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The Horsehead Nebula
Horsehead Nebula Barnard 33
Description: Dark Nebula
Position (J2000): R.A. 05h 40m 59.00s Dec. -02° 27' 30.0"
Distance: About 490 pc (1,600 light-years)
Dimensions: Approximately 0.67 pc (2.2 light-years) horizontal
Image Credit: ESO
Release Date: January 25, 2002
Closeup: N01-12a Related: N0949
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ABOUT THIS IMAGE:
A new, high-resolution
color image of one of the most photographed celestial objects, the famous
"Horsehead Nebula" (IC 434) in Orion, has been produced from
data stored in the VLT Science Archive. The original CCD frames were obtained
in February 2000 with the FORS2 multi-mode instrument at the 8.2-m VLT
KUEYEN telescope on Paranal (Chile). The comparatively large field-of-view
of the FORS2 camera is optimally suited to show this extended object and
its immediate surroundings in impressive detail.
The image shows the famous "Horsehead Nebula", which is situated in the Orion molecular cloud complex. Its official name is Barnard 33 and it is a dust protrusion in the southern region of the dense dust cloud Lynds 1630, on the edge of the HII region IC 434. The distance to the region is about 1400 light-years (430 pc).
This beautiful color image was produced from three images obtained with the multi-mode FORS2 instrument at the second VLT Unit Telescope ( KUEYEN ), some months after it had "First Light", cf. eso9944. The image files were extracted from the VLT Science Archive Facility and the photo constitutes a fine example of the subsequent use of such valuable data. Details about how the photo was made are available below.
The comparatively large field-of-view of the FORS2 camera (nearly 7 x 7 arcmin 2) and the detector resolution (0.2 arcsec/pixel) make this instrument optimally suited for imaging of this extended object and its immediate surroundings. There is obviously a wealth of detail, and scientific information can be derived from the colors shown in this photo. Three predominant colors are seen in the image: red from the hydrogen (H-alpha) emission from the HII region; brown for the foreground obscuring dust; and blue-green for scattered starlight.
The blue-green regions
of the Horsehead Nebula correspond to regions not shadowed from the light
from the stars in the H II region to the top of the picture and scatter
stellar radiation towards the observer; these are thus `mountains' of
dust . The Horse's `mane' is an area in which there is less dust along
the line-of-sight and the background (H-alpha) emission from ionized hydrogen
atoms can be seen through the foreground dust.
Dust and molecules can exist in cold regions of interstellar space which are shielded from starlight by very large layers of gas and dust. Astronomers refer to elongated structures, such as the Horsehead, as `elephant trunks' (never mind the zoological confusion!) which are common on the boundaries of HII regions. They can also be seen elsewhere in Orion - another well-known example is the pillars of M16 (the "Eagle Nebula") made famous by the fine HST image..
Such structures are
only temporary as they are being constantly eroded by the expanding region
of ionized gas and are destroyed on timescales of typically a few thousand
years. The Horsehead as we see it today will therefore not last forever
and minute changes will become observable as the time passes
The HII region to
the west (top of picture) is ionized by the strong radiation from the
bright star Sigma Orionis, located just below the southernmost star in
Orion's Belt. The chain of dust and molecular clouds are part of the Orion
A and B regions (also known as Orion's `sword').
information about the photos