081223 A Christmas cluster

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A Christmas cluster

BY DR EMILY BALDWIN

ASTRONOMY NOW

Posted: 23 December, 2008

The festive season has arrived for astronomers at the European Southern Observatory, in the form of a spectacular image of NGC 2264, which includes the sparkling blue baubles of the Christmas Tree star cluster.

It was William Herschel who discovered NGC 2264 in the late 18th century, in the somewhat obscure constellation of Monoceros the Unicorn located around 2,600 light years away, not far from the more familiar outline of Orion the Hunter.

The cluster is extremely bright and can easily be seen with binoculars, but with a small telescope the stars resemble the glittering lights on a Christmas tree. The dazzling star at the top of the ‘tree’ is bright enough to be seen with the unaided eye and is a massive multiple star system that only emerged from the surrounding dust and gas a few million years ago.

NGC 2264 with its Christmas Tree Cluster, Cone Nebula, Fox Fur Nebula, star forming regions and more besides. Image: ESO.

As well as the Christmas Tree Cluster there is a feast of other intriguing structures embedded within the gas and dust. At the bottom of the frame is the dark triangular feature of the Cone Nebula, a region of molecular gas flooded by the harsh light of the brightest cluster members. And at the top right of the image a patch of gas displays a curious fur-like texture that has led to the name Fox Fur Nebula.

Much of the image appears red because the huge clouds of gas are glowing under the intense ultraviolet light streaming from energetic hot young stars. The stars themselves appear blue as they are hotter, younger and more massive than our own Sun. Some of this blue light is scattered by dust, as seen in the upper part of the image.

This fascinating region forms an ideal laboratory for studying how stars are born, and the entire area shown here is just a small 30 light year wide part of an even greater cloud of molecular gas that is in the process of spawning the next generation of stars. In the region between the tip of the Cone Nebula and the brightest star at the top of the picture there are several stellar birthing grounds where young stars are forming. There is even evidence of the intense stellar winds from these youthful embryos blasting out the hidden stars in the making.

Happy Christmas!