Subspace ][ A terminology of the boundary between what a mortal can imagine at maximum about the Immortal Lord of the Dominions.

Astronomical Unit (AU) ][ A unit of distance equals to the average distance between the Earth and the Sun (about 150 Million kilometers or 93 Million miles).

Big Bang ][ The theoretical initial explosion that began the expansion of the universe.

Black Hole ][ An object whose escape velocity exceeds the speed of light.

Dark Energy ][ An exotic form of energy whose negative pressure currently accelerates the expansion of the Universe.

Dark Matter ][ Matter that can be detected only by its gravitational interactions; it appears to be quite abundant throughout the Universe.

Escape Velocity ][ The minimum velocity an object must achieve to escape the gravitational attraction of another object, such as a planet or a star.

Event Horizon ][ The surface of the sphere around a black hole from within which nothing can escape. Its radius is the Schwarzchild Radius.

Inertia ][ The tendency of an object to resist a change in its motion. Mass is the measurement of an inertia of an object.

Light Year ][ The distance light travels in one year (about 9.46 Trillion kilometers).

Light Second, -Minute, -Hour, -Day ][ The distance light travels in one second is a light second (about 300,000 kilometers or 186,000 miles). A light minute is equals to 60 light seconds, that is how, light hour and light can be calculated.

Mass ][ Mass is the measurement of an inertia of an object.

Main Sequence ][ The part of the H.R. diagram containing the great majority of stars; it forms a diagonal line across the diagram.

Magnetic Field ][ A magnetic field exists in a region of space if magnetic forces can be detected in that region.

Magnification ][ The ration of the angular size of an object when it is seen through the instrument to its angular size when seen with the naked eye. 1x is the general naked eye power. 10x is the 10 times magnification as compared to the naked eye.

Orbit ][ Constant angular falling of an object. Parent object (such as Earth) curves out before the curve of the path of the object (such as Moons or artificial satellite) thus never hitting the parent object.

Quasar ][ The Quasi Stellar Radio Source. A small, intense celestial source of radiation with a very large redshift i.e., an extremely bright galaxy.

Radiation ][ The transfer of energy by electromagnetic waves.

Supergiant ][ The evolutionary stage of a massive star after it leaves the main sequence; at this stage, the star has a very great luminosity and size (100 to 1,000 times the Sun's diameter).

Spectrum ][ The order of colors or wavelengths produced when the light is dispersed.

Spectrometer ][ An instrument that measures the wavelengths present in electromagnetic radiation.

Spectrograph ][ A spectrometer that produces an image of the spectrum.

Star ][ A self-luminous celestial body.

Stellar Parallax ][ The apparent annual shifting of nearby stars with respect to background stars, measures as the angle of shift.

Supernova ][ The catastrophic explosion of a star, during which the star becomes billions of times brighter.

Transit ][ The passage of a planet in front of its star.

Wavelength ][ The distance from a point on a wave, such as the crest, to the next corresponding point, such as the next crest.

Weight ][ The gravitational force between an object and the planetary/stellar body where the object is located.

White Dwarf ][ The burnt-out relic of a low mass star. (Typical diameter is 0.01 that of the Sun about the size of Earth).

Zenith ][ The point in the sky located directly overhead.

Zodiac ][ The band that lies 9 degrees on either side of the ecliptic on the celestial sphere.