The Seven Sisters in a Silver Braid
Glitter like a swarm of fireflies tangled in a silver braid.”
– Alfred, Lord Tennyson
These are the famous Seven Sisters, the Pleiades, caught two nights ago in New Mexico skies. This bright star cluster stands out easily to the unaided eye in the winter sky, shining in the shoulder of Taurus.
What the eye does not see is the “silver braid” – the dim dust that surrounds the Pleiades. The stars light the dust, causing it to shine blue near the stars. Farther out, the dust is much dimmer and glows with pale tints of cyan and red.
The dust clouds were once thought to be what was leftover from the formation of the stars, now estimated to have occurred about 100 million years ago. However, current theory suggests that the natal dust of the Pleiads would have long since dispersed.
Instead, the silvery braids of dust that surround the Seven Sisters are just nearby dust clouds in Taurus that the stars are passing through, and illuminating with their hot blue light.
The Pleiades, as familiar as they are – they have been mentioned in ancient texts and myths dating back thousand of years – remain a source of scientific controversy. Astronomers argue over their distance, with different methods providing different results. But the best recent measurement puts them 440 light years away.
Technical notes: This is a stack of 10 x 12 minute exposures at ISO 400 with the Canon 5D MkII camera and 92mm TMB refractor at f/4.4. I shot the images November 16 from near Silver City, New Mexico.
– Alan, November 18, 2014 / © 2014 Alan Dyer