Sirius is a star system and is the brightest star in Earh's sky, It is twice as bright as Canopus, the next brightest star. The name 'Sirius' derives from the ancient Greek Σείριος (Seirios) meaning 'Glowing' or 'Scorcher'. It is seen in the constellation Canis Major, The Greater dog which is seen next to the constellation of Orion. What the naked 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, called Sirius B. The distance separating Sirius A from its companion varies between 8.2 and 31.5 AU. Sirius appears beight because of it's luminosity and proximity to Earth which is at a distance of 8.6 light years. The Sirius System is one of Earth's near neighbours.
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Sirius is gradually moving closer to the Solar System, so it will slightly increase in brightness over the next 60,000 years. After that time its distance will begin to increase and it will become fainter, but it will continue to be the brightest star in the Earth's night sky for the next 210,000 years. Sirius A is twice as massive as our Sun. It is 25 times more luminous than our Sun but has significantly less 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.
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Sirius is gradually known as the "Dog Star", reflecting its prominence in it's constellation, Canis Major. 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 in the Southern Hemisphere the star marked winter and was an important reference for their navigation around the Pacific Ocean. Even if it is the brightest star, it is not as bright as The Moon, Venus, Mercury, Jupiter, Saturn and so on. Sirius can even be observed in daylight with the naked eye under the right conditions. Ideally, the sky should be very clear, with the observer at a high altitude, the star passing overhead, and the Sun low down on the horizon. These observing conditions are more easily met in the southern hemisphere, due to the southerly declination of Sirius.
