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binary stars

a star system with two stars

eclipsing binary

a binary star system in which one star periodically blocks the light from the other

open cluster

a star cluster that has a loose, disorganized appearance and contains no more than a few thousands

globular cluster

a large, round, densely-packed grouping of older stars


a huge group of single stars, star systems, star clusters, dust, and gas bound together by gravity

spiral galaxies

a galaxy with a bulge in the middle and arms that spiral outward in a pinwheel pattern

elliptical galaxies

a galaxy shaped like a round or flattened ball, generally containing only old stars

irregular galaxies

a galaxy that does not have a regular shape


an enormously bright, distant galaxy with a giant black hole at its center


all of space and everything in it

scientific notation

a mathematical method of writing numbers using powers of ten

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