Seven Sisters: Past, present, and future


By Tom Burns - Stargazing



We denizens of the 21st century tend to look at the sky with a scientific eye, and, of course, there’s nothing wrong with that.

We know the stars are giant hydrogen bombs. We see the constellations as helpful conveniences to make the sky less confusing.

We are beginning to forget that humans used to tell stories about the stars — that our relationship with the starry vault was once personal and not pedantic.

There are moments, I must confess, when I feel a strong sense of compassion for those who see only the physical characteristics of the stars. Seemingly at least, they have never seen the familiar stars of winter reflected vividly in the perfectly still and perfectly clear lake of our deepest emotional and spiritual identity.

We must listen to everything the stars tell us if we are to discover who we are in this vast and glorious cosmos. We must open up our hearts as well as our minds. And we must remember that humanity is a family with many children. Each of those children has value. Each has something to say.

Thus, this week we’ll certainly look at the scientific facts, but we’ll add an old Polynesian tale I heard when I visited Hawaii a while ago. The story describes the origin of the sky’s most beautiful star cluster, the Pleiades, or Seven Sisters.

High in the south around 7:30 p.m. is a tiny, dipper-shaped collection of six stars, easily visible to the unaided eye. They can be found up and to the right from the V-shaped head of Taurus, the Bull.

The bright star in the Bull’s head is another character in the Polynesian story. Aldebaran, the angry red eye of the Bull, is the dominant star in that quadrant of the sky.

Present-day astronomers know much about the origin of the Pleiades. They are, after all, among the most studied stars in the firmament.

The stars of the Pleiades were born out of the same cloud of hydrogen gas starting about 150 million years ago.

The stars are weakly bound by gravity and hence travel through space together. A core cluster of about 80 stars clumps together in an area about eight light-years wide. (One light-year equals about six trillion miles.)

Outside the core, the cluster contains as many as 1,000 stars. The cluster’s outer stars are tenuously held together by gravity in an area about 43 light-years wide.

The whole shebang is relatively close to us at 444 light-years away.

The average age of the stars is only about 100 million years. They are young, blue and hot. By comparison, our daystar, the sun, has reached a staid 5 billion years old.

Over the next 750 million years, the cluster’s stars will slowly drift away from each other. As they travel through space, gravitational interaction with other residents of our Milky Way galaxy will lure stars from the cluster.

Why are six stars called “Seven Sisters”?

Of course, it’s simply possible that some folks in the distant past saw more than six stars. Only six are easily visible to my aging, unaided eye. A simple set of binoculars reveals a couple of dozen more.

However, experienced observers looking from dark-sky locations have reported seeing more than six stars. Nine stars are bright enough to be theoretically visible to the average unaided eye.

Eagle-eyed amateur astronomer Bob King reported seeing 14 in 2014. Robert Burnham’s famous Celestial Handbook dubiously claims that “at least 20 stars in the group … might be glimpsed under the finest conditions.”

Even the ancient Greeks, who gave the cluster its name, were puzzled. They apparently saw only six stars and wondered at the stories, old even to them, that told of seven stars.

The Seven Sisters in question were nymphs, innocent companions to Artemis, the goddess of the hunt. Their names were Maia, Electra, Taygete, Alcyone, Celaeno, Sterope and Merope, the youngest of the sisters.

Various Greek storytellers tried to explain the missing Pleiad. In one old story, the Pleiades were pursued by Orion, the mighty hunter, for (ahem) immoral purposes. To save the innocent sisters, Zeus turned them into doves, which flew into the sky to become the stars we see today. One sister got lost and didn’t ascend to the starry vault.

Another version says that the missing sister is Electra, who veiled her face when she saw the city of Troy burning. Another sister, Celaeno, was zapped by lightning.

Another story casts Merope in the role of the lost Pleiad. All her other sisters had married immortal gods. She got hitched to a mere mortal.

Horrors! Her sisters drove her away because of her unforgivable celestial faux pas. In shame, she dropped her hair in front of her face and turned into a comet. (In this context, “comet” means “hairy star.”) She flew away, leaving six stars in the cluster.

The upshot: I can imagine a gaggle of youthful faces sitting under the stars and listening to an ancient sage sonorously intoning one of the stories about the Seven Sisters. One youthful wag turns to another and whispers, “That old fogey is half blind. I can see seven stars, no problemo.”

So check out this most beautiful and mysterious of star clusters. Binoculars give the most pleasing view. Most telescopes, which work at higher magnification, cannot encompass the entire expanse of the stellar group.

Photographically, the cluster is a sight to behold. Because the star group travels through space, it is bound to encounter obstacles along the way. Currently, the Pleiades is passing through a cloud of dust and gas.

The blue light of the stars is reflected in the clouds, producing a stunning effect that you can see here: https://en.wikipedia.org/wiki/Pleiades#/media/File:Pleiades_large.jpg.

The 19th-century British poet Alfred Lord Tennyson might have been looking at an early black-and-white photograph when he describes the Pleiades as ”glitter(ing) like a swarm of fireflies caught in a silver braid.” The “silver braid” of nebulosity is invisible to the naked eye.

Of all the tales people have told about the Pleiades, my favorite is that old Polynesian story.

Long before humans lived on our planet, there was a star so supremely bright that it outshone Aldebaran, the bright red star below it in the constellation we now call Taurus.

It put to shame even Sirius, the brightest star in our contemporary sky. Brilliant Sirius, yet another character in the tale, shines far down and to the left of Aldebaran on the left side of the familiar constellation Orion.

That brightest of all stars was called Mara-Riki, or Little Eyes. So enamored was it of its own beauty that it began to boast to nearby stars that it was more lovely even than the gods themselves. The gods did not take Mara-Riki’s vanity well. They appointed Tane, guardian of the four pillars of heaven, to drive Little Eyes from the starry sky.

Realizing that vanity was not the singular purview of the brightest of stars, Tane asked Sirius and Aldebaran, the nearby bright stars, for their help. The two stars had always been jealous of Mara-Riki’s brilliance, so they willingly participated in the conspiracy.

Together, the three headed for their brighter enemy, but it saw them coming and hid under the waters of the heavenly river we call the Milky Way. Sirius, whose brilliance extended to an agile mind, quickly dammed the great river of light. Thus revealed, Mara-Riki ran away so fast that it began to disappear in the distance.

The powerful Tane picked up Aldebaran. With a mighty throw, he hit the unfortunate fugitive. The blow was so enormous that it smashed Mara-Riki into six dimmer pieces.

Fragmented and in pain, the six stars limped their way back to their former abode near the now brighter star Aldebaran. No longer do they outshine the Bull’s angry eye. Now Sirius reigns supreme as the most brilliant star in the dark bowl of night.

You’d think the formerly brilliant Mara-Riki would have learned something from these events. Pride, after all, to our western sensibilities “goeth before a fall.”

It’s pretty tough to go from the brightest bulb in the cosmos to a scattered, little cluster of stars. Wouldn’t most of us be deeply despondent over those events?

Perhaps true, indomitable vanity is something to admire if it helps us discover our truest identities. To this very day, Mara-Riki still occasionally looks down with its six eyes upon its reflection in the still ocean water.

It whispers to itself that it is far lovelier as the glorious Pleiades than it ever was as a mere star. And, in fact, Mara-Riki is right.

If you ever see those Little Eyes reflected in your own, you will know exactly what I mean.

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By Tom Burns

Stargazing

Tom Burns is the former director of the Perkins Observatory in Delaware.

Tom Burns is the former director of the Perkins Observatory in Delaware.