Active Galaxy

A galaxy which releases large amounts of energy from its centre, the active galactic nucleus. The central engine of an active galaxy probably is a supermassive black hole. Seyfert galaxies, quasars and blazars are active galaxies.

Optics

Elements (glasses, mirror, telescope, ...) used to see or visualise something.

Stop Codon

Any of three mRNA sequences (UGA, UAG, UAA) that do not code for an amino acid and thus signal the end of protein synthesis.