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38 Cards in this Set
- Front
- Back
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star
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large, glowing balls of gas that generate hear and light through nuclear fusion in their cores
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planet
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(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
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moon
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an object that orbits a planet
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asteroid
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a relatively small and rocky object that orbits a star
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comet
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a relatively small and ice-rich object that orbits a star
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solar system
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a star system, including a star and planets that orbit it
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star system
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a star and any planets and other materials that orbit it
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galaxy
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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
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cluster
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a collection of galaxies bound together by gravity
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supercluster
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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
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universe
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the sum total of all matter and energy
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observable universe
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the portion of the entire universe that can be seen from earth.
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astronomical units
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the average distance between the Earth and the Sun, about 150 million kilometers
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light-year
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distance light can travel in one year--9.46 trillion kilmeters
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rotation
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the spinning of an object on its axis
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orbit (revolution)
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the orbital motion of one object around another
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expansion
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the average distance between galaxies is increasing
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age of the universe
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about 14 billion years (13.7)
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age of our solar system
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4.6 billion years
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constellation
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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
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celestial sphere
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the seeming dome around the earth which the stars appear to lie on
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north celestial pole
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the point directly over the north pole on the celestial sphere
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south celestial pole
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the point directly over the south pole on the celestial sphere
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celestial equator
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the projection of the earth's equator on the celestial sphere
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ecliptic
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the path the sun follows as it appears from Earth
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local sky
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our half of the celestial sphere
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horizon
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the boundary between Earth and sky
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zenith
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the point directly over head
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meridian
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an imaginary half circle stretching from the horizon due south through the zenith, to the horizon due north
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angular size
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the angle an object appears to span in your field of view
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angular distance
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the angle that appears to separate two objects
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arcminutes
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60 in each degree
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zodiac
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the constellations along the eliptic
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summer solstice
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when the sun is highest in the sky (for Northern hemisphere)
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winter solstice
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when the sun is lowest in the sky (for Northern hemisphere)
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equinox
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when sunlight falls equally on both hemipheres
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sidereal period
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the time it takes to orbit the sun
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synodic period
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the time between alignments
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