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The arrows could hit animals or people and were feared when walking at night. Comets were conceived as smoking stars and as bad omens, e.g., announcing the death of a ruler. [9] Ancient Chinese records of comet apparitions have been particularly useful to modern astronomers. They are accurate, extensive, and consistent over three millennia.
Around forty comets have had their orbits calculated based entirely on ancient Chinese records. [2] Of the well known comets, besides Halley, Brian G. Marsden suggested, based on Chinese and other ancient observations, that the Great Comet of 1106 was a previous apparition of Comet Ikeya–Seki. [14]
Comets whose aphelia are near a major planet's orbit are called its "family". [81] Such families are thought to arise from the planet capturing formerly long-period comets into shorter orbits. [82] At the shorter orbital period extreme, Encke's Comet has an orbit that does not reach the orbit of Jupiter, and is known as an Encke-type comet.
The Great Comet being depicted as the harbinger of war and death in a Dutch pamphlet (1619) As was common at the time, this comet was also seen in a flood of writings as an ominous harbinger of various misfortunes and as a warning and "rod of wrath" sent by God. [15] One Thuringian chronicle stated: [16]
Diodorus wrote that the comet was believed by some to have foretold the decline of the Spartans, and describes the debate over its nature. [8]During their term of office, after the Lacedaemonians had held the supremacy in Greece for almost five hundred years, a divine portent foretold the loss of their empire... and a little later, to the surprise of all, the Spartans were defeated in a great ...
Periodic comets usually have elongated elliptical orbits, and usually return to the vicinity of the Sun after a number of decades. The official names of non-periodic comets begin with a "C"; the names of periodic comets begin with "P" or a number followed by "P". Comets that have been lost or disappeared have names with a "D". Comets whose ...
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.
The Discourse on Comets (Italian: Discorso delle Comete) was a pamphlet published in 1619 with Mario Guiducci as the named author, though in reality it was mostly the work of Galileo Galilei. In it Galileo conjectured that comets were not physical bodies but atmospheric effects like the aurora borealis .