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open star cluster

What are the Pleiades?

Famous open star cluster of young stars, visible to the naked eye as a small dipper-shaped knot of six or more stars.

Worth knowing about the Pleiades

You see the Pleiades as they were 439.8 years ago.

Why it stands out
Most people see six stars, not seven; sharp eyes under a dark sky can pick out nine or ten, or more.
What it is
An open star cluster — a loose group of over a thousand young stars born together; the brightest are hot and blue.
How we know: Comparing its hottest, brightest stars to stellar-evolution models gives its age: about 100 million years.
Its name and its story
Named for seven sisters in Greek mythology (daughters of Atlas and Pleione), placed among the stars by Zeus to protect them from Orion; also known as Subaru (Japan) and Matariki (Māori).
The Pleiades (Seven Sisters) — A model, seen from the Earth, with north up.
The numbers
Acrossabout 14 light-years
Distance from us439.8 light-years
How big it looks1.8 degrees — about 4 full Moons across

We use 439.8 light-years, from Gaia’s parallaxes of its members (Hunt & Reffert 2023). A radio parallax of a few members gives 444.2 (Melis et al. 2014).

How anyone knows this

Things like it

The Beehive Cluster (Praesepe)open star clusterNaked eyeThe Scorpius-Centaurus OB AssociationOB associationNaked eyeThe Hercules Cluster (M13)globular star clusterBinoculars
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