Orion Glossary
Special | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | ALL
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AstrologyThe study of the movements and relative positions of celestial bodies claimed as having an influence on human affairs and the natural world. Astrology is not a science. | |
AstronomyAstronomy is the scientific study of stars, space, and the physical universe as a whole. | |
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Big CrunchAn hypothesis that, if there were enough matter in the Universe, the expansion of the Universe would eventually become a contraction, leading to a big crunch. This hypothesis is no longer believed to be valid. | |
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Doppler effectThe process by which the wavelength of a wave is altered when the source of the wave is moving with respect to the observer. Motion away from an observer causes the wavelength to be perceived as longer than that with which it was emitted; motion towards an observer causes the wavelength to be perceived as shorter than that with which it was emitted. | |
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Giant Molecular CloudA dense cloud of cold dust and gas within which stars form, extending for many billions of kilometres and typically containing more than a million solar masses of material. | |
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Harvard Spectral ClassificationA commonly used classification scheme for stars by which the temperature of a star is denoted by the assignment of a letter in the sequence OBAFGKM, running from hottest (O) to coolest (M) | |
Hertzsprung-Russell (HR) diagramA diagnostic diagram whereby the evolutionary state of a star may be discerned via a combination of stellar temperature and luminosity. Named after its originators Ejnar Hertzsprung and Henry Norris Russell. | |
Hubble deep fieldA project with the Hubble Space Telescope to obtain a series of very deep exposures to search for distant galaxies at high redshift. | |
Hubble’s lawThe observation that, for distant galaxies, the greater a galaxy’s distance, the greater the redshift of the radiation received from that galaxy. | |