Glossary – B


any light detected that is not coming from the source.
in the beginning of the universe, particles and anti-particles were created in equal numbers. Since particles and their anti-particles annihilate each other, some mechanism must have caused more particles than anti-particles to remain in the Universe. The creation of more ordinary matter than anti-matter is known as baryogenesis.
baryons are particles made of three quarks. While three quarks can be combined to make many different types of particles, the most common baryons occurring naturally in the Universe are protons and neutrons.
Baryonic Matter
matter that is built out of groupings of three quarks, called baryons. The most common and stable baryons are the proton and neutron.
Big Bang
this famous theory suggests that the universe was not always as it is today, and that at one point everything was compressed down into an extremely small point of unimaginable heat and density. Then, in the most violent and energetic event ever to occur, the universe began to expand and evolve into its present state. This rapid expansion was aptly named the “big bang.” The term, big bang, was coined by an English astronomer, Sir Fred Hoyle, to mock the theory. He was a proponent of the steady state theory, which suggests that the universe looks, on the whole, the same at all times and places. In order to explain Hubble’s observations, this theory was modified to include the spontaneous creation of matter, which would keep the density of the universe at a constant value. The steady state theory had too many holes in it to be viable and was eventually dropped. However, the moniker, big bang, to describe the hot, dense beginning of the universe stuck and is now a part of astronomical vocabulary.
the word binary simply means there are two of something. When applied to a star system, it means that instead of having a single star, two stars orbit their common center of gravity.
Binary System
this is a system of two stars, very close to each other, that orbit around their common center of mass. They are actually quite common.
Binary Energy
the energy it takes to break apart the nucleus of an atom into its constituent parts. Since energy is conserved, this amount of energy is also released when those parts fuse together to form a heavy nucleus. The graph below is called the curve of binding energy. It is a plot of the binding energy of all atomic nuclei (vertical axis) vs. their mass (horizontal axis). Notice that the curve rises steeply to a peak value, then drops slowly as mass increases. The peak of the curve is at Fe56 (Iron with mass 56). Stars produce energy by combining light elements, to the left of the iron peak, into heavier elements. This process is called nuclear fusion. The difference in binding energy between the initial and final nuclei is released as heat. Fusion beyond the iron peak does not release energy. Instead it requires that energy be input. That is why stars are not able to continue stable nuclear fusion of elements heavier than iron. Those elements are produced by different processes, typically accompanying supernova explosions.
Black Hole
an object so small and dense that inside its event horizon, the escape velocity is faster than the speed of light. In an active galaxy, the central black hole may have millions or even billions of times the Sun’s mass. One type of black hole is formed from the collapsed core of a star after it goes supernova. Its gravity is so intense not even light can escape from inside the event horizon.
a quasar that one is viewing directly down the jet axis.
Bremsstrahlung Radiation
commonly referred to as braking radiation, this is a process where X-rays are produced as electrons decelerate in high-speed encounters with protons and nuclei.
the amount of light an observer sees from an object like a star. Brightness is measured in watts per distance squared (W/d2).
Brown Dwarf
cosmic objects that are too small to be stars and too large to be planets. They have the same composition as stars but because of their low mass are unable to sustain nuclear fusion (if they ever manage to get fusion started) at their cores.