Astronomy Ch 6
Terms
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- absolute zero
- The theoretical lowest possible temperature at which a material contains no extractable heat energy. Zero on the Kelvin temperature scale. (p. 108)
- absorption line
- A dark line in a spectrum. Produced by the absence of photons absorbed by atoms or molecules. (p. 110)
- absorption spectrum (dark-line spectrum)
- A spectrum that contains absorption lines. (p. 110)
- Balmer series
- A series of spectral lines produced by hydrogen in the near-ultraviolet and visible parts of the spectrum. The three longest-wavelength Balmer lines are visible to the human eye. (p. 111)
- blue shift
- A Doppler shift toward shorter wavelengths caused by a velocity of approach. (p. 105)
- bright-line spectrum
- See emission spectrum.
- continuous spectrum
- A spectrum in which there are no absorption or emission lines. (p. 110)
- Coulomb force
- The electrostatic force of repulsion or attraction between charged bodies. (p. 105)
- dark-line spectrum
- See absorption spectrum.
- Doppler effect
- The change in the wavelength of radiation due to relative radial motion of source and observer. (p. 115)
- electron
- Low-mass atomic particle carrying a negative charge. (p. 104)
- emission line
- A bright line in a spectrum caused by the emission of photons from atoms. (p. 110)
- emission spectrum (bright-line spectrum)
- A spectrum containing emission lines. (p. 110)
- energy level
- One of a number of states an electron may occupy in an atom, depending on its binding energy. (p. 106)
- excited atom
- An atom in which an electron has moved from a lower to a higher energy level. (p. 106)
- ground state
- The lowest permitted electron energy level in an atom. (p. 107)
- heat
- Energy stored in a material as agitation among its particles. (p. 107)
- ion
- An atom that has lost or gained one or more electrons. (p. 105)
- ionization
- The process in which atoms lose or gain electrons. (p. 105)
- isotopes
- Atoms that have the same number of protons but a different number of neutrons. (p. 105)
- joule (J)
- A unit of energy equivalent to a force of 1 newton acting over a distance of 1 m. One joule per second equals 1 watt of power. (p. 109)
- Kelvin temperature scale
- A temperature scale using Celsius degrees and based on zero at absolute zero. (p. 107)
- Kirchhoff 's laws
- A set of laws that describe the absorption and emission of light by matter. (p. 110)
- L dwarf
- A main-sequence star cooler than an M star. (p. 114)
- Lyman series
- Spectral lines in the ultraviolet spectrum of hydrogen produced by transitions whose lowest energy level is the ground state. (p. 111)
- molecule
- Two or more atoms bonded together. (p. 105)
- neutron
- An atomic particle with no charge and about the same mass as a proton. (p. 104)
- nucleus (of an atom)
- The central core of an atom containing protons and neutrons. Carries a net positive charge. (p. 104)
- Paschen series
- Spectral lines in the infrared spectrum of hydrogen produced by transitions whose lowest energy level is the third. (p. 111)
- permitted orbit
- One of the energy levels in an atom that an electron may occupy. (p. 106)
- proton
- A positively charged atomic particle contained in the nucleus of an atom. The nucleus of a hydrogen atom. (p. 104)
- quantum mechanics
- The study of the behavior of atoms and atomic particles. (p. 105)
- radial velocity (Vr)
- That component of an object's velocity directed away from or toward Earth. (p. 116)
- redshift
- A Doppler shift toward longer wavelengths caused by a velocity of recession. (p. 115)
- spectral class or type
- A star's position in the temperature classification system O, B, A, F, G, K, M. Based on the appearance of the star's spectrum. (p. 113)
- spectral line
- A line in a spectrum at a specific wavelength produced by the absorption or emission of light by certain atoms. (p. 104)
- spectral sequence
- The arrangement of spectral classes (O, B, A, F, G, K, M) ranging from hot to cool. (p. 113)
- T dwarf
- A very cool, low-mass star or brown dwarf located below the L stars on the main sequence. (p. 114)
- temperature
- A measure of the agitation among the atoms and molecules of a material. The intensity of heat. (p. 107)
- transition
- The movement of an electron from one atomic energy level to another. (p. 111)
- wavelength of maximum intensity
- The wavelength at which a perfect radiator emits the maximum amount of energy. Depends only on the object's temperature. (p. 108)