Sirius astrological symbol was listed by Heinrich Cornelius Agrippa. Many cultures have historically attached special significance to Sirius, particularly in relation to dogs. It is often colloquially called the "Dog Star" as the brightest star of Canis Major, the "Great Dog" constellation. It was classically depicted as Orion's dog. The Ancient Greeks thought that Sirius's emanations could affect dogs adversely, making them behave abnormally during the "dog days," the hottest days of the summer. The Romans knew these days as "dies caniculares", and the star Sirius was called Canicula, "little dog." The excessive panting of dogs in hot weather was thought
Sirius flattening of its disk. This is at marked variance with the similar-sized Vega, which rotates at a much faster 274 km/s and bulges prominently around its equator. A weak magnetic field has been detected on the surface of Sirius A. Stellar models suggest that the star formed during the collapsing of a molecular cloud, and that after years, its internal energy generation was derived entirely from nuclear reactions. The core became convective and used the CNO cycle for energy generation. It is predicted that Sirius A will have completely exhausted the store of hydrogen at its core within a billion