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Horsehead Nebula, Flame
Nebula and the Orion Belt
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Orion is the master of the winter skies.
He lords over the heavens from late fall to early spring, with his hunting
dog Sirius trailing at his feet.
The constellation's main feature is of course the three stars which form
the "belt" across the middle of Orion: from west to east Mintaka, Alnilam,
and Alnitak. Even the Bible makes reference to this famous group.
The last of these stars is also known as zeta Orionis, and is a well known
triple star system. The primary is a blue-white star, and its companion
(165º, 2.3") is a dull red. Close by, just to the south, is the renowned
Horsehead Nebula, a so-called dark nebula that is not visible in scopes
but quite spectacular in long-exposure photographs.
Alnitak is also responsible for another great feature in this region.
Infact, excites the hot gases in NGC 2024 (Flame Nebula) causing it to
glow in almost unique and beautiful colours, predominantly shell-pink, but
ranging from yellow to deep orange. The dark central area is caused by a
lane of dust in the foreground.
This image has been chosen as
NASA Astronomy Picture of the Day
for
October 13, 2005 and December 29, 2006
 Remarkable
features
Click the image to
view and interact with the hi-res image.
Alnitak is
a supergiant star with a brightness 35,000 times greater than
the Sun. Its mass is 20 times the solar mass.
Its visual magnitude is 2.05.
Alnilam is
40,000 brighter and 20 massive than the Sun. Lie at a distance
of 1,500 light-years from the Earth. its visual magnitude
is 1.70.
Mintaka is the third
supergiant star in the Orion Belt, 20,000 times the bright of
the Sun. Its visual magnitude is 2.23.
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Find Chart
The position of
the Orion Belt (in the red circle)
in Orion.
Image from Cartes du Ciel.
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This image is a composite from black and
white images taken with the Palomar Observatory's 48-inch (1.2-meter) Samuel
Oschin Telescope as a part of the second National Geographic Palomar Observatory
Sky Survey (POSS II). The images were recorded on two type
of glass photographic plates - one sensitive to red light and the other
to blue and later they were digitized. Credit:
Caltech,
Palomar Observatory,
Digitized Sky Survey.
In order to produce the color image seen
here, I worked with a total of 48 different frames,
24 for each color band, coming from
4 different plates taken between 1987 and 1991.
Original file is 15,919x12,650
pixels with a resolution of about 1 arcsec per pixel. The image show an area
of sky large 4.4° x 3.5° (for
comparison, the full-Moon is about 0.5° in diameter).
Color composite, copyright: Davide
De Martin.
Other images of
the same celestial field found online
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