The curious case of Pleiades: The 7 sisters

-Written by Yash Jagtap, reviewed by Muskan Agarwal

The Pleiades is a famous open star cluster, generally visible as six stars, but the stories surrounding the Pleiades call them seven sisters. What happened to the lost Pleiad? Why are there variations of stories? Where did these stories originate?

The general public considers astronomy a very fancy art form (yes, an art form, it’s more than science). To look at clear skies, one needs to go away from the light pollution of cities. Observing the night sky is not a very common activity among the masses these days, but this was not the case thousands of years ago when there was no light pollution and people had no distractions; people gazed at the skies every day. 

A bit about our ancestors

Humans are keen observers, and we tend to find patterns and connect them with ourselves. That is what our ancestors did. They looked up in the night sky – saw patterns – connected the dots – tried to make sense of it in the form of stories – and used the regularity of the night sky for agricultural purposes, ceremonies, etc. The sky was their calendar, their god and guide. One such entity has guided our ancestors and still continues to amaze us- The Pleiades. And recently, some revelations have come forward, which date back to 100,000 years and connect humans and the sky more. 

The present

First, let’s talk about this star cluster in modern scientific terms. M45 is located in the constellation Taurus. It is an open star cluster. Its structure looks like a duplicate version of the Big Dipper (the asterism). The stars in this cluster are relatively new, formed around 115 to 125 million years ago. The stars have a shorter life span compared to our Sun and they are hot, blue, and interstellar dust surrounds this cluster. This cluster is visible in the night sky due to its apparent magnitude of 1.6. Now let’s come to the stories surrounding this group of stars-

Stories of the Pleiades and a slight mystery

There are a lot of stories that represent the Pleiades as a group of children, a busy market, etc. However, we won’t consider those as they are not so important contextually and are not relevant and popular. Instead, we will focus on stories that are similar in different parts of the world, and also discuss the reasons for the same.

Greek mythology: Orion the Hunter is chasing the Pleiades, the seven sisters. These seven are the daughters of Atlas (Titan God) and Pleione (Ocean nymph). Atlas was sentenced to hold up the sky on his shoulders due to his rebellion against Zeus; he couldn’t protect his daughters from Orion. Hence, Zeus turned the seven sisters into Stars to safeguard them.

Want to read more about constellations? Read our blog here 

Aboriginal Australian stories: Many Aboriginal cultures associate Orion as a Hunter or a group of men chasing young women/girls, i.e. the Pleiades.

Both the stories are quite old and are passed on from generation to generation; these stories date before the Aboriginal people had any contact with the outside world. But still, folk tales from both parts of the world are quite similar.

Another enigma surrounding the Pleiades is that some stories from European, African and Aboriginal consider the Pleiades six instead of seven sisters/women and point out that one is dim or invisible. 

Let’s see what the possible answers to the above two expressions are.

A logical answer to Pleiades mysteries

As we all know that the universe is constantly changing, and a newly formed open cluster like the Pleiades will also go through a few changes. The cluster is currently passing through a cloud of reflective dust, which is not the remnant from the cluster itself but from some other interstellar dust.

The stars Atlas and Pleione optically appear very close to each other; Pleione is small and behind Atlas. In today’s time with the naked eye, we can see only one, and in rare conditions both are visible. Now, if we consider the movement of this cluster in the past 100,000 years, we found that the stars Atlas and Pleione were far apart from where they are today and appeared as two separate stars.

And according to the ‘Out of Africa Hypothesis’, ancestors of Europeans and Aboriginal Australians were closely related and originated from Africa in 100,000 BC. And these people saw the Pleiades clearly as seven stars. Ancestors of aboriginal people migrated from Africa following the coast of India and China and eventually reaching Papua New Guinea and then arriving in Northern Australia and along with them, they brought the stories of the ‘Seven’ sisters. They came in a single wave between 40,000 BC and 50,000 BC. Since then, they have had an uninterrupted culture until 1788 when the Europeans arrived.

Similarly, ancestors of Europeans also brought similar stories which stayed with them. As the story was passed from generation to generation, it went through minor changes, and different subgroups came up with their variation. Although, the interpretation that was very major and is found in both European and Aboriginal Folk Tales- is considering the Pleiades as Six stars.

This variation might have happened when the reflective cloud surrounding the Pleiades caused Glare and made one of the stars invisible to the naked eye (also considering the movement of clusters as mentioned above). So people came up with stories that explain one star’s dimming or invisibility. 

In Hindu star folktales as mentioned in old texts around 2500 years ago, the story goes as follows- The seven stars of the big dipper asterism represent the seven sages and each of them was married. Their wives together are called Krithika. Now there was another man “Agni”, who was in love with the Krithikas but as they all were married Agni lost hope and wandered the forests in vain.

Now, Svaha was in love with Agni, but as he was in vain, Svaha decided to disguise herself as six Krithikas. She successfully married Agni while she had changed her appearance, but later when they had children the false rumours spread that they were the children of the six Krithikas. Which led to the separation of six out of the seven couples. The six Krithika stayed separate as the Pleiades while Arundhati stayed with Vaishistha in the Saptarshi itself both as double stars which we today call as Alcor-Mizar. 

This does show that even Indians saw the Pleiades as six and not seven. And thus, we can see that the Pleiades has come a long way, from our ancestors to us. We are genuinely fascinated, and we can see that people in Ancient times were quite keen observers of the night sky.

Stay tuned on our website for more such Astronomical history mysteries.

Enjoyed reading this article? Consider reading: Murphy’s Law: Will it go wrong?