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absolute magnitude

the actual (true) brightness of a star

apparent magnitude

the brightness of a star as seen from Earth

barred spiral galaxy

a galaxy that is similar to a spiral galaxy, except that the spiral arm pattern originates from a bar of material that passes through the nucleus of the galaxy.

binary star

a system of two stars that revolve around each other under their mutual gravitation

black hole

final stage in the evolution of a very massive star, where the core's mass collapses to a point that its gravity is so strong that not even light can escape


stars that appear to travel in a circle around the celestial poles


A group of stars that form a pattern in the sky

elliptical galaxy

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


a collection of stars, dust, and gas bound together by gravity

giant star

a very large, cool, bright star; much larger than the sun

globular cluster

spherically shaped group of hundreds of stars located around the core of the Milky Way Galaxy

H-R Diagram

Hertzsprung-Russell diagram, a graph that shows the relationship between a star's surface temperature and absolute magnitude

irregular galaxy

a galaxy that does not fit into any other category; one with an irregular shape

light year

the distance light travels in one year (9.5 trillion kilometers)

main-sequence star

a normal