TYCHOS glossary

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Animation of a binary star system

This is a glossary of terms, celestial bodies and researchers in the TYCHOS book, first published by Simon Shack on March 21st, 2018.[T 1]

List of terms

Mainstream terms used in the TYCHOS book
Term Description Chapters
bold in detail
binary star/binary system a binary star is a star system consisting of two stars orbiting around their common barycenter. These systems, especially when more distant, often appear to the unaided eye as a single point of light, and are then revealed as multiple by other means. 1, 3, 4, 5, 9, 12, 13, 14, 15, 17, 18, 19, 20, 21, 24, 27, 28 [T 2]
[WPT 1]
adaptive optics a technology used to improve the performance of optical systems by reducing the effect of incoming wavefront distortions by deforming a mirror in order to compensate for the distortion. It is used in astronomical telescopes to remove the effects of atmospheric distortion. 1 [T 3]
[WPT 2]
apparent magnitude a number that is a measure of its brightness as seen by an observer on Earth. The brighter an object appears, the lower its magnitude value (i.e. inverse relation). 35 [T 4]
[WPT 3]
Shack-Hartmann principle an optical instrument used for characterizing an imaging system. It is a wavefront sensor commonly used in adaptive optics systems. Shack–Hartmann sensors are used to characterize eyes for corneal treatment of complex refractive errors. 1 [T 2]
[WPT 4]
Equation of Time the discrepancy between two kinds of solar time. The word equation is used in the medieval sense of "reconcile a difference". The two times that differ are the apparent solar time, which directly tracks the diurnal motion of the Sun, and mean solar time, which tracks a theoretical mean Sun with noons 24 hours apart. 26 [T 5]
[WPT 5]
Sothic cycle a period of 1,461 Egyptian civil years of 365 days each or 1,460 Julian years averaging 365¼ days each. During a Sothic cycle, the 365-day year loses enough time that the start of its year once again coincides with the heliacal rising of the star Sirius on 19 July in the Julian calendar. 25, 33 [T 6]
[WPT 6]
analemma a diagram showing the variation of the position of the Sun in the sky over the course of a year, as viewed at a fixed time of day and from a fixed location on the Earth. 26 [T 5]
[WPT 7]
sidereal year the time taken by the Earth to orbit the Sun once with respect to the fixed stars. 31 [T 7]
[WPT 8]
sidereal day approximately 23 hours, 56 minutes, 4.0905 SI seconds. The sidereal day is 0.0084 seconds shorter than Earth's period of rotation relative to the fixed stars. 31 [T 7]
[WPT 9]
solar year/tropical year the time that the Sun takes to return to the same position in the cycle of seasons, as seen from Earth; for example, the time from vernal equinox to vernal equinox, or from summer solstice to summer solstice. 31 [T 7]
[WPT 10]
solar day/civil day 31 [T 7]
[WPT 11]
anomalistic year the time taken for the Earth to complete one revolution with respect to its apsides. Its average duration is 365.259636 days (365 d 6 h 13 min 52.6 s). 31 [T 7]
[WPT 12]
tidal locking occurs when the long-term interaction between a pair of co-orbiting astronomical bodies drives the rotation rates into a harmonic ratio with the orbital period. 11 [T 8]
[WPT 13]
aberration of light an astronomical phenomenon which produces an apparent motion of celestial objects about their true positions, dependent on the velocity of the observer. Aberration causes objects to appear to be displaced towards the direction of motion of the observer compared to when the observer is stationary. 34 [T 9]
[WPT 14]
