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Light-year

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The light-year is a unit of length used to express astronomical distances and measures about 9.5 trillion kilometres or 5.9 trillion miles. [1]

100 relations: A0620-00, Age of the universe, Andromeda Galaxy, Arthur Eddington, Astrometry, Astronomical Almanac, Astronomical constant, Astronomical system of units, Astronomical unit, Black hole, Bright giant, Canopus, CfA2 Great Wall, Clabon Allen, Coherence (units of measurement), Comoving and proper distances, Cosmic background radiation, Distance measures (cosmology), Earth, Einstein protocol, Ephemeris time, Epoch (astronomy), Foot (unit), Friedrich Bessel, Galactic Center, Galaxy, Galaxy cluster, Galaxy groups and clusters, Gliese 581, Globular cluster, Great Attractor, Gregorian calendar, Heliometer, Hercules–Corona Borealis Great Wall, Hill sphere, Hippolyte Fizeau, Huygens (spacecraft), Imperial units, International Astronomical Union, International System of Units, Interstellar medium, ISO/IEC 80000, Joseph von Fraunhofer, Julian year (astronomy), KEK, Kilometre, Large Magellanic Cloud, Léon Foucault, Length, Light-second, ..., Long and short scales, Luminiferous aether, Luminosity, Messier object, Metre, Metric system, Mile, Milky Way, Minute and second of arc, Moon, N. David Mermin, Nanosecond, NASA, New Horizons, Observable universe, Oort cloud, Orders of magnitude (length), Parallax, Parsec, Pluto, Popular science, Proxima Centauri, Quasar, R136a1, Radius, Rose Center for Earth and Space, Saturn, Significant figures, Simon Newcomb, Sirius, Sloan Great Wall, Solar System, Space probe, Speed of light, Spiral galaxy, Star, Star system, Subtended angle, Sun, Tau Ceti, Titan (moon), Triangulum Galaxy, Tropical year, Unit of length, United States customary units, Virgo Cluster, Voyager 1, Year, 3C 273, 61 Cygni. Expand index (50 more) »

A0620-00

A0620-00 (abbreviated from 1A 0620-00) is a binary star system in the constellation of Monoceros.

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Age of the universe

In physical cosmology, the age of the universe is the time elapsed since the Big Bang.

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Andromeda Galaxy

The Andromeda Galaxy, also known as Messier 31, M31, or NGC 224, is a spiral galaxy approximately 780 kiloparsecs (2.5 million light-years) from Earth, and the nearest major galaxy to the Milky Way.

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Arthur Eddington

Sir Arthur Stanley Eddington (28 December 1882 – 22 November 1944) was an English astronomer, physicist, and mathematician of the early 20th century who did his greatest work in astrophysics.

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Astrometry

Astrometry is the branch of astronomy that involves precise measurements of the positions and movements of stars and other celestial bodies.

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Astronomical Almanac

The Astronomical AlmanacThe Astronomical Almanac for the Year 2015, (United States Naval Observatory/Nautical Almanac Office, 2014).

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Astronomical constant

An astronomical constant is a physical constant used in astronomy.

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Astronomical system of units

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

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Astronomical unit

The astronomical unit (symbol: au, ua, or AU) is a unit of length, roughly the distance from Earth to the Sun.

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Black hole

A black hole is a region of spacetime exhibiting such strong gravitational effects that nothing—not even particles and electromagnetic radiation such as light—can escape from inside it.

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Bright giant

The luminosity class II in the Yerkes spectral classification is given to bright giants.

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Canopus

Canopus, also designated Alpha Carinae (α Carinae, abbreviated Alpha Car, α Car), is the brightest star in the southern constellation of Carina, and the second-brightest star in the night-time sky, after Sirius.

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CfA2 Great Wall

The Great Wall (also called Coma Wall), sometimes specifically referred to as the CfA2 Great Wall, is an immense galaxy filament.

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Christmas

Christmas is an annual festival commemorating the birth of Jesus Christ,Martindale, Cyril Charles.

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Christmas and holiday season

The Christmas season, also called the festive season, or the holiday season (mainly in the U.S. and Canada; often simply called the holidays),, is an annually recurring period recognized in many Western and Western-influenced countries that is generally considered to run from late November to early January.

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Christmas Eve

Christmas Eve is the evening or entire day before Christmas Day, the festival commemorating the birth of Jesus.

