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Astronomical unit

Index Astronomical unit

The astronomical unit (symbol: au, or AU) is a unit of length defined to be exactly equal to. [1]

Table of Contents

  1. 155 relations: Aberration (astronomy), Agreement (linguistics), Al-Battani, Al-Biruni, Al-Farghani, Albert A. Michelson, Albert Einstein, American Astronomical Society, Angular frequency, Apollo program, Apsis, Archimedes, Aristarchus of Samos, Arithmetic underflow, Arthur Robert Hinks, Astronomical constant, Astronomical system of units, Astronomy, Astronomy & Astrophysics, Barycentric Dynamical Time, Cayenne, Celestial mechanics, Celestial Mechanics and Dynamical Astronomy, Christiaan Huygens, Cleomedes, Cosmic distance ladder, Earth, Earth radius, Earth's orbit, Edmond Halley, Edwin Gifford, Ellipse, Elliptic orbit, Ephemeris, Eratosthenes, Eris (dwarf planet), Eusebius, Floating-point arithmetic, Frame of reference, French Guiana, Galactic Center, Gaussian gravitational constant, General Conference on Weights and Measures, General relativity, Gerald J. Toomer, Giovanni Domenico Cassini, Godfried Wendelen, Gravitational constant, Harold Spencer Jones, Hipparchus, ... Expand index (105 more) »

  2. Units of measurement in astronomy

Aberration (astronomy)

In astronomy, aberration (also referred to as astronomical aberration, stellar aberration, or velocity aberration) is a phenomenon where celestial objects exhibit an apparent motion about their true positions based on the velocity of the observer: It causes objects to appear to be displaced towards the observer's direction of motion.

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Agreement (linguistics)

In linguistics, agreement or concord (abbreviated) occurs when a word changes form depending on the other words to which it relates.

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Al-Battani

Abū ʿAbd Allāh Muḥammad ibn Jābir ibn Sinān al-Raqqī al-Ḥarrānī aṣ-Ṣābiʾ al-Battānī (محمد بن جابر بن سنان البتاني), usually called al-Battānī, a name that was in the past Latinized as Albategnius, (before 858929) was an astronomer, astrologer and mathematician, who lived and worked for most of his life at Raqqa, now in Syria.

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Al-Biruni

Abu Rayhan Muhammad ibn Ahmad al-Biruni (ابوریحان بیرونی; أبو الريحان البيروني; 973after 1050), known as al-Biruni, was a Khwarazmian Iranian scholar and polymath during the Islamic Golden Age.

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Al-Farghani

Abū al-ʿAbbās Aḥmad ibn Muḥammad ibn Kathīr al-Farghānī (أبو العبّاس أحمد بن محمد بن كثير الفرغاني) also known as Alfraganus in the West (870), was an astronomer in the Abbasid court in Baghdad, and one of the most famous astronomers in the 9th century.

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Albert A. Michelson

Albert Abraham Michelson FFRS FRSE (surname pronunciation anglicized as "Michael-son", December 19, 1852 – May 9, 1931) was a Prussian-born American physicist of Jewish descent, known for his work on measuring the speed of light and especially for the Michelson–Morley experiment.

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Albert Einstein

Albert Einstein (14 March 1879 – 18 April 1955) was a German-born theoretical physicist who is widely held as one of the most influential scientists. Best known for developing the theory of relativity, Einstein also made important contributions to quantum mechanics. His mass–energy equivalence formula, which arises from relativity theory, has been called "the world's most famous equation".

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American Astronomical Society

The American Astronomical Society (AAS, sometimes spoken as "double-A-S") is an American society of professional astronomers and other interested individuals, headquartered in Washington, DC.

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Angular frequency

In physics, angular frequency (symbol ω), also called angular speed and angular rate, is a scalar measure of the angle rate (the angle per unit time) or the temporal rate of change of the phase argument of a sinusoidal waveform or sine function (for example, in oscillations and waves).

