Table of Contents
65 relations: Aberration (astronomy), Ancient Egypt, Apsis, Astrometry, Astronomical coordinate systems, Astronomical object, Astronomy, Axial precession, Bede, Buddhist calendar, Celestial mechanics, Civil time, Constellation, Coordinated Universal Time, Earth, Ecliptic, Ecliptic coordinate system, Ephemeris, Ephemeris time, Epoch, Equator, Equatorial coordinate system, Equinox (celestial coordinates), Friedrich Wilhelm Bessel, Gregorian calendar, Hebrew calendar, Heliacal rising, Henry Draper Catalogue, Hindu calendar, Hipparcos, Infinity, Instant, International Astronomical Union, International Atomic Time, International Celestial Reference System and its realizations, Islamic calendar, ΔT (timekeeping), Julian calendar, Julian day, Julian year (astronomy), List of non-standard dates, Longitude of the ascending node, Lunar calendar, Lunisolar calendar, Mean anomaly, Mean longitude, Meridian (astronomy), Midnight, Minor planet, Noon, ... Expand index (15 more) »
- Astronomical epochs
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.
See Epoch (astronomy) and Aberration (astronomy)
Ancient Egypt
Ancient Egypt was a civilization of ancient Northeast Africa.
See Epoch (astronomy) and Ancient Egypt
Apsis
An apsis is the farthest or nearest point in the orbit of a planetary body about its primary body.
See Epoch (astronomy) and Apsis
Astrometry
Astrometry is a branch of astronomy that involves precise measurements of the positions and movements of stars and other celestial bodies.
See Epoch (astronomy) and Astrometry
Astronomical coordinate systems
In astronomy, coordinate systems are used for specifying positions of celestial objects (satellites, planets, stars, galaxies, etc.) relative to a given reference frame, based on physical reference points available to a situated observer (e.g. the true horizon and north to an observer on Earth's surface).
See Epoch (astronomy) and Astronomical coordinate systems
Astronomical object
An astronomical object, celestial object, stellar object or heavenly body is a naturally occurring physical entity, association, or structure that exists within the observable universe.
See Epoch (astronomy) and Astronomical object
Astronomy
Astronomy is a natural science that studies celestial objects and the phenomena that occur in the cosmos.
See Epoch (astronomy) and Astronomy
Axial precession
In astronomy, axial precession is a gravity-induced, slow, and continuous change in the orientation of an astronomical body's rotational axis.
See Epoch (astronomy) and Axial precession
Bede
Bede (Bēda; 672/326 May 735), also known as Saint Bede, the Venerable Bede, and Bede the Venerable (Beda Venerabilis), was an English monk, author and scholar.
See Epoch (astronomy) and Bede
Buddhist calendar
The Buddhist calendar is a set of lunisolar calendars primarily used in Tibet, Cambodia, Laos, Myanmar, Bangladesh, India, Sri Lanka, Thailand and Vietnam as well as in Malaysia and Singapore and by Chinese populations for religious or official occasions.
See Epoch (astronomy) and Buddhist calendar
Celestial mechanics
Celestial mechanics is the branch of astronomy that deals with the motions of objects in outer space.
See Epoch (astronomy) and Celestial mechanics
Civil time
In modern usage, civil time refers to statutory time as designated by civilian authorities.
See Epoch (astronomy) and Civil time
Constellation
A constellation is an area on the celestial sphere in which a group of visible stars forms a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object.
See Epoch (astronomy) and Constellation
Coordinated Universal Time
Coordinated Universal Time (UTC) is the primary time standard globally used to regulate clocks and time.
See Epoch (astronomy) and Coordinated Universal Time
Earth
Earth is the third planet from the Sun and the only astronomical object known to harbor life.
See Epoch (astronomy) and Earth
Ecliptic
The ecliptic or ecliptic plane is the orbital plane of Earth around the Sun.
See Epoch (astronomy) and Ecliptic
Ecliptic coordinate system
In astronomy, the ecliptic coordinate system is a celestial coordinate system commonly used for representing the apparent positions, orbits, and pole orientations of Solar System objects.
See Epoch (astronomy) and Ecliptic coordinate system
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.
See Epoch (astronomy) and Ephemeris
Ephemeris time
The term ephemeris time (often abbreviated ET) can in principle refer to time in association with any ephemeris (itinerary of the trajectory of an astronomical object).
See Epoch (astronomy) and Ephemeris time
Epoch
In chronology and periodization, an epoch or reference epoch is an instant in time chosen as the origin of a particular calendar era.
