94 relations: Angular diameter, Anjana (Cantabrian mythology), Apsis, Aquarius (constellation), Aries (constellation), Astronomical year numbering, Atmospheric refraction, Axial precession, Barycenter, Brady Haran, Capricornus, Cassini–Huygens, Celestial coordinate system, Celestial equator, Celestial sphere, Cetus, Communications satellite, Constellation, Culmination, Daytime, Diurnal motion, Earth, Earth's orbit, Ecliptic, Ecliptic coordinate system, Epoch (astronomy), Equation of time, Equator, Equatorial coordinate system, Equinox (celestial coordinates), First Council of Nicaea, First Point of Aries, Genitive case, Geostationary orbit, Gregorian calendar, Harvest, Hebrew calendar, Hemispheres of Earth, Horizon, Hour angle, International Astronomical Union, Iranian calendars, Islamic calendar, Julian calendar, Julius Caesar, Kōreisai, Lady Day, Latin, Latitude, Leo (constellation), ..., Libra (astrology), Longitude, March equinox, Middle latitudes, Minute and second of arc, Neologism, Night, Northern Hemisphere, Nowruz, Pisces (constellation), Planetshine, Pope Gregory XIII, Precession, Protologism, Radius, Refraction, Right ascension, Rings of Saturn, Season, September equinox, Sidereal time, Solstice, Songkran, Southern Hemisphere, Spring (season), Subsolar point, Sun, Sun outage, Sun path, Sunlight, Sunrise, Taurus (constellation), Tekufah, Terminator (solar), The Nuttall Encyclopædia, The Planetary Society, Time zone, Tropical year, Twilight, University of Nottingham, Usenet, Virgo (constellation), Zenith, Zodiac. Expand index (44 more) » « Shrink index
The angular diameter, angular size, apparent diameter, or apparent size is an angular measurement describing how large a sphere or circle appears from a given point of view.
The Anjana (Cantabrian: (Western), (Eastern)) (from jana, a former word for witches during the Middle Ages) are one of the best known fairies of Cantabrian mythology.
An apsis (ἁψίς; plural apsides, Greek: ἁψῖδες) is an extreme point in the orbit of an object.
Aquarius is a constellation of the zodiac, situated between Capricornus and Pisces.
Aries is one of the constellations of the zodiac.
Astronomical year numbering is based on AD/CE year numbering, but follows normal decimal integer numbering more strictly.
Atmospheric refraction is the deviation of light or other electromagnetic wave from a straight line as it passes through the atmosphere due to the variation in air density as a function of height.
In astronomy, axial precession is a gravity-induced, slow, and continuous change in the orientation of an astronomical body's rotational axis.
The barycenter (or barycentre; from the Ancient Greek βαρύς heavy + κέντρον centre) is the center of mass of two or more bodies that are orbiting each other, which is the point around which they both orbit.
Brady John Haran (born 18 June 1976) is an Australian-born British independent filmmaker and video journalist who is known for his educational videos and documentary films produced for BBC News and his YouTube channels, the most notable being Periodic Videos and Numberphile.
Capricornus is one of the constellations of the zodiac.
The Cassini–Huygens mission, commonly called Cassini, was a collaboration between NASA, the European Space Agency (ESA), and the Italian Space Agency (ASI) to send a probe to study the planet Saturn and its system, including its rings and natural satellites.
In astronomy, a celestial coordinate system is a system for specifying positions of celestial objects: satellites, planets, stars, galaxies, and so on.
The celestial equator is the great circle of the imaginary celestial sphere on the same plane as the equator of Earth.
In astronomy and navigation, the celestial sphere is an abstract sphere with an arbitrarily large radius concentric to Earth.
Cetus is a constellation.
A communications satellite is an artificial satellite that relays and amplifies radio telecommunications signals via a transponder; it creates a communication channel between a source transmitter and a receiver at different locations on Earth.
A constellation is a group of stars that are considered to form imaginary outlines or meaningful patterns on the celestial sphere, typically representing animals, mythological people or gods, mythological creatures, or manufactured devices.
In astronomy, the culmination of a planet, star, or constellation is its transit over an observer's meridian.
On Earth, daytime is roughly the period of the day during which any given point in the world experiences natural illumination from especially direct sunlight.
Diurnal motion (lit, from dies, lit. "day") is an astronomical term referring to the apparent daily motion of stars around Earth, or more precisely around the two celestial poles.
Earth is the third planet from the Sun and the only astronomical object known to harbor life.
Earth's orbit is the trajectory along which Earth travels around the Sun.