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Apollo program

The Apollo program, also known as Project Apollo, was the United States human spaceflight program carried out by the National Aeronautics and Space Administration (NASA), which succeeded in preparing and landing the first men on the Moon from 1968 to 1972.

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Apsis

An apsis is the farthest or nearest point in the orbit of a planetary body about its primary body.

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Archimedes

Archimedes of Syracuse was an Ancient Greek mathematician, physicist, engineer, astronomer, and inventor from the ancient city of Syracuse in Sicily.

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Aristarchus of Samos

Aristarchus of Samos (Ἀρίσταρχος ὁ Σάμιος, Aristarkhos ho Samios) was an ancient Greek astronomer and mathematician who presented the first known heliocentric model that placed the Sun at the center of the universe, with the Earth revolving around the Sun once a year and rotating about its axis once a day.

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Arithmetic underflow

The term arithmetic underflow (also floating point underflow, or just underflow) is a condition in a computer program where the result of a calculation is a number of more precise absolute value than the computer can actually represent in memory on its central processing unit (CPU).

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Arthur Robert Hinks

Arthur Robert Hinks, CBE, FRS (26 May 1873 – 14 April 1945) was a British astronomer and geographer.

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Astronomical constant

An astronomical constant is any of several physical constants used in astronomy. Astronomical unit and astronomical constant are units of measurement in astronomy.

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Astronomical system of units

The astronomical system of units, formerly called the IAU (1976) System of Astronomical Constants, is a system of measurement developed for use in astronomy. Astronomical unit and astronomical system of units are units of measurement in astronomy.

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Astronomy

Astronomy is a natural science that studies celestial objects and the phenomena that occur in the cosmos.

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Astronomy & Astrophysics

Astronomy & Astrophysics (A&A) is a monthly peer-reviewed scientific journal covering theoretical, observational, and instrumental astronomy and astrophysics.

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Barycentric Dynamical Time

Barycentric Dynamical Time (TDB, from the French Temps Dynamique Barycentrique) is a relativistic coordinate time scale, intended for astronomical use as a time standard to take account of time dilation when calculating orbits and astronomical ephemerides of planets, asteroids, comets and interplanetary spacecraft in the Solar System.

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Cayenne

Cayenne (Kayenn) is the prefecture of French Guiana, an overseas region and department of France located in South America.

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Celestial mechanics

Celestial mechanics is the branch of astronomy that deals with the motions of objects in outer space.

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Celestial Mechanics and Dynamical Astronomy

Celestial Mechanics and Dynamical Astronomy is a scientific journal covering the fields of astronomy and astrophysics.

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Christiaan Huygens

Christiaan Huygens, Lord of Zeelhem, (also spelled Huyghens; Hugenius; 14 April 1629 – 8 July 1695) was a Dutch mathematician, physicist, engineer, astronomer, and inventor who is regarded as a key figure in the Scientific Revolution.

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Cleomedes

Cleomedes (Κλεομήδης) was a Greek astronomer who is known chiefly for his book On the Circular Motions of the Celestial Bodies (Κυκλικὴ θεωρία μετεώρων), also known as The Heavens (Caelestia).

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Cosmic distance ladder

The cosmic distance ladder (also known as the extragalactic distance scale) is the succession of methods by which astronomers determine the distances to celestial objects.

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Earth

Earth is the third planet from the Sun and the only astronomical object known to harbor life.

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Earth radius

Earth radius (denoted as R🜨 or RE) is the distance from the center of Earth to a point on or near its surface.

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Earth's orbit

Earth orbits the Sun at an average distance of 149.60 million km (8.317 light minutes, 92.96 million mi) in a counterclockwise direction as viewed from above the Northern Hemisphere.

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Edmond Halley

Edmond (or Edmund) Halley (–) was an English astronomer, mathematician and physicist.

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Edwin Gifford

Edwin Hamilton Gifford, DD (18 December 1820 – 4 May 1905) was an eminent Anglican priest, schoolmaster, and author of the second half of the 19th century.

