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38 Cards in this Set

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  • Back
star
large, glowing balls of gas that generate hear and light through nuclear fusion in their cores
planet
(1) orbits a star, (2) is large enough for its own gravity to make it round, (3) has cleared most other objects from its path
moon
an object that orbits a planet
asteroid
a relatively small and rocky object that orbits a star
comet
a relatively small and ice-rich object that orbits a star
solar system
a star system, including a star and planets that orbit it
star system
a star and any planets and other materials that orbit it
galaxy
a great island of stars in space, containing a few hundred million to a trillion stars, all held together by gravity and orbiting a common center
cluster
a collection of galaxies bound together by gravity
supercluster
a gigantic region of space where many individual galaxies and many groups and clusters of galaxies are packed more closely together than elsewhere in the universe
universe
the sum total of all matter and energy
observable universe
the portion of the entire universe that can be seen from earth.
astronomical units
the average distance between the Earth and the Sun, about 150 million kilometers
light-year
distance light can travel in one year--9.46 trillion kilmeters
rotation
the spinning of an object on its axis
orbit (revolution)
the orbital motion of one object around another
expansion
the average distance between galaxies is increasing
age of the universe
about 14 billion years (13.7)
age of our solar system
4.6 billion years
constellation
region of the sky with well-defined borders; also stars which seem to lie close to each other on the celestial sphere and seem to make a pattern
celestial sphere
the seeming dome around the earth which the stars appear to lie on
north celestial pole
the point directly over the north pole on the celestial sphere
south celestial pole
the point directly over the south pole on the celestial sphere
celestial equator
the projection of the earth's equator on the celestial sphere
ecliptic
the path the sun follows as it appears from Earth
local sky
our half of the celestial sphere
horizon
the boundary between Earth and sky
zenith
the point directly over head
meridian
an imaginary half circle stretching from the horizon due south through the zenith, to the horizon due north
angular size
the angle an object appears to span in your field of view
angular distance
the angle that appears to separate two objects
arcminutes
60 in each degree
zodiac
the constellations along the eliptic
summer solstice
when the sun is highest in the sky (for Northern hemisphere)
winter solstice
when the sun is lowest in the sky (for Northern hemisphere)
equinox
when sunlight falls equally on both hemipheres
sidereal period
the time it takes to orbit the sun
synodic period
the time between alignments