A very old story
“Story, as it turns out, was crucial to our evolution -- more so than opposable thumbs. Opposable thumbs let us hang on; story told us what to hang on to.”
– Lisa Cron
Stories are an integral part of the human experience, we've told too many and for too long for them to not be. And perhaps more stories have been told of the heavens than anything else. And it is one such story that we'll be visiting today, a story which might be familiar to some of us perhaps.
The tale of the 7 sisters
“And if longing seizes you for sailing the stormy seas,
when the Pleiades flee mighty Orion
and plunge into the misty deep”
– Hesiod, Works and Days
Orion, Taurus and the Pleiades in a ceaseless
cosmic chase
Maia, Elektra, Taygete, Alcyone, Celaeno, Sterope, Merope. 7 sisters, daughters of the Titan Atlas. They were renowned for their beauty, which made them an object of pursuit for men. However, one chance encounter with the mighty hunter Orion is what sealed their fate. Orion, mighty and proud, wanted the sisters for himself after falling for them. After a relentless chase, the sisters pleaded to Zeus for help. Zeus (unexpectedly) did help and immortalized the sisters in the form of stars. Later on however, Orion was also immortalized in the heavens and the chase continued, now in the sky. Taurus, the bull, was then put between the sisters and the hunter to protect them. And to this day, this cosmic drama ensues. The sisters flee, the hunter gives chase and the bull stands as a bulwark between them.
Echoed through the ages
The legend that was recounted above is from Greek mythology. However, the Pleiades have struck human fancy in all corners of the world and for a long time. There are very similar stories of seven sisters being pursued in numerous cultures around the world, including the Chinese, native Americans and Aborigines.
The Nebra sky disc, the small cluster of 7 stars at the upper right
is generally accepted to represent the Pleiades
The earliest known recorded reference to the cluster is from Chinese astronomers, dating back to 2357 BC. They are also featured on the Nebra sky disc discovered in Germany, a bronze disc which is the oldest known map of the night sky, dating back to 1600 BC.
It is very apparent from these facts that the Pleiades, and the story around them have been known for a fairly long time, about 4000 years. It is indeed a very old story but a curious fact might suggest that the story might be even older.
7 sisters, or 6?
The Pleiades have unanimously been known to represent 7 sisters, across mythologies. But what is most peculiar is the fact that the cluster only houses 6 stars visible to the naked eye. Why, then, do the legends seem to be so adamant on a count of 7?
Data from the Gaia space observatory, and others, show that the stars of the Pleiades are moving relative to each other. Two of the stars, Pleione and Atlas, are too close to each other to be resolved with the naked eye, and hence essentially appear as one. However, rewinding time to around 100,000 years ago, the two stars were much farther. Perhaps far enough from each other to be resolved by the naked eye! If one were to believe this, admittedly, speculative hypothesis, it'd suggest the origins of the story of the seven sisters to date back to as long ago as 100,000 years!
Some cool science tidbits
The more scientifically tempered among us might start to become a bit disgruntled, does the Pleiades have to offer anything besides a bedtime story? And fear not, it does!
A colour composite image of the Pleiades
At 444 light years away, the Pleiades is one of the closest and best studied star clusters in the sky. The most prominent stars are hot, blue stars of spectral class O/B formed ~100 million years ago. The very pretty nebulosity seen around the brighter stars in most images is a reflection nebula. It was thought to be leftover dust from the formation of the stars, but later studies revealed it to be an unrelated dust cloud the cluster is passing through currently.
One of the more important scientific results from the Pleiades is its use in calibrating the cosmic distance ladder. Owing to its relative proximity to us, the distance to the cluster has been measured using a set of different methods to enhance the accuracy of the measurement and then calibrating other distances based on it. Since knowing the distance to objects, and hence the cosmic distance ladder, is very important for doing astronomy, one can say a lot of our understanding of the cosmos depends on us knowing the distance to the Pleiades.
Closing
“Our obligation to survive is owed not just to ourselves but also to that Cosmos, ancient and vast, from which we spring.”
– Carl Sagan
An extremely amateur picture of the Pleiades
The heavens have been a source of fancy for us ever since the first human looked up. The story of the Pleiades is but one of the many, many stories humans have dreamt up while gazing at the sky through the ages. And while one might be correct in thinking that these stories are now obsolete, they do seem to pluck a string with a lot of us; appealing to some very deep seated emotion of ours.
Perhaps it's our longing for the stars, to find our place in all the splendour that the universe exhibits night after night. Some part of our being knows that is where we come from, that we are of the cosmos. And perhaps these stories are our way, however insignificant and obsolete, of finding our place among the stars. A place that every human who has ever looked up finds their heart yearning for.
References for images
https://upload.wikimedia.org/wikipedia/commons/e/e9/Nebra_disc_1.jpg (Nebra sky disc)
https://upload.wikimedia.org/wikipedia/commons/f/fb/Orion%2C_Taurus_and_Pleiades.jpg (Orion, Taurus, Pleiades)
https://upload.wikimedia.org/wikipedia/commons/4/4e/Pleiades_large.jpg (The Pleiades)
Other references
https://doi.org/10.48550/arXiv.2101.09170 (The lost Pleiad)
https://hubblesite.org/contents/news-releases/2004/news-2004-20.html (Pleiades and the distance ladder)
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