Orion The Hunter
The constellation Orion is an easily recognisable star grouping visible
in the northern hemisphere in even the most light polluted skies. Orion is
depicted in many ways: as a hunter
wielding a club and shield, brandishing
a sword and shield, or clubbing a lion.
These however are just visualisations
interpreting a pattern in the stars.
The best way to identify Orion is by
finding the two bright stars Betelgeuse
and Rigel. If you draw a line between
these stars there should be a line of
three stars in the middle. Even on a
night with poor visibility you should be
able to see these stars.
Betelgeuse is Orion’s shoulder, and
Rigel is his leg or ankle. The three stars
in the middle Alnitak, Alnilam, and
Mintaka (left to right) form Orion’s belt.
To the right of Betelgeuse above and to
the right of the belt is Bellatrix forming
Orion’s other shoulder. Drawing a line
through the middle star in Orion’s belt is
Saiph representing Orion’s knee.
On a darker night with good visibility
you will be able to see some of the
fainter parts of the constellation. The
most interesting is the Great Nebula in
Orion. The Orion Nebula can be seen
just under Orion’s belt and will look like
a smudge or cloud to the naked eye.
This nebula is a good example of a star forming region in the galaxy.
What you are actually seeing is a cloud of stellar dust about 24 light years
across and 1,340 light years away.
Looking at the nebula with different instruments reveals ever increasing
amounts of detail. Starting with the naked eye you can see a gray smudge,
moving up to binoculars the cloud starts to form in your vision. With a low
powered telescope you can see the nebula and a few stars, but the stars
are all merged together into a single light source.
As you use ever increasing magnification eyepieces or more powerful
telescopes other details start to emerge and you can start to see some of
the individual stars in the nebula. With the highest magnification you will
see the trapezium. This at first appears as four stars arranged in a rectangle.
However, those of you with sharp eyes will be able to separate out all six
stars in the cluster.
Up to now what we have seen has all been in monochrome. The vivid
colors of the pictures that you see of the nebula are only obtained using
long exposure photography. The long exposure capability of the camera
allows more photons of light to be recorded thus capturing the colors of
the nebula.
The human eye is a very clever device. In order to compensate for low
light levels it switches to monochrome to allow more detail to be seen. This
allows us to see some of the faint details of the celestial wonders, but not to
appreciate their full glory.
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Image: Stellarium
By Mike Barrett
www.RocketSTEM.org