{{Starbox astrometry |

$\backslash begin\{smallmatrix\}M\_v\backslash \; =\backslash \; m\; +\; 5\; (\backslash log\_\{10\}\; \{\backslash pi\}\; +\; 1)\backslash \; =\backslash \; -1.47\; +\; 5\; (\backslash log\_\{10\}\{0.37921\}\; +\; 1)\backslash \; =\backslash \; 1.42\backslash end\{smallmatrix\}$

See: / 11.18 (B)}}

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. Pronounced , the name Sirius is derived from the Ancient Greek Σείριος. The star has the Bayer designation α Canis Majoris (α CMa, or 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 of spectral type A1V, termed Sirius A, and a faint white dwarf companion of spectral type DA2, termed Sirius B.

Sirius appears bright due to both its intrinsic luminosity and its closeness to the Earth. 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 ( ). It is the subject of more myth and folklore than any other star apart from the sun.Fact: date=January 2009 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.

Sirius, known in Ancient Egypt as Sopdet (Greek: Sothis), is recorded in the earliest astronomical records. During the era of the Middle Kingdom, Egyptians based their calendar on the heliacal rising of Sirius, namely the day it becomes visible just before sunrise after moving far enough away from the glare of the sun. This occurred just before the annual flooding of the Nile and the summer solstice, after a 70 day absence from the skies. The hieroglyph for Sothis features a star and a triangle. Sothis was identified with the great goddess Isis who formed a part of a trinity with her husband Osiris and their son Horus, while the 70 day period symbolised the passing of Isis and Osiris through the duat (Egyptian underworld).

The Ancient Greeks believed that the appearance of Sirius heralded the hot and dry summer, and feared its effects on making plants wilt, men weaken and women become aroused. Due to its brightness, Sirius would have been noted to twinkle more in the unsettled weather conditions of early summer. To Greek observers, this signified certain emanations which caused its malign influence. People suffering its effects were said to be astroboletos/αστροβολητος or 'star-struck'. It was described as 'burning' or 'flaming' in literature. The season following the star's appearance came to be known as the Dog Days of summer. The inhabitants of the island of Ceos in the Aegean Sea would offer sacrifices to Sirius and Zeus to bring cooling breezes, and would await the reappearance of the star in summer. If it rose clear, it would portend good fortune; if it was misty or faint then it foretold (or emanated) pestilence. Coins retrieved from the island from the third century BC feature dogs or stars with emanating rays, highlighting Sirius' importance. The Romans celebrated the heliacal setting of Sirius around April 25, sacrificing a dog, along with incense, wine, and a sheep, to the goddess Robigo so that the star's emanations would not cause wheat rust on wheat crops that year.