Chapter 2 Flashcards
(59 cards)
rotation
the spin of an object around an internal axis
horizon
the horizontal line defining the lower edge of the sky
altitude
the angular distance from a point in the sky to a point on the horizon directly below it
latitude
a measure of location specifying north-south position on earth running from 0° at the equator to 90° north (north pole) and 90° south (south pole)
longitude
a measure of location specifying east-west position on earth running
angular size
angular distance measured on a sphere (such as earth or the celestial sphere) in degrees, arcminutes, and arcseconds
celestial sphere
an imaginary transparent sphere surrounding earth, on which positions of stars, planets, and other celestial bodies are projected from extensions of earths coordinate system.
celestial equator
the extension of earth’s equator onto the celestial sphere
Polaris
the star that is found very near earths celestial north pole (hence called the north star) and around which the sky of the northern hemisphere appears to turn
north celestial pole
the extension of earths north pole onto the celestial sphere
south celestial pole
the extension of earths south pole onto the celestial sphere
zenith
the point on the sky directly overhead from an observer
meridian
a circular arc crossing the celestial sphere and passing through the local zenith and celestial pole
declination
the position of an object on the celestial sphere, measured similarly to latitude on earth
sidereal day
the time taken by earth to rotate in its axis relative to the stars
solar day
the time between successive crossings of the same meridian in the sky by the sun
small-angle formula
a mathematical relation between the angular size of an object as measured on the sky and the objects distance and physical size
arcminute
a measure of angular size. there are 60 arcminutes in a degree
analemma
the figure eight pattern formed by charting the daily position of the sun at noon over the course of the year
summer solstice
the day with the most hours of sunlight, when the sun appears highest in the sky
winter solstice
the day with the fewest hours of daylight when the sun appears lowest in the sky
equinox
a day when the hours of daylight and darkness are equal. the autumn equinox occurs on approximately september 21, spring equinox approximately march 21
orbit
the cyclical path in space that one object makes around another object
ellipse
a geometric form in the space of an oval or circle, in which the sum of the distances from two points (foci) to every point in the ellipse is constant.
