Glossary

blackbody:
an object that is an ideal radiator when hot and a perfect absorber when cool. It absorbs radiation that falls upon it, reflecting no light: hence it appears to be black. Stars are considered blackbodies. The radiation emitted by blackbodies obey several simple laws (Wien's Law, The Stefan-Boltzmann Law).

carbon:
a chemical element occurring in nature as diamond and graphite and forming a constituent of coal, petroleum, and limestone.

cataclysmic:
a violent change or upheaval.

curvature of space:
the blending of space by a mass, as described according to Einstein's General Theory of Relativity. Black Holes bend the space around them, curving it so that the region within the black hole is cut off from the rest of the Universe. The Universe too may be curved in such a way as to make its volume finite.

degeneracy pressure:
the pressure created in a dense gas by the interaction of its electrons. Degeneracy pressure does not depend on temperature.

degenerate:
fallen from a former, higher or normal condition.

electrons:
a low-mass, negatively charged sub-atomic particle. Electrons orbit the atomic nucleus but may at times be torn free.

escape velocity:
the speed an object needs to move away from another body in order not to be pulled back by its gravitational attraction. Mathematically the escape velocity, v, is defined as ((2GM)/(R)) where M is the body's mass, R, is its radius and G is the gravitational constant.

event horizon:
the location of the surface of a black hole. An outside observer cannot see in past the event horizon.

fusion:
the union of atomic nuclei to form heavier nuclei with the release of huge quantities of energy.

gravitational redshift:
the shift in wavelength of electromagnetic radiation (light) created by a body's gravitational field as the radiation moves away from the body. Only extremely dense objects, such as white dwarfs, produce a significant redshift of their radiation.

Hawking Radiation:
radiations that black holes are hypothesized to emit as a result of quantum effects. This radiation leads to the extremely slow evaporation of black holes.

helium:
a very light nonflammable gaseous chemical element occurring in various natural gases.

hydrogen:
a gaseous colorless odorless highly flammable chemical element that is the lightest of the elements.

hydrostatic equilibrium:
the condition in which pressure and gravitational forces in a star or planet are in balance. Without such balance, bodies will either collapse or expand.

iron:
a metallic chemical element that rusts easily, is attracted by magnets, can be readily shaped, and is vital to biological process.

luminosity:
the amount of energy radiated per second by a body. For example, the wattage of a light bulb defines its luminosity. Stellar luminosity is usually measured in units of the Sun's luminosity, approximately 4X1026 watts.

nucleosynthesis:
the formation of heavy elements by such nuclear burning processes.

nucleus:
the core of an atom around which the electrons orbit. The nucleus has a positive electric charge and comprises most of an atom's mass.

pulsar:
a spinning neutron star that emits beams of radiation that happen to sweep across the Earth each time the star spins. We observe the radiation as regularly spaced pulses.

radius:
a straight line extending from the center of a circle or sphere to the circumference or surface.

silicon:
a nonmetallic chemical element that is found in nature always combined with some other substance and that is the most abundant element next to oxygen in the Earth's crust.

synchrotron radiation:
a form of nonthermal radiation emitted by charges particles spiraling at nearly the speed of light in a magnetic field. Pulsars and radio galaxies emit synchronous radiation. The radiation gets its name because it was first seen in synchrotrons, a type of atomic accelerator.

subatomic physics:
physics relating to the inside of an atom or to particles smaller than an atom.

superfluidity:
a condition in which a fluid has no friction (technically, the absence of viscosity.)

Wien's Law:
a relation between a body's temperature and the wavelength at which it emits radiation most intensely. Hotter bodies radiate more intensely at shorter wavelengths.

blackbody:	an object that is an ideal radiator when hot and a perfect absorber when cool. It absorbs radiation that falls upon it, reflecting no light: hence it appears to be black. Stars are considered blackbodies. The radiation emitted by blackbodies obey several simple laws (Wien's Law, The Stefan-Boltzmann Law).
carbon:	a chemical element occurring in nature as diamond and graphite and forming a constituent of coal, petroleum, and limestone.
cataclysmic:	a violent change or upheaval.
curvature of space:	the blending of space by a mass, as described according to Einstein's General Theory of Relativity. Black Holes bend the space around them, curving it so that the region within the black hole is cut off from the rest of the Universe. The Universe too may be curved in such a way as to make its volume finite.
degeneracy pressure:	the pressure created in a dense gas by the interaction of its electrons. Degeneracy pressure does not depend on temperature.
degenerate:	fallen from a former, higher or normal condition.
electrons:	a low-mass, negatively charged sub-atomic particle. Electrons orbit the atomic nucleus but may at times be torn free.
escape velocity:	the speed an object needs to move away from another body in order not to be pulled back by its gravitational attraction. Mathematically the escape velocity, v, is defined as ((2GM)/(R)) where M is the body's mass, R, is its radius and G is the gravitational constant.
event horizon:	the location of the surface of a black hole. An outside observer cannot see in past the event horizon.
fusion:	the union of atomic nuclei to form heavier nuclei with the release of huge quantities of energy.
gravitational redshift:	the shift in wavelength of electromagnetic radiation (light) created by a body's gravitational field as the radiation moves away from the body. Only extremely dense objects, such as white dwarfs, produce a significant redshift of their radiation.
Hawking Radiation:	radiations that black holes are hypothesized to emit as a result of quantum effects. This radiation leads to the extremely slow evaporation of black holes.
helium:	a very light nonflammable gaseous chemical element occurring in various natural gases.
hydrogen:	a gaseous colorless odorless highly flammable chemical element that is the lightest of the elements.
hydrostatic equilibrium:	the condition in which pressure and gravitational forces in a star or planet are in balance. Without such balance, bodies will either collapse or expand.
iron:	a metallic chemical element that rusts easily, is attracted by magnets, can be readily shaped, and is vital to biological process.
luminosity:	the amount of energy radiated per second by a body. For example, the wattage of a light bulb defines its luminosity. Stellar luminosity is usually measured in units of the Sun's luminosity, approximately 4X1026 watts.
nucleosynthesis:	the formation of heavy elements by such nuclear burning processes.
nucleus:	the core of an atom around which the electrons orbit. The nucleus has a positive electric charge and comprises most of an atom's mass.
pulsar:	a spinning neutron star that emits beams of radiation that happen to sweep across the Earth each time the star spins. We observe the radiation as regularly spaced pulses.
radius:	a straight line extending from the center of a circle or sphere to the circumference or surface.
silicon:	a nonmetallic chemical element that is found in nature always combined with some other substance and that is the most abundant element next to oxygen in the Earth's crust.
synchrotron radiation:	a form of nonthermal radiation emitted by charges particles spiraling at nearly the speed of light in a magnetic field. Pulsars and radio galaxies emit synchronous radiation. The radiation gets its name because it was first seen in synchrotrons, a type of atomic accelerator.
subatomic physics:	physics relating to the inside of an atom or to particles smaller than an atom.
superfluidity:	a condition in which a fluid has no friction (technically, the absence of viscosity.)
Wien's Law:	a relation between a body's temperature and the wavelength at which it emits radiation most intensely. Hotter bodies radiate more intensely at shorter wavelengths.