The ecliptic is the circular path on the celestial sphere that the Sun follows over the course of a year; it is the basis of the ecliptic coordinate system.
The ecliptic coordinate system is a celestial coordinate system commonly used for representing the apparent positions and orbits of Solar System objects.
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.
The equation of time describes the discrepancy between two kinds of solar time.
An equator of a rotating spheroid (such as a planet) is its zeroth circle of latitude (parallel).
The equatorial coordinate system is a celestial coordinate system widely used to specify the positions of celestial objects.
In astronomy, equinox is a moment when the vernal point, celestial equator, and other such elements are taken to be used in the definition of a celestial coordinate system.
The First Council of Nicaea (Νίκαια) was a council of Christian bishops convened in the Bithynian city of Nicaea (now İznik, Bursa province, Turkey) by the Roman Emperor Constantine I in AD 325.
The First Point of Aries, also known as the Cusp of Aries, is the location of the vernal equinox, used as a reference point in celestial coordinate systems.
In grammar, the genitive (abbreviated); also called the second case, is the grammatical case that marks a word, usually a noun, as modifying another word, also usually a noun.
A geostationary orbit, often referred to as a geosynchronous equatorial orbit (GEO), is a circular geosynchronous orbit above Earth's equator and following the direction of Earth's rotation.
The Gregorian calendar is the most widely used civil calendar in the world.
Harvesting is the process of gathering a ripe crop from the fields.
The Hebrew or Jewish calendar (Ha-Luah ha-Ivri) is a lunisolar calendar used today predominantly for Jewish religious observances.
In geography and cartography, the hemispheres of Earth refer to any division of the globe into two hemispheres (from Ancient Greek ἡμισφαίριον hēmisphairion, meaning "half of a sphere").
The horizon or skyline is the apparent line that separates earth from sky, the line that divides all visible directions into two categories: those that intersect the Earth's surface, and those that do not.
In astronomy and celestial navigation, the hour angle is one of the coordinates used in the equatorial coordinate system to give the direction of a point on the celestial sphere.
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.
The Iranian calendars (گاهشماری ایرانی Gâhshomâriye Irâni) are a succession of calendars invented or used for over two millennia in Iran (Persia).
The Islamic, Muslim, or Hijri calendar (التقويم الهجري at-taqwīm al-hijrī) is a lunar calendar consisting of 12 months in a year of 354 or 355 days.
The Julian calendar, proposed by Julius Caesar in 46 BC (708 AUC), was a reform of the Roman calendar.
Gaius Julius Caesar (12 or 13 July 100 BC – 15 March 44 BC), known by his cognomen Julius Caesar, was a Roman politician and military general who played a critical role in the events that led to the demise of the Roman Republic and the rise of the Roman Empire.
, or and Kōreisai, are days of worship in Japan that began in 1878 to pay respects to the past emperors and imperial family members.
In the western liturgical year, Lady Day is the traditional name in some English speaking countries of the Feast of the Annunciation (25 March), known in the 1549 Prayer Book of Edward VI and the 1667 Book of Common Prayer as "The Annunciation of the (Blessed) Virgin Mary" but more accurately (as currently in the 1997 Calendar of the Church of England) termed "The Annunciation of our Lord to the Blessed Virgin Mary".
Latin (Latin: lingua latīna) is a classical language belonging to the Italic branch of the Indo-European languages.
In geography, latitude is a geographic coordinate that specifies the north–south position of a point on the Earth's surface.
Leo is one of the constellations of the zodiac, lying between Cancer the crab to the west and Virgo the maiden to the east.
Libra (♎) is the seventh astrological sign in the Zodiac.
Longitude, is a geographic coordinate that specifies the east-west position of a point on the Earth's surface.
The March equinox or Northward equinox is the equinox on the Earth when the subsolar point appears to leave the southern hemisphere and cross the celestial equator, heading northward as seen from Earth.
The middle latitudes (also called the mid-latitudes, sometimes midlatitudes, or moderate latitudes) of Earth lie between 23°26'22" and 66°33'39" north, and between 23°26'22" and 66°33'39" south.
A minute of arc, arcminute (arcmin), arc minute, or minute arc is a unit of angular measurement equal to of one degree.
A neologism (from Greek νέο- néo-, "new" and λόγος lógos, "speech, utterance") is a relatively recent or isolated term, word, or phrase that may be in the process of entering common use, but that has not yet been fully accepted into mainstream language.
