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The open cluster NGC 6520 and Barnard 86 in the constellation Sagittarius

Short Object description:

Our image shows the bright open star cluster NGC 6520 and its strange neighbor Barnard 86, a dark cloud that reminds us of the silhouette of a gecko. The cosmic couple stands against the background of millions of stars in the brightest part of our Milky Way. The stars of the Milky Way in this region of the sky are so densely crowded that there is hardly any dark sky left between them.

This part of the constellation Sagittarius is home to one of the most densely populated star fields in the entire sky - the great Sagittarius star cloud. The multitude of bright stars create a dramatic contrast to black dark clouds like Barnard 86 in the center of this image, taken with our 12.5 inch Planewave Astrograph.
Barnard 86, a so-called Bok globule, was described by his discoverer Edward Emerson Barnard as a "drop of ink on a bright star background". Barnard was an American astronomer who, among numerous other contributions to science, discovered and photographed a large number of comets, dark clouds and a Jupiter moon. As an exceptionally gifted visual observer and astrophotographer, Barnard was the first to make long time exposures to study dark clouds. Barnard included the object in his catalogue of dark nebulae in 1905.

Barnard 86 lies in front of the star field when viewed from Earth. The small grains of dust that make up the cold and dense dark cloud absorb the light of the stars behind it and it appears opaque. Presumably we can see here the remains of the molecular cloud which collapsed to form the nearby star cluster NGC 6520. The few stars that seem to stand in the middle of Barnard 86 are in reality in the foreground, between us and the dark cloud.

As a young open cluster of stars, NGC 6520 contains many hot stars. Its blue-white glow reveals its low age. Usually open star clusters consist of several thousand stars that have formed at the same time and are therefore of the same age. They usually stay together for only a comparatively short time - a few hundred million years - before slowly drifting apart. The age of the stars in NGC 6520 is estimated to be "only" 150 million years. Together with Barnard 86, the star cluster stands at a distance of almost 2000 light years from our solar system. NGC 6520 was discovered on 24 May 1784 by Friedrich Wilhelm Herschel.

Click here or the thumbnail image for a comparison with the size of the Moon.

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