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Christmas traditions

Christmas traditions vary from country to country.

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Clabon Allen

Clabon Walter (Cla) Allen FRAS, (28 December 1904 – 11 December 1987) was an Australian astronomer, director of the University of London Observatory and author of Astrophysical Quantities.

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Coherence (units of measurement)

A coherent system of units is based on a system of quantities in such a way that the equations between the numerical values expressed in coherent units have exactly the same form, including numerical factors, as the corresponding equations between the quantities.

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Comoving and proper distances

In standard cosmology, comoving distance and proper distance are two closely related distance measures used by cosmologists to define distances between objects.

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Cosmic background radiation

Cosmic background radiation is electromagnetic radiation from the big bang.

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Distance measures (cosmology)

Distance measures are used in physical cosmology to give a natural notion of the distance between two objects or events in the universe.

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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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Einstein protocol

Einstein protocol is a standard used for precisely measuring the distance between two objects in space.

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Ephemeris time

The term ephemeris time (often abbreviated ET) can in principle refer to time in connection with any astronomical ephemeris.

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Epoch (astronomy)

In astronomy, an epoch is a moment in time used as a reference point for some time-varying astronomical quantity, such as the celestial coordinates or elliptical orbital elements of a celestial body, because these are subject to perturbations and vary with time.

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Foot (unit)

The foot (feet; abbreviation: ft; symbol: ′, the prime symbol) is a unit of length in the imperial and US customary systems of measurement.

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Friedrich Bessel

Friedrich Wilhelm Bessel (22 July 1784 – 17 March 1846) was a German astronomer, mathematician, physicist and geodesist.

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Galactic Center

The Galactic Center is the rotational center of the Milky Way.

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Galaxy

A galaxy is a gravitationally bound system of stars, stellar remnants, interstellar gas, dust, and dark matter.

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Galaxy cluster

A galaxy cluster, or cluster of galaxies, is a structure that consists of anywhere from hundreds to thousands of galaxies that are bound together by gravity with typical masses ranging from 1014–1015 solar masses.

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Galaxy groups and clusters

Galaxy groups and clusters are the largest known gravitationally bound objects to have arisen thus far in the process of cosmic structure formation.

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Gliese 581

Gliese 581 is a star of spectral type M3V (a red dwarf) at the center of the Gliese 581 planetary system, about 20 light years away from Earth in the Libra constellation.

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Globular cluster

A globular cluster is a spherical collection of stars that orbits a galactic core as a satellite.

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Great Attractor

The Great Attractor is an apparent gravitational anomaly in intergalactic space at the center of the local Laniakea Supercluster, in which the Milky Way is located, in the so-called Zone of Avoidance that is notoriously difficult to observe in visible wavelengths due to the obscuring effects of our own galactic plane.

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Gregorian calendar

The Gregorian calendar is the most widely used civil calendar in the world.

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Heliometer

A heliometer (from Greek ἥλιος hḗlios "sun" and measure) is an instrument originally designed for measuring the variation of the sun's diameter at different seasons of the year, but applied now to the modern form of the instrument which is capable of much wider use.

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Hercules–Corona Borealis Great Wall

Hercules–Corona Borealis Great Wall or the Great GRB Wall.

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Hill sphere

An astronomical body's Hill sphere is the region in which it dominates the attraction of satellites.

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Hippolyte Fizeau

Armand Hippolyte Louis Fizeau FRS FRSE MIF (23 September 181918 September 1896) was a French physicist, best known for measuring the speed of light in the namesake Fizeau experiment.

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Huygens (spacecraft)

Huygens was an atmospheric entry probe that landed successfully on Saturn's moon Titan in 2005.

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Imperial units

The system of imperial units or the imperial system (also known as British Imperial or Exchequer Standards of 1825) is the system of units first defined in the British Weights and Measures Act of 1824, which was later refined and reduced.

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International Astronomical Union

The International Astronomical Union (IAU; Union astronomique internationale, UAI) is an international association of professional astronomers, at the PhD level and beyond, active in professional research and education in astronomy.

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International System of Units

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

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Interstellar medium

In astronomy, the interstellar medium (ISM) is the matter and radiation that exists in the space between the star systems in a galaxy.

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ISO/IEC 80000

ISO 80000 or IEC 80000 is an international standard promulgated jointly by the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC).