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Ellipse

In mathematics, an ellipse is a plane curve surrounding two focal points, such that for all points on the curve, the sum of the two distances to the focal points is a constant.

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Elliptic orbit

In astrodynamics or celestial mechanics, an elliptic orbit or elliptical orbit is a Kepler orbit with an eccentricity of less than 1; this includes the special case of a circular orbit, with eccentricity equal to 0.

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Ephemeris

In astronomy and celestial navigation, an ephemeris (pl. ephemerides) is a book with tables that gives the trajectory of naturally occurring astronomical objects as well as artificial satellites in the sky, i.e., the position (and possibly velocity) over time.

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Eratosthenes

Eratosthenes of Cyrene (Ἐρατοσθένης; –) was a Greek polymath: a mathematician, geographer, poet, astronomer, and music theorist.

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Eris (dwarf planet)

Eris (minor-planet designation: 136199 Eris) is the most massive and second-largest known dwarf planet in the Solar System.

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Eusebius

Eusebius of Caesarea (Εὐσέβιος τῆς Καισαρείας; 260/265 – 30 May 339), also known as Eusebius Pamphilus (from the Εὐσέβιος τοῦ Παμφίλου), was a Greek Syro-Palestinian historian of Christianity, exegete, and Christian polemicist.

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Floating-point arithmetic

In computing, floating-point arithmetic (FP) is arithmetic that represents subsets of real numbers using an integer with a fixed precision, called the significand, scaled by an integer exponent of a fixed base.

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Frame of reference

In physics and astronomy, a frame of reference (or reference frame) is an abstract coordinate system whose origin, orientation, and scale are specified by a set of reference points―geometric points whose position is identified both mathematically (with numerical coordinate values) and physically (signaled by conventional markers).

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French Guiana

French Guiana (or; Guyane,; Lagwiyann or Gwiyann) is an overseas department and region of France located on the northern coast of South America in the Guianas and the West Indies.

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Galactic Center

The Galactic Center is the barycenter of the Milky Way and a corresponding point on the rotational axis of the galaxy.

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Gaussian gravitational constant

The Gaussian gravitational constant (symbol) is a parameter used in the orbital mechanics of the Solar System.

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General Conference on Weights and Measures

The General Conference on Weights and Measures (abbreviated CGPM from the Conférence générale des poids et mesures) is the supreme authority of the International Bureau of Weights and Measures (BIPM), the intergovernmental organization established in 1875 under the terms of the Metre Convention through which member states act together on matters related to measurement science and measurement standards.

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General relativity

General relativity, also known as the general theory of relativity and Einstein's theory of gravity, is the geometric theory of gravitation published by Albert Einstein in 1915 and is the current description of gravitation in modern physics.

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Gerald J. Toomer

Gerald James Toomer (born 23 November 1934) is a historian of astronomy and mathematics who has written numerous books and papers on ancient Greek and medieval Islamic astronomy.

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Giovanni Domenico Cassini

Giovanni Domenico Cassini, also known as Jean-Dominique Cassini (8 June 1625 – 14 September 1712) was an Italian (naturalised French) mathematician, astronomer and engineer.

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Godfried Wendelen

Godfried Wendelen or Govaert Wendelen, Latinized Godefridus Wendelinus, or sometimes Vendelinus and in French-language sources referred to as Godefroy Wendelin (6 June 1580 – 24 October 1667) was an astronomer and Catholic priest sometimes referred to as the Ptolemy of his time.

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Gravitational constant

The gravitational constant is an empirical physical constant involved in the calculation of gravitational effects in Sir Isaac Newton's law of universal gravitation and in Albert Einstein's theory of general relativity.

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Harold Spencer Jones

Sir Harold Spencer Jones KBE FRS FRSE PRAS (29 March 1890 – 3 November 1960) was an English astronomer.

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Hipparchus

Hipparchus (Ἵππαρχος, Hipparkhos; BC) was a Greek astronomer, geographer, and mathematician.

