17: Analyzing Starlight Flashcards
a measure of the amount of light received by Earth from a star or other object - that is, how bright an object appears in the sky, as contrasted with its luminosity
apparent brightness
an object intermediate in size between a planet and a star, from about 1/100 of the mass of the Sun to 0.075 the mass of the Sun - capable of deuterium fusion, but not hydrogen fusion
brown dwarf
difference between the magnitudes of a star or other object measured in light of two different spectral regions - for example, blue minus visual (B–V) magnitudes
color index
a star of exaggerated size with a large, extended photosphere
giant
the total amount of energy at all wavelengths that a star emits per second
luminosity
an older system, created by Hipparchus, of measuring the amount of light we receive from a star or other luminous object - the larger the ___, the fainter an object appears
magnitude
the angular change per year in the direction of a star as seen from the Sun
proper motion
motion toward or away from the observer - the component of relative velocity that lies in the line of sight
radial velocity
the total (three-dimensional) speed and direction with which an object is moving through space relative to the Sun
space velocity
the classification of stars according to their temperatures using the characteristics of their spectra - the types are O, B, A, F, G, K, and M with L, T, and Y added recently for cooler star-like objects that recent survey have revealed
spectral class
process of measuring the apparent brightness of stars
photometry
hydrogen lines in the visible part of the electromagnetic spectrum
Balmer lines
term for all elements that are heavier than hydrogen and helium
metals
fraction of a star’s mass that is composed of elements heavier than hydrogen and helium
metallicity
spectral lines becoming wider if a star is rotating rapidly due to greater spread of Doppler shifts - degree of wideness tells us speed at which the star is rotating
line broadening