apparent retrograde motion the apparent motion of a planet in a direction opposite to that of other bodies within its system, as observed from a particular vantage point. Direct motion or prograde motion is motion in the same direction as other bodies. 5, 6, 7, 9 [WPT 15]
apsidal precession the precession (rotation) of the orbit of a celestial body. More precisely, it is the gradual rotation of the line joining the apsides of an orbit, which are the points of closest and farthest approach. 28 [T 10]
[WPT 16]
axial tilt the angle between an object's rotational axis and its orbital axis, or, equivalently, the angle between its equatorial plane and orbital plane. 8 [T 11]
[WPT 17]
circumbinary a planet that orbits two stars instead of one. Because of the short orbits of some binary stars, the only way for planets to form is by forming outside the orbit of the two stars. 9, 14, 29 [WPT 18]
equinoctial precession a change in the orientation of the rotational axis of a rotating body. In astronomy, precession refers to any of several slow changes in an astronomical body's rotational or orbital parameters. An important example is the steady change in the orientation of the axis of rotation of the Earth, known as the precession of the equinoxes. 22 [T 12]
[WPT 19]
[WPT 20]
astronomical unit (AU) a unit of length, roughly the distance from Earth to the Sun. However, that distance varies as Earth orbits the Sun, from a maximum (aphelion) to a minimum (perihelion) and back again once a year. Originally conceived as the average of Earth's aphelion and perihelion, it was defined exactly as 149,597,870,700 metres or about 150 million kilometres (93 million miles) since 2012. 5, 15, 17, 26, 32, 33, 36 [WPT 21]
right ascension (RA) [WPT 22]
declination (DECL) [WPT 23]
perigee [WPT 24]
apogee [WPT 24]
perihelion [WPT 25]
aphelion [WPT 25]
conjunction (inferior/superior) [WPT 26]
prograde [WPT 27]
retrograde [WPT 27]
equinox [WPT 28]
solstice [WPT 29]
proper motion the astronomical measure of the observed changes in the apparent places of stars or other celestial objects in the sky, as seen from the center of mass of the Solar System, compared to the abstract background of the more distant stars. 36 [T 13]
[WPT 30]
radial velocity the rate of change of the distance between the object and the point. That is, the radial velocity is the component of the object's velocity that points in the direction of the radius connecting the object and the point. In astronomy, the point is usually taken to be the observer on Earth, so the radial velocity then denotes the speed with which the object moves away from or approaches the Earth. 36 [T 13]
[WPT 31]
Michelson-Morley experiment experiment performed between April and July, 1887 by Albert A. Michelson and Edward W. Morley in Cleveland, Ohio. It compared the speed of light in perpendicular directions, in an attempt to detect the relative motion of matter through the aether. The result was negative, in that the expected difference between the speed of light in the direction of movement through the presumed aether, and the speed at right angles, was found not to exist. 19 [T 14]
[WPT 32]
General Relativity (GR) the geometric theory of gravitation published by Albert Einstein in 1915 and the current description of gravitation in modern physics. 28 [T 10]
[WPT 33]
Binary Research Institute The Binary Research Institute was formed in 2001 to support and fund research regarding the hypothesis that the Sun is part of a binary star system. 1, 14, 18, 24, 30 [1]
NEAVE planetarium interactive sky map for exploring the stars and planets. 7, 8 [2]
SCOPE planetarium free online model of solar system and night sky. 7 [3]
Stellarium free open source planetarium for your computer. It shows a realistic sky in 3D, just like what you see with the naked eye, binoculars or a telescope. 7, 8 [4]
