The last two stars in the Winter Hexagon asterism, Sirius and Procyon, are two of the brightest stars in the night sky. Their constellations, however, are real dogs. Specifically, they are Canis Major and Canis Minor, the Big and Little Dogs.
Orion has pointed to the other stars in the Hexagon, and these two are no
exception. The two shoulder stars point toward Procyon, in Canis Minor (KAH-niss
or KAY-niss), about 30 degrees to the left. The belt stars point to Sirius,
20 degrees below and to the left in Canis Major. Sirius, in fact, appears
to be waiting at Orion's feet, and is also called the Dog Star. Procyon,
Sirius, and Orion's shoulder Betelgeuse form an almost-equilateral triangle,
sometimes called the Winter Triangle.
Sirius (SEAR-ee-us) may be called a dog, but at -1.4 magnitude, it is the
brightest star visible in the night sky. Its name means "scorching." The
phrase "dog days of summer" came about because Sirius rises with the sun
in summer. It was believed that the star's brightness amplified the sun's
heat. Procyon (PRO-see-on) is no slouch, either. At magnitude 0.4, it is
between Rigel and Betelgeuse in brightness. Because it rises about an hour
before Sirius, it bears a name meaning "before the dog."
Both of the stars, coincidentally, have white dwarf companion stars. The
companion of Sirius is called the Pup. It would be a respectable star on
its own, but Sirius outshines it so greatly that the Pup can only be seen
with a 10 inch or larger telescope.
From a dark location, you may be able to see that the constellations sit
on opposite sides of the winter Milky Way. (The Milky Way is dimmer in winter
than in summer because Earth is facing the outer edge of our galaxy, which
is less densely populated than the center.) Arab legends explain this by
telling how two companions or two sisters became separated when one was able
to cross a river and the other was not. Procyon, the dimmer of the two stars,
is usually considered to be the weaker one who was left behind.
In Greco-Roman mythology, the two constellations are often referred to as
Orion's hunting dogs, but there are many more legends about them. One says
that they belonged to a mortal who made the mistake of watching Diana, goddess
of the hunt, skinnydipping. Furious, Diana sicced the dogs on their master.
Another story says that the dogs are under the table of twins Castor and
Pollux, waiting to gobble up the crumbs they drop. The stars of the Milky
Way represent those crumbs.
Apparently the Big Dog got himself some of those crumbs. Just below Sirius
is an open star cluster. M41, The Little Beehive, is about as wide as the
moon, and can be seen in binoculars.
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