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Sirius, also known as Alpha Canis Majoris, is the brightest star in Earth's night sky. Its name is derived from the Latin word "sērius," meaning "scorching" or "burning." Sirius is a binary star system composed of two stars: Sirius A and Sirius B. Sirius A is a main-sequence star of spectral type A1V, approximately twice the mass of the Sun and about 25 times as luminous. Sirius B is a white dwarf, a stellar remnant that is much smaller and fainter than Sirius A.

The Sirius system is located about 8.6 light-years away from Earth in the constellation Canis Major. This proximity makes it a significant object of study for astronomers. The brightness of Sirius has led to its mention in various mythologies and historical records across different cultures. Ancient Egyptians, for instance, associated the star's heliacal rising (its appearance just before sunrise after a period of invisibility) with the annual flooding of the Nile River.

Sirius is an important star in astronomical observation due to its brightness and relative closeness. Its distinct bluish-white color is a characteristic that distinguishes it from many other stars. The discovery of Sirius B in 1862 was a landmark event, providing the first concrete evidence for the existence of white dwarf stars. The two stars in the system orbit each other with a period of approximately 50 years. The apparent motion of Sirius across the sky is also a factor in its prominence and visibility throughout the year.