Browse this alphabetical dictionary of astronomy terms, from absolute magnitude to zenith. Visitors can suggest new words or corrections to existing entries.
Reference promotes the use of standardised astronomical terminology, with discussion of subject coverage, construction and length.
Look up the term that describes the difference between a star's apparent position and its true position, caused by motion of the observer.
Find a description of a device that was once used in astronomical observations. Tap into photographs of the instrument.
Encyclopedia defines the AU and its significance in measuring the solar system. Gives a rough estimate of its value in kilometers and miles.
Learn about this imaginary navigation tool used in determining star positions and time.
Find a reference listing for the term used in astronomy relating to a star's color and its temperature.
Find an encyclopedia entry on systems used to describe an object's location in space.
Presents the two hypotheses which make up this heliocentric theory developed by the 16th-century astronomer Nicolaus Copernicus.
Consult this encyclopedia article to find speculations about the material that comprises dark matter.
Learn about the Earth, the Sun, the zodiac and the equinoxes. Links to a multimedia presentation.
Defines the celestial equator, the great circle on the celestial sphere that parallel's the equator on Earth.
Check out the field of astronomy that investigates anti-matter, quasars, black holes and other exotic objects through gamma-ray observations.
Defines the kind of full moon experienced in late fall and emitting strong moonlight during the night.
Read about the orbit, purpose and projects designed for this space-based observatory.
Find out about astronomical observations made through telescopes that work with infrared radiation rather than light.
Learn about the worldwide scientific studies in solar astronomy conducted between 1964 and 1965.
Describes the international collaborative project from July 1957 through December 1958 that resulted in geological and astronomical discoveries.
Check out photos and explanations of the gas and particulate matter found between stars and other galaxies.
Read about the three laws describing the movement of planets and their orbits, promulgated by Johannes Kepler.
Find out the name of the Venus morning star and historical references to this planet.
Find out about a constellation containing Vega, Beta Lyrae and Epsilon Lyrae.
Defines how the brightness of a star is determined when viewed from the earth.
Find out why chunks of extraterrestrial rock burn upon contact with the atmosphere.
Describes the asteroid and comet sources of these chunks of extraterrestrial metal and rock that have fallen to earth.
Find out why these diffuse astronomical objects may be the birthplace of new stars.
Learn the characteristic differences between explosive stars that disappear or linger.
Provides a brief overview of the origins and varieties of observatory buildings used to view astronomical or meteorological events.
Browse a scientific definition and journal links related to the astronomical term referring to a celestial body's path through space.
Astronomical term refers to the apparent change in a star's location depending on the Earth's cycle and is used to determine distance.
Provides a scientific definition of the term parsec, used in astronomy to measure distances in interstellar space.
Describes the ancient school of thought propounded by Ptolemy, who asserted that the Earth was the center of the universe.
Describes the history and methodology of this field, which involves reflecting radio waves off of extraterrestrial objects.
Discover details on the location, composition and behavior of these celestial bands of charged protons and electrons.
Learn about an optical phenomenon noted in astronomical observations and read two explanations for why it occurs.
Defines this central term in astronomy and physics and provides links to articles on time and relativity theory.
Describes the optical principles at work in this instrument, chronicles its development and details its astronomical applications.
Describes an astronomical event in which one object, be it a star or a planet, passes in front of another.
Read about this telescopic tool used by astronomers to observe the motion of celestial body across a meridian.
Introduces a branch of the field which observes UV radiation produced by celestial bodies. Discusses its contributions to astronomical knowledge.
Browse through an A-Z list of definitions to astronomical terms. Includes links to information in more depth.
Find the answer to this astronomy question from this 1997 post. Includes general and special relativity information and links to potentially useful and related FAQs.
Offers an extensive, yet pretty simplistic look at what exactly the speed of light means and stands for in astronomical and practical terms.