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Copernicus rejected the ninth and tenth spheres, placed the orb of the Moon around the Earth, and moved the Sun from its orb to the center of the universe. The planetary orbs circled the center of the universe in the following order: Mercury, Venus, the great orb containing the Earth and the orb of the Moon, then the orbs of Mars, Jupiter, and ...
Nicole Oresme (c. 1323-1382) explained the motion of the spheres in traditional terms of the action of intelligences but noted that, contrary to Aristotle, some intelligences are moved; for example, the intelligence that moves the Moon's epicycle shares the motion of the lunar orb in which the epicycle is embedded. [55]
A diagram of a typical nautical sextant, a tool used in celestial navigation to measure the angle between two objects viewed by means of its optical sight. Celestial navigation, also known as astronavigation, is the practice of position fixing using stars and other celestial bodies that enables a navigator to accurately determine their actual current physical position in space or on the ...
The number used to identify stars in navigation publications and star charts. [Note 2] Common name The name of the star commonly used navigation publications and star charts. Bayer designation: Another name of the star which combines a Greek letter with the possessive form of its constellation's Latin name. Etymology of common name
A-type star In the Harvard spectral classification system, a class of main-sequence star having spectra dominated by Balmer absorption lines of hydrogen. Stars of spectral class A are typically blue-white or white in color, measure between 1.4 and 2.1 times the mass of the Sun, and have surface temperatures of 7,600–10,000 kelvin.
One possibility is that these stars were much larger than current stars: several hundred solar masses, and possibly up to 1,000 solar masses. Such stars would be very short-lived and last only 2–5 million years. [32] Such large stars may have been possible due to the lack of heavy elements and a much warmer interstellar medium from the Big Bang.
In Orphic cosmogony Phanes / ˈ f eɪ ˌ n iː z / (Ancient Greek: Φάνης, romanized: Phánēs, genitive Φάνητος) or Protogonos / p r oʊ ˈ t ɒ ɡ ə n ə s / (Ancient Greek: Πρωτογόνος, romanized: Prōtogónos, lit.
The phrase "fixed star" is technically incorrect, but nonetheless it is used in an historical context, and in classical mechanics. When used as a visual reference for observations, they usually are called background stars or simply distant stars, still retaining the intuitive meaning of they being "fixed" in some practical sense.