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The word comet derives from the Old English cometa from the Latin comēta or comētēs. That, in turn, is a romanization of the Greek κομήτης 'wearing long hair', and the Oxford English Dictionary notes that the term (ἀστὴρ) κομήτης already meant 'long-haired star, comet' in Greek.
Common targets of amateur astronomers include the Sun, the Moon, planets, stars, comets, meteor showers, and a variety of deep-sky objects such as star clusters, galaxies, and nebulae. Astronomy clubs are located throughout the world and many have programs to help their members set up and complete observational programs including those to ...
Periodic comets (also known as short-period comets) are comets with orbital periods of less than 200 years or that have been observed during more than a single perihelion passage [1] (e.g. 153P/Ikeya–Zhang). "Periodic comet" is also sometimes used to mean any comet with a periodic orbit, even if greater than 200 years.
Stardust's discovery of crystalline silicates in the dust of comet Wild 2 implies that the dust formed above glass temperature (> 1000 K) in the inner disk region around a hot young star, and was radially mixed in the solar nebula from the inner regions a larger distance from the star or the dust particle condensed in the outflow of evolved red ...
This unique spiral galaxy, which is situated 3.2 billion light-years from the Earth, has an extended stream of bright blue knots and diffuse wisps of young stars. [2] It rushes at 3.6 million km/h (1000km/s [2]) through the cluster Abell 2667 and therefore, like a comet, shows a tail, with a length of 600,000 light-years.
In an attempt to link the 1843 and 1880 comets to the comet in 1106 and 371 BC, Kreutz measured the fragments of the 1882 comet and determined that it was likely a fragment of the 1106 comet. He then designated that all sungrazing comets with similar orbital characteristics as these few comets would be part of the Kreutz Group. [4]
In Greek antiquity the ideas of celestial spheres and rings first appeared in the cosmology of Anaximander in the early 6th century BC. [7] In his cosmology both the Sun and Moon are circular open vents in tubular rings of fire enclosed in tubes of condensed air; these rings constitute the rims of rotating chariot-like wheels pivoting on the Earth at their centre.
A comet tail and coma are visible features of a comet when they are illuminated by the Sun and may become visible from Earth when a comet passes through the inner Solar System. As a comet approaches the inner Solar System, solar radiation causes the volatile materials within the comet to vaporize and stream out of the nucleus , carrying dust ...