See Epoch (astronomy) and Epoch
Equator
The equator is a circle of latitude that divides a spheroid, such as Earth, into the Northern and Southern hemispheres.
See Epoch (astronomy) and Equator
Equatorial coordinate system
The equatorial coordinate system is a celestial coordinate system widely used to specify the positions of celestial objects.
See Epoch (astronomy) and Equatorial coordinate system
Equinox (celestial coordinates)
In astronomy, an equinox is either of two places on the celestial sphere at which the ecliptic intersects the celestial equator.
See Epoch (astronomy) and Equinox (celestial coordinates)
Friedrich Wilhelm Bessel
Friedrich Wilhelm Bessel (22 July 1784 – 17 March 1846) was a German astronomer, mathematician, physicist, and geodesist.
See Epoch (astronomy) and Friedrich Wilhelm Bessel
Gregorian calendar
The Gregorian calendar is the calendar used in most parts of the world.
See Epoch (astronomy) and Gregorian calendar
Hebrew calendar
The Hebrew calendar (translit), also called the Jewish calendar, is a lunisolar calendar used today for Jewish religious observance and as an official calendar of Israel.
See Epoch (astronomy) and Hebrew calendar
Heliacal rising
The heliacal rising of a star or a planet occurs annually when it first becomes visible above the eastern horizon at dawn just before sunrise (thus becoming "the morning star") after a complete orbit of the Earth around the Sun.
See Epoch (astronomy) and Heliacal rising
Henry Draper Catalogue
The Henry Draper Catalogue (HD) is an astronomical star catalogue published between 1918 and 1924, giving spectroscopic classifications for 225,300 stars; it was later expanded by the Henry Draper Extension (HDE), published between 1925 and 1936, which gave classifications for 46,850 more stars, and by the Henry Draper Extension Charts (HDEC), published from 1937 to 1949 in the form of charts, which gave classifications for 86,933 more stars.
See Epoch (astronomy) and Henry Draper Catalogue
Hindu calendar
The Hindu calendar, also called Panchanga, is one of various lunisolar calendars that are traditionally used in the Indian subcontinent and Southeast Asia, with further regional variations for social and Hindu religious purposes.
See Epoch (astronomy) and Hindu calendar
Hipparcos
Hipparcos was a scientific satellite of the European Space Agency (ESA), launched in 1989 and operated until 1993.
See Epoch (astronomy) and Hipparcos
Infinity
Infinity is something which is boundless, endless, or larger than any natural number.
See Epoch (astronomy) and Infinity
Instant
In physics and the philosophy of science, instant refers to an infinitesimal interval in time, whose passage is instantaneous.
See Epoch (astronomy) and Instant
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.
See Epoch (astronomy) and International Astronomical Union
International Atomic Time
International Atomic Time (abbreviated TAI, from its French name temps atomique international) is a high-precision atomic coordinate time standard based on the notional passage of proper time on Earth's geoid.
See Epoch (astronomy) and International Atomic Time
International Celestial Reference System and its realizations
The International Celestial Reference System (ICRS) is the current standard celestial reference system adopted by the International Astronomical Union (IAU).
See Epoch (astronomy) and International Celestial Reference System and its realizations
Islamic calendar
The Hijri calendar (translit), or Arabic calendar also known in English as the Muslim calendar and Islamic calendar, is a lunar calendar consisting of 12 lunar months in a year of 354 or 355 days.
See Epoch (astronomy) and Islamic calendar
ΔT (timekeeping)
In precise timekeeping, ΔT (Delta T, delta-T, deltaT, or DT) is a measure of the cumulative effect of the departure of the Earth's rotation period from the fixed-length day of International Atomic Time (86,400 seconds).
See Epoch (astronomy) and ΔT (timekeeping)
Julian calendar
The Julian calendar is a solar calendar of 365 days in every year with an additional leap day every fourth year (without exception).
See Epoch (astronomy) and Julian calendar
Julian day
The Julian day is the continuous count of days since the beginning of the Julian period, and is used primarily by astronomers, and in software for easily calculating elapsed days between two events (e.g. food production date and sell by date).
See Epoch (astronomy) and Julian day
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.
See Epoch (astronomy) and Julian year (astronomy)
List of non-standard dates
Several non-standard dates are used in calendars for various purposes: some are expressly fictional, some are intended to produce a rhetorical effect (such as sarcasm), and others attempt to address a particular mathematical, scientific or accounting requirement or discrepancy within the calendar system.
See Epoch (astronomy) and List of non-standard dates
Longitude of the ascending node
The longitude of the ascending node (symbol ☊) is one of the orbital elements used to specify the orbit of an object in space.