Night or nighttime (sp. night-time or night time) is the period of time between sunset and sunrise, when the Sun is below the horizon.
The Northern Hemisphere is the half of Earth that is north of the Equator.
Nowruz (نوروز,; literally "new day") is the name of the Iranian New Year, also known as the Persian New Year, which is celebrated worldwide by various ethno-linguistic groups as the beginning of the New Year.
Pisces is a constellation of the zodiac.
Planetshine is the dim illumination, by sunlight reflected from a planet, of all or part of the otherwise dark side of any moon orbiting the body.
Pope Gregory XIII (Gregorius XIII; 7 January 1502 – 10 April 1585), born Ugo Boncompagni, was Pope of the Catholic Church from 13 May 1572 to his death in 1585.
Precession is a change in the orientation of the rotational axis of a rotating body.
Protologism is a term invented in the early 2000s by Mikhail Epstein, an American literary theorist, to refer to a new word which has not gained wide acceptance in the language.
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.
Refraction is the change in direction of wave propagation due to a change in its transmission medium.
Right ascension (abbreviated RA; symbol) is the angular distance measured only eastward along the celestial equator from the Sun at the March equinox to the (hour circle of the) point above the earth in question.
The rings of Saturn are the most extensive ring system of any planet in the Solar System.
A season is a division of the year marked by changes in weather, ecology, and amount of daylight.
The September equinox (or Southward equinox) is the moment when the Sun appears to cross the celestial equator, heading southward.
Sidereal time is a timekeeping system that astronomers use to locate celestial objects.
A solstice is an event occurring when the Sun appears to reach its most northerly or southerly excursion relative to the celestial equator on the celestial sphere.
Songkran is a term derived from the Sanskrit word, (or, more specifically) and used to refer to the traditional New Year celebrated in Thailand, Laos, Cambodia, Myanmar, Sri Lanka, parts of northeast India, parts of Vietnam and Xishuangbanna, China.
The Southern Hemisphere is the half of Earth that is south of the Equator.
Spring is one of the four conventional temperate seasons, following winter and preceding summer.
The subsolar point on a planet is where its sun is perceived to be directly overhead (in zenith); that is where the sun's rays are hitting the planet exactly perpendicular to its surface.
The Sun is the star at the center of the Solar System.
A Sun outage, Sun transit or Sun fade is an interruption in or distortion of geostationary satellite signals caused by interference (background noise) of the sun when it falls directly behind a satellite which an earth station is trying to receive data or transmit data to.
Sun path, sometimes also called day arc, refers to the daily and seasonal arc-like path that the Sun appears to follow across the sky as the Earth rotates and orbits the Sun.
Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light.
Sunrise or sun up is the instant at which the upper edge of the Sun appears over the horizon in the morning.
Taurus (Latin for "the Bull") is one of the constellations of the zodiac, which means it is crossed by the plane of the ecliptic.
Tekufot (Hebrew: תקופות, singular: tekufah, literally, "turn" or "cycle") are the four seasons of the year recognized by Talmud writers.
A terminator or twilight zone is a moving line that divides the daylit side and the dark night side of a planetary body.
The Nuttall Encyclopædia: Being a Concise and Comprehensive Dictionary of General Knowledge is a late 19th-century encyclopedia, edited by Rev.
The Planetary Society is an American internationally active, non-governmental, nonprofit foundation.
A time zone is a region of the globe that observes a uniform standard time for legal, commercial, and social purposes.
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.
Twilight on Earth is the illumination of the lower atmosphere when the Sun itself is not directly visible because it is below the horizon.
The University of Nottingham is a public research university in Nottingham, United Kingdom.
Usenet is a worldwide distributed discussion system available on computers.
Virgo is one of the constellations of the zodiac.
The zenith is an imaginary point directly "above" a particular location, on the imaginary celestial sphere.
The zodiac is an area of the sky that extends approximately 8° north or south (as measured in celestial latitude) of the ecliptic, the apparent path of the Sun across the celestial sphere over the course of the year.
Autumn Equinox, Autumnal Equinox, Autumnal equinox, Autumnal point, Dynamical equinox, Ecuinox, Equilux, Equinoctial Points, Equinoctial point, Equinoctial point/History1, Equinoctial points, Equinoxal, Equinoxes, Fall solstice, First Point in Aries, First Point of Libra, First point in Aries, First point of Aries, First point of Libra, First point of aries, First point of libra, Invernal equinox, Spring Equinox, Spring equinox, Spring meridian, Spring solstice, Vernal Equinox, Vernal equinox point, Vernal point, 秋分.