The Orion Cloud and Association
In the direction of the constellation Orion, approximately centered on the
Great Orion Nebula M42 and
M43, there
drifts a giant cloud of interstellar gas and dust within the Milky Way galaxy.
This cloud was formed when a density wave, related to the Galaxy’s spiral
structure, moved through the medium of the Galactic disk. It is about 1600
light years away and several hundred light years across.
This giant cloud, or complex of clouds, of interstellar matter and young stars
contains, besides M42 and M43 and the nebulosity associated with them
(NGC 1973-5-7), a number of famous objects:
(also containing NGC 2024 = Orion B),
and the reflection nebulae around M78.
Our image on the right shows the whole constellation Orion with bright reddish
Betelgeuse slightly left and above the middle, and bright blueish-white Rigel
at the lower right. The brightest nebula, in the “sword” of Orion and below
his belt stars, is the Great Nebula M42 with M43, with the faint extension to
North (up), NGC 1973-5-7. At the left-most belt star, Zeta Orionis, the
Horsehead Nebula region with Orion B is conspicuous. The huge, delicate bow
around this region, spanning the southern (lower) half of the constellation,
is Barnard’s Loop. Very north in Orion, around the star Lambda, is another
very faint and round, huge nebulous cloud.
Our image was obtained by Sven Kohle and Till Credner of
on October 29, 1995 at 3:25 UT from Calar Alto with a f=55 mm 1/3.5 photo lens
on Kodak Ektachrome 400 Elite film, exposed 60 minutes (without filter).
The image is copyrighted by the observers.
UKS image of a great portion of the Orion cloud.
The bright nebula near the bottom is the Great Orion nebula
M42 with its northern part
M43 and northern extension NGC 1973-5-7.
nebula complex around the star Zeta Orionis,
consisting of bright Orion B (NGC 2024) left of the star, and IC 434
with the conspicuous dark Horsehead Nebula,
plus various small nebulae.
The whole region is filled with gas and dust, but only parts have yet formed
stars (i.e., clusters) and are thus illuminated.
Barnard’s Loop extends far beyond this
image and cannot be traced here very well, as it is brightest at its edges.
This image is copyrighted and may be used for private purpose
only. For any other kind of use, including internet mirroring and storing on
CD-ROM, please contact
Coral Cooksley of the
At least three remarkable stars are observed to escape from the Orion complex
with high space velocities:
- AE Aurigae, a variable of spectral type O9.5 and about 6th magnitude
(corresponding to an absolute magnitude of – 2.5 at its 1,600 light year
distance, variations being erratic between 5.4 and 6.1 magnitude, according
to Burnham), which illuminates the diffuse nebula IC 405, also called the
“Flaming Star Nebula”, escaping at about 130 km/s,
- 53 Arietis (apparent mag 6.09, spectrum B2 V) escaping with 60 km/s,
- Mu Columbae (5.16 mag, spectrum O9.5 V) running away at about 120 km/s.
They must have left the Orion cloud about 2–5 million years ago, and it is
speculated that they might have speeded up somehow during supernova explosions
(perhaps of companion stars in multiple systems).
- More images of the Orion Cloud
Last Modification: 27 Jun 1998, 12:00 MET