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Joseph von Fraunhofer

Joseph Ritter von Fraunhofer (6 March 1787 – 7 June 1826) was a Bavarian physicist and optical lens manufacturer.

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Julian year (astronomy)

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

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KEK

, known as KEK, is a Japanese organization whose purpose is to operate the largest particle physics laboratory in Japan, situated in Tsukuba, Ibaraki prefecture.

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Kilometre

The kilometre (International spelling as used by the International Bureau of Weights and Measures; SI symbol: km; or) or kilometer (American spelling) is a unit of length in the metric system, equal to one thousand metres (kilo- being the SI prefix for). It is now the measurement unit used officially for expressing distances between geographical places on land in most of the world; notable exceptions are the United States and the road network of the United Kingdom where the statute mile is the official unit used.

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Large Magellanic Cloud

The Large Magellanic Cloud (LMC) is a satellite galaxy of the Milky Way.

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Léon Foucault

Jean Bernard Léon Foucault (18 September 1819 – 11 February 1868) was a French physicist best known for his demonstration of the Foucault pendulum, a device demonstrating the effect of the Earth's rotation.

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Length

In geometric measurements, length is the most extended dimension of an object.

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Light-second

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

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Long and short scales

The long and short scales are two of several large-number naming systems for integer powers of ten that use the same words with different meanings.

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Luminiferous aether

In the late 19th century, luminiferous aether or ether ("luminiferous", meaning "light-bearing"), was the postulated medium for the propagation of light.

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Luminosity

In astronomy, luminosity is the total amount of energy emitted per unit of time by a star, galaxy, or other astronomical object.

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Messier object

The Messier objects are a set of 110 astronomical objects, of which 103 were included in lists published by French astronomer Charles Messier in 1771 and 1781.

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Metre

The metre (British spelling and BIPM spelling) or meter (American spelling) (from the French unit mètre, from the Greek noun μέτρον, "measure") is the base unit of length in some metric systems, including the International System of Units (SI).

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Metric system

The metric system is an internationally adopted decimal system of measurement.

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Mile

The mile is an English unit of length of linear measure equal to 5,280 feet, or 1,760 yards, and standardised as exactly 1,609.344 metres by international agreement in 1959.

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Milky Way

The Milky Way is the galaxy that contains our Solar System.

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Minute and second of arc

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

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Moon

The Moon is an astronomical body that orbits planet Earth and is Earth's only permanent natural satellite.

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N. David Mermin

Nathaniel David Mermin (born 1935) is a solid-state physicist at Cornell University best known for the eponymous Mermin–Wagner theorem, his application of the term "boojum" to superfluidity, his textbook with Neil Ashcroft on solid-state physics, and for contributions to the foundations of quantum mechanics and quantum information science.

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Nanosecond

A nanosecond (ns) is an SI unit of time equal to one thousand-millionth of a second (or one billionth of a second), that is, 1/1,000,000,000 of a second, or 10 seconds.

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NASA

The National Aeronautics and Space Administration (NASA) is an independent agency of the executive branch of the United States federal government responsible for the civilian space program, as well as aeronautics and aerospace research.

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New Horizons

New Horizons is an interplanetary space probe that was launched as a part of NASA's New Frontiers program.

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New Year

New Year is the time or day at which a new calendar year begins and the calendar's year count increments by one.

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New Year's Day

New Year's Day, also called simply New Year's or New Year, is observed on January 1, the first day of the year on the modern Gregorian calendar as well as the Julian calendar.

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New Year's Eve

In the Gregorian calendar, New Year's Eve (also known as Old Year's Day or Saint Sylvester's Day in many countries), the last day of the year, is on 31 December which is the seventh day of Christmastide.

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Observable universe

The observable universe is a spherical region of the Universe comprising all matter that can be observed from Earth at the present time, because electromagnetic radiation from these objects has had time to reach Earth since the beginning of the cosmological expansion.

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Oort cloud

The Oort cloud, named after the Dutch astronomer Jan Oort, sometimes called the Öpik–Oort cloud, is a theoretical cloud of predominantly icy planetesimals proposed to surround the Sun at distances ranging from.

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Orders of magnitude (length)

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

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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 semi-angle of inclination between those two lines.

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Parsec

The parsec (symbol: pc) is a unit of length used to measure large distances to astronomical objects outside the Solar System.

