from the intransitive verb meaning 'to cluster together'.

Did You Know?

• The Pleiades contains over 1,000 stars, with the brightest six or seven easily visible to the naked eye.
• In Japan, the cluster is known as Subaru, meaning 'to cluster together'.

Physical Composition and Stellar Future

The Pleiades, catalogued as Messier 45, is an open star cluster situated in the northwest of the constellation Taurus, roughly 444 light-years from Earth. This proximity makes it the nearest Messier object and the most obvious naked-eye star cluster in the night sky. The cluster holds over 1,000 stars, dominated by hot, luminous blue B-type stars that all formed within the last 100 million years. Its six or seven brightest members are readily visible without optical aid. Embedded within the cluster are reflection nebulae NGC 1432 and NGC 1435, the latter known as the Merope Nebula, along with an HII region. Early astronomers assumed these dust clouds were residual material from stellar formation, but modern understanding holds they are an unrelated interstellar dust cloud the stars are currently traversing, drifting at approximately 18 km/s relative to the cluster. Computer simulations indicate the Pleiades originated from a compact configuration once resembling the Orion Nebula, and astronomers project the grouping will persist for roughly another 250 million years before gravitational interactions with the surrounding galactic environment tear it apart.

Ancient Timekeeping and the Vernal Point

Around 2330 BC, the Pleiades occupied the vernal point on the ecliptic, a positional fact that made the asterism indispensable to ancient calendar-makers across multiple civilizations. In the Indian subcontinent, the Atharvaveda, compiled between roughly 1200 and 1000 BC, lists the cluster as the first nakṣatra under the name Kṛttikā, a term that literally translates to "the Cuttings" or "Those that mark the break of the year." In Mesopotamia, the MUL.APIN compendium, the earliest known treatise of Babylonian astronomy recovered from the library of Assurbanipal at Nineveh and dated no later than 627 BC, opens its catalogue of stellar deities on the Moon's path with this asterism. Ancient Arab astronomers likewise began their anwāʾ calendar with al-Thurayyā, and an older Yemeni system was so closely tied to the cluster's position that it earned the name "Calendar of the Pleiades," with a month called khams defined by the angular gap between the Sun and the stars. The Nebra sky disc, a bronze artifact from Germany dated to approximately 1600 BC, depicts the cluster in a prominent position between the Sun and the Moon, underscoring its symbolic weight in northern European prehistory.

Naming, Etymology, and Mythological Layers

The name Pleiades traces back to the Ancient Greek Πλειάδες, most likely rooted in plein (πλεῖν), meaning "to sail," a reference to the cluster's practical role in signaling the opening of the Mediterranean navigation season, which began with the stars' heliacal rising. In later Classical Greek mythology, the name was retrofitted to describe seven divine sisters, and eventually to a mythical mother figure, Pleione, producing the interpretation "daughters of Pleione." Scholars note, however, that the functional sailing name almost certainly preceded the mythological associations, with the mother-figure emerging in subsequent interpretive traditions. The Indo-European root *pe/ol-/pl-, carrying the sense of "multiplicity, crowd, assembly," has also been proposed as a linguistic source for the term. The cluster has long been described as resembling "a tiny dipper," a comparison that distinguishes it clearly from the Little Dipper, or Ursa Minor. Together with the nearby open cluster of the Hyades, the Pleiades form a configuration known as the Golden Gate of the Ecliptic, a pairing that has held symbolic significance in various astronomical and mythological traditions.

Global Cultural Presence and Observability

Thanks to the exceptional brightness of its member stars, the Pleiades remain visible from most locations on Earth, even in areas burdened by significant light pollution. The cluster is a striking sight in winter across the Northern Hemisphere and can be spotted from mid-southern latitudes as well. Its universal recognizability has earned it names and stories in virtually every culture with a recorded sky tradition. The Celts knew it as Tŵr Tewdws in Welsh and Streoillín in Irish; pre-colonial Filipinos called it Mapúlon, Mulo-pulo, or Muró-púro, and read its appearance as the start of the new year. Hawaiians named it Makaliʻi, Māori called it Matariki, and Indigenous Australian traditions from multiple groups incorporated it into their cosmologies. Persians referred to it as Parvīn or Parvī, Arabs as al-Thurayyā, Chinese as mǎo (昴), Quechua as Qullqa meaning "the storehouse," and Japanese as Subaru (昴). The Maya, Aztec, Sioux, and Kiowa peoples all wove the cluster into their own celestial narratives, making the Pleiades one of the most cross-culturally referenced objects in the entire night sky.