Canis Major Constellation
The Canis Major constellation is one of the original 48 constellations listed by Ptolemy in the 2nd century. These constellations formed the basis for the modern list agreed by the IAU. Constellations from the southern hemisphere, unable to be seen from the Mediterranean, represent the majority of additions. The ‘Great Dog’ has both mythological references and great significance as it includes the brightest star in the sky. As a constellation that is both easy to locate and trace it is popular for amateur stargazers.
Symbolism: Big Dog
Neighbouring constellations: Orion (north east), Lepus (east), Canis Minor (north), horizon (south – for northern hemisphere observers)
Stars brighter than 3 magnitude: 5
Primary stars: 10 (Tail, Hips, Back Leg, Chest, Front Leg, Front Lower Body, Back Lower Body, Neck, Ear, Nose)
Latitude: 11.03 – 32.25 degrees south
Northern Hemisphere Season: Winter (January – March)
Which months can you see Canis Major constellation?
For observers in the northern hemisphere Canis Major is visible from January to March, while in the southern hemisphere it is visible from November to April. Canis Major lies between 10-30 degrees southern latitude. Therefore, the further south your position the higher it will appear in the night sky.
Canis Major is not possible to see throughout the northern hemisphere summer, as it passes in the daytime sky. As the constellation declination is at southern latitudes, it remains below the equator for most northern hemisphere latitudes at the beginning of winter. Although it becomes visible in the southern sky during winter from January to March. At its maximum range it is possible to see at latitudes between +60 and -90. However, the lower latitudes will have visibility for longer periods of the year.
How to find Canis Major constellation?
Canis Major constellation is visible in the southern sky during winter months for observers in the northern hemisphere. To find Canis Major without any reference points is possible as ‘Sirius’ – the brightest star in the sky – is part of this constellation. Sirius marks the chest of the dog and regardless how you locate the constellations you will use this star that is significantly brighter than any others to identify the remainder of the constellation.
Canis Major is best located using either the small and easily identified asterism of Orion’s belt, or the large asterism of the winter hexagon. To identify Sirius using Orions belt, move westward approximately 7 times the length of the belt west following an imaginary continuation of the belt. If you have identified the winter hexagon or winter triangle then Sirius forms a corner in each asterism.
Tracing the shape of Canis Major constellation
The body of the dog is the easiest to identify, with the 5 brightest stars in the constellation marking the extremities.
- Sirius is by far the brightest star in this area of the sky are represents the chest of the dog.
- East of Sirius around the length of Orion’s belt is Mirzam marking the front feet
- South-west of Sirius – located around 3 times the length of the front leg, the star Wezen marks the hips at the backend of the dog.
- The tail continues in the same direction and is a similar length as the front leg marked by Aludra.
- From Wezen the back leg is slightly shorter than the front leg. Adhara is the second brightest star in the constellation marking the back foot.
The head of the dog is less apparent than the body. There are 3 stars forming a triangle to the west of Sirius. They are far dimmer but with a clear visual idea of the body it becomes easier to identify the head.
Canis Major in the Ancient World
Greek mythology of Laelaps
The Canis Major constellation relates to the Greek mythology story of Laelaps and the Teumessian fox. Laelaps was the hunting dog who would always catch its prey. Zeus gave Laelaps as a gift to Europa of Crete and in time came under ownership of Procris. Procris entrusted it to her husband Cephalus along with a spear that never missed. However, motivated by jealousy she hid in the forest to monitor him during a hunt and he inadvertently killed her with the spear.
Cephalus was banished for the murder and during his exile was commissioned to hunt the Teumessian fox. The Teumessian fox was a gigantic fox that the gods had created as a punishment against the Thebes and was destined never to be caught. The god given destiny of each created a paradox and Zeus turned them both to stone.
Sirius was an important star in ancient Egypt signalled the seasonal floods. The calendar of the Pharaohs began on the first day Sirius appeared on the horizon.
Canis Majoris, recognised in the tales of the constellations as the hunting dog of Orion. The dog forms part of a wider story of the relationship between the constellations as part of Orions battle with Taurus the bull. The dog trails Orion but also pursues the hare represented by the constellation Lepus.
Sirius (-1.46m, 8.6ly, #1)
Sirius from the Greek word ‘scorching’ is the brightest star visible from earth with apparent magnitude of -1.46. Sirius is a dual star at a distance of 8.6 light years. It is the 5th closest star to earth (discluding the sun), but only Alpha Centaurus ahead of it is prominent. Because of its prominence the star has over 50 names across different ancient cultures, particularly in reference to dogs and its identity as the dog star. Sirius forms part of both the Winter Hexagon and Winter Triangle.
In ancient times Sirius would appear in mid to low latitudes in the northern hemisphere in mid July. Its appearance marked the beginning of the Egyptian year and was the indicator of seasonal floods. In many Mediterranean cultures the appearance of Sirius marked the ‘dog days’ where intense heatwaves would impact people and their animals and crops. Sirius has a latitude of 17 degrees south and became important for Polynesian sailors as an indicator of the path of true east-west. The star marks the chest of the dog in Canis Major.
Adhara (+1.5m, 430ly, #22)
Adhara from the Arabic for ‘virgins’ is the 22nd brightest star with an apparent magnitude of +1.5. 4.7 million years ago it was the brightest star in the night sky with an apparent magnitude of -3.99. Adhara is 430 light years from earth. The Arabic name Adhara originates from its inclusion in a navigation asterism of the virgins. The star marks the back feet of the dog in Canis Major.
Wezen (+1.83, 1,792ly, #36)
Wezen from the Arabic word for ‘weight’ is the 36th brightest star with an apparent magnitude of +1.83. Its distance is 1,792 light years from earth. The name weight, said to be in reference to the low trajectory of the star through the sky when viewed from the northern hemisphere. It is however accurate given the size, luminosity and burn rate of the star. It is the 3rd brightest star over 1,000 light years from earth. The star marks the hips of the dog in Canis Major.
Mirzam (+1.98m, 499ly, #46)
Mirzam from the Arabic word for ‘heralding’ is the 46th brightest star with an apparent magnitude of +1.98. Its distance is 499 light years from earth. The name references it rising above the horizon prior to Sirius. The star marks the front feet of the dog in Canis Major.
Aludra (+2.45m, 3,198ly, #87)
Aludra is an Arabic female name is the 87th brightest star with an apparent magnitude of +2.45. Its distance is 3,198 light years from earth. The name Aludra is in reference to the star as one of the stars in the asterism ‘the virgins’. The star marks the tail of the dog in Canis Major.
Deep sky objects
Messier 41 – A cluster of 100 stars around 2,300 light years away with an apparent magnitude of 4.5.
Canis Major Dwarf Galaxy – The nearest galaxy located 25,000 light years away. The galaxy has over a billion stars but is difficult to observe as it is obscured by the milky way.
NGC2207 & IC2163 – only possible to see with a telescope, with apparent magnitudes of 12.2 & 11.6 respectively. These two colliding galaxies are in the process of merging.