As an expert in astronomy, I can tell you that Sirius is not a white dwarf. Sirius, also known as the Dog Star, is actually the brightest star in our night sky. It's a main sequence star, which means it's currently in the phase of its life where it's fusing hydrogen into helium in its core. White dwarfs, on the other hand, are the remnants of stars that have exhausted their nuclear fuel and shed their outer layers. They are typically much smaller, denser, and dimmer than main sequence stars like Sirius.

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A white dwarf's faint luminosity comes from the emission of stored thermal energy; no fusion takes place in a white dwarf wherein mass is converted to energy. The nearest known white dwarf is Sirius B, at 8.6 light years, the smaller component of the Sirius binary star.read more >>