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Barnard 33
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The Horsehead Nebula (Barnard 33) was first recorded on the 6th February, 1888 by William Henry Pickering on photographic plate B2312, with a 90 minutes exposure, using the 8-inch Bache Astrograph from Harvard College Observatory, Cambridge, Massachusetts. (and later identified by Williamina Fleming)

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RE: Horsehead nebula
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Horsehead nebula 

Stack of 43 x 10 second images captured with a 100mm refactor and Canon EOS350D camera. ISO 800.



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Hubble Sees a Horsehead of a Different Colour

Astronomers have used NASA's Hubble Space Telescope to photograph the iconic Horsehead Nebula in a new, infrared light to mark the 23rd anniversary of the famous observatory's launch aboard the space shuttle Discovery on April 24, 1990.
Looking like an apparition rising from whitecaps of interstellar foam, the iconic Horsehead Nebula has graced astronomy books ever since its discovery more than a century ago. The nebula is a favourite target for amateur and professional astronomers. It is shadowy in optical light. It appears transparent and ethereal when seen at infrared wavelengths. The rich tapestry of the Horsehead Nebula pops out against the backdrop of Milky Way stars and distant galaxies that easily are visible in infrared light.
 
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IC434
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IC434 - from kleinfriesen observatory 48



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Horsehead nebula
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Title: The Horsehead nebula, a template source for interstellar physics and chemistry
Authors: Maryvonne Gerin (LERMA), Jérôme Pety (IRAM), Javier R. Goicoechea

We present a summary of our previous investigations of the physical and chemical structure of the Horsehead nebula, and discuss how these studies led to advances on the understanding of the impact of FUV radiation on the structure of dense interstellar clouds. Specific molecular tracers can be used to isolate different environments, that are more sensitive to changes in the FUV radiation or density than the classical tracers of molecular gas : the CO isotopologues or the dust (sub)millimetre continuum emission. They include the HCO or CCH radicals for the FUV illuminated interfaces, or the molecular ions H^{13}CO^+, DCO^+ and other deuterated species (DNC, DCN) for the cold dense core. We discuss future prospects in the context of Herschel and ALMA.

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Title: An Infrared Census of Star Formation in the Horsehead Nebula
Authors: Brendan P. Bowler, William H. Waller, S. Thomas Megeath, Brian M. Patten, Motohide Tamura

At ~ 400 pc, the Horsehead Nebula (B33) is the closest radiatively-sculpted pillar to the Sun, but the state and extent of star formation in this structure is not well understood. We present deep near-infrared (IRSF/SIRIUS JHKs) and mid-infrared (Spitzer/IRAC) observations of the Horsehead Nebula in order to characterise the star forming properties of this region and to assess the likelihood of triggered star formation. Infrared colour-colour and colour-magnitude diagrams are used to identify young stars based on infrared excess emission and positions to the right of the Zero-Age Main Sequence, respectively. Of the 45 sources detected at both near- and mid-infrared wavelengths, three bona fide and five candidate young stars are identified in this 7' by 7' region. Two bona fide young stars have flat infrared SEDs and are located at the western irradiated tip of the pillar. The spatial coincidence of the protostars at the leading edge of this elephant trunk is consistent with the Radiation-Driven Implosion (RDI) model of triggered star formation. There is no evidence, however, for sequential star formation within the immediate ~ 1.5' (0.17 pc) region from the cloud/H II region interface.

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The Horsehead Nebula is a dark nebula in the Orion constellation. One of the most beautiful space objects.



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A deep exposure of the famous Horsehead Nebula in Orion shows that the dark familiar shaped indentation, visible just below centre, is part of a vast complex of absorbing dust and glowing gas.


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Credit: Star Shadows Remote Observatory

To bring out details of the Horsehead's pasture, amateur astronomers at the Star Shadow Remote Observatory in New Mexico, US, fixed a small telescope on the region for over seven hours filtering out all but a very specific colour of red light emitted by hydrogen. They then added the image to a full colour frame taken over three hours. The resulting spectacular picture details an intricate tapestry of gaseous wisps and dust-laden filaments that were created and sculpted over eons by stellar winds and ancient supernovas. The Horsehead Nebula lies 1,500 light years distant towards the constellation of Orion. Two stars from the Orion's Belt can be found in the above image.

Star Shadows Remote Observatory is a cooperative venture owned and operated by Rick Gilbert, Jack Harvey, John Pierce, and Jim Thibert.

-- Edited by Blobrana at 11:18, 2006-02-21

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Velocity field and star formation in the Horsehead nebula
Authors: Pierre Hily-Blant (IRAM), David Teyssier (SRON), Sabin Philipp (MPIFR), Rolf Gusten (MPIFR)

Using large scale maps in C18O(2-1) and in the continuum at 1.2mm obtained at the IRAM-30m antenna with the Heterodyne Receiver Array (HERA) and MAMBO2, researchers investigated the morphology and the velocity field probed in the inner layers of the Horsehead nebula.
The data reveal a non--self-gravitating (m/mvir = 0.3) filament of dust and gas (the "neck", diameter = 0.15-0.30 pc) connecting the Horsehead western ridge, a Photon-Dominated Region illuminated by sigmaOri, to its parental cloud L1630. Several dense cores are embedded in the ridge and the neck.
One of these cores appears particularly peaked in the 1.2 mm continuum map and corresponds to a feature seen in absorption on ISO maps around 7 micr. Its \cdo emission drops at the continuum peak, suggestive of molecular depletion onto cold grains.
The channel maps of the Horsehead exhibit an overall north-east velocity gradient whose orientation swivels east-west, showing a somewhat more complex structure than was recently reported by \cite{pound03} using BIMA CO(1-0) mapping. In both the neck and the western ridge, the material is rotating around an axis extending from the PDR to L1630 (angular velocity=1.5-4.0 km/s).
Moreover, velocity gradients along the filament appear to change sign regularly (3 km/s/pc, period=0.30 pc) at the locations of embedded integrated intensity peaks. The nodes of this oscillation are at the same velocity. Similar transverse cuts across the filament show a sharp variation of the angular velocity in the area of the main dense core.
The data also suggest that differential rotation is occurring in parts of the filament. they present a new scenario for the formation and evolution of the nebula and discuss dense core formation inside the filament.


The astronomers estimate that most of the neck will take about 4 million years to spin around.


Position(2000): RA = 05 : 40.9 Dec = -02 : 28
The dark nebula that forms the Horsehead itself is known as Barnard 33 (B 33).
The red background is the emission nebula IC 434.

The Horsehead Nebula in Orion, is part of a large, dark, molecular cloud. The unusual shape was first discovered on a photographic plate in the late 1800s. The red glow originates from hydrogen gas predominantly behind the nebula, ionised by the nearby bright star Sigma Orionis.
The Horsehead is caused mostly by thick dust, although the lower part of the Horsehead's neck casts a shadow to the left. Streams of gas leaving the nebula are funnelled by a strong magnetic field. Bright spots in the Horsehead Nebula's base are young stars just in the process of forming.
The nebula lies 1500 light years away.

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-- Edited by Blobrana at 19:48, 2006-01-31

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