|Canis Major, the big Dog of the skies,
passes directly overhead in southern Australia. He is depicted looking
towards his master, the giant Orion, and the fleeing shape of Lepus the
Hare, underneath Orion's feet. As he rises in the east
with Orion he seems to be lying on his back in the Milky Way, with several
bright stars marking his spine and legs.
Image © www.arttoday.com
This old chart shows the placement of Canis Major
in the sky near Orion and Lepus.
On his shoulder shines Sirius, the brightest
star in the sky. Most of the mythology of Canis Major is connected
to Sirius as the constellation itself did not take on it current form until
Roman times. Sirius is not the closest star though it is still close
to us, lying at 8.7 light years away. It is a hot white star
that will shine brightly for a long time to come. It is also a known
binary system, with a tiny white dwarf star, coloquially known as 'the
Pup', circling the brighter primary every 50 years. Most of the time
it is lost in the glare of the primary but it can swing out far enough
to be seen in amateur telescopes. This will next be possible in the
years 2020 to 2025.
Sirius means "Scorching", named so by the
ancient Greeks as it rose and set with the Sun during the northern hemisphere
Summer 3000 years ago. It was thought that the combined heat of the
two stars caused the hot weather of late Summer. It was also commonly
known as the Dog star, a tradition that reaches far back before Babylonian
times. This is also where the expression "the dog days of Summer"
Sirius was important to the ancient Egyptians.
They watched for the heliacal rising of Sirius to indicate the start of
the annual flooding of the Nile River (a heliacal rising is when
a star is first seen in the eastern sky before dawn after it has "passed
behind" the Sun). Some references connect Sirius with the god Osiris,
as the name is similar in sound. Others connect Sirius with Anubis
the Jackal-headed god. It is interesting to note that the Chinese
connected Sirius with a canine figure as well, but the Australian Aborigines
saw it as an eagle.
As another point of interest, even though
Sirius passes overhead in southern Australia it is visible at some point
every night of the year! During late June and early July it is possible
to see Sirius setting in the west just after sunset and then see it rise
in the east just before sunrise the next day. This makes it the brightest
non-circumpolar star that you can see rise and set in one night.
Mirzam the Announcer (beta (b)
Canis majoris) marks the front paw of the Dog. It was so called as
it heralded the imminent rising of Sirius.
Wezen the Weight (delta (d)
Canis majoris) marks the base of the tail. It was called this
as apparently from the northern hemisphere it seems reluctant to rise above
the horizon. This would be an optical illusion as a result of the
star's far southerly declination. Here in southern Australia it rises
at the same time as Sirius.
This article is ©2000
Stargazers Astronomy Shop