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CHAMÄLEON + ONJALA OBSERVATORY DeepSky | SITEMAP HOME CHAMÄLEON |
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| « back to overview Nebula | Load higher resolution (1800 x 1800 Pixel 3500 x 4000 Pixel) | Object description |
Our image shows a 2-part mosaic of some large dark clouds in the constellation Ophiuchus together with the planet Jupiter. Image orientation: north top and east left.
In Ophiuchus lie numerous, large dark clouds, which were first catalogued photographically by the American astronomer Edward Emerson Barnard. The complete catalog of over 300 dark clouds by Barnard can be found at this URL. Barnard was self-taught and one of the pioneers of astrophotography. In more recent times he was followed by detailed studies of K. Dobashi in infrared light.
Dark clouds or dark nebulae are large collections of interstellar matter which either absorb the light of stars behind them (e.g. the Coal Sack) or cover parts of H-II regions or reflection nebulae (e.g. Barnard 33, the Horsehead Nebula in the constellation Orion). The shape of such dark clouds is usually irregular and without clearly defined outer boundaries. Many of the dark clouds have proper names, such as the Serpentine Nebula or the Pipe Nebula.
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The
cold hydrogen gas in these clouds is in the form of molecules, which is why
they are also called molecular clouds. The hydrogen gas is mixed with dust,
which is responsible for the light absorption. Larger dark nebulae are called
giant molecular clouds and can measure several hundred light years. They are
regions of active star formation, an example of such a giant cloud is the Orion
OB 1 region. These clouds contain several million times the mass of the
Sun. At the top of our mosaic in the center of the image is the planet Jupiter, surrounded by garland-like dark clouds, see also the image version with object markers. North (above) the bright blue star (Theta Oph) at the left edge of the image is Barnard 72, the snake nebula. To the right below Barnard 72 is a small, roughly kidney-shaped dark cloud, Barnard 68, which is one of the densest dark clouds with an absorption in the visual spectral range of nearly 20 magnitudes. South of Theta Ophiuchus lies a large complex of dark clouds that have Barnard catalog numbers from 59 to78. This complex is also known as the pipe nebula. Theta Ophiuchusis a beta Cephei type variable star. It is assigned to spectral type B0 IV and shines in deep blue color. Just right above Theta is the star HD 156 992, which has spectral class K3 and shines in a rich yellow-orange color. Furthermore the mosaic shows a larger number of globular clusters, among others NGC 6287, 6325, 6284, 6355, 6293, 6116. The brightest globular cluster in the image is Messier 19. « Click here or the thumbnail to load a large annoted image. |
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