Science

n2doc

(47,953 posts) Wed Feb 13, 2013, 08:35 PM Feb 2013

"A drop of ink on the luminous sky"

This image from the Wide Field Imager on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile, shows the bright star cluster NGC 6520 and its neighbour, the strange gecko-shaped dark cloud Barnard 86. This cosmic pair is set against millions of glowing stars from the brightest part of the Milky Way — a region so dense with stars that barely any dark sky is seen across the picture.

This part of the constellation of Sagittarius (The Archer) is one of the richest star fields in the whole sky — the Large Sagittarius Star Cloud. The huge number of stars that light up this region dramatically emphasise the blackness of dark clouds like Barnard 86, which appears at the centre of this new picture from the Wide Field Imager, an instrument mounted on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile.

This object, a small, isolated dark nebula known as a Bok globule [1], was described as “a drop of ink on the luminous sky” by its discoverer Edward Emerson Barnard [2], an American astronomer who discovered and photographed numerous comets, dark nebulae, one of Jupiter’s moons, and made many other contributions. An exceptional visual observer and keen astrophotographer, Barnard was the first to use long-exposure photography to explore dark nebulae.

Through a small telescope Barnard 86 looks like a dearth of stars, or a window onto a patch of distant, clearer sky. However, this object is actually in the foreground of the star field — a cold, dark, dense cloud made up of small dust grains that block starlight and make the region appear opaque. It is thought to have formed from the remnants of a molecular cloud that collapsed to form the nearby star cluster NGC 6520, seen just to the left of Barnard 86 in this image.

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http://www.eso.org/public/news/eso1307/