Why do so many cultures call the Pleiades 'seven sisters' and tell of a lost one?
From ancient Greece (Aratus, 3rd century BC: 'only six are visible') to Aboriginal Australia, the Pleiades are seven sisters, and many cultures add a story about one sister who is lost or hiding, because most people see six stars. Norris and Norris (2021) proposed the stories are about 100,000 years old: Pleione, the 7th star, is hidden today in the glare of Atlas 5 arcminutes away, but 100,000 years ago it was about 8.4 arcminutes away and seven stars showed.
How it connects
This mystery has this clue
The six visible Pleiads are the six bright ones; then comes the biggest brightness step in the cluster
This mystery has this clue
Pleione is drifting toward Atlas: 5.0 arcmin apart now, about 8.6 arcmin 100,000 years ago
This mystery has this hunch or step
The lost-sister stories date from 100,000 years ago, when Pleione stood clear of Atlas
This mystery has this clue
Aratus: seven named, 'only six are visible to the eyes' (3rd century BC)
This mystery has this hunch or step
Checked the 100,000-year 'lost Pleiad' claim with star catalogues