TYCHOS-specific terms used in the TYCHOS book
Term Description Chapters
bold in detail
TYCHOS a revised model of our solar system. Its basic orbital configuration is based on the semi-Tychonian model as defined by Longomontanus in his Astronomia Danica (1622), a monumental work regarded as Tycho Brahe’s “testament”. Although the semi-Tychonic and the TYCHOS models are geometrically similar, they significantly differ in that the latter assigns an orbit to Earth – whereas the former considers Earth as a motionless (albeit diurnally-rotating) celestial body. All [T 15]
[T 16]
Annual Constant of Precession (ACP) 16, 19, 20, 22, 24, 27, 30 [T 12]
Empiric Sidereal Interval (ESI) 6, 7, 10 [T 17]
geoptical 34 [T 9]
PVP orbit 19 [T 14]
PVP constant 19 [T 14]
True Mean Synodic Period (TMSP) 11, 17, 27 [T 18]
Tychosium 2D a bi-dimensional overhead view (as seen from above Earth's North Pole) of our Sun-Mars 'geoaxial' binary system. 21 [T 19]
Tychosium 3D 21 [T 20]
TYCHOS Great Year (TGY) 32 [T 21]

List of celestial bodies

Note: bodies with a higher apparent magnitude than ~4 (city) or 6 (faintest) are not visible with the naked eye

Celestial bodies (not) mentioned in the TYCHOS book
Name App. magnitude Description Chapters
bold in detail
Earth Home. All [WPB 1]
Sun -26.74 Our star, accompanied by Mars in a binary system. All [WPB 2]
Moon -12.74 Moon of Earth. Preface, 2, 3, 4, 5, 9, 10, 11, 15, 16, 17, 18, 20, 23, 27, 28, 29, 30, 31 [T 18]
[WPB 3]
Mercury -2.6-5.7 Junior moon of the Sun. Preface, 1, 2, 3, 5, 7, 9, 10, 11, 13, 15, 16, 17, 19, 27, 28, Epilogue [T 22]
[WPB 4]
Venus -4.9 to -3.8 Senior moon of the Sun. 1, 2, 3, 5, 7, 9, 10, 11, 12, 13, 15, 17, 20, 27 [T 23]
[WPB 5]
Mars -3.0-1.6 Binary companion of the Sun. Preface, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 19, 20, 21, 26, 27, 36, Epilogue [T 24]
[WPB 6]
Jupiter -2.94 to -1.6 P-type planet. 2, 3, 6, 8, 9, 12, 13, 14, 16, 17, 20, 26, 27, 29, 36 [T 25]
[WPB 7]
Saturn -0.24-1.47 P-type planet. 2, 3, 6, 9, 13, 15, 29, 35, 36 [T 25]
[WPB 8]
Uranus 5.32-5.9 P-type planet. 9, 13, 15, 29 [T 25]
[WPB 9]
Neptune 7.78-8.02 P-type planet. 9, 13, 15, 29 [T 25]
[WPB 10]
Pluto 13.65-16.3 P-type planet. 9, 15, 29 [T 25]
[WPB 11]
Phobos 11.8 Senior moon of Mars. 3, 5 [T 26]
[WPB 12]
Deimos 12.89 Junior moon of Mars. 3, 5 [T 26]
[WPB 13]
Ganymede 4.38-4.61 Largest Galilean moon of Jupiter. 3 [WPB 14]
Io 5.02 Innermost Galilean moon of Jupiter. 3, 26 [WPB 15]
Europa 5.29 Smallest Galilean moon of Jupiter. 3 [WPB 16]
Callisto 5.65 2nd-largest Galilean moon of Jupiter. [WPB 17]
Titan 8.2-9.0 Largest moon of Saturn. [WPB 18]
Iapetus 10.2-11.9 3rd-largest moon of Saturn. [WPB 19]
Rhea 10 2nd-largest moon of Saturn. [WPB 20]
Tethys 10.2 2nd-brightest moon of Saturn. [WPB 21]
Dione 10.4 3rd of inner moons of Saturn. [WPB 22]
Enceladus 11.7 6th-largest moon of Saturn. [WPB 23]
Mimas 12.9 Largest moon of Saturn. [WPB 24]
Triton 13.47 Largest moon of Neptune. [WPB 25]
Titania 13.9 Largest moon of Uranus. [WPB 26]
Oberon 14.1 2nd-largest moon of Uranus. [WPB 27]
Ariel 14.4 4th-largest moon of Uranus. [WPB 28]
Umbriel 14.5 3rd-largest moon of Uranus. [WPB 29]
Miranda 15.8 5th-largest moon of Uranus. [WPB 30]
Main Asteroid Belt Asteroid belt between Mars and Jupiter. 14 [WPB 31]
Kuiper Belt Kuiper object belt outside of orbit of Neptune. 14 [WPB 32]
Sirius -1.46 Brightest star in the night sky, binary system. 1, 3, 4, 6, 32, 33 [T 27]
[WPB 33]
Vega -0.02-0.07 5th-brightest star in the night sky. 5, 14, 19, 26, 36 [WPB 34]
Fomalhaut 1.16 18th-brightest star in the night sky. Binary star system with exoplanets, 2nd-brightest star with exoplanets, after Pollux. 14 [WPB 35]
Deneb 1.25 19th brightest star in the night sky. 35 [WPB 36]
