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Difference between revisions of "Sirius"
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[[File:36-Sopdet.jpg|200px|thumb|Sirius was personified as the goddess Sopdet by the ancient Egyptians]] | [[File:36-Sopdet.jpg|200px|thumb|Sirius was personified as the goddess Sopdet by the ancient Egyptians]] | ||
'''Sirius''' (/ˈsɪriəs/) is the brightest star in the night sky. Its name is derived from the Greek word Σείριος (Seirios, lit. 'glowing' or 'scorching'). The star is designated α Canis Majoris, Latinized to Alpha Canis Majoris, and abbreviated Alpha CMa or α CMa. With a visual apparent magnitude of −1.46, Sirius is almost twice as bright as Canopus, the next brightest star | '''Sirius''' (/ˈsɪriəs/) is the brightest star in the night sky. Its name is derived from the Greek word Σείριος (Seirios, lit. 'glowing' or 'scorching'). The star is designated α Canis Majoris, Latinized to Alpha Canis Majoris, and abbreviated Alpha CMa or α CMa. With a visual apparent magnitude of −1.46, Sirius is almost twice as bright as Canopus, the next brightest star. | ||
Sirius appears bright because of its intrinsic luminosity and its proximity to the Solar System. | Sirius is a binary star consisting of a main-sequence star of spectral type A0 or A1, termed Sirius A, and a faint white dwarf companion of spectral type DA2, termed Sirius B. The distance between the two varies between 8.2 and 31.5 astronomical units as they orbit every 50 years. | ||
==Characteristics== | |||
Sirius appears bright because of its intrinsic luminosity and its proximity to the Solar System. | |||
The Sirius system is one of [[Earth]]'s nearest neighbours at a distance of 8.611 light years. However, Sirius is gradually moving closer to the Solar System, so it is expected to increase in brightness slightly 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 approximately the next 210,000 years. | |||
Sirius A is about twice as massive as the [[Sun]] and has an absolute visual magnitude of +1.42. It is 25 times as luminous as 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 A is about twice as massive as the [[Sun]] and has an absolute visual magnitude of +1.42. It is 25 times as luminous as 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. | ||
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Bright stars were important to the ancient Polynesians for navigation of the Pacific Ocean. They also served as latitude markers; the declination of Sirius matches the latitude of the archipelago of Fiji at 17°S and thus passes directly over the islands each sidereal day. Sirius served as the body of a "Great Bird" constellation called Manu, with Canopus as the southern wingtip and Procyon the northern wingtip, which divided the Polynesian night sky into two hemispheres. | Bright stars were important to the ancient Polynesians for navigation of the Pacific Ocean. They also served as latitude markers; the declination of Sirius matches the latitude of the archipelago of Fiji at 17°S and thus passes directly over the islands each sidereal day. Sirius served as the body of a "Great Bird" constellation called Manu, with Canopus as the southern wingtip and Procyon the northern wingtip, which divided the Polynesian night sky into two hemispheres. | ||
It marked the onset of winter for the Māori, whose name Takurua described both the star and the season. Its culmination at the [[winter solstice]] was marked by celebration in Hawaii, where it was known as Ka'ulua, "Queen of Heaven." | It marked the onset of winter for the Māori, whose name Takurua described both the star and the season. Its culmination at the [[winter solstice]] was marked by celebration in Hawaii, where it was known as Ka'ulua, "Queen of [[Heaven]]." | ||
==Islam== | ==Islam== | ||