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B

Bar
A unit of measure of atmospheric pressure. One bar is equal to 0.987 atmospheres, 1.02 kg/cm2, 100 kilopascal, and 14.5 lbs/square inch.

Big Bang
The theory that suggests that the universe was formed from a single point in space during a cataclysmic explosion about 18 billion years ago. The force of the explosion accounts for the current expansion of the universe.

Binary
A system of two stars that revolve around a common centre of gravity.

Black Hole
The collapsed core of a massive star. Stars that are very massive will collapse under their own gravity when their fuel is exhausted. The collapse continues until all matter is crushed out of existence into what is known as a singularity. The gravitational pull is so strong that not even light can escape.

Blueshift
A shift in the lines of an object's spectrum toward the blue end. Blueshift indicates that an object is moving toward the observer. The larger the blueshift, the faster the object is moving.

Bolide
A term used to describe an exceptionally bright meteor. Bolides typically will produce a sonic boom.

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