Radar ranging radial velocity radiant radio astronomy radio beam radio galaxy radio source radio star radio telescope radio wave ray red dwarf red giant red shift. These are some of the most common astronomy terms used in the field. Browse the list to become more familiar with the hobby and science of astronomy. Below is a list of useful Astronomy words. These big words were created by scientists to explain what happens in Outer Space. It is useful to know these words.


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International Comet Quarterly

No matter or radiation can escape from within the event horizon Evolutionary Track — The path in an H-R diagram followed by the point representing the changing luminosity and temperature of a star as it evolves Exosphere — The outer part of the glossary of astronomy terms.

Atoms and ions can escape from the exosphere directly into space Explosion Model — A model for the formation of clusters of galaxies in which the clusters form at the intersections of expanding shells of matter driven outward by gigantic explosions Extinction — The dimming of starlight due to absorption and scattering by interstellar dust particles.

In a geocentric model of the solar system, the planets moved about the Glossary of astronomy terms Geodesic — The path in spacetime followed by a light beam or a freely moving object Giant — A star larger and more luminous than a main sequence star dwarf of the same temperature and spectral type Giant Impact Theory — The theory of the origin of the Moon that holds that the Moon formed from debris blasted into orbit when the Earth was struck by a Mars-size body Giant Molecular Cloud — An unusually large molecular cloud that may contain as much as 1 million solar masses Gibbous Phase — The phase of the moon at which the near side of the Moon is more than half illuminated by sunlight.

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Granules appear bright because they are hotter than the descending gas that separates them Gravitational Glossary of astronomy terms — A massive body that bends light passing near it. A gravitational lens can distort or focus the light of background sources of electromagnetic radiation Gravitational Potential Energy — The energy stored in a glossary of astronomy terms subject to the gravitational attraction of another body.

As the body falls, its gravitational potential energy glossary of astronomy terms and is converted into kinetic energy Gravitational Redshift — The increase in the wavelength of electromagnetic radiation that occurs when the radiation travels outward through the gravitational field of a body Gravity — The force of attraction between two bodies generated by their masses Great Attractor — A great concentration of mass toward which everything in our part of the universe apparently is being pulled Great Circle — A circle that bisects a sphere.

The celestial equator and ecliptic are examples of great circles Great Red Spot — A reddish elliptical spot about 40, km by 15, km in size in the southern hemisphere of the atmosphere of Jupiter.

Appendix:List of astronomical terms

Because its atmosphere blocks the outward passage of infrared radiation emitted by the ground and lower atmosphere, the planet cannot cool itself effectively and becomes hotter than it would be without an atmosphere Ground State — The lowest energy level glossary of astronomy terms an atom HII Region — A region of ionized hydrogen surrounding a hot star.

Ultraviolet radiation from the star keeps the gas in the HII region ionized Habitable Zone — The range of distances from a star within which liquid water can exist on the surface of an Earth-like planet Half-life — The time required for half of the atoms glossary of astronomy terms a radioactive substance to disintegrate Heliocentric — Centered on the Sun.

A body moving with a speed greater than escape velocity follows a hyperbola Ideal Gas Law — The equation of state for a low-density gas in which pressure is proportional to the product of density and temperature Igneous Rock — A rock formed by solidification of molten material Impetus — A theory of motion, developed in the fourteenth and fifteenth centuries, that motion could continue only so long as a force was at work Inclination — The tilt of the rotation axis or orbital plane of a body Index of Refraction — The ratio of the speed of light in a vacuum to the speed of light in a particular substance.

The index of refraction, which always has a value greater than 1. Luminosity class ranges from I for a supergiant to V for a dwarf main sequence star Luminosity Function — The distribution of stars or galaxies according to their luminosities.

A luminosity function is often expressed as the number of objects per unit volume of space that are brighter than a given absolute magnitude or luminosity.

Lyman A Forest — The large number glossary of astronomy terms absorption lines seen at wavelengths just longer than the wavelength of the Glossary of astronomy terms a line of hydrogen in the spectrum of a quasar. Apparent magnitude describes the brightness of a star as we see it.

Astronomical Glossary

Absolute magnitude describes the intrinsic brightness of a star Main Sequence — The region in an H-R diagram occupied by stars that are fusing hydrogen into helium in their cores. The main sequence runs from hot, luminous stars to cool, glossary of astronomy terms stars Main Sequence Lifetime — The length of time that a star spends as a main sequence star Major Axis — The axis of an ellipse that passes through both foci.

The major axis is the longest straight line that can be drawn inside an ellipse Mantle — The part of a planet lying between its crust and its core Maria — A dark, smooth region on the Moon formed by flows glossary of astronomy terms basaltic lava Mascon — A concentration of mass below the surface of the Moon that slightly alters the orbit of a spacecraft orbiting the Moon Mass — A measure of the amount of matter a body contains.

Mass is also a measure of the inertia of a body Mass Number — A measure of the mass of a nucleus given by the total number of protons and neutrons in the nucleus Mass-Luminosity Relation — The relationship between luminosity and mass for stars.

Stars of similar types are also found grouped together in specific regions of the chart, including main sequencered giantand white dwarf stars.

Hill sphere Also called the Hill glossary of astronomy terms.

Glossary of Astronomy Terms

These big words were created by scientists to explain what happens in Outer Space. That would ruin all the fun.


Rather, learn these Astronomy words one by one as you explore and learn about our Universe. Word Defination Absolute magnitude How bright a star would look if it were Absolute zero The lowest possible temperature,