Alpha Centauri 1.33 Binary/triple star system, closest to Earth. Exoplanet found around Proxima Centauri. 1, 35, 36 [T 4]
[WPB 37]
Regulus 1.4 21st brightest star in the night sky. 4+ star system. Near ecliptic. 6 [WPB 38]
Polaris 1.86-2.13 North Star, binary system. Preface, 5, 8, 18, 19, 34, Epilogue [T 14]
[WPB 39]
Delta Capricorni 2.81 Binary system. 7 [WPB 40]
Tau Ceti 3.5 Single star, possibly 5 exoplanets. 14 [WPB 41]
Thuban 3.65 PVP Pole Star over time. 19 [WPB 42]
Epsilon Eridani 3.74 Single star, exoplanet and asteroid belt supposed. 14 [WPB 43]
Beta Pictoris 3.86 Single star, exoplanet found. 14 [WPB 44]
61 Cygni 5.2 Binary star system, first star (system) where parallax was measured by Bessel. 36 [T 13]
[WPB 45]
55 Cancri 5.95 Binary star system, 5 exoplanets found. 14 [WPB 46]
Barnard's Star 9.51 Wandering star, highest proper motion. Preface [WPB 47]
Canopus -0.74 2nd-brightest star in the night sky. [WPB 48]
Arcturus -0.05 4th-brightest star in the night sky. [WPB 49]
Capella 0.03-0.16 6th-brightest star in the night sky, double binary star system. [WPB 50]
Rigel 0.05-0.18 7th-brightest star in the night sky, brightest of Orion, 3 to 5 star system. [WPB 51]
Procyon 0.34 8th-brightest star in the night sky, binary system. [WPB 52]
Betelgeuse 0.0-1.3 9th-brightest star in the night sky, 2nd-brightest of Orion. [WPB 53]
Achernar 0.40-0.46 10th-brightest star in the night sky, binary system. [WPB 54]
Beta Centauri 0.61 11th-brightest star in the night sky. Triple star system. [WPB 55]
Altair 0.76 12th-brightest star in the night sky, breaking up? [WPB 56]
Alpha Crucis 0.76 13th-brightest star in the night sky. Multiple star system. [WPB 57]
Aldebaran 0.75-0.95 14th-brightest star in the night sky. Likely hosting exoplanets. [WPB 58]
Antares 0.6-1.6 15th-brightest star in the night sky. Likely largest known star. [WPB 59]
Spica 0.97-1.04 16th-brightest star in the night sky, binary system. [WPB 60]
Pollux 1.14 17th-brightest star in the night sky. Has the closest exoplanet to Earth. [WPB 61]
Mimosa 1.23-1.31 20th-brightest star in the night sky, binary system. [WPB 62]
Bellatrix 1.59-1.64 25th-brightest star in the night sky. Right shoulder of Orion (seen from Northern hemisphere, the left shoulder is Betelgeuse). [WPB 63]
Pleiades 1.6 Seven stars appearing close together. [WPB 64]
Gamma Crucis 1.64 Single star. [WPB 65]
Alnilam 1.69 Central star of Orion's Belt. Single star. [WPB 66]
Alnitak 1.77 Left star of Orion's Belt (seen from Northern hemisphere). Triple star system. [WPB 67]
Alioth 1.77 31st-brightest star in the night sky. Leftmost and brightest star of the Big Dipper. [WPB 68]
Dubhe 1.79 2nd-brightest star of the Big Dipper. Has a companion. [WPB 69]
Alkaid 1.86 3rd-brightest star of the Big Dipper. Single star. [WPB 70]
Castor 1.93 Triple star system. [WPB 71]
Mizar 2.04 4th-brightest star of the Big Dipper. Visual double star, part of quadruple system with Alcor. [WPB 72]
Saiph 2.09 Left foot of Orion (seen from Northern hemisphere, the right foot is Rigel). [WPB 73]
Algol 2.12-3.39 Triple star system. [WPB 74]
Mintaka 2.23 Right star of Orion's Belt (seen from Northern hemisphere). Multiple star system. [WPB 75]
Merak 2.37 5th-brightest star of the Big Dipper. Single star. [WPB 76]
Phecda 2.43 6th-brightest star of the Big Dipper. Astrometric binary. [WPB 77]
Alderamin 2.51 Pole Star over time. [WPB 78]
Megrez 3.31 7th-brightest (dimmest) star of the Big Dipper. Two companions. [WPB 79]
Large Magellanic Cloud 0.9 The 3rd-closest galaxy to the Milky Way in the constellations of Dorado and Mensa. [WPB 80]
Andromeda Galaxy 3.44 The nearest major galaxy to the Milky Way in the constellation of Andromeda. [WPB 81]

List of researchers

