Sirius facts for kids
Sirius is the brightest star in the night sky. It is a binary star system in Canis Major, near Orion. It has an apparent magnitude of −1.46. The system is between 200 and 300 million years old. It was originally composed of two bright bluish stars.
Sirius appears bright because of its intrinsic luminosity and its position (it is relatively close to Earth). At a distance of 2.6 parsecs (8.6 ly), the Sirius system is one of Earth's near neighbours.
The Egyptians called this star 'Sopdet'. They relied on it to predict when the flood season would start. Sirius is sometimes called the Dog Star. The phrase the dog days of summer means the hottest days of summer.
Sirius A
Sirius A is about twice as massive as the Sun and has an absolute magnitude of 1.42. It is 25 times more luminous than the Sun, but has a significantly lower luminosity than other bright stars such as Canopus or Rigel.
Sirius B
Originally, Sirius B had about five times the mass of the Sun. and was a B-type star (roughly B4–5) when it still was on the main sequence.
Sirius B used up its resources and became a red giant. Then it shed its outer layers and collapsed into its present state as a white dwarf, about 120 million years ago. Its mass now is about the same as the Sun.
Modern significance
Sirius features on the coat of arms of Macquarie University, and is the name of its alumnae journal. Seven ships of the Royal Navy have been called HMS Sirius since the 18th century, with the first being the flagship of the First Fleet to Australia in 1788. The Royal Australian Navy subsequently named a vessel HMAS Sirius in honor of the flagship. American vessels include the USNS Sirius (T-AFS-8) as well as a monoplane model—the Lockheed Sirius, the first of which was flown by Charles Lindbergh. The name was also adopted by Mitsubishi Motors as the Mitsubishi Sirius engine in 1980. The name of the North American satellite radio company CD Radio was changed to Sirius Satellite Radio in November 1999, being named after "the brightest star in the night sky". Sirius is one of the 27 stars on the flag of Brazil, where it represents the state of Mato Grosso.
Composer Karlheinz Stockhausen, who wrote a piece called Sirius, is claimed to have said on several occasions that he came from a planet in the Sirius system. To Stockhausen, Sirius stood for "the place where music is the highest of vibrations" and where music had been developed in the most perfect way.
Sirius has been the subject of poetry. Dante and John Milton reference the star, and it is the "powerful western fallen star" of Walt Whitman's "When Lilacs Last in the Dooryard Bloom'd", while Tennyson's poem The Princess describes the star's scintillation:
...the fiery Sirius alters hue
And bickers into red and emerald.
Related pages
Images for kids
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Hubble Space Telescope image of Sirius A and Sirius B. The white dwarf can be seen to the lower left. The diffraction spikes and concentric rings are instrumental effects.
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Sirius (bottom) and the constellation Orion (right). The three brightest stars in this image—Sirius, Betelgeuse (top right) and Procyon (top left)—form the Winter Triangle. The bright star at top center is Alhena, which forms a cross-shaped asterism with the Winter Triangle.
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The orbit of Sirius B around A as seen from Earth (slanted ellipse). The wide horizontal ellipse shows the true shape of the orbit (with an arbitrary orientation) as it would appear if viewed straight on.
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A Chandra X-ray Observatory image of the Sirius star system, where the spike-like pattern is due to the support structure for the transmission grating. The bright source is Sirius B. Credit: NASA/SAO/CXC
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Comparison of Sirius A and the Sun, to scale and relative surface brightness
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Size comparison of Sirius B and Earth
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A bust of Sopdet, Egyptian goddess of Sirius and the fertility of the Nile, syncretized with Isis and Demeter
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Sirius midnight culmination at New Year 2022 local solar time
See also
In Spanish: Sirio para niños
