Interesting Facts About Sirius, the Dog Star

Interesting Facts About Sirius, the Dog Star

The constellation Canis Major contains the brightest star in the night sky, Sirius, a blue-white star 8.16 light distant and radiating more than 20 times the energy of our own sun. In actual fact, Sirius A has a companion star, the white dwarf Sirius B, which rotates around their center of common mass once every 50 years, but it is around 10,000 times fainter than Sirius A, which in turn accounts for much of the apparent brightness (-1.46 mag.) we see here back on Earth.

Quick Facts

• 6h 45m 8.9s (right ascension), -16°42’52.1 (declination)
Spectral TypeMain sequence white star (A1V)
• Distance to Earth: 8.611 light-years.
• Constellation: Canis Major
• Magnitude: -1.46
• Rotational Velocity: 16 km per second
• Radius: 740,000 miles (x71% sun)
• Surface temp: 10,000C (18,000F)
• Mass: 2.02 solar masses
• Luminosity: 25 times as luminous as the Sun

Sirius in History

Set just southeast of the prominent constellation Orion, the brightest star in the night sky is visible from all parts of the Earths’ surface, and naturally held great importance for ancient civilizations. In ancient Egypt, for instance, Osiris, the God of Life, Death, Fertility and Rebirth was connected with Sirius because every year just prior to the heliacal rising (rising with the Sun) of the “Star of Isis” the river Nile flooded its banks, and even though the flood could (and did) often bring death and destruction, it also brought about a revitalization of the Nile Valley by depositing a layer of fertile silt, which was perhaps a fitting celebration of the everlasting cycles of life. Sirius’ heliacal rising also marked the beginning of the Egyptian year.

Like the Egyptians, the ancient Greeks and Romans associated this time of the year with hot sultry weather, known as “The Dog Days of Summer”, that runs from July 3 to August 11, but incorrectly surmised that during the “dog days” the Earth became hotter due to the combined heat and luminosity of Sirius and the Sun. Observers believed these lethargic, hot days blighted by disease were the result of emanations caused by malignant influences, with those afflicted said to be “star-struck” or suffering from astroboletosor. As Homer noted in his classic the Iliad:

“Sirius rises late in the dark, liquid sky
On summer nights, star of stars,
Orion’s Dog they call it, brightest
Of all, but an evil portent, bringing heat
And fevers to suffering humanity.”

Around 70 B.C, Greek astronomer Geminus put forward a more scientific explanation of the phenomenon, and as he wrote:

“It is generally believed that Sirius produces the heat of the Dog Days, but this is an error, for the star merely marks a season of the year when the sun’s heat is the greatest.”

Sirius in Mythology

Sirius, the Dog StarThe “Dog Star” is well represented in the mythologies of many cultures, and references to the star can be traced all the way to Neolithic times. To the ancient Greeks, Sirius in Canis Major represented Orion’s faithful hunting dog, which each night would help his master chase the constellation of Lepus the Hare across the sky.

One of the most enchanting tales associated with Sirius long history, however, comes from India, where the star is known as “Svana”, the faithful dog of Prince Yudhistira. The story relates the journey that Prince Yudhistira (in company with his dog Svana), and his four brothers once undertook to find the kingdom of heaven. However, the journey proved too arduous for the fickle brothers, who each abandoned the search in favor of more earthly pleasures and desires. After a long and dangerous journey, the prince found the entrance to heaven, but the gatekeeper, Lord Indra, would not allow the dog Svana to enter heaven with his master Prince Yudhistira.

Taking huge offense at this, the prince related the events of the journey, during which he stressed the fact that although his brothers had abandoned him, his faithful companion Svana, did not, and followed him (Yudhistira) freely, and of his own accord. Thus, if he were denied entry into heaven because of his dog, he would refuse entry if it were granted to him alone. At this, Lord Indra recognized the purity of the princes’ heart, and welcomed them both to paradise where, as the story relates, they reside to this day.

The Sirius “Mystery”

Long before Sirius was proven to have a small companion in the form of a white dwarf star, the Dogon people of Mali in Africa had placed Sirius and its companion at the centre of their religion. They knew for instance that its period was 50 years, and that it had an elliptical orbit. The actual orbit was only determined fairly recently, and was found to be 50.04 years, and as the Dogon said it does, Sirius was found to be rotating about its own axis as well.

The wisdom of the Dogon also predicts a third star in the system, named “Emme Ya” which means “Sorghum Female”, but to date, not even the Hubble Space Telescope has been able to find evidence of a third star, nor the single satellite that is said to circle the Sorghum Female. The Dogon also recount tales of three-legged spacecraft that brought intelligent, amphibious, but humanoid beings to Earth, and use the many rock paintings in the surrounding mountains that depict these beings, as proof of the origin of their self-proclaimed ancient knowledge. It is however more likely that their knowledge of the Sirius system derives from contact with Chinese seafarers who were known to have been in the area about 500 years ago.

Whatever the truth of the matter though, Sirius will blaze in the sky for many millions of years more, during which it will no doubt give rise to nearly as many tales.