Geocentrists in green, heliocentrists in yellow and geo-heliocentrists in orange

Researchers (not) referred to in the TYCHOS book
Name Centuries Description Chapters Notes
Simon Shack 21st Author of TYCHOS. [T 28]
Tycho Brahe 16/17th Danish astronomer responsible for the development of the Tychonian model, upon which the TYCHOS is based. Preface, 1, 2, 3, 5, 6, 18, 26, 31, 33, 34, 35, 36 [WPR 1]
Hipparchus -2nd Greek astronomer, geographer, and mathematician, is considered the founder of trigonometry but is most famous for his incidental discovery of precession of the equinoxes. 30, 32, 36 [WPR 2]
Sosigenes of Alexandria -1st Greek astronomer from Ptolemaic Egypt who, according to Roman historian Pliny the Elder, was consulted by Julius Caesar for the design of the Julian calendar. 32 [WPR 3]
Ptolemy 2nd Greco-Roman mathematician, astronomer, geographer and astrologer responsible for the development of the geocentric model. 6, 18, 27, 30, 36 [WPR 4]
Aztec astronomy 15th- Archaeoastronomy of the Aztec, central Mexico. Preface, 27, 32 [T 18]
[WPR 5]
Maya astronomy 15th- Archaeoastronomy of the Maya, Yucatán, Mexico and Guatemala. Preface, 6, 32, 33 [T 17]
[WPR 6]
Nilakantha Somayaji 15/16th Indian mathematician and astronomer of the Kerala school of astronomy and mathematics. One of his most influential works was the comprehensive astronomical treatise Tantrasamgraha completed in 1501. Preface, 2 [T 29]
[WPR 7]
Longomontanus 16/17th Danish astronomer who really developed Tycho's geoheliocentric model empirically and publicly to common acceptance in the 17th century in his 1622 astronomical tables. He published the voluminous Astronomia Danica (1622), regarded as the testament of Tycho Brahe. Preface, 5, 12 [WPR 8]
Nicolaus Copernicus 16th Polish/Prussian mathematician and astronomer who formulated a model of the universe that placed the Sun rather than the Earth at the center of the universe. The publication of Copernicus' model in his book De revolutionibus orbium coelestium in 1543 was a major event in the history of science, triggering the Copernican Revolution. Preface, 5, 6, 18, 35, 36, Epilogue [WPR 9]
Galileo Galilei 16/17th Italian polymath, central figure in the transition from natural philosophy to modern science and transformation of the scientific Renaissance into a scientific revolution. Galileo's championing of heliocentrism and Copernicanism was controversial during his lifetime, when most subscribed to either geocentrism or the Tychonic system. Preface, 12 [WPR 10]
Johannes Kepler 17th German mathematician, astronomer, and astrologer, best known for his laws of planetary motion, based on his works Astronomia nova, Harmonices Mundi, and Epitome of Copernican Astronomy, provided one of the foundations for Isaac Newton's theory of universal gravitation. Preface, 5, 6, 11, 20, 26, Epilogue [WPR 11]
Giovanni Cassini 17th Italian mathematician, astronomer and engineer. Discoverer of 4 moons of Saturn. 36 [WPR 12]
Giovanni Riccioli 17th Italian astronomer and Catholic priest in the Jesuit order. He is known, for his experiments with pendulums and with falling bodies, for his discussion of 126 arguments concerning the motion of the Earth, for describing the first binary star system and for introducing the current scheme of lunar nomenclature. 1 [WPR 13]
Cristoph Scheiner 17th German Jesuit priest, physicist and astronomer. 12 [WPR 14]
Isaac Newton 17/18th English mathematician, astronomer, theologian, author and physicist, widely recognised as one of the most influential scientists of all time, and a key figure in the scientific revolution. His book Philosophiæ Naturalis Principia Mathematica (1687), laid the foundations of classical mechanics. Preface, 4, 10, 28, Epilogue [WPR 15]
