Sirius in fiction below)—and even if such were eventually discovered, with an estimated age of 230 million years the system is too young to have fostered the development of life or a complex biosphere. Sirius AB is the alpha star of the constellation Canis Major (the great dog, sometimes styled as Orion's hunting dog), whence its cognomen "the dog star". The most commonly used proper name of this star comes through the Latin "Sirius", from the Greek Σείριος ("Seirios", "glowing" or "scorcher"). The ancient Greeks observed that the appearance of Sirius heralded the hot and dry "dog days" of summer, and feared that
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