A unit of distance used by astronomers. It is equivalent to 3.26 light years, or 19.2 trillion miles. A kiloparsec is 1,000 parsecs and a megaparsec is one million parsecs. A halo of gas and dust ejected by low mass stars near the end of their evolution. The nebula ultimately disperses back into the interstellar gas, enriching this gas with material from the star.
Many astronomers believe quasars are a more energetic version of nearby active galaxies.
The process whereby ionized atoms capture free electrons, thus reducing their state of ionization. The opposite of ionization. This term can have different meanings depending on context. For example, at light wavelengths of 1000 Angstroms and a resolution of 30,000, FUSE can observe details in a spectrum as small as 0.033 Angstroms. An instrument that separates radiation into a spectrum and records the spectrum in one way or another for later analysis.