Big Bang: The event in which the universe was born. The origin of space, time and matter.
Binary Star: Two stars that revolve around each other under their mutual gravitational attraction.
Black Hole: A compact region of space within which gravity is so powerful no material object, light or any other kind of radiation can escape.
Blue Shift: The displacement of spectral lines to shorter wavelengths that occurs when a light source is approaching an observer.
Brown-Dwarf Star: A body that forms in the same way as a star but contains too little mass to become hot enough in order to ignite nuclear-fusion reactions.