The Pleiades

To the naked eye you can make out six or seven of them, packed together like a tiny dipper in the winter sky. The Pleiades are one of the closest star clusters to us, and one of humanity's oldest companions: many cultures saw in them a small group of sisters. To the Greeks, the seven daughters of Atlas, pursued across the sky by Orion the hunter.

They are in fact a good thousand stars born together about a hundred million years ago, in the constellation of Taurus. Recent measurements by the Gaia satellite place the cluster about 444 light-years away. The brightest are large blue stars, young and hot.

Around them drifts a bluish veil that photography reveals. For a long time it was thought to be the cloud that gave birth to them. We now know that is not so: this dust is not theirs; the cluster is merely passing through it, by chance, on its journey across the Galaxy. It simply scatters back the blue light of the stars, like fog lit by a lighthouse.