Come To Know Pleiades Star Cluster, Aka Seven Sisters

The Pleiades star cluster – also known as the Seven Sisters or M45 – is visible from virtually every part of the globe. It can be seen from as far north as the North Pole, and farther south than the southernmost tip of South America. It looks like a tiny misty dipper of stars.

If you’re familiar with the famous constellation Orion, it can help you be sure you’ve found the Pleiades. See the three stars in a row in Orion? That’s Orion’s Belt. Draw a line through these stars to the V-shaped pattern of stars with a bright star in its midst. The V-shaped pattern is the Face of Taurus the Bull. The bright star in the V – called Aldebaran – depicts the Bull’s Eye. A bit past Aldebaran, you’ll see the Pleiades cluster, which marks the Bull’s Shoulder.

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Star field with bright glowing spot and dipper-shaped group of prominent stars.
Tom Wildoner of the Dark Side Observatory wrote: “I was lucky on the evening on March 27, 2020, to capture this nice view of the planet Venus approaching the Pleiades star cluster in the constellation Taurus.” Thank you, Tom!
Star chart of constellation Orion with arrow pointing to Aldebaran, and Pleiades farther on.
If you can find the prominent constellation Orion, you can find the Pleiades. Orion’s Belt points to the bright reddish star Aldebaran … then generally toward the Pleiades.
The Pleiades and Aldebaran. The star name Aldebaran comes from an Arabic word for follower. It’s thought to be a reference to this star’s forever chasing the Pleiades across the heavens. As a general rule, the Pleiades cluster rises into the eastern sky before Aldebaran rises, and sets in the west before Aldebaran sets.

The only exception to this rule happens at far southern latitudes – for example, at South America’s Tierra del Fuego – where the Pleiades rise a short while after Aldebaran rises.

In our Northern Hemispheres skies, the Pleiades cluster is associated with the winter season. It’s easy to imagine this misty patch of icy-blue suns as hoarfrost clinging to the dome of night. Frosty November is often called the month of the Pleiades, because it’s at this time that the Pleiades shine from dusk until dawn. But you can see the Pleiades cluster in the evening sky well into April.

Starry sky with small distinct cluster of stars near the horizon’s glow.
View larger. | Claire L. Shickora wrote from Delight’s Hot Springs Resort in California in early November 2018: “The Pleiades was outstanding, even with the local light pollution!”
At least a dozen bright stars in glowing blue wispy clouds against very starry background.
Fred Espenak – aka Mr. Eclipse – posted this image at EarthSky Facebook on November 18, 2018. He wrote: “M45, the Pleiades star cluster. It’s visible on November nights in the eastern sky as a tiny dipper-shaped clump of stars. Definitely one of the most beautiful open star clusters in the sky. This image is a stack of 20 individual 5-minute exposures through a Takahashi Epsilon 180ED Hyperbolic Astrograph using a Canon 6D DSLR.” Thanks, Fred!
Glowing star cluster in slightly cloudy twilit sky above finely detailed trees.
Tom Wildoner in Weatherly, Pennsylvania, captured this image on October 31, 2016. He wrote: “It shows the Seven Sisters, Pleiades star cluster, rising in the east behind some maple trees still sporting some late leaves.”
Legend of the Lost Pleiad. Most people see six, not seven, Pleiades stars in a dark country sky.

However, the story about the lost seventh Pleiad harbors a universal theme. The astronomer Robert Burnham Jr. found the lost Pleaid myth prevalent in the star lore of European, African, Asian, Indonesian, Native American and Aboriginal Australian populations.

Moreover, Burnham suggested that the “lost Pleiad” may have basis in fact. After all, modern astronomy has found that the seventh-brightest Pleiades star – Pleione – is a complicated and hard-to-understand “shell star” that goes through numerous permutations. These changes cause this star to vary in brightness.

Plus people with exceptional eyesight have been known to see many more stars in the Pleiades cluster. Claims go up as high as 20 stars. Agnes Clerke, an astronomer and writer in the late 1800s, reported that Michael Maestlin, the mentor of Johannes Kepler, mapped out 11 Pleiades stars before the invention of the telescope.

To see more than six or seven Pleiades stars, you must have very good eyesight (or a pair of binoculars). And you must be willing to spend time under a dark, moonless sky. Stephen O’Meara, a dark-sky connoisseur, claims that eyes dark-adapted for 30 minutes are six times more sensitive to light than eyes dark-adapted for 15 minutes. The surest way to see additional Pleiades stars is to look at this cluster through binoculars or low power in a telescope.

A Greek nymph viewed from the back floating in the air with a circle of dancing nymphs beyond.
The Lost Pleiad, a painting by French artist William-Adolphe Bouguereau (1825-1905). Image via Wikimedia Commons.
Pleiades as calendar, in history and in modern science. Historically, the Pleiades have served as a calendar for many civilizations. The Greek name “Pleiades” probably comes from a word meaning “to sail.” In the ancient Mediterranean world, the day that the Pleiades cluster first appeared in the morning sky before sunrise announced the opening of the navigation season.

The modern-day festival of Halloween originates from an old Druid rite that coincided with the midnight culmination of the Pleiades cluster. It was believed that the veil dividing the living from the dead is at its thinnest when the Pleiades culminates – reaches its highest point in the sky – at midnight.

On a lighter note, the Zuni of New Mexico call the Pleiades the “Seed Stars,” because this cluster’s disappearance in the evening sky every spring signals the seed-planting season.

In both myth and science, the Pleiades are considered to be sibling stars. Modern astronomers say the Pleiades stars were born from the same cloud of gas and dust some 100 million years ago. This gravitationally bound cluster of several hundred stars looms some 430 light-years distant, and these sibling stars drift through space together at about 25 miles per second (40 km/sec). Many of these Pleiades stars shine hundreds of times more brightly than our sun.

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Closeup of numerous close together bright stars in glowing blue clouds.
The Pleiades – aka the Seven Sisters – captured by Greg Hogan in Kathleen, Georgia, on October 31, 2016.
Roundish patch of bright glowing blue with stars in it against starry background.
The Pleiades star cluster by Ernie Rossi in Florida. Russ Drum submitted it and wrote: “The Pleiades (aka the Seven Sisters) is an open star cluster located in the constellation Taurus the Bull. It’s also known as the Halloween Cluster because it’s almost overhead in the sky at midnight on Halloween, October 31.”
Bottom line: What is the Pleiades – or Seven Sisters – star cluster? How to see it in your night sky.

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