Sirius

Sirius, also known as the Dog Star, is the brightest star in Earth's night sky. It lies in the constellation Canis Major and is a prominent feature of the winter skies in the Northern Hemisphere.

It is a binary star system consisting of Sirius A, a hot white main-sequence star (spectral type A1V), and a faint companion, Sirius B, a white dwarf. Sirius A shines with about 25 times the Sun’s luminosity and has a surface temperature around 9,900 kelvin, giving it a blue-white hue. The system is located about 8.6 light-years from Earth, making it one of the nearest naked-eye stars. The apparent magnitude of Sirius can reach about −1.46, making it easily visible even in light-polluted skies. There are no confirmed exoplanets in the Sirius system.

Sirius B orbits Sirius A with a period of roughly 50 years, at an average separation of about 20 astronomical units. The mass of Sirius B is near one solar mass, while Sirius A is more massive, around 2 solar masses.

Etymology and cultural significance: The name Sirius derives from the Greek Seirios, meaning scorching or glowing. Historically, the heliacal rising of Sirius around the onset of summer was associated with the hot season in various cultures; in ancient Egypt it signaled the Nile flood cycle and the new year. The phrase Dog Days of Summer originates from this star’s appearance in the sky.

Observational and scientific notes: Sirius has contributed to understanding stellar evolution, binary star dynamics, and white dwarfs.