A fascinating star that has captured the attention of astronomers and cultures throughout history: introducing Sirius

Sirius, also known as the Dog Star, is one of the brightest stars in the night sky. It is located in the constellation Canis Major and can be easily spotted by its bright white-blue light.

Sirius is a main-sequence star, which means it is currently in the phase of its life where it is burning hydrogen into helium in its core. It has a mass that is about twice that of the Sun, and it is about 25 times more luminous than the Sun. Sirius is also relatively close to Earth, at a distance of only about 8.6 light-years away.

Hubble Space Telescope image of Sirius A and Sirius B. The white dwarf can be seen to the lower left. NASA, ESA, H. Bond (STScI), and M. Barstow (University of Leicester)

Moreover, Sirius is actually a binary star system. The primary star, Sirius A, is the one that we see as the bright point of light in the sky. The companion star, Sirius B, is a white dwarf that is much smaller and fainter than Sirius A. In fact, Sirius B is so small and faint that it was not even discovered until the mid-19th century.

The discovery of Sirius B was actually quite important in the history of astronomy because it provided the first direct evidence of the existence of white dwarfs. White dwarfs are the remnants of stars that have exhausted their nuclear fuel and have lost the whole of their external plasma envelope, leaving their bare and very small-sized nucleus. They are very dense, with a mass that is comparable to that of the Sun but a size that is comparable to that of the Earth.

Sirius has also a great cultural significance. It has been observed and studied by various civilizations throughout history, including the ancient Greeks and Egyptians. In ancient Egypt, Sirius was particularly important because it first appeared in the sky just before the annual flooding of the Nile River, which was a key event for the country’s agricultural system.


W. S. Adams 1915 PASP 27 236

James Liebert et al 2005 ApJ 630 L69

If you like our job, and wish to support, please send a donation