See Epoch (astronomy) and Longitude of the ascending node
Lunar calendar
A lunar calendar is a calendar based on the monthly cycles of the Moon's phases (synodic months, lunations), in contrast to solar calendars, whose annual cycles are based on the solar year.
See Epoch (astronomy) and Lunar calendar
Lunisolar calendar
A lunisolar calendar is a calendar in many cultures, incorporating lunar calendars and solar calendars.
See Epoch (astronomy) and Lunisolar calendar
Mean anomaly
In celestial mechanics, the mean anomaly is the fraction of an elliptical orbit's period that has elapsed since the orbiting body passed periapsis, expressed as an angle which can be used in calculating the position of that body in the classical two-body problem.
See Epoch (astronomy) and Mean anomaly
Mean longitude
Mean longitude is the ecliptic longitude at which an orbiting body could be found if its orbit were circular and free of perturbations.
See Epoch (astronomy) and Mean longitude
Meridian (astronomy)
In astronomy, the meridian is the great circle passing through the celestial poles, as well as the zenith and nadir of an observer's location.
See Epoch (astronomy) and Meridian (astronomy)
Midnight
Midnight is the transition time from one day to the next – the moment when the date changes, on the local official clock time for any particular jurisdiction.
See Epoch (astronomy) and Midnight
Minor planet
According to the International Astronomical Union (IAU), a minor planet is an astronomical object in direct orbit around the Sun that is exclusively classified as neither a planet nor a comet.
See Epoch (astronomy) and Minor planet
Noon
Noon (or midday) is 12 o'clock in the daytime.
See Epoch (astronomy) and Noon
Orbital elements
Orbital elements are the parameters required to uniquely identify a specific orbit.
See Epoch (astronomy) and Orbital elements
Orbital mechanics
Orbital mechanics or astrodynamics is the application of ballistics and celestial mechanics to the practical problems concerning the motion of rockets, satellites, and other spacecraft.
See Epoch (astronomy) and Orbital mechanics
Orbital plane of reference
In celestial mechanics, the orbital plane of reference (or orbital reference plane) is the plane used to define orbital elements (positions).
See Epoch (astronomy) and Orbital plane of reference
Osculating orbit
In astronomy, and in particular in astrodynamics, the osculating orbit of an object in space at a given moment in time is the gravitational Kepler orbit (i.e. an elliptic or other conic one) that it would have around its central body if perturbations were absent.
See Epoch (astronomy) and Osculating orbit
Perturbation (astronomy)
In astronomy, perturbation is the complex motion of a massive body subjected to forces other than the gravitational attraction of a single other massive body.
See Epoch (astronomy) and Perturbation (astronomy)
Polynomial
In mathematics, a polynomial is a mathematical expression consisting of indeterminates (also called variables) and coefficients, that involves only the operations of addition, subtraction, multiplication and exponentiation to nonnegative integer powers, and has a finite number of terms.
See Epoch (astronomy) and Polynomial
Precession
Precession is a change in the orientation of the rotational axis of a rotating body.
See Epoch (astronomy) and Precession
Proper motion
Proper motion is the astrometric 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.
See Epoch (astronomy) and Proper motion
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.
See Epoch (astronomy) and Semi-major and semi-minor axes
Sirius
Sirius is the brightest star in the night sky.
See Epoch (astronomy) and Sirius
Sun
The Sun is the star at the center of the Solar System.
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.
See Epoch (astronomy) and Terrestrial Time
Theoretical astronomy
Theoretical astronomy is the use of analytical and computational models based on principles from physics and chemistry to describe and explain astronomical objects and astronomical phenomena.
See Epoch (astronomy) and Theoretical astronomy
Universal Time
Universal Time (UT or UT1) is a time standard based on Earth's rotation.
See Epoch (astronomy) and Universal Time
5145 Pholus
5145 Pholus is an eccentric centaur in the outer Solar System, approximately in diameter, that crosses the orbit of both Saturn and Neptune.
See Epoch (astronomy) and 5145 Pholus
See also
Astronomical epochs
- Epoch (astronomy)
- Great Year
References
Also known as 1875.0, 1900.0, 1950.0, 2000.0, Astronomical epoch, B1875, B1875.0, B1900, B1900.0, B1950.0, B2000.0, Besselian epoch, Besselian year, Epoch astronomy, Epoch in astronomy, Epochal moment, J1900, J1900.0, J1950, J1950.0, J2000, J2000.0, Julian epoch, Standard epoch 2000.