Ole Roemer 17th/18th Danish astronomer who in 1676 made the first quantitative measurements of the speed of light, persuaded the king to introduce the Gregorian calendar in Denmark-Norway — something Tycho Brahe had argued for in vain a hundred years earlier. 26 [WPR 16]
James Bradley 18th English astronomer and priest. Best known for two fundamental discoveries in astronomy, the aberration of light (1725–1728), and the nutation of the Earth's axis (1728–1748). Preface, 26, 34, Epilogue [T 9]
[WPR 17]
Pathani Samanta 19th Indian astronomer and scholar who measured the distance from earth with a bamboo pipe and many other traditional instruments that he built. His observations, research and calculations were compiled into a book Siddhanta Darpana. Preface, 2, 6 [WPR 18]
Friedrich Bessel 19th German astronomer, mathematician, physicist and geodesist. He was the first astronomer who determined reliable values for the distance from the sun to another star by the method of parallax. 36 [WPR 19]
Simon Newcomb 19th Canadian–American astronomer, applied mathematician and autodidactic polymath, made important contributions to timekeeping. 30, 36 [WPR 20]
Rudolf Steiner 19/20th Austrian philosopher, social reformer, architect and esotericist, founded an esoteric spiritual movement, anthroposophy, with roots in German idealist philosophy and theosophy; other influences include Goethean science and Rosicrucianism. Preface [WPR 21]
Albert Einstein 20th German-born theoretical physicist who developed the theory of relativity, awarded Nobel Prize for Physics in 1921. Preface, 3, 4, 6, 10, Epilogue [WPR 22]
John Knight Fotheringham 20th British historian who was an expert on ancient astronomy and chronology. He established the chronology of the Babylonian dynasties. 30 [WPR 23]
Robert Russell Newton 20th American physicist, astronomer, and historian of science, known for his work on change of the rotation rate of the Earth, and historical observations of eclipses. 30 [WPR 24]
Vittorio Goretti 20th Italian amateur astronomer and a discoverer of minor planets, discovered 32 main-belt asteroids. 36 [WPR 25]
Theodor Landscheidt 20th German author, astrologer and amateur climatologist. 13 [WPR 26]
Karl-Heinz Homann 20th/21st German electronic technician. 33 [T 30]
Howard Margolis 20th/21st American social scientist. His study of social theory focused on the underpinnings of individual choice and judgment that shape aggregate social outcomes. 1 [T 31]
[WPR 27]
James Schombert 20th/21st American astrophysicist (1984, Yale), Fields of research: Galaxy Surveys, Evolution and Properties of Galaxies. 1 [T 32]
Walter Cruttenden 20th/21st American amateur theoretical archaeo-astronomer and author of the binary theory of precession. 1, 18, 24, 30, 33 [T 33]
Anthony Ayiomamitis 21st Greek astrophotographer. 26 [7]
Christopher Graney 21st American professor of physics and astronomy. Preface, 5 [8]
Aristotle -4th Greek philosopher and scientist, considered the "Father of Western Philosophy". [WPR 28]
Theophrastus -3rd Greek biologist and physicist, student of Aristotle. Published Heaven. [WPR 29]
Eratosthenes -3rd Greek mathematician, geographer, astronomer, invented the discipline of geography, best known for being the first person to calculate the circumference of the Earth and also the first to calculate the tilt of the Earth's axis. He may have accurately calculated the distance from the Earth to the Sun and invented the leap day, created the first map of the world, incorporating parallels and meridians. He also calculated the Sun's diameter at about 27 times that of the Earth, in reality it is approximately 109 times. [WPR 30]
