Why An Open Star Cluster Pleiades Called ‘Seven Sisters’ ?

Source : cwjames

People both modern & ancient have long known of the Pleiades or Seven Sisters, a small collection of stars in the constellation Taurus.

But this famous assembly point the world’s oldest story, one told by our ancestors in Africa nearly 100,000 years ago, a speculative new study proposed. To make this case, the paper authors draw on similarities between Greek & Indigenous Australian myths about the constellation. But one expert said that similarities in these myths might be pure chance, not a sign that they emerged from a common origin.

The Pleiades are a part of what astronomers call, an open star cluster, a set of stars all born around the same time. Telescopes have identified more than 800 stars in the region, though most humans can spot only about 6 on a clear, dark night.

Yet cultures around the world have often mentioned this constellation with the number seven, calling them, the Seven Sisters, Seven Maidens, or “Seven Little Girls”. This head scratcher has puzzled many scientists, like astrophysicist Ray Norris of Western Sydney University and Commonwealth Scientific & Industrial Research Organization (CSIRO) Astronomy & Space Science in Australia.

Norris has worked with Indigenous Australians and learned many of their sky stories, including those of various groups who identify the Pleiades as seven girls being chased-by the constellation Orion, who is a hunter in these tales. This storyline is extremely almost like the one in ancient Greek legends about these constellations.

“I’ve always thought, ‘Oh that’s really weird,'” Norris said.

The case is not entirely surprising, given that both Orion & the Pleiades are bright & prominent celestial features, which Earth‘s rotation makes it look to us just like the former is chasing the latter across the night sky. Some researchers have tried to elucidate the narrative resemblance through simple cultural exchange, said Norris, given that Europeans arrived in Australia more than 2 centuries ago. But such a timescale isn’t long enough for the story to have become so deeply-embedded across different, far-flung Australian cultures, he added.

Norris noted that one among the Seven Sisters, a star referred to as Pleione, is usually lost in the glare of a close-by star called Atlas, making it invisible to most human eyes. But 100,000 years ago, when humans were first emerging from African continent and spreading over the world, the 2 stars would be more separated in the night sky, perhaps accounting for why the Pleiades are named for seven beings in many stories. In other words, our ancestors who had not yet left Africa first came-up with the story, then carried this story about the night sky with them as they migrated to Europe, across Asia & eventually to Australia.

“You’ve got these 2 bits of circumstantial evidence,” said Norris. “Together they create an interesting hypothesis.” Along-with a co-author, he posted a paper January 25 about this possibility to the pre-print database arXiv. Their study has been accepted to, but not yet published in a peer-reviewed journal.

While noting that it is a “fun & evocative idea,” astronomer & archaeo-historian Bradley Schaefer of Louisiana State University in Baton Rouge, who wasn’t involved in the work, didn’t think the explanation likely.

“Humans are humans,” in order that they will populate the sky with male & female figures. By chance alone, about half the time, you’d expect a given constellation to be related to men & half the time with women. Which means,” about one-quarter of that time, Orion will be male & the Pleiades will be female,” Schaefer said.

Given the large number of traditional stories, simple coincidences between any given 2 cultures are likely to crop-up, Schaefer said. He also pointed-out that the Norris paper used outdated stellar positioning information to model the distance between Pleione & Atlas 100,000 years ago. The correct data places them twice closer during this epoch, meaning there wouldn’t be much significant change in how the constellation seemed to our ancestors.

Norris’ paper doesn’t entirely hinge-on this fact, mentioning that the stars in the Pleiades are thought to vary with brightness and maybe 100,000 years ago, one among the very faint stars was far more visible, though nobody knows what proportion these stars vary in brightness over the long-term.

It’s possible the hypothesis is correct, Schaefer said, but the available evidence is not convincing. It provides a “lesson of what it takes to-prove something like this,” he added.

He gave as a counter-example the Big Dipper, another well-known constellation, that cultures across Eurasia describe it as a bear. In this case, evidence suggests at least some tales about the Big Dipper likely did emerge from a common-origin story, he said.

For example, in a significant number of those, the ladle of the Dipper is given because the body of the bear and the three stars of the handle are identified as its tail (though bears do not have long tails).

Yet in many of the folk stories of Siberian people in the Eastern Russia, where people also recognize the Big Dipper as a bear, there’s an alteration. The ladle still the bear’s body, but the three stars of the handle are branded as the three hunters chasing the bear. Mizar, the central star of the handle, features a small faint companion referred to as Alcor and in the Siberian stories Alcor is a bird helping-lead the hunters to the bear, Schaefer said.

A significant number of Native American tales, told by peoples spread across the North American, continent north of the Rio Grande, have a really similar set-up for the Big Dipper, including the bear, hunters & steering bird, he added. Given that an excellent deal of other evidence shows that humans migrated over an ancient land bridge in the Bering Strait between modern-day Russia & Alaska thousands of years ago, Schaefer thought it had been far more likely that these Big Dipper stories share a common origin.

Even this explanation isn’t universally accepted by archeo-historians, he added. But the various shared “characteristics mean that it’s an evocative, fun & certain true story,” he said. It’d not be the titanic 100,000 years suggested timespan of Orion & the Pleiades, but having a tale that’s at least 14,000-year-old remains quite impressive, Schaefer said.

“That makes the Great Bear the oldest intellectual property of humanity,” he said.

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