The Pleiades / Seven Sisters
The Pleiades are easy to love: a tiny blue-white cluster in Taurus, visible to the naked eye, beautiful in binoculars, and wrapped in mythology from cultures around the world.
Image credit: Davide De Martin & the ESA/ESO/NASA Photoshop FITS Liberator. Built from DSS2 red and blue survey data with a generated green channel.
Also Known As
M45, Messier 45, Seven Sisters
Constellation
Taurus
Object Type
Open star cluster
Best Viewing
Late fall through winter in the Northern Hemisphere
A young blue cluster moving through dust
The Pleiades are an open star cluster, meaning the stars formed together and remain loosely held by gravity. The brightest members are hot, young, blue-white stars. Their famous glow comes from reflection nebulosity: dust in space scattering blue light from the stars.
It is tempting to imagine the blue haze as leftover material from the cluster’s birth, but the better explanation is more poetic: the Pleiades are currently passing through a separate cloud of interstellar dust.
Three views of the Seven Sisters
DSS2 / FITS Liberator
Processed by Davide De Martin in Venezia, Italy, using Digitized Sky Survey 2 data in red and blue bands with a generated green layer.
Hubble Close-Up
Taken from space by Hubble. This image focuses on the dust stream near Merope, one of the famous bright stars of the cluster.
ESO / S. Brunier
A wide photographic view credited to ESO/S. Brunier. The source page does not list a single observing site, so the location is left unstated rather than guessed.
The star cluster people noticed everywhere
The Pleiades have no single discoverer because people have watched them since antiquity. Galileo was among the first known observers to turn a telescope toward them, revealing more stars than the naked eye could separate.
In Greek mythology, the Seven Sisters were daughters of Atlas and Pleione. A common story says Orion pursued them, and Zeus placed them in the sky. The names most often listed are Alcyone, Asterope, Celaeno, Electra, Maia, Merope, and Taygete.
The fun “scandal” is the missing seventh sister. Why call them the Seven Sisters when many people only see six? Some myths blame Merope hiding her face; others point to Electra. In practice, visibility depends on eyesight, sky darkness, and the stars’ closeness to one another.
One of the easiest deep-sky objects to enjoy
Look toward Taurus during late fall and winter. The Pleiades look like a tiny misty dipper. From a reasonably dark sky, they are obvious to the naked eye. Binoculars are usually better than a telescope because they keep the whole cluster in view.
Best setup
Use your eyes first, then binoculars. A small telescope can be beautiful, but it may zoom in too far for the whole cluster.
Best season
For Minnesota and most of the Northern Hemisphere, October through March is the comfortable window, with December especially strong.
Primary sources: NASA Messier 45 guide, ESO Pleiades image and facts, ESA/Hubble FITS Liberator Pleiades image, and Britannica mythology reference.
More astronomy notes
Continue through the astronomy section for beginner-friendly notes, image credits, viewing tips, history, and the stories behind the night sky.