Macrobius 4th/5th Roman writer who presented a discourse upon the nature of the cosmos, transmitting much classical philosophy to the later Middle Ages. In astronomy, this work is noted for giving the diameter of the Sun as twice the diameter of the Earth. [WPR 31]
Martianus Capella 5th Latin prose writer of Late Antiquity, one of the earliest developers of the system of the seven liberal arts that structured early medieval education. His single encyclopedic work was De nuptiis Philologiae et Mercurii. [WPR 32]
Aryabhata 5th/6th Indian mathematician and astronomer. He ascribed the apparent motions of the heavens to the Earth's rotation. He may have believed that the planet's orbits as elliptical rather than circular. Aryabhata correctly insisted that the Earth rotates about its axis daily, and that the apparent movement of the stars is a relative motion caused by the rotation of the Earth, contrary to the then-prevailing view, that the sky rotated. He described a geocentric model of the solar system, in which the Sun and Moon are each carried by epicycles. They in turn revolve around the Earth. In this model, the motions of the planets are each governed by two epicycles, smaller and larger. The order of the planets in terms of distance from Earth is taken as: the Moon, Mercury, Venus, the Sun, Mars, Jupiter, Saturn, and the asterisms. [WPR 33]
Azophi 10th Persian astronomer who identified the Large Magellanic Cloud and made the earliest recorded observation of the Andromeda Galaxy, the first galaxies other than the Milky Way to be observed from Earth. He observed that the ecliptic plane is inclined with respect to the celestial equator and more accurately calculated the length of the tropical year. He observed and described the stars, their positions, their magnitudes and their colour. For each constellation, he provided two drawings, one from the outside of a celestial globe, and the other from the inside (as seen from the Earth). [WPR 34]
Alhazen 10th/11th Arab mathematician, astronomer, and physicist, honored as Ptolemaeus secundus, kept a geocentric universe and assumed that celestial motions are uniformly circular, which required the inclusion of epicycles to explain observed motion, published in The Model of the Motions of Each of the Seven Planets (~1038). [WPR 35]
Avicenna 11th Persian polymath who is regarded as one of the most significant physicians, astronomers, thinkers and writers of the Islamic Golden Age. He claimed to have observed Venus as a spot on the Sun, there was a transit on May 24, 1032, to help establish that Venus was, at least sometimes, below the Sun in Ptolemaic cosmology, i.e. the sphere of Venus comes before the sphere of the Sun when moving out from the Earth in the prevailing geocentric model. He considered the motion of the solar apogee, which Ptolemy had taken to be fixed. [WPR 36]
Avempace 11th Arab Andalusian polymath, astronomer, physicist and philosopher. He published a theory in which the motion of the stars and planets is uniform and circular, and in agreement with observation. [WPR 37]
Averroes 12th Andalusian Moorish polymath, philosopher, mathematician and astronomer. Popularized the work of Aristotle. [WPR 38]
Al 13th Persian polymath, astronomer, mathematician and physicist. Followed up on Ptolemy and in The Limit of Accomplishment concerning Knowledge of the Heavens discussed the possibility of heliocentrism. [WPR 39]
Ulugh Beg 15th Persian astronomer and mathematician, built an enormous observatory, similar to Tycho Brahe's later Uraniborg. Using it, he compiled the 1437 Zij-i-Sultani of 994 stars, considered the greatest star catalogue between those of Ptolemy and Brahe. He determined the length of the sidereal year as 365.2570370...d = 365d 6h 10m 8s (an error of +58 seconds) and a more precise value of tropical year as 365d 5h 49m 15s, which has an error of +25 seconds, making it more accurate than Copernicus's estimate. He determined the Earth's axial tilt as 23;30,17 degrees (23.5047 degrees). [WPR 40]
