Astronomical Glossary

12-Hour Clock

24-Hour Clock

A

Aldebaran--Star Aldebaran

a.m. = Ante-Meridiem (Morning: Midnight to a moment before Noon)

Antares--Star Antares

Annular Solar Eclipse -- Link 1 *** Link 2 ***** Tips for Safe Viewing: Eclipse of the Sun / Solar Eclipse

Aphelion of Earth: Link 1 *** Link 2

Apogee of Moon: Link 1 *** Link 2

Apparition - An appearance; in astronomy, the period of observation of a returning periodic comet. (answers.com)

Appulse

Ascending node

Asterism

Astronomical Magnitude - See Magnitude

Astronomical Twilight --- Twilight

Astronomical Unit

Astronomy

Astronomy and Other Sciences ---
Frequently Asked Questions (FAQ)

Astrophysics developed by nineteenth century Allegheny Observatory Astronomers Samuel Pierpont Langley and James E. Keeler.

Autumnal Equinox

Averted Vision

B

Beehive--Star Cluster (Open): Beehive / Praesepe (M44)

Black Moon: Link 1 * Link 2 * Link 3

Blue Moon: Link 1 * Link 2 ***

C

Calendar Blue Moon

Calendar

Calendar - Lunar

Calendar - Solar

Calendar Blue Moon *** Blue Moon

Calendar Date

Calendar Era

Calendar Year

Celestial equator

Celsius (temperature scale) - Imprecisely known as Centigrade, in previous decades.

Centigrade (temperature scale) - Imprecise term for Celsius.

Periodic Table of Chemical Elements

Civil Twilight --- Twilight

Clusters of Stars -- Star Cluster (Open): Beehive / Praesepe (M44) *** Star Cluster (Open): M35 *** Star Cluster (Open): Pleiades (M45)

Conjunction -- Inferior Conjunction *** Superior Conjunction

Constellation

Coordinated Universal Time

CROSS-QUARTER (XQ) - PREFERRED DEFINITION:
Having no formal astronomical definition, "cross-quarter" here is defined as the moment in time precisely half-way between an adjacent equinox and solstice, or adjacent solstice and equinox.
(Source: Eric G. Canali, Former Floor Manager of Pittsburgh's original Buhl Planetarium and Institute of Popular Science and the Founder and Manager of the South Hills Backyard Astronomers amateur astronomy club)
More information:
Cross-Quarter Day - Astronomical (Traditional)

Culminate/Culmination (Astronomy definition)

D

Daylight Hours

Daylight Saving Time

Descending node

Direct and Retrograde motion of planetary bodies - Also see Motion (of planetary bodies)

Diurnal motion

Double-shadow transit - Shadows of two objects transiting or crossing the visible disk of a third object. Often used in reference to shadows of two of the Galilean moons crossing the visible disk of the Planet Jupiter.

E

Earthshine

Eastern Standard Time

Eastern Daylight Saving Time

Eclipse -- Lunar Eclipse -- Link 1 *** Link 2 *** Penumbral Eclipse -- Link 1 *** Link 2 *** Solar Eclipse -- Link 1 *** Link 2 *** Annular Solar Eclipse -- Link 1 *** Link 2 ***** Tips for Safe Viewing: Eclipse of the Sun / Solar Eclipse

Ecliptic

Periodic Table of Chemical Elements

Elongation *** Greatest Elongation

Equilux - The actual day with equal hours and minutes of the Sun above the horizon, and equal hours and minutes of the Sun below the horizon. Occurs twice each year, approximately 3-to-4 days before the Vernal Equinox and 3-to-4 days after the Autumnal Equinox. (March 16, September 25)

EQUINOX - PREFERRED DEFINITION:
Equinox (EQX) - The Spring or Autumn quarter begins as the Earth's terminator, the boundary-line between night and day, momentarily crosses the North and South Poles. Therefore, with the Earth's day/night bounary line briefly poised simultaneously over both poles, only on dates near these times of year are the number of hours of night and day equal all over the globe.
(Source: Eric G. Canali, Former Floor Manager of Pittsburgh's original Buhl Planetarium and Institute of Popular Science and the Founder and Manager of the South Hills Backyard Astronomers amateur astronomy club)
More Information:
Equinox -- Vernal Equinox *** Autumnal Equinox

F

First Quarter Moon Phase

Fortnight

Frequently Asked Questions (FAQ) -
Astronomy and Other Sciences

Full Moon Phase -- Link 1 *** Link 2

G

Geocentric

Geocentric orbit

Greatest Elongation *** Elongation

H

Heliocentric: Link 1 *** Link 2

Horizon: Link 1 *** Link 2

I

Inferior Conjunction

J

K

L

Last (or "Third") Quarter Moon Phase

Lunar Calendar

Lunar Eclipse -- Link 1 *** Link 2

Lunar Tides

M

Magnitude

Meridian (astronomy)

Mini-Moon

Minimum (Astronomy definition) - minimum brightness observed or predicted, often for a variable star.

Moon or Satellite of a planet

Moon of Earth -- Link 1 *** Link 2 ***** Phases: Phases of Moon Defined -- New Moon *** First Quarter *** Full Moon Phase -- Link 1 *** Link 2 *** Last (or "Third") Quarter

Motion (of planetary bodies) - Direct and Retrograde motion *** Stationary (Astronomy definition)

N

Nautical Twilight --- Twilight

Neap Tides --- Link 1 *** Link 2

New Moon Phase

Nova

O

Occultation

Opposition

Orbit *** Planetary Orbit

Orbital Periods - Sidereal Period, Synodic Period, Draconic Period, Anomalistic Period, Tropical Period.

