Pleiades Star Cluster: A Stellar Guide on The Seven Sisters

For centuries, the Pleiades star cluster has captured the imaginations of skywatchers, poets, and astronomers alike. Often referred to as the “Seven Sisters”, this luminous cluster of stars is one of the closest and most easily visible star clusters from Earth. The Pleiades are a compact open cluster primarily consisting of blue giant stars, only about 375–400 light years from us and about 40 light-years wide. About 1,000 stars reside in the Pleiades cluster in total.

The Pleiades star cluster is part of the constellation Taurus the Bull but is far from the Hyades and the rest of the naked-eye stars of the Bull, which is why many scholars have historically counted them as their own mini-constellation. The cluster is identified as Messier 45 or M45 in shorthand, though most people just refer to the cluster as “the Pleiades” or “Pleaides Cluster” or the Japanese name “Subaru”.

Plaiades Star Cluster Photographed using H-alpha mod Nikon Z6 & Samyang 135mm
Fornax Lightrack ii tracking mount

With an estimated age of around 250 million years, the Pleiades star cluster is relatively young in cosmic terms, like most open star clusters, which typically last no more than a billion years before they gradually drift apart. Moreover, a key feature of the Pleiades is the presence of a reflection nebula, a type of nebula where a cloud of interstellar dust reflects the light of nearby stars. In the case of the Pleiades, the blue light from the young, hot stars of the cluster is scattered in all directions by the surrounding dust, originally thought to be leftover material from the cluster’s formation. The nebula surrounding the Pleiades is actually entirely unrelated to the cluster.

Also nestled amongst the bright blue giants of the Pleiades cluster is Teide 1, the first brown dwarf ever discovered. Brown dwarfs are curious celestial objects, often dubbed “failed stars” because they occupy the ambiguous space between the largest planets and the smallest main-sequence stars. Their inability to sustain hydrogen fusion like a proper star makes them intriguing subjects of study.

Star Cluster Pleiades in Mythology

The Pleiades, with its tight-knit cluster of stars, has not just been a focal point for astronomers but has also captured the imagination of civilizations throughout history. For whatever reason, despite at least nine stars in the cluster being visible to the naked eye even under sub-par conditions, most myths center around the number seven or six, ignoring the fairly prominent stars Pleione and Celaeno, as well as even Taygeta in some cases. These stars are packed quite close to the brighter members of the cluster, and thus they may have been ignored because many ancient skywatchers had sub-par eyesight. In addition to the lack of eyeglasses in ancient civilizations, many people would have almost constant on-and-off or permanently scratched corneas from living in dirty conditions. This causes more glare and apparent spikes emanating from brighter stars, which can mask nearby dim ones, such as Pleione and Celaeno. In some cases, scratched corneas—or just inherently bad eyes—could be enough to blur the stars Maia and Taygeta together too.

However, that’s not the only explanation. Pleione was closer to the much brighter star Atlas in the distant past – albeit 100,000 years ago. The oddly similar myths surrounding the cluster, independent of seemingly any cultural or chronological association, could mean that the Pleiades have resided in the myths and legends of humans since anatomically modern Homo Sapiens have walked the Earth. The cluster is depicted in the 17,000-year-old Lascaux cave paintings alongside Taurus and Orion, which are similarly ancient constellations that also appear to have consistently similar mythologies across cultures and over time.

Regardless of the inaccuracy of their count by earlier generations, perhaps the most famous of all of the Pleiades’ tales—as well as its name—comes from ancient Greece. The Pleiades were said to be the seven daughters of the Titan Atlas and the sea-nymph Pleione. These sisters were Alcyone, Merope, Celaeno, Taygete, Sterope, Electra, and Maia. As the story goes, to protect them from the hunter Orion’s incessant pursuit, Zeus transformed them into doves and then into stars. Merope, the only mortal among the sisters, shines less brightly than her siblings due to her mortal lineage.

The other most familiar interpretation of the Pleiades comes from Japan. In Japan, the Pleiades are called “Subaru,” which means “united” or “gathered together,” a reflection of the cluster’s appearance. The automaker Subaru derives its name from this star cluster, and its emblem showcases a stylized representation of the Pleiades. The Subaru Telescope in Hawaii, one of the largest in the world with an 8.2-meter primary mirror, is also named after the cluster.

For the Native Americans, the Pleiades had various interpretations. Some tribes viewed them as seven boys who danced their way into the sky. The Kiowa tribe tells a story of seven girls who were chased by bears and were saved when they were placed in the sky, with the pursuing bears turning into Ursa Major, or the Great Bear, which coincidentally appears similar in shape to the cluster (and is itself a very large and spread out open cluster, once much like the Seven Sisters). In Vedic literature, the Pleiades are referred to as the star cluster ‘Krittika‘ and are associated with the god of war, Kartikeya, who was raised by the sisters represented by the cluster.

In New Zealand, the Pleiades are called Matariki and are associated with the Maori New Year. Their re-emergence in the winter sky marks a time of remembrance, celebration, and the sowing of new crops. The Berber cultures of North Africa likewise celebrate the cluster as a bearer of good crops, albeit for the fall harvest season.

In ancient Mesopotamian folklore and various successor civilizations, the Pleiades were associated with the goddess Ishtar, or Inanna, who was also associated with the planet Venus. During the springtime months in the evening, in years when Venus is visible after sunset, the “evening star” does lie around the stars of Taurus or near the cluster itself, which may explain the linkage between the two. Ishtar herself was associated with springtime and fertility, as well as love. Aphrodite/Venus in Greek and Roman mythology were influenced by Ishtar, and they are all likely to be derived from a common Indo-European predecessor goddess.

The Pleiades are also mentioned in the Bible in the books of Job and Amos, a testament to their prominence in ancient skies. They are cited as evidence of God’s might and creation: He can move the stars in the cluster, but Job cannot.

Interestingly, Islamic historian Ibn Ishaq reports that scholars of the Islamic world were aware of twelve stars in the Pleiades star cluster—around the actual number of stars most observers will be able to spot with the unaided eye at a glance. In Arabic, the cluster is referred to as Thurayya. This name made its way into the Turkish and Farsi languages as Soraya or Suraya, which is a common female first name in many parts of the world even today. The name of the Pleiades cluster itself in Farsi is Parveen, which is also a commonly used first name for women.

An amateur astronomer and telescope maker from Connecticut who has been featured on TIME Magazine, National Geographic, Sky & Telescope, La Vanguardia, and The Guardian. Zane has owned over 425 telescopes, of which around 400 he has actually gotten to take out under the stars.

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