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Pluto

Pluto (minor planet designation: 134340 Pluto) is a dwarf planet in the Kuiper belt, a ring of bodies beyond Neptune.

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Popular science

Popular science (also called pop-science or popsci) is an interpretation of science intended for a general audience.

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Proxima Centauri

Proxima Centauri, or Alpha Centauri C, is a red dwarf, a small low-mass star, about from the Sun in the constellation of Centaurus.

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Quasar

A quasar (also known as a QSO or quasi-stellar object) is an extremely luminous active galactic nucleus (AGN).

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R136a1

RMC 136a1 (usually abbreviated to R136a1) is a Wolf–Rayet star located at the center of R136, the central condensation of stars of the large NGC 2070 open cluster in the Tarantula Nebula.

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Radius

In classical geometry, a radius of a circle or sphere is any of the line segments from its center to its perimeter, and in more modern usage, it is also their length.

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Rose Center for Earth and Space

The Rose Center for Earth and Space is a part of the American Museum of Natural History in New York City.

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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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Significant figures

The significant figures (also known as the significant digits) of a number are digits that carry meaning contributing to its measurement resolution.

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Simon Newcomb

Simon Newcomb (March 12, 1835 – July 11, 1909) was a Canadian–American astronomer, applied mathematician and autodidactic polymath, who was Professor of Mathematics in the U.S. Navy and at Johns Hopkins.

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Sirius

Sirius (a romanization of Greek Σείριος, Seirios,."glowing" or "scorching") is a star system and the brightest star in the Earth's night sky.

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Sloan Great Wall

The Sloan Great Wall (SGW) is a cosmic structure formed by a giant wall of galaxies (a galaxy filament).

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Solar System

The Solar SystemCapitalization of the name varies.

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Space probe

A space probe is a robotic spacecraft that does not orbit the Earth, but, instead, explores further into outer space.

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Speed of light

The speed of light in vacuum, commonly denoted, is a universal physical constant important in many areas of physics.

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Spiral galaxy

Spiral galaxies form a class of galaxy originally described by Edwin Hubble in his 1936 work The Realm of the Nebulae(pp. 124–151) and, as such, form part of the Hubble sequence.

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Star

A star is type of astronomical object consisting of a luminous spheroid of plasma held together by its own gravity.

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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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Subtended angle

In geometry, an angle subtended by an arc, line segment, or other curve is one whose two rays pass through the endpoints of the arc.

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Sun

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

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Tau Ceti

Tau Ceti, Latinized from τ Ceti, is a single star in the constellation Cetus that is spectrally similar to the Sun, although it has only about 78% of the Sun's mass.

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Titan (moon)

Titan is the largest moon of Saturn.

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Triangulum Galaxy

The Triangulum Galaxy is a spiral galaxy approximately 3 million light-years (ly) from Earth in the constellation Triangulum.

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Tropical year

A tropical year (also known as a solar year) is 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.

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Unit of length

A unit of length refers to any discrete, pre-established length or distance having a constant magnitude which is used as a reference or convention to express linear dimension.

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United States customary units

United States customary units are a system of measurements commonly used in the United States.

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Virgo Cluster

The Virgo Cluster is a cluster of galaxies whose center is 53.8 ± 0.3 Mly (16.5 ± 0.1 Mpc) away in the constellation Virgo.

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Voyager 1

Voyager 1 is a space probe launched by NASA on September 5, 1977.

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Year

A year is the orbital period of the Earth moving in its orbit around the Sun.

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2018

2018 has been designated as the third International Year of the Reef by the International Coral Reef Initiative.

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2019

2019 (MMXIX) will be a common year starting on Tuesday of the Gregorian calendar, the 2019th year of the Common Era (CE) and Anno Domini (AD) designations, the 19th year of the 3rd millennium, the 19th year of the 21st century, and the 10th and last year of the 2010s decade.

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3C 273

3C 273 is a quasar located in the constellation Virgo.

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61 Cygni

61 Cygni Not to be confused with 16 Cygni, a more distant system containing two G-type stars harboring the gas giant planet 16 Cygni Bb.

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Redirects here:

Light Year, Light month, Light year, Light years, Light-Year, Light-month, Light-years, Lightyear, Lightyears, Mly.

References

[1] https://en.wikipedia.org/wiki/Light-year

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