Mathematics and Society - OS X Lion Server

ASTRONOMY GLOSSARY cir-mercircumpolar star. A star near acelestial pole which is visible fromone position on earth throughout theyear. The star is always above thehorizon as viewed from that position.concentric circles. Circles in a planeall having the same center.conic seotion. The curve of intersectionof a hollow cone and a plane.Circles, ellipses, parabolas, hyperbolasare conic sections.oonstellation. A group of stars towhich a name has been assigned.A circle on the celestialpasses through both ce1esoresoentmoon. A phase of the moon inwhich the lighted portion is less thanhalf of a full moon.deolination. The angular distance,measured in degrees, of an objectnorth or south of the celestialequator.diameter. A line segment passingthrough the center of a circle whoseendpoints are on the circle.ecleptio. The apparent path of thesun among the stars.ellipse. The curve of intersectionformed when a plane, not parallel tothe base, cuts completely through ahollow cone.anellipseequation of time. The difference beasundial and timetween time read onread on a clock.equatorial system. A method for locatingobjects on the celestial sphere.equinox. One of the intersections ofthe ecliptic and the celestial equator.gibbous moon. A phase of the moon inwhich the lighted portion is more thanhalf but not completely all of a fullmoon.gnomon. The upright portion of a sundialthat casts a shadow.hemisphere.hour oircle.sphere thattia1 poles.Half of a sphere.hyperbola. The curves of intersectionformed when a plane cuts through bothnappes of a hollow cone.hyperbolalatitude. A number in degrees thatgives a point's angular distance northor south from the equator. Latitudeis used in giving locations on theearth.light year. The distance light travelsin one year; about 9.5 x 10 12 kilometres.longitude. A number in degrees thatgives a point's angular distance eastor west from the prime meridian (ameridian passing through Greenwich,England). Longitude is used in givinglocations on the earth.magnetic deolination.ference between trueic north.The angular difnorthand magnet-meridian (celestial). A circle in thesky that passes directly overhead andthrough the north and south celestialpoles.122