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Sirius A and B artwork

Artist's impression

Sirius, also known as Alpha Canis Majoris, is the brightest star, in its constellation, the southern hemisphere, and in the entire night sky. It is located $ 8.6 $ light years away in the constellation Canis Major, and is also known as the Dog star. Sirius A is orbited by a white dwarf called Sirius B.

Properties

Sirius A has a diameter $ 1.711 $ times that of the Sun, and a temperature of $ 9,940 $ degrees Kelvin, making it a type-A star. It is $ 25 $ times brighter than the Sun, but unlike the other stars in the night sky, it is not as luminous as them. As for Sirius B, it is $ 0.0084 $ times the Sun's diameter, which is smaller than Earth. It orbits Sirius A at a distance of around $ 2 * 10^9 $ kilometers. When viewed from the night sky, Sirius A has a magnitude of $ -1.47 $.

The ancient Egyptians relied on Sirius during a possible flood of the Nile. If Sirius were to rise up much higher in the sky, they believed a flood was incoming.

Other historical observers of Sirius observed the star as having a deep red hue, comparable to Mu Cephei. However, since the secondary star in the system is a white dwarf, theories at the time believed that Sirius B was a red giant or a red dwarf at the time. However, the too-short lifespan of $ 500 $ years and the lack of a surrounding Planetary Nebula contradict these theories. Thus, the most likely explanation is that when near the horizon, Sirius will give the impression that it is flashing with tints of red, white, and blue.

References