Canopus (/kəˈnoʊpəs/; α Car, α Carinae, Alpha Carinae) is the brightest star in the southern constellation of Carina and Argo Navis, and the second brightest star in the night-time sky, after Sirius. Canopus's visual magnitude is −0.72, and it has an absolute magnitude of −5.53.
Canopus is a supergiant of spectral type F. Canopus is essentially white when seen with the naked eye (although F-type stars are sometimes listed as "yellowish-white"). It is located in the far southern sky, at a declination of −52° 42' (2000) and a right ascension of 06h24.0m.
Canopus is lying 310 light years (96 parsecs) from our solar system; this is based on a parallax measurement of 10.43 ± 0.53 mas. The difficulty in measuring Canopus' distance stemmed from its unusual nature. Canopus has been classified as a F0 II or F0 Ib (Ib referring to "less luminous supergiant") star, and such stars are rare and poorly understood; they are stars that can be either in the process of evolving to or away from red giant status. This in turn made it difficult to know how intrinsically bright Canopus is, and therefore how far away it might be. Direct measurement was the only way to solve the problem. Canopus is too far away for Earth-based parallax observations to be made, so the star's distance was not known with certainty until the early 1990s.
The surface temperature of Canopus has been estimated at 7350 ± 30 K.
Other stars appear brighter only during relatively temporary periods, during which they are passing our solar system at a much closer distance than Canopus. About 90,000 years ago, Sirius moved close enough that it became brighter than Canopus, and that will remain the case for another 210,000 years.
Canopus is a strong source of X-rays, which are probably produced by its corona, magnetically heated to around 15 million K. The temperature has likely been stimulated by fast rotation combined with strong convection percolating through the star's outer layers. The star's surface temperature is too cool to account for the X-rays.
Canopus in Science Fiction
- Dune (1965) and other novels in the Dune universe by Frank Herbert. The third planet from Canopus is the desert planet Arrakis (Dune), the only source of the "melange spice," the most important and valuable substance in the universe. Arrakis, with its giant sandworms, its Bedouin-like human inhabitants (the Fremen?) clinging to the most precarious of ecological niches through fanatical scrupulousness in water conservation, and its overall concern with ecological themes, is possibly the most convincing planetary romance environment created by any science fiction author. The planet Wallach IX is supposed to be the ninth planet of Laoujin (Laou Jin), vilket är det kinesiska namnet för Canopus. But in the Dune Universe Wallach IX i not mentioned as one of the planets in the same system as Arrakis.
- "Where No Man Has Gone Before" (1966), episode of Star Trek: The Original Series? written by Samuel A. Peeples?, as part of the film, television, and print franchise originated by Gene Roddenberry?. The fictional sonnet Nightingale Woman is ascribed as written by "Tarbolde of Canopus" in the year 1996.
- "The Ultimate Computer" (1968), episode of Star Trek: The Original Series written by D. C. Fontana?, as part of the film, television, and print franchise originated by Gene Roddenberry. The USS Enterprise visits the planet Alpha Carinae II?. In the remastered version of the series (2008), the planet was refurbished and given a more realistic appearance.
- "The Eye of the Beholder" (1974), episode 15 of Star Trek: The Animated Series? written by David P. Harmon, as part of the film, television, and print franchise originated? by Gene Roddenberry. The Enterprise crew beams down to the planet Lactra VII? to discover a series of unusual environments, including one constructed as a copy of the desert planet Canopus III? (compare Canopus: Dune above). While exploring, the crew meets the Lactrans?, a group of twenty foot slugs with intellectual capacities far beyond their own. The team is captured by the Lactrans to be made part of a zoo collection.
- Shikasta? (1979), first novel in the Canopus in Argos? series by literature Nobelist Doris Lessing?. The series fictionally reinterprets the past history of the planet Shikasta (Earth) as playing out under the influence of three galactic empires: Canopus?, Sirius?, and their mutual enemy, Puttiora?. The novel Shikasta is presented in the form of a series of reports by Canopean emissaries to Shikasta—but at a deeper level, it is a record of their struggle to come to terms with human sexuality, politics, and mortality, all through the lens of Sufi mysticism.
- BattleTech? (1984), wargame and related products launched by The FASA Corporation. The Magistracy of Canopus? is an interstellar nation in the fictional setting of BattleTech. The magistracy was formed by defectors and soldiers from forces attached to the defense forces of Andurien?.
- Frontier: Elite II? (1993) and Frontier: First Encounters? (1995), computer games written by David Braben? et al. Canopus has colonies dedicated to mining, including two dwarf planets that share the name Camp Lawrence?.
- A system in The Escape Velocity Universe
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