Particulars:
General:
A constellation, which is the head of a constellation family,
located in the equatorial region of the sky and belongs certainly
to the most famous constellations. It extends from RA=4h 40m to
RA=6h 20m and DECL=+23 degrees to DECL=+8 degrees.
In some ways the central part of this constellation reminds on a
oblique sand-glass. In wintertime Orion is a magnificent
constellation which can easily be found by the the three stars
forming a line building the belt of the Hunter (these stars are
sometimes called Jacob's Ladder or Jacob's Stick).
The belt stars point towards Sirius, the brightest star in the
constellation of the Larger Dog, Canis Maioris, situated SE of
Orion.
From his belt there hangs a well defined dagger (known as
"Sword of Orion"), which is known for one of the most
famous nebulas in the sky: The Large Orion Nebula (M42).
Orion lies close enough to the Milky Way to be interesting enough
to be swept even with low-power telescopes or binoculars.
Additionally to the data given above there is a skychart to
locate the stars and objects.
Stars and objects
The shoulder star alpha Ori, Betelgeuse, is a variable red giant;
its brightness varies from 0.4 mag to 1.3 mag with no set period.
It belong to the 20 brightest stars in the sky. During it
pulsations the diameter of the star varies from 300 to 400 times
the diameter of the sun.
The leg of the hunter, beta Ori, Rigel
(arab.: the foot), is a blue-white giant of 0.08 mag. This makes
it the sixth brightest star in the sky and the brightest in the
constellation Orion. With medium sized telescopes it is possible
to distinguish the companion of Rigel, a 7th mag star (smaller
telescopes may fail to reveal the companion because of the glare
of Rigel).
This constellation offers a great number of binaries and multiple
stars:
For binoculars and smaller telescopes the following stars are of
interest: delta Ori, Mintaka (arab.: upper
end of the girdle), a blue-white star of 2.2 mag with a 7th mag
companion. iota Ori, a 3rd mag and a 7th mag star forming
an unequal double; in the same field the wider double Struve
747 can be found - a pair of a 5th mag and a 6th mag star. lamba
Ori, a tight pair of 4th and 6th mag stars. sigma Ori
is a terrific multiple star; in binoculars this blue-white star
of 4 mag and a 7th mag companion can be resolved; using a small
telescope two closer companions of 7th mag and 10th mag are
revealed. These stars are grouped in a way that they look like a
planet with moons. If the resolution is not too high in the same
telescopic field as sigma Ori the triple star Struve
761 can be seen. It consists of a triangle of 8th mag and 9th
mag stars. Together with sigma Ori this triple star gives
a delightfully rich grouping. NGC 1981, a little cluster
of 10 stars including the binary Struve 750, a pair of a
6th mag and a 8th mag star.
The multiple star theta1 Ori, the northern star of the
dagger of the Hunter is also called the Trapezium;
it is located in the heart of the Orion nebula. This group of
stars has been formed from the gas of the nebula, which now glows
in their light. Small telecopes (about 2-inch and higher) show
four stars, ranging from 5th mag to 8th mag, which form a
rectangular figure. Scopes with an aperture of about 100 mm show
two more stars of 11th mag in this group.
Next to it lies theta2 Ori, a duo of a 5th and a 6th mag
star.
For resolving the tight double of zeta Ori (Alnitak) in
its consisting parts, a bright star of 2.02 mag and a 4th mag
companion, scopes with an apertur of at least 75mm and a high
resolution are required. Further more there is a wider companion
of 10th mag.
Eta Ori is a difficult pair. Scopes with an aperture of
100 mm and higher are necessary to split it into its 4th mag and
5th mag stars.
The constellation Orion became most famous for its nebula. The
Messier database has detailed information about The Large Orion
Nebula M 42 and M 43, the DeMairan nebula, which is a part of the
Orion Nebula.
Around October 21 each year the famous Orionid meteor shower
reaches its peak. Coming from the the border to the constellation
gemini as much as 20 meteors per hour can be seen. More
information about this meteor shower and the Chi Orionids,
which are active around the beginning of december can be found in
the meteor shower calendar by Gary Kronk. (Readers in the US
might use the original site of Gary Kronk).
Mythological Background:
According to greek mythology Orion died being stung by a
scorpion. He is set such in the sky that he sets in the west
while his slayer, the Scorpius raises in the east.
Followed by his two dogs he is now fighting the bull Taurus.
According to Secrets of the Night Sky (Bob Berman, William
Morrow &Co, 1995) the ancient Sumerians saw in this star
pattern a sheep. The name Betelgeuse literally means
"the armpit"; in case of the Sumerians it meant
"the armpit of the sheep."