A star system with two stars.
A binary star system in which one star periodically blocks the light from the other.
A star cluster that has a loose, disorganized appearance and contains no more than a few thousand stars.
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.
A galaxy with a bulge in the middle and arms that spiral outward in a pinwheel pattern.
A galaxy shaped like a round or flattened ball, generally containing only old stars.
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.
A mathematical method of writing numbers using powers of ten.