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79 Cards in this Set

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angular diameter
arc angle across an object
annular eclipse
an eclipse of the sun in which the moon is too distant to cover the sun completely, so a ring of sunlight is seen around the moon
arc angle
measurement of the angle between two objects or two parts of the same object
celestial equator
a great circle on the celestial sphere 90° from the celestial poles
celestial poles
points about which the celestial sphere appears to rotate
celestial sphere
a hypothetical sphere of very large radius centered on the observer; the apparent sphere of the night sky
circumpolar star
all the stars that never set at a given latitude; all the stars between Polaris and the northern horizon
constellation
any of the 88 contiguous regions that cover the entire celestial sphere
declination
the coordinate on the celestial sphere exactly analogous to latitude on earth; measured north and south of the celestial equator
degree
a unit of angular measurement
diurnal motion
cyclic motion with a one-day period
eclipse path
the track of the tip of the moon's shadow along the earth's surface during a total or annular solar eclipse
ecliptic
the annual path of the sun on the celestial sphere; the plane of the earth's orbit around the sun
equinox
either of the two days of the year when the sun crosses the celestial equator and is therefore directly over the earth's equator
gravitation
tendency of all matter to attract all other matter
line of nodes
the line along which the plane of the moon's orbit intersects the plane of the ecliptic
lunar eclipse
an eclipse during which the earth blocks light that would have struck the moon
lunar phase
names given to the apparent shapes of the moon as seen from the earth
north celestial pole
the location on the celestial sphere directly above the earth's northern rotation pole
partial eclipse
a lunar or solar eclipse in which the eclipsed object does not appear completely covered
penumbra
the portion of a shadow in which only part of the light source is covered by the shadow making body
penumbral eclipse
a lunar eclipse in which the moon passes only through the earth's penumbra
precession
slow, conical motion of the earth's axis of rotation caused by the graviational pull of the moon and sun on the earth's equatorial bulge
precession of the equinoxes
the slow, westward motion of the equinoxes along the ecliptic because of earths precession
revolution
the orbit of one body around another
right ascension
the celestial coordinate analogous to longitude on earth and measured around the celestial equator from the vernal equinox
rotation
the spinning of a body about an axis passing through it
sidereal month
the period of the moon's revolution about the earth measured with respect to the moon's location among the stars
sideral period
the orbital period of one object about another measured with respect to the stars
solar corona
the sun's outer atmosphere
solar day
from noontime to the next noontime; for earth 24 hours
solar eclipse
an eclipse during which the moon blocks the sun
south celestial pole
the location on the celestial sphere directly above the earth's south rotation pole
summer solstice
the point on the ecliptic where the sun is farthest north of the celestial equator
synodic month
the period of revolution of the moon with respect to the sun; the length of one cycle of lunar phases
terminator
the line dividing day and night on the surface of the any body orbiting the sun; the line of sunset or sunrise
total eclipse
sun is completely hidden by the moon
umbra
the central, completely dark portion of a shadow
vernal equinox
point on the ecliptic where sun crosses the celestial equator from south to north; beginning of spring
winter solstice
sun is farthest south from equator
zenith
the point on the celestial sphere directly overhead
geocentric
belief that earth is at center of universe
cosmology
theory of overall structure and evolution of universe
direct motion
gradual, eastward motion of a planet against the background of stars as seen from earth
retrograde motion
the occassional backward (westward) apparent motion of a planet against the background stars as seen from earth (illusion)
heliocentric
sun centered
configurations
a particular geometric arrangement of the earth, a planet, and the sun
inferiour conjunction
the configuration when mercury or venus is directly between the sun and the earth
superiour conjunction
the configuration when a planet is behind the sun as seen from earth
elongation
the angle between a planet and the sun as seen from earth
parallax
the variation in angle that occurs when viewing a nearby object from different places
focus
the two points inside an ellipse
major axis
longest diameter across and ellipse
semimajor axis
half of the longest dimension of an ellipse
orbital eccentricity
the shape of a planet's orbit around the sun
perihelion
planet is nearest the sun
aphelion
planet is farthest from sun
law of equal areas
keplers second law each planet's speed decreases as it moves from perihelion to aphelion
astronomical unit
the average distance between the earth and sun
galilean moons
four moons near jupiter
acceleration
rate at which velocity changes with time
mass
total number of particles it contains
weight
force with which you push down on a scale due to gravity...
conservation of angular momentum
total amount of angular momentum in an isolated system remains constant
angular momentum
measurement of how much energy is stored in an object due to its rotation and revolution
solar system
one star, the sun, and everything that orbits it
solar nebula
the cloud of gas and dust from which the sun and the rest of the solar system formed
protosun
the sun prior to the time when hydrogen fusion began in its core
protoplanetary disks (proplyd)
a disk of material encircling a protostar or a newborn star
planetessimals
primordial asteriodlike object from which planets accreted
protoplanets
the embryonic stage of a planet when it is growing because of collisions with planetessimals
accretion
the gradual accumulation of matter by an astronomical body
orbital inclinations
tilt or angle of an objects orbital plane around the sun compared to the ecliptic
craters
circular depression
asteroids
any rocky object larger then a few hundred meters in diameter
terrestrial planets
any of the planets mercury venus earth or mars; composition and density similar to earth
albedo
fraction of sunlight that a planet, asteriod, or satellite scatters directly back into space
extrasolar planets
planets outside the solar system
radial motion
motion toward or away from us