Saturday, July 23, 2016


From my email:
Sirius is the brightest star in the night sky with a visual apparent magnitude of −1.46, almost twice as bright as Canopus, the next brightest star. The star has the Bayer designation Alpha Canis Majoris. What the naked eye perceives as a single star is actually a binary star system, consisting of a white main sequence star termed Sirius A, and a faint white dwarf companion called Sirius B. At a distance of 2.6 parsecs (8.6 light years), the Sirius system is one of our near neighbors. Sirius A is about twice as massive as the Sun and has an absolute visual magnitude of 1.42. It is 25 times more luminous than the Sun but has a significantly lower luminosity than other bright stars such as Canopus or Rigel. The system is between 200 and 300 million years old. It was originally composed of two bright bluish stars. The more massive of these, Sirius B, consumed its resources and became a red giant before shedding its outer layers and collapsing into its current state as a white dwarf around 120 million years ago. Sirius is also known colloquially as the "Dog Star", reflecting its prominence in its constellation, Canis Major. The heliacal rising of Sirius marked the flooding of the Nile in Ancient Egypt and the 'Dog Days' of summer for the Ancient Greeks, while to the Polynesians it marked winter and was an important star for navigation around the Pacific Ocean.

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