Orion, the Hunter
In the winter skies, the most prominent pattern of stars is known
to us as Orion. This is rightfully so, as this constellation contains
more bright stars than any of the other 87, and includes brilliant
blue-white Rigel, seventh brightest of all stars, and blood-red
Betelgeuse. These mark the corners of a near-rectangle (with Bellatrix
and Saiph), which frames an arrow-straight line of the three stars
Alnitak, Alnilam and Mintaka. Many cultures since time began have
viewed these stars as a giant hero, and consequently there are
many different stories from around the globe. The Greeks have
two well-known legends about Orion's fate. One concerns his hunting
prowess, such that he had no fear of any beast. When he threatened
to kill every one of the animals, Gaia, Goddess of the Earth became
furious and commanded a scorpion to sting Orion. The consequence
of this duel is that Orion and Scorpius are never seen in the
sky at the same time, one setting in the west as the other rises
in the east.
The other Greek story involves Diana, Goddess of the Hunt, who
fell madly in love with the strong and handsome Orion. When she
continued to neglect her hunting duties, her brother Apollo tricked
her into shooting an arrow at a dark item in the ocean to show
her skill. The target, however, was Orion swimming, and Diana's
aim was perfect and the hero was killed. In her grief, Diana pleaded
with Zeus to place Orion in the sky, together with his hunting
dogs, Canis Major and Canis Minor, so that he would never be forgotten.
The Chinese asterism corresponding to Orion is Tsan, Supreme Commander
of the defenders of the villages. Nomadic barbarians periodically
plundered the food supplies of the farmers during the winter.
To guard against such raids, each autumn the people would choose
a leader to organize their protection. In the ancient Chinese
hierarchy of the heavens, Tsan is in the sixth and seventh houses
of the White Tiger.
A dusty bright nebula contrasts
dramatically with a dusty dark nebula in this Hubble Space Telescope
image. NGC 1999 shines by reflecting light from the nearby embedded
variable star V380 Orionis, seen here just left of center. Unlike
emission nebulae, whose reddish glow comes from excited atoms
of gas, reflection nebulae have a bluish cast as their interstellar
dust grains preferentially reflect blue starlight. Extending right
of center, the ominous dark nebula is a condensation of cold molecular
gas and dust so dense that it blocks light. It lies in front of
the bright nebula, silhouetted against the ghostly nebular glow.
New stars will likely form within the dark cloud, called a Bok
globule, as self-gravity continues to compress its dense gas and
dust. NGC 1999 lies about 1500 light-years away in the constellation
Orion, about one degree south of the well known Orion nebula,
M42. Image Credit: NASA and
The Hubble Heritage Team (STScI)
You could spend most of your available observing hours during
winter enjoying the objects in Orion. There are three Messier
objects, M42 (the Great Nebula) and M43, and M78, a reflection
nebula well worth investigating. The Horsehead Nebula is a challenge
for amateur telescopes. There are also a number of multiple stars
for study, including the famous Trapezium in the Orion Nebula.
There are at least seven stars in this system. Orion is home to
the late-October Orionid meteor shower, the radiant lying between
Betelgeuse and the foot of the twin Castor.
And there is Betelgeuse
(Beetle Juice in popular lingo). Betelgeuse is so huge that, if it replaced
the Sun at the center of our Solar System, its outer atmosphere would extend
past the orbit of Jupiter. This star pulsates irregularly, its magnitude ranging
from 0.4 to about 1.2.