Sirius also known as the Dog Star is the brightest star in the sky and shines at a magnitude of around -1.46. Located in the constellation of Canis Major, it is nine times brighter than any first magnitude star. It has a diameter 1.8 times of the Sun and a mass 2.35 times of the Sun. Even though the surface temperature of Sirius is around 10,000 degrees K, it's superb brilliance is due to the relative closeness of the star. Of, course it's not really close, the distance is unimaginable for humans. At a distance of 8.7 light years, it is the fifth nearest star and if you know where to look can easily be seen in the daytime.
Sirius has been known throughout human history but is probably more associated with the ancient Egyptians who called it Anubis depicted as a god with a dog's head. Also, the Egyptians believed that the rising of Sirius in the early morning sky was an indication of the coming of the annual flooding of the River Nile. The Dog Star tag comes because the constellation was thought to be one of Orion's hunting dogs. The other dog is the constellation of Canis Minor.
Sirius has a white dwarf companion star called Sirius B or “The Pup”. This is a very unusual star as the mass is nearly equal to the Sun but incredibly has a diameter 40 to 50 times smaller than our Sun. This means that a cubic inch of the stars material would weigh around 2¼ tons on Earth. To put this into perspective this would be a 2¼ ton sugar cube! In 1976, Robert Temple made news with another unusual story about Sirius B. In his book, The Sirius Mystery, he speculated that Earth had been visited a few thousand years ago by amphibious beings from a planet around Sirius. He claimed that the Dogon tribe from Mali believed that Sirius has a dark, invisible companion star with a 50-year orbit. The companion is very heavy and made of a special metal which is not found on Earth! This is an accurate description of our knowledge of Sirius B, after it was observed with powerful telescopes, and described by scientists using the theories of quantum mechanics and relativity. How did the Dogon come by this knowledge?
Temple's book says that long ago an ark descended to the ground amid a great wind and brought amphibious beings, known as the Nommo, who gave the Dogon the information about Sirius B. This information was related to 2 visitors Griaule and Dieterlen who were investigating the tribe. The nature of the knowledge imparted is consistent with a visit by a science attentive person in the 1930s or 1940s when the discovery of the nature of Sirius B was being widely discussed in popular science books. This information could then have been woven into the Dogon's existing mythology in time to give Griaule and Dieterlen something very interesting to write home about.
A variation on this theme is that the knowledgeable visitor and the source of the information might have been Griaule himself. Though an anthropologist, Griaule had studied astronomy in Paris. He was aware of the discovery of Sirius B and may have over interpreted the Dogon responses to his questions. What do you think?
Shining in the winter sky low down in the south, Sirius is a beautiful star in any telescope and indeed with the naked eye. If it is clear outside right now, go and have a look!