Sirius The Dog Star Is The Bright Leader Of The Pack

Sirius the alpha star of the constellation Canis Major is the brightest star in the night sky. The next brightest star would be Canopus from the constellation Carina.

Just left and slightly below(southeast) the three stars of the belt of the Orion constellation, this star is easy to find.

This is actually a binary star system about 8.6 light-years away.

Combined the two stars(A;B) that make up the system appear in the sky with an apparent magnitude of -1.46. Alone A has an apparent magnitude of -1.47.

Only the Moon, Venus and Jupiter are regularly brighter  in the night sky.

Sometimes Mercury and Mars can also appear brighter.

Sirius left of Orion constellation

Running After The Dog

Right Ascension: 6 hours

Declination: -17 degrees

Visible between latitudes: +73 and -90 degrees

Apparent Magnitude: -1.46

With a declination of -17 degrees most of the world can see the star at some point.

The main star Sirius A is a blue-white star.

The companion is a white dwarf star known as Sirius B. It was a more massive star, about 5 times the Sun's mass, that consumed all its fuel, became a red giant and then a white dwarf.

Sirius and M41

photo courtesy and © T. Credner & S. Kohle,

The main star "A", has a mass that is double that of the Sun and is 25 times brighter. The companion dwarf has almost as much mass as the Sun(98%) in a body about the size of Earth.

At their closest approach to each other the two stars are nearly impossible for the backyard stargazer to separate. You would need at least a 12inch(300mm) aperture scope and good seeing conditions. As they draw apart in their orbit it does become possible to distinguish them in slightly smaller scopes under the right conditions.

Open cluster M47 is visible south of the "Dog Star". Naked-eye visible under dark skies but best seen in binoculars and low power telescopes. 

Going For A Walk

The star is steadily heading south due to precession and in 12,000 years or so will be almost invisible to the northern hemisphere. Although it is moving closer to the Solar System as a whole and will be the brightest star in our night sky for another couple hundred-thousand years.

In the southern hemisphere south of -73 degrees latitude the star becomes circumpolar, meaning it is always above the horizon.

During early July in the southern hemisphere it can be seen at two different times during the day...In the morning as it rises before the Sun and then in the evening when it sets after the Sun.


Myth has the two dogs hunting along with Orion.

Taurus the bull and Lepus the hare are hunted by Orion and his dogs by the river Eridanus. Monoceros is between Canis Major and Canis Minor.

The name means "scorcher" and the star also heralded the coming of the Nile floods and the hot days of summer. These are known as the “Dog Days”.

Canis Major is known as the “Greater dog” and this is the “Dog Star”. Alpha Canis Majoris is the dog's nose.

Canis Minor the “Lesser Dog” with its bright star Procyon is close by.

It joins with Procyon and Betelgeuse to form the Winter Triangle and is part of the Winter Circle...


› Sirius
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