19: Celestial Distances Flashcards
a star that belongs to a class of yellow supergiant pulsating stars - vary periodically in brightness, and the relationship between their periods and luminosities is useful in deriving distances to them
cepheid
a graph that displays the time variation of the light from a variable or eclipsing binary star or, more generally, from any other object whose radiation output changes with time
light curve
a classification of a star according to its luminosity within a given spectral class - our Sun, a G2V star, is V, for example
luminosity class
an apparent displacement of a nearby star that results from the motion of Earth around the Sun (defined as 1/2 the total change in direction, measured in arcseconds)
parallax
a unit of distance in astronomy, equal to 3.26 light-years - at a distance of 1 ___, a star has a parallax of 1 arcsecond
parsec
the longer the period of a variable star (the time it takes to vary), the greater its luminosity
period-luminosity relation
a variable star that pulsates in size and luminosity - periodically changes diameter
pulsating variable star
one of a class of giant pulsating stars with periods shorter than 1 day, useful for finding distances
RR Lyrae
the amount of space light covers in one second - 299,792,458 meters - 500 in one AU
light-second
a type of radio wave that can bounce off solid objects - key to modern determination of solar system dimensions
radar
use of two different vantage points some distance apart to achieve a sense of how far objects are (like depth perception in our eyes)
triangulation
distance between two observing stations in triangulation
baseline
spacecraft launched in 1989 that measured distances for thousands of stars out to about 300 light-years with an accuracy of 10 to 20% - successor Gaia was launched in 2013
Hipparcos
chain of methods to determine distances of cosmic objects, each one building on another
cosmic distance ladder
