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Star
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A giant ball of hot, glowing gases (usually hydrogen & helium)
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Nuclear Fusion
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A process where the nuclei of atoms join and emit energy as light, heat and other electromagnetic radiation.
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Apparent Magnitude Scale
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A measurement of a celestial object's brightness when viewed from Earth (the more positive the number the dimmer the star).
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Absolute Magnitude Scale
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A measurement of a celestial object's brightness if viewed from the same distance; a measure of a celestial object's actual brightness or luminosity.
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Hertzsprung-Russel Diagram (HR)
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A graph that plots a star's temperature on the x-axis and absolute magnitude on the y-axis.
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Main Sequence
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A diagonal band most stars fall into when plotted on the HR Diagram..
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Speed of Light
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Light travels at 300,000 km/s.
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Light-Year
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The distance that light travels in a year (9,500,000,000,000 km).
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Parsec
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Approx. 3.26 light-years.
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Parallax
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The effect where an object appears to move when viewed from two different positions.
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Galaxy
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A group of stars held together by their gravity, galaxies form three shapes, elliptical, spiral and irregular.
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Constellation
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An imaginary picture in the night sky made up of stars.
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Nebula(e)
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A cloud of gas and dust held together by the gravity of the hydrogen atoms within it.
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Protostar
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When the center of a nebula heats up and pressure increases.
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Hydrostatic Equilibrium
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The balance of the forces of a star's gravity and energy output.
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Red giant
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Hydrogen decreases, gravity is stronger than energy output, a new type of nuclear fusion begins, releasing more energy, reaching a new hydrostatic equilibrium and cooling to red.
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Planetary Nebula
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Helium supply decreases in a red giant and the outer region fades to a shell.
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White Dwarf
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The core of a planetary nebula continues nuclear fusion, increases energy rate and temperature to get a small, white hot star.
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Black Dwarf
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The result of a white dwarf cooling and fading away.
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Red Supergiant
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A continuation of the red giant until iron is formed, resulting in a much larger, red star.
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Supernova
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The event where a red supergiant runs out of energy and collapses, resulting in a large explosive death.
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Neutron Star
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The aftermath of a supernova with a mass of less than 3 solar masses, an incredibly dense star with a diameter of only tens of kilometers.
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Black Hole
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The result of a supernova with a mass greater than 3 solar masses, a region of space with an extraordinary gravitational pull and density that even light cannot escape.
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Absorbtion Spectrum
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A spectrum with lines missing from the pattern due to elements of the star absorbing their light wavelengths, therefore removing them from the spectrum.
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Emission Spectrum
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The pattern of wavelengths (or frequencies) that appear as coloured lines on a spectrascope; the light wavelengths that are emitted from certain gases when they return to a stable state.
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Doppler Effect
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The effect that occurs when an object is moving slower than the speed of sound; waves in front of the object compress while waves behind disperse.
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Red Shift
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An increase in wavelength of radiation emitted by a celestial body which shifts the absorption spectra in the red direction of the spectrum, indicating that the object is moving away from the Earth.
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Blue Shift
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A decrease in wavelength of radiation emitted by a celestial bosy which shifts the absorption spectra in the red direction of the spectrum, indicating that the object is moving towards the Earth.
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Huibble's Law
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The further the galaxy, the higher the tendency to have a more red-shifted spectra; the ffurther the galaxy, the faster it was moving away.
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Big Bang Theory
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the theory that the universe began from a hot dense state which has continued to expand and will continue to do so.
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Singularity
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A single, dense, hot point.
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Cosmic Microwave Background Radiation
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A form of electromagnetic radiation in the microwave spectrum left over from the formation of the Universe; evidence of the Bug Bang theory.
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Cheatography n. The art of mapping complex subjects into clear, instantly navigable reference guides.
