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Astronomy 4-5.4

electromagnetic radiation changing electric and magnetic fields that travel through space and transfer energy from one place to another; examples are light and radio waves
wavelength the distance between successive peaks or troughs of a wave, usually represented by a lowercase Greek lambda
nanometer a unit of distance equaling one-billionth of a meter, commonly used to measure the wavelength of light
angstrom a unit of distance commonly used to measure the wavelength of light
ultraviolet the portion of the electromagnetic spectrum with wavelengths shorter than violet light, between visible light and X-rays
x-rays electromagnetic waves with wavelengths shorter than ultraviolet light
gamma rays the shortest-wavelength electromagnetic waves
photon a quantum of electromagnetic energy that carries an amount of energy that depends inversely on its wavelength
atmospheric window wavelength region in which our atmosphere is transparent - at visual, radio, and some infrared wavelengths
refracting telescope a telescope that forms images by bending light with a lens
reflecting telescope a telescope that forms images by reflecting light with a mirror
primary lens in a refracting telescope, the largest lens
primary mirror in a reflecting telescope, the largest mirror
eyepiece a short-focal-length lens used to enlarge the image in a telescope. the lens nearest the eye
focal length of a lens or mirror is the distance from that lens or mirror to the point where it focuses parallel rays of light
chromatic aberration a distortion found in refracting telescopes because lenses focus different colors at slightly different distances. images are consequently surrounded by color fringes
optical telescope telescope that gathers visible light
radio telescope telescope that gathers radio radiation
light-gathering power the ability of a telescope to collect light; proportional to the area of the telescope's primary lens or mirror
resolving power the ability of a telescope to reveal fine detail. depends on the diameter of the telescope's primary lens or mirror
diffraction fringe blurred fringe surrounding any image, caused by the wave properties of light. because of this, no image detail smaller than the fringe can be seen
interferometer separated telescopes combined to produce a virtual telescope with the resolution of a much larger-diameter telescope
seeing atmospheric conditions on a given night. when the atmosphere is unsteady, producing blurred images, the seeing is said to be poor
adaptive optics a computer-controlled optical system in an astronomical telescope used to partially correct for seeing
magnifying power the ability of a telescope to make an image larger
light pollution the illumination of the night sky by waste light from cities and outdoor lighting, which prevents the observation of faint objects
sidereal tracking the continuous movement of a telescope to keep it pointed at a star as Earth rotates
secondary mirror can reflect the light through a hole in the primary mirror
cassegrain focus focal arrangement that may be the most common form of astronomical telescope
newtonian focus arrangement that Isaac Newton used in his first reflecting telescope, inconvenient for large telescopes
schmidt-cassegrain focus a thin correcting plate improves the image but is too slightly curved to introduce serious chromatic aberration
photographic plate the first image-recording device used with telescopes; it records the brightness of objects ,but with only moderate precision
photometer sensitive astronomical instrument that measures the brightness of individual objects very precisely
charge-coupled device an electronic device consisting of a large array of light-sensitive elements used to record very faint images
array detector device for collecting and recording electromagnetic radiation using multiple individual detectors arrayed on the surface of a chip; for example, a CCD electronic camera
digitized converted to numerical data that can be read directly into a computer memory for later analysis
false-color image a representation of graphical data with added or enhanced color to reveal detail
spectrograph a device that separates light by wavelengths to produce a spectrum
spectrum a range of electromagnetic radiation spread into its component wavelengths (colors); for example, a rainbow
grating a piece of material in which numerous microscopic parallel lines are scribed. light encountering a grating is dispersed to form a spectrum
spectral line a feature in a spectrum at a specific wavelength produced by the absorption or emission of light by certain atoms
transits of venus rare occasions when venus can be seen as a tiny dot directly between Earth and the sun
density mass per volume
atom the smallest unit of a chemical element, consisting of a nucleus containing protons and neutrons plus a surrounding cloud of electrons
nucleus the central core of an atom containing protons and neutrons that carries a net positive charge
proton a positively charged atomic particle contained in the nucleus of a hydrogen atom
neutron an atomic particle with no charge and about the same mass as a proton
isotope a form of an atom with the same number of protons but a different number of neutrons
electron low-mass atomic particle carrying a negative charge
molecule two or more atoms bonded together
heat energy contained in matter in the form of agitation of its particles
temperature a measure of the agitation among the atoms and molecules of a material
Kelvin temperature a temperature scale using Celsius degrees and based on zero being equal to absolute zero
absolute zero he theoretical lowest possible temperature at which a material contains no extractable heat energy. zero on the Kelvin temperature scale
blackbody radiation spectrum of radiation emitted by an ideal perfect radiator. the spectrum is continuous and its characteristics depend only on the object's temperature
wavelength of maximum intensity the wavelength at which the radiation emitted by a glowing object is most intense. depends inversely on the object's temperature
wien's law the hotter a glowing object is, the shorter will be its wavelength of maximum intensity, inversely proportional to its temperature
stefan-boltzmann law hotter objects emit more energy than cooler objects of the same size, in proportion to the fourth power of temperature
photosphere the bright visible surface of the sun
sunspot relatively dark spot on the sun that contains intense magnetic fields
granulation the fine structure of bright grains with dark edges covering the sun's surface
convection circulation in a fluid driven by heat. hot material rises and cool material sinks
coulomb force the electrostatic force of repulsion or attraction between charged bodies
ion an atom that has lost or gained one or more electrons
ionization the process in which atoms lose or gain electrons
binding energy the energy needed to pull an electron away from its atom
quantum mechanics the study of behavior of atoms and atomic particles
permitted orbit one of the unique orbits that an electron may occupy in an atom
energy level one of a number of states an electron may occupy in an atom, depending on its binding energy
excited atom an atom in which an electron has moved from a lower to a higher energy level
ground state the lowest permitted electron energy level in an atom
quantum jump jumps of electrons from one orbit or energy state to another
doppler effect the change in the wavelength of radiation due to relative radial motion of source and observer
blueshift a doppler shift toward shorter wavelengths caused by a velocity of approach
redshift a doppler shift toward longer wavelengths caused by a velocity of recession
radial velocity that component of an object's velocity directed away from or toward the observer
Created by: pace_sauce