P

Parallax - Actually motion parallax

Penumbral Eclipse -- Link 1 *** Link 2

Perigee of Moon: Link 1 *** Link 2

Perihelion of Earth: Link 1 *** Link 2 *** Link 3 *** Link 4

Periodic Table of Chemical Elements

Phases of Earth's Moon -- Phases of Earth's Moon Defined -- New Moon *** First Quarter *** Full Moon Phase -- Link 1 *** Link 2 *** Last (or "Third") Quarter

Pi

Planet *** Dwarf Planet *** Minor Planet *** Asteroid *** Planetoid

Planetarium - Planetarium Concept Born 1914

p.m. = Post-Meridiem (Afternoon & Evening: a moment after Noon to a moment before Midnight of the next day)

Q

Quadrature (includes definition for Astronomy)

R

Retrograde and Direct motion of planetary bodies - Link 1 - Link 2 - Also see Motion (of planetary bodies)

Rise (of celestial body)

S

Saros Eclipse Cycle

Satellite or Moon of a planet

SEASONS - PREFERRED DEFINITION:
Seasons - The annual spans of time framed by the solstices and their adjacent equinoxes. Of course, although the dates of the solstices and equinoxes remain the same, the season's name will be its opposite when comparing Southern Hemisphere locations to the Northern Hemisphere or vice versa.
** Seasonal Quarters - Although each "season" actually contains a slightly different number of days from the other three, "quarters" remains a common descriptive term for these four sectors of the Earth's orbit.
** Seasonal Weather - The local weather norms traditionally associated with a time of year. All annual extended weather sequences ultimately are driven by the effects marked by the astronomical quarterdays (the solstices and equinoxes) which frame the seasonal quarters of the year.
More Information
(Source: Eric G. Canali, Former Floor Manager of Pittsburgh's original Buhl Planetarium and Institute of Popular Science and the Founder and Manager of the South Hills Backyard Astronomers amateur astronomy club)

Set (of celestial body)

Sidereal Year

Solar Calendar

Solar Eclipse -- Link 1 *** Link 2 *** Annular Solar Eclipse -- Link 1 *** Link 2 ***** Tips for Safe Viewing: Eclipse of the Sun / Solar Eclipse

SOLSTICE - PREFERRED DEFINITION:
Solstice (SOLC) - Either of the two extremes of the Earth's constant 23.4-degree axial tilt, relative to the sunlight falling on its surface. Only at the June Solstice is the Earth's North Pole tilted the full 23.4 degrees towards the Sun...and only at the December Solstice is it tilted the full 23.4 degrees away from the Sun.
(Source: Eric G. Canali, Former Floor Manager of Pittsburgh's original Buhl Planetarium and Institute of Popular Science and the Founder and Manager of the South Hills Backyard Astronomers amateur astronomy club)
More Information:
Solstice -- Summer Solstice *** Winter Solstice

Spectroscopy

Spring Tides --- Link 1 *** Link 2

Standard Time

Star

Star Cluster

Stationary (Astronomy definition) - Also see Motion (of planetary bodies)

Summer Solstice

Sun of Earth - Link 1 *** Link 2 *** Link 3

Sunrise *** Sunset

Super Moon

Superior Conjunction

T

Terminator ---
Graphic showing the Terminator at the time of a Solstice and at the time of an Equinox. [Graphic (c) Copyright 2005 Eric G. Canali, former Floor Operations Manager of Pittsburgh's original Buhl Planetarium and Institute of Popular Science and Founder of the South Hills Backyard Astronomers amateur astronomy club. Use permission granted for only non-profit use with credit to author.]
How the Earth's Terminator was used to help save the Apollo 13 spacecraft.

Tides-- Lunar Tides

"Third" (or Last) Quarter Moon Phase

Transit (astronomical): Link 1 *** Link 2 *** Also see Double-shadow transit

Twilight

U

Universal Time

V

Vernal Equinox

Visibility

W

Winter Solstice

X

X-Rays
(Also see: "Crowd-Funding Saves Tesla Electricity Lab"; Nikola Tesla may have been the true discoverer of X-Rays.)

Y

Z

Zenith

Zodiac in Astronomy

Zodiacal Light

Celestial Objects --

Planets (Planet defined)

Planet Mercury

Planet Venus

Planet Earth -- Aphelion *** Perihelion *** Perihelion of Earth

** Moon of Earth -- Apogee *** Perigee

*** Moon Phases: Phases of Moon Defined -- New Moon *** First Quarter *** Full Moon Phase -- Link 1 *** Link 2 *** Last (or "Third") Quarter

Planet Mars

Planet Jupiter

Planet Saturn

Planet Uranus

Planet Neptune

Pluto - See Dwarf Planet Pluto

Eris - See Dwarf Planet Eris

Xena - See Dwarf Planet Eris

Ceres - See Dwarf Planet 1 Ceres

Minor Planets (Dwarf Planets and Asteroids/Planetoids)
(Definitions of Minor Planet, Dwarf Planet, Asteroid, Planetoid)

List of solar system bodies formerly considered planets

Dwarf Planet Eris

Xena - See Dwarf Planet Eris

Dwarf Planet Pluto

1 Ceres (Dwarf Planet)

2 Pallas

3 Juno

4 Vesta

Stars

Star Aldebaran

Star Antares

Star Regulus

Star Rigel

Star Spica

Star Clusters

Star Cluster (Open): Beehive / Praesepe (M44)

Star Cluster (Open): M35

Star Cluster (Open): Pleiades (M45)