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IAU (1976) System of Astronomical Constants

The International Astronomical Union at its XVIth General Assembly in Grenoble in 1976, accepted (Resolution No. 1) a whole new consistent set of astronomical constantsIAU(1976) ibidem: Commission 4 (Ephemerides) recommendations 1,2,3,5,6: pp.52..67 recommended for reduction of astronomical observations, and for computation of ephemerides.

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Imperial units

The imperial system of units, imperial system or imperial units (also known as British Imperial or Exchequer Standards of 1826) is the system of units first defined in the British Weights and Measures Act 1824 and continued to be developed through a series of Weights and Measures Acts and amendments.

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Inflection

In linguistic morphology, inflection (less commonly, inflexion) is a process of word formation in which a word is modified to express different grammatical categories such as tense, case, voice, aspect, person, number, gender, mood, animacy, and definiteness.

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Integer overflow

In computer programming, an integer overflow occurs when an arithmetic operation on integers attempts to create a numeric value that is outside of the range that can be represented with a given number of digits – either higher than the maximum or lower than the minimum representable value.

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International Astronomical Union

The International Astronomical Union (IAU; Union astronomique internationale, UAI) is an international non-governmental organization (INGO) with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach, education, and development through global cooperation.

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International Bureau of Weights and Measures

The International Bureau of Weights and Measures (Bureau international des poids et mesures, BIPM) is an intergovernmental organisation, through which its 59 member-states act on measurement standards in areas including chemistry, ionising radiation, physical metrology, as well as the International System of Units (SI) and Coordinated Universal Time (UTC).

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International Earth Rotation and Reference Systems Service

The International Earth Rotation and Reference Systems Service (IERS), formerly the International Earth Rotation Service, is the body responsible for maintaining global time and reference frame standards, notably through its Earth Orientation Parameter (EOP) and International Celestial Reference System (ICRS) groups.

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International Organization for Standardization

The International Organization for Standardization (ISO) is an independent, non-governmental, international standard development organization composed of representatives from the national standards organizations of member countries.

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International System of Units

The International System of Units, internationally known by the abbreviation SI (from French Système international d'unités), is the modern form of the metric system and the world's most widely used system of measurement.

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ISO/IEC 80000

ISO 80000 or IEC 80000, Quantities and units, is an international standard describing the International System of Quantities (ISQ).

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James Gregory (mathematician)

James Gregory (November 1638 – October 1675) was a Scottish mathematician and astronomer.

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Jérôme Lalande

Joseph Jérôme Lefrançois de Lalande (11 July 1732 – 4April 1807) was a French astronomer, freemason and writer.

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Jean Picard

Jean Picard (21 July 1620 – 12 July 1682) was a French astronomer and priest born in La Flèche, where he studied at the Jesuit Collège Royal Henry-Le-Grand.

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Jean Richer

Jean Richer (1630–1696) was a French astronomer and assistant (élève astronome) at the French Academy of Sciences, under the direction of Giovanni Domenico Cassini.

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Jeremiah Horrocks

Jeremiah Horrocks (16183 January 1641), sometimes given as Jeremiah Horrox (the Latinised version that he used on the Emmanuel College register and in his Latin manuscripts), – See footnote 1 was an English astronomer.

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Jet Propulsion Laboratory

Jet Propulsion Laboratory (JPL) is a Federally Funded Research and Development Center (FFRDC) in La Cañada Flintridge, California, Crescenta Valley, United States.

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Johannes Kepler

Johannes Kepler (27 December 1571 – 15 November 1630) was a German astronomer, mathematician, astrologer, natural philosopher and writer on music.

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John Flamsteed

John Flamsteed (19 August 1646 – 31 December 1719) was an English astronomer and the first Astronomer Royal.

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Julian year (astronomy)

In astronomy, a Julian year (symbol: a or aj) is a unit of measurement of time defined as exactly 365.25 days of SI seconds each.

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Jupiter

Jupiter is the fifth planet from the Sun and the largest in the Solar System.

