Wednesday, 20 January 2016

M45, the Pleiades

The Pleiades were the seven daughters of Atlas, the giant of Greek mythology who carried the Earth on his shoulders. Zeus attached them to the sky so they could escape ruthless Orion who was set to hunt them down and kill them. In the winter sky you can still see Orion hopelessly chasing them towards the west, without ever catching them.

Astronomically speaking, the Pleiades are the brightest, the most famous and probably also the closest of all star clusters, with a distance currently estimated at around 440 lightyears. The main stars are still incredibly hot but with an age of over 100.000 years they've outgrown their "baby star" status and are ready to start their voyage through our galaxy. Calculations have shown that the cluster will be completely dispersed by interstellar gravitational forces within the next 250.000 years. Curiously enough, we can still observe a lot of nebulosity around the main stars and for a long time scientists have held the belief that this was dust and gas left over from the stars' birth. Recent analysis however, found that the stars are indeed too old for that and that the original gas and dust from their birth has already dissolved into space. It is therefore believed that the cluster is just coincidentally passing through a very dusty part of our galaxy. The fierce heat of these young stars reflects on the dark dustclouds and makes them visible to us. 

The best way to observe this cluster is... the naked eye. Just look up to the south on a winter's evening and you can't miss them. Also an ordinary pair of field binoculars (a 7x50 or 10x50 would do perfectly) will yield an amazing view. With my 24x100 binoculars, the magnification was a bit exaggerated to my taste. The more you increase magnification, the more you're looking "through" a cluster. But the bright nebulosity surely made up for that.


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