Astronomy Picture of the Day
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September 25, 1995
Orion's Horsehead Nebula
Photograph made from plates taken with the
UK Schmidt Telescope.
Colour photography by David Malin.
The black indentation to the red
seen just to the right of
centre of the above photograph is one of the most famous features in any
nebulae on the sky. Because of its shape, it is known as the
Nebula. The bright star near the centre is
located in the belt of the familiar constellation of Orion.
The horse head feature is dark because it is really a dense
dust cloud which lies
in front of the bright nebula and blocks the light.
Like clouds in our sky, this cosmic cloud has chanced to assume
a recognizable shape. After thousands of years, the
internal motions of the cloud will alter its appearance.
The emission nebula's
red colour is caused by electrons recombining with protons to form
Also visible in the picture are blue
This type of nebula contains dust which
preferentially reflects the blue light of nearby stars.
Tomorrow's picture: Star Trails in Southern Skies
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