Muisca astronomy 15th- Archaeoastronomy of the Muisca, Altiplano Cundiboyacense, Colombia. [WPR 41]
Valentin Naboth 16th German mathematician, astronomer and astrologer, author of a general textbook on astrology Enarratio elementorum astrologiae. Renowned for calculating the mean annual motion of the Sun, his writings are chiefly devoted to commenting upon Ptolemy and the Arabian astrologers. [WPR 42]
Thomas Digges 16th English mathematician and astronomer, translated Copernicus' work in English. He attempted to determine the parallax of the 1572 supernova observed by Tycho Brahe, and concluded it had to be beyond the orbit of the Moon. This contradicted the accepted view of the universe, according to which no change could take place among the fixed stars. [WPR 43]
Simon Marius 16th/17th German astronomer, who in 1614 published his work Mundus Iovialis describing the planet Jupiter and its moons. He discovered the planet's four major moons some days before Galileo Galilei. Marius concluded that the geocentric Tychonic system, in which the planets circle the Sun while the Sun circles the Earth, must be the correct world system, or model of the universe. [WPR 44]
Christiaan Huygens 17th Dutch physicist, mathematician, astronomer and inventor, who is widely regarded as one of the greatest scientists of all time and a major figure in the scientific revolution. Inventor of the telescope and discoverer of Titan, largest moon of Saturn, published in Systema saturnium in 1659. [WPR 45]
Charles Messier 18th French astronomer most notable for publishing an astronomical catalogue consisting of nebulae and star clusters that came to be known as the 110 "Messier objects". [WPR 46]
William Herschel 18th/19th German-English astronomer who improved determination of the rotation period of Mars, the discovery that the Martian polar caps vary seasonally, the discovery of the moons of Uranus Titania and Oberon and Enceladus and Mimas of Saturn. In addition, Herschel discovered infrared radiation. [WPR 47]
John Herschel 19th English polymath, mathematician, astronomer, chemist, inventor, and experimental photographer. He originated the use of the Julian day system in astronomy and named seven moons of Saturn and four moons of Uranus. Involved in the Beavers on the Moon astronomy hoax. [WPR 48]
James South 19th British astronomer who together with John Herschel produced a catalogue of 380 double stars in 1824, reobserving many of the double stars that had been discovered by William Herschel. He observed another 458 double stars over the following year. [WPR 49]
Friedrich von Struve 19th German-Russian astronomer and geodesist, discovered a very large number of double stars and in 1827 published his double star catalogue Catalogus novus stellarum duplicium. He was also the first to measure the parallax of Vega. [WPR 50]
Angelo Secchi 19th Italian Jesuit astronomer, one of the first scientists to state authoritatively that the Sun is a star, revised Friedrich Georg Wilhelm von Struve's catalog of double stars, compiling data for over 10,000 binaries, discovered three comets, and drew some of the first color illustrations of Mars, the first to describe "channels" (canali) on the surface. He observed and made drawings of solar eruptions and sunspots, and compiled records of sunspot activity, proved that the solar corona and coronal prominences observed during a solar eclipse were part of the Sun, and not artifacts of the eclipse and discovered solar spicules. [WPR 51]

See also





Celestial bodies


Other links

External links