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Karl Rudolph Powalky

Karl Rudolph Powalky (19 June 1817 – 11 July 1881) was a German astronomer known for his computational work on estimating cometary paths and minor planets and for his estimation of the solar parallax at.

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Kepler's laws of planetary motion

In astronomy, Kepler's laws of planetary motion, published by Johannes Kepler between 1609 and 1619, describe the orbits of planets around the Sun.

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Kuiper belt

The Kuiper belt is a circumstellar disc in the outer Solar System, extending from the orbit of Neptune at 30 astronomical units (AU) to approximately 50 AU from the Sun.

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Length

Length is a measure of distance.

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Li (unit)

Li (lǐ, or 市里, shìlǐ), also known as the Chinese mile, is a traditional Chinese unit of distance. Astronomical unit and Li (unit) are units of length.

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Light-second

The light-second is a unit of length useful in astronomy, telecommunications and relativistic physics. Astronomical unit and light-second are units of length and units of measurement in astronomy.

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Light-year

A light-year, alternatively spelled light year (ly or lyr), is a unit of length used to express astronomical distances and is equal to exactly 9,460,730,472,580.8 km (Scientific notation: 9.4607304725808 × 1012 km), which is approximately 5.88 trillion mi. Astronomical unit and light-year are units of length and units of measurement in astronomy.

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Line segment

In geometry, a line segment is a part of a straight line that is bounded by two distinct end points, and contains every point on the line that is between its endpoints.

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Lunar distance

The instantaneous Earth–Moon distance, or distance to the Moon, is the distance from the center of Earth to the center of the Moon. Astronomical unit and Lunar distance are units of length and units of measurement in astronomy.

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Lunar phase

A lunar phase or Moon phase is the apparent shape of the Moon's directly sunlit portion as viewed from the Earth (because the Moon is tidally locked with the Earth, the same hemisphere is always facing the Earth).

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Mars

Mars is the fourth planet from the Sun.

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Mercury (planet)

Mercury is the first planet from the Sun and the smallest in the Solar System.

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Metre

The metre (or meter in US spelling; symbol: m) is the base unit of length in the International System of Units (SI). Astronomical unit and metre are units of length.

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Metric system

The metric system is a decimal-based system of measurement.

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Milky Way

The Milky Way is the galaxy that includes the Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye.

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Minute and second of arc

A minute of arc, arcminute (arcmin), arc minute, or minute arc, denoted by the symbol, is a unit of angular measurement equal to of one degree.

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Monthly Notices of the Royal Astronomical Society

Monthly Notices of the Royal Astronomical Society (MNRAS) is a peer-reviewed scientific journal in astronomy, astrophysics and related fields.

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Myriad

Myriad (from Ancient Greek label) is technically the number 10,000 (ten thousand); in that sense, the term is used in English almost exclusively for literal translations from Greek, Latin or Sinospheric languages (Chinese, Japanese, Korean, and Vietnamese), or when talking about ancient Greek numerals.

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NASA

The National Aeronautics and Space Administration (NASA) is an independent agency of the U.S. federal government responsible for the civil space program, aeronautics research, and space research.

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Nature Physics

Nature Physics is a monthly peer-reviewed scientific journal published by Nature Portfolio.

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Near-Earth object

A near-Earth object (NEO) is any small Solar System body orbiting the Sun whose closest approach to the Sun (perihelion) is less than 1.3 times the Earth–Sun distance (astronomical unit, AU).

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Neptune

Neptune is the eighth and farthest known planet from the Sun.

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New Scientist

New Scientist is a popular science magazine covering all aspects of science and technology.

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Nicolaus Copernicus

Nicolaus Copernicus (19 February 1473 – 24 May 1543) was a Renaissance polymath, active as a mathematician, astronomer, and Catholic canon, who formulated a model of the universe that placed the Sun rather than Earth at its center.

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Noel Swerdlow

Noel Mark Swerdlow (9 September 1941 – 24 July 2021) was a professor emeritus of history, astronomy and astrophysics at the University of Chicago.

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Non-SI units mentioned in the SI

While the International System of Units (SI) is used throughout the world in all fields, many non-SI units continue to be used in the scientific, technical, and commercial literature.

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Numerical model of the Solar System

A numerical model of the Solar System is a set of mathematical equations, which, when solved, give the approximate positions of the planets as a function of time.

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Ole Rømer

Ole Christensen Rømer (25 September 1644 – 19 September 1710) was a Danish astronomer who, in 1676, first demonstrated that light travels at a finite speed.

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On the Sizes and Distances (Aristarchus)

On the Sizes and Distances (of the Sun and Moon) (Περὶ μεγεθῶν καὶ ἀποστημάτων|) is widely accepted as the only extant work written by Aristarchus of Samos, an ancient Greek astronomer who lived circa 310–230 BCE.

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Oort cloud

The Oort cloud, sometimes called the Öpik–Oort cloud, is theorized to be a vast cloud of icy planetesimals surrounding the Sun at distances ranging from 2,000 to 200,000 AU (0.03 to 3.2 light-years).

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Orders of magnitude (length)

The following are examples of orders of magnitude for different lengths.

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Pappus of Alexandria

Pappus of Alexandria (Πάππος ὁ Ἀλεξανδρεύς; AD) was a Greek mathematician of late antiquity known for his Synagoge (Συναγωγή) or Collection, and for Pappus's hexagon theorem in projective geometry.

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Parallax

Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight and is measured by the angle or half-angle of inclination between those two lines.

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Parallax in astronomy

The most important fundamental distance measurements in astronomy come from trigonometric parallax, as applied in the stellar parallax method.

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Paris

Paris is the capital and largest city of France.

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Parsec

The parsec (symbol: pc) is a unit of length used to measure the large distances to astronomical objects outside the Solar System, approximately equal to or (AU), i.e.. Astronomical unit and parsec are units of length and units of measurement in astronomy.

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Parts-per notation

In science and engineering, the parts-per notation is a set of pseudo-units to describe small values of miscellaneous dimensionless quantities, e.g. mole fraction or mass fraction.

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Photon

A photon is an elementary particle that is a quantum of the electromagnetic field, including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force.

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Posidonius

Posidonius (Ποσειδώνιος, "of Poseidon") "of Apameia" (ὁ Ἀπαμεύς) or "of Rhodes" (ὁ Ῥόδιος), was a Greek politician, astronomer, astrologer, geographer, historian, mathematician, and teacher native to Apamea, Syria.

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Praeparatio evangelica

Preparation for the Gospel (Εὐαγγελικὴ προπαρασκευή, Euangelikē proparaskeuē), commonly known by its Latin title Praeparatio evangelica, is a work of Christian apologetics written by Eusebius in the early part of the fourth century AD.

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Proper length

Proper length or rest length is the length of an object in the object's rest frame.

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Proxima Centauri

Proxima Centauri is a small, low-mass star located away from the Sun in the southern constellation of Centaurus.

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Ptolemy

Claudius Ptolemy (Πτολεμαῖος,; Claudius Ptolemaeus; AD) was an Alexandrian mathematician, astronomer, astrologer, geographer, and music theorist who wrote about a dozen scientific treatises, three of which were important to later Byzantine, Islamic, and Western European science.

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Radar

Radar is a system that uses radio waves to determine the distance (ranging), direction (azimuth and elevation angles), and radial velocity of objects relative to the site.

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Royal Astronomical Society

The Royal Astronomical Society (RAS) is a learned society and charity that encourages and promotes the study of astronomy, solar-system science, geophysics and closely related branches of science.

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Rudolphine Tables

The Rudolphine Tables (Tabulae Rudolphinae) consist of a star catalogue and planetary tables published by Johannes Kepler in 1627, using observational data collected by Tycho Brahe (1546–1601).

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Russian Academy of Sciences

The Russian Academy of Sciences (RAS; Росси́йская акаде́мия нау́к (РАН) Rossíyskaya akadémiya naúk) consists of the national academy of Russia; a network of scientific research institutes from across the Russian Federation; and additional scientific and social units such as libraries, publishing units, and hospitals.

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Saturn

Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter.

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Scientific journal

In academic publishing, a scientific journal is a periodical publication designed to further the progress of science by disseminating new research findings to the scientific community.

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Secular variation

The secular variation of a time series is its long-term, non-periodic variation (see decomposition of time series).

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Semi-major and semi-minor axes

In geometry, the major axis of an ellipse is its longest diameter: a line segment that runs through the center and both foci, with ends at the two most widely separated points of the perimeter.

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Seven Years' War

The Seven Years' War (1756–1763) was a global conflict involving most of the European great powers, fought primarily in Europe and the Americas.

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Simon Newcomb

Simon Newcomb (March 12, 1835 – July 11, 1909) was a Canadian–American astronomer, applied mathematician, and autodidactic polymath.

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Solar mass

The solar mass is a standard unit of mass in astronomy, equal to approximately. Astronomical unit and solar mass are units of measurement in astronomy.

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Solar radius

Solar radius is a unit of distance used to express the size of stars in astronomy relative to the Sun. Astronomical unit and Solar radius are units of length.

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Solar System

The Solar SystemCapitalization of the name varies.

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Speed of light

The speed of light in vacuum, commonly denoted, is a universal physical constant that is exactly equal to). According to the special theory of relativity, is the upper limit for the speed at which conventional matter or energy (and thus any signal carrying information) can travel through space.

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Stadion (unit)

The stadion (plural stadia, στάδιον; latinized as stadium), also anglicized as stade, was an ancient Greek unit of length, consisting of 600 Ancient Greek feet (podes). Astronomical unit and stadion (unit) are units of length.

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Standard gravitational parameter

In celestial mechanics, the standard gravitational parameter μ of a celestial body is the product of the gravitational constant G and the total mass M of the bodies.

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Star system

A star system or stellar system is a small number of stars that orbit each other, bound by gravitational attraction.

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Sun

The Sun is the star at the center of the Solar System.

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Sunlight

Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light.

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Telemetry

Telemetry is the in situ collection of measurements or other data at remote points and their automatic transmission to receiving equipment (telecommunication) for monitoring.

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Telescope

A telescope is a device used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation.

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Terrestrial Time

Terrestrial Time (TT) is a modern astronomical time standard defined by the International Astronomical Union, primarily for time-measurements of astronomical observations made from the surface of Earth.

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The Sand Reckoner

The Sand Reckoner (Ψαμμίτης, Psammites) is a work by Archimedes, an Ancient Greek mathematician of the 3rd century BC, in which he set out to determine an upper bound for the number of grains of sand that fit into the universe.

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Theory of relativity

The theory of relativity usually encompasses two interrelated physics theories by Albert Einstein: special relativity and general relativity, proposed and published in 1905 and 1915, respectively.

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Time dilation

Time dilation is the difference in elapsed time as measured by two clocks, either because of a relative velocity between them (special relativity), or a difference in gravitational potential between their locations (general relativity).

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Toise

A toise (symbol: T) is a unit of measure for length, area and volume originating in pre-revolutionary France. Astronomical unit and toise are units of length.

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Transit of Venus

A transit of Venus takes place when Venus passes directly between the Sun and the Earth (or any other superior planet), becoming visible against (and hence obscuring a small portion of) the solar disk.

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Truncation

In mathematics and computer science, truncation is limiting the number of digits right of the decimal point.

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Tycho Brahe

Tycho Brahe (born Tyge Ottesen Brahe,; 14 December 154624 October 1601), generally called Tycho for short, was a Danish astronomer of the Renaissance, known for his comprehensive and unprecedentedly accurate astronomical observations.

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Uncrewed spacecraft

Uncrewed spacecraft or robotic spacecraft are spacecraft without people on board.

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Unit of length

A unit of length refers to any arbitrarily chosen and accepted reference standard for measurement of length. Astronomical unit and unit of length are units of length.

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United Kingdom Hydrographic Office

The United Kingdom Hydrographic Office (UKHO) is the UK's agency for providing hydrographic and marine geospatial data to mariners and maritime organisations across the world.

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United States customary units

United States customary units form a system of measurement units commonly used in the United States and most U.S. territories, since being standardized and adopted in 1832.

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United States Naval Observatory

The United States Naval Observatory (USNO) is a scientific and military facility that produces geopositioning, navigation and timekeeping data for the United States Navy and the United States Department of Defense.

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Uranus

Uranus is the seventh planet from the Sun.

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Venus

Venus is the second planet from the Sun.

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Voyager 1

Voyager 1 is a space probe launched by NASA on September 5, 1977, as part of the Voyager program to study the outer Solar System and the interstellar space beyond the Sun's heliosphere.

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Voyager 2

Voyager 2 is a space probe launched by NASA on August 20, 1977, as a part of the Voyager program.

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Zhoubi Suanjing

The Zhoubi Suanjing, also known by many other names, is an ancient Chinese astronomical and mathematical work.

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Zij

A zij (zīj) is an Islamic astronomical book that tabulates parameters used for astronomical calculations of the positions of the sun, moon, stars, and planets.

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1639 transit of Venus

The first known observations and recording of a transit of Venus were made in 1639 by the English astronomers Jeremiah Horrocks and his friend and correspondent William Crabtree.

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433 Eros

Eros (minor planet designation (433) Eros) is a stony asteroid of the Amor group, and the first discovered, and second-largest near-Earth object.

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See also

Units of measurement in astronomy

References

[1] https://en.wikipedia.org/wiki/Astronomical_unit

Also known as 1 AU, 1AU, AU (astronomy), Astronomical Units, Distance from the earth to the sun, Distance to the Sun, Earth-Sun distance, Solar unit, .

, IAU (1976) System of Astronomical Constants, Imperial units, Inflection, Integer overflow, International Astronomical Union, International Bureau of Weights and Measures, International Earth Rotation and Reference Systems Service, International Organization for Standardization, International System of Units, ISO/IEC 80000, James Gregory (mathematician), Jérôme Lalande, Jean Picard, Jean Richer, Jeremiah Horrocks, Jet Propulsion Laboratory, Johannes Kepler, John Flamsteed, Julian year (astronomy), Jupiter, Karl Rudolph Powalky, Kepler's laws of planetary motion, Kuiper belt, Length, Li (unit), Light-second, Light-year, Line segment, Lunar distance, Lunar phase, Mars, Mercury (planet), Metre, Metric system, Milky Way, Minute and second of arc, Monthly Notices of the Royal Astronomical Society, Myriad, NASA, Nature Physics, Near-Earth object, Neptune, New Scientist, Nicolaus Copernicus, Noel Swerdlow, Non-SI units mentioned in the SI, Numerical model of the Solar System, Ole Rømer, On the Sizes and Distances (Aristarchus), Oort cloud, Orders of magnitude (length), Pappus of Alexandria, Parallax, Parallax in astronomy, Paris, Parsec, Parts-per notation, Photon, Posidonius, Praeparatio evangelica, Proper length, Proxima Centauri, Ptolemy, Radar, Royal Astronomical Society, Rudolphine Tables, Russian Academy of Sciences, Saturn, Scientific journal, Secular variation, Semi-major and semi-minor axes, Seven Years' War, Simon Newcomb, Solar mass, Solar radius, Solar System, Speed of light, Stadion (unit), Standard gravitational parameter, Star system, Sun, Sunlight, Telemetry, Telescope, Terrestrial Time, The Sand Reckoner, Theory of relativity, Time dilation, Toise, Transit of Venus, Truncation, Tycho Brahe, Uncrewed spacecraft, Unit of length, United Kingdom Hydrographic Office, United States customary units, United States Naval Observatory, Uranus, Venus, Voyager 1, Voyager 2, Zhoubi Suanjing, Zij, 1639 transit of Venus, 433 Eros.