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Messier 45: Difference between revisions
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==History== | ==History== | ||
The Pleiades are a prominent sight in winter in the Northern Hemisphere, and have been known since antiquity to cultures all around the world, including the Celts, Māori, Aboriginal Australians, the Persians, the Arabs (known as Thurayya), the Chinese, the Japanese, the Maya, the Aztec, and the Sioux and Cherokee. In Hinduism, the Pleiades are known as Krittika and are associated with the war-god Kartikeya (Murugan, Skanda), who derives his name from them. The god is raised by the six Krittika sisters, also known as the Matrikas. He is said to have developed a face for each of them. | The Pleiades are a prominent sight in winter in the Northern Hemisphere, and have been known since antiquity to cultures all around the world, including the Celts, Māori, Aboriginal Australians, the Persians, the Arabs (known as Thurayya), the Chinese, the Japanese, the Maya, the Aztec, and the Sioux and Cherokee. In Hinduism, the Pleiades are known as Krittika and are associated with the war-god Kartikeya (Murugan, Skanda), who derives his name from them. The god is raised by the six Krittika sisters, also known as the Matrikas. He is said to have developed a face for each of them.<ref>[http://en.wikipedia.org/wiki/Pleiades Pleiades]]</ref> | ||
[[File:330px-M45map.jpg|thumb|Map of the Pleiades]] | [[File:330px-M45map.jpg|thumb|Map of the Pleiades]] | ||
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==Distance== | ==Distance== | ||
The distance to the Pleiades can be used as an important first step to calibrate the cosmic distance ladder. As the cluster is so close to the Earth, its distance is relatively easy to measure and has been estimated by many methods. Accurate knowledge of the distance allows astronomers to plot a Hertzsprung-Russell diagram for the cluster, which, when compared to those plotted for clusters whose distance is not known, allows their distances to be estimated. Other methods can then extend the distance scale from open clusters to galaxies and clusters of galaxies, and a cosmic distance ladder can be constructed. Ultimately astronomers' understanding of the age and future evolution of the universe is influenced by their knowledge of the distance to the Pleiades. Yet some authors argue that the controversy over the distance to the Pleiades discussed below is a red herring, since the cosmic distance ladder can (presently) rely on a suite of other nearby clusters where consensus exists regarding the distances as established by Hipparcos and independent means (e.g., the Hyades, [[Coma Berenices]] cluster, etc | The distance to the Pleiades can be used as an important first step to calibrate the cosmic distance ladder. As the cluster is so close to the Earth, its distance is relatively easy to measure and has been estimated by many methods. Accurate knowledge of the distance allows astronomers to plot a Hertzsprung-Russell diagram for the cluster, which, when compared to those plotted for clusters whose distance is not known, allows their distances to be estimated. Other methods can then extend the distance scale from open clusters to galaxies and clusters of galaxies, and a cosmic distance ladder can be constructed. Ultimately astronomers' understanding of the age and future evolution of the universe is influenced by their knowledge of the distance to the Pleiades. Yet some authors argue that the controversy over the distance to the Pleiades discussed below is a red herring, since the cosmic distance ladder can (presently) rely on a suite of other nearby clusters where consensus exists regarding the distances as established by Hipparcos and independent means (e.g., the Hyades, [[Coma Berenices]] cluster, etc.<ref>[http://en.wikipedia.org/wiki/Pleiades Pleiades]]</ref> | ||
==Brightest Stars== | ==Brightest Stars== | ||
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==Possible Planets== | ==Possible Planets== | ||
Analyzing deep-infrared images obtained by the Spitzer Space Telescope and Gemini North telescope, astronomers discovered that one of the cluster's stars – HD 23514, which has a mass and luminosity a bit greater than that of the Sun, is surrounded by an extraordinary number of hot dust particles. This could be evidence for planet formation around HD 23514 | Analyzing deep-infrared images obtained by the Spitzer Space Telescope and Gemini North telescope, astronomers discovered that one of the cluster's stars – HD 23514, which has a mass and luminosity a bit greater than that of the Sun, is surrounded by an extraordinary number of hot dust particles. This could be evidence for planet formation around HD 23514.<ref>[http://en.wikipedia.org/wiki/Pleiades Pleiades]]</ref> | ||