Pleiades: The Seven Sisters Stars on Halloween

What Are the Pleiades?

The Pleiades, also known as the Seven Sisters, is a tightly packed cluster of stars. It’s technically an “asterism” (a pattern of stars of similar brightness) versus an official constellation and appears in the northwest of the constellation Taurus. The Pleiades are among the nearest star clusters to Earth, and one of the most easily seen with the naked eye. 

How Old is the Pleiades Star Cluster?

No obstetrician attended the birth of the Pleiades, 60 million years ago. As these fiercely hot suns awakened from the dazzling and dangerous gaseous nursery, the newborn stars materialized like a distant sunrise in the skies of Earth 400 light years away.

The Pleiades gave the ancients a sense of time. Over 10,000 years ago, hunter-gatherers in the Palaeolithic period were able to observe the Pleiades appear in late October and disappear in April, thus signaling winter’s end and the beginning of the new agricultural season. (They are summer stars in the Southern Hemisphere with the opposite interpretation.) We know this because representations of this prominent pattern of stars appear on paintings in the cave of Lascaux (France), which date from 15000 BCE (before the common era).

Pleiades Meaning and Symbolism

The star cluster seems harmless. But that wasn’t always the case. In ancient times, the Pleiades had a strange reputation. Such medieval rituals as the pagan Black Sabbath and All Hallow’s Eve (which evolved into our own Halloween) were set to occur when the Pleiades reached their highest point at midnight. Some have speculated that the rituals could have originated as commemorating some ancient catastrophe that resulted in great loss of life. Some believe they may be linked to the Atlantis myth, itself perhaps a legend that evolved from the Santorini Volcano’s awesome eruption in 1450 BC that devastated the Minoan civilization on nearby Crete.        

The Pleiades had an odd importance to civilizations throughout time and around the world. In Egypt, they were revered as one of the forms of the goddess Isis. In ancient Persia, the date in which they reached their highest midnight ascendancy was marked with ceremony. In Mayan and Aztec culture, this same yearly occasion had a forbidding undertone and was given tremendous importance—with at least one city’s streets and pyramid aligned with the setting of the Pleiades.

Why is Pleiades called the Seven Sisters?

The seven sisters comes from Greek mythology. The Pleiads were the seven daughters of Atlas, a Titan who held up the sky, and the Oceanid Pleione, the protectress of sailing. The sisters have names: Alcyone, Asterope, Electra, Celaeno, Maia, Merope, and Taygete.

Stars of Subaru

In Japan, this star cluster’s ancient name is Subaru. Until very recently, the six Japanese companies that merged to produce automobiles in 1953 placed a crude star map of the Pleiades on each of their cars. Over the years, its single brighter star has been portrayed as ever-more luminous and increasingly separated from the others, perhaps revealing some corporate infighting.

The Lost 7th Sister

But why seven sisters? That’s the real mystery. After all, normal eyesight readily sees only six, the same number found on the Subaru insignia.

Of course, how many stars you can perceive tells as much about the purity of your sky as the state of your vision. However, civilizations as disparate as the ancient Greeks, Australian aborigines, and Japanese all possessed legends of the “lost Pleiad” which have persisted through the centuries? Even two thousand years ago, a Greek poet wrote:

           “…their number seven, though the myths often say…that one has passed away.”         

One clue is that, as binoculars reveal, they’re blue—a color that indicates stellar youth. Young, hot, giant stars are often unstable, gobbling up their nuclear fuel in an adolescent frenzy that frequently produces instability.

They’re in their infancy even today: our own sun has been around 250 times longer. The dinosaurs gazed unconcernedly into a sky empty of the Sisters, which sprang into view just before we ourselves did. So maybe one of these newborns lost a bit of its light.   Since all massive stars die young, the Pleiades will be long gone when most of the galaxy’s stars are still enjoying middle age.

Toddling gracefully across November’s chilly skies —and very much linked with Halloween—the newborn sisters are only for now.

What’s the Moon phase this Halloween? Check out our Moon Phase Calendar to find out, and learn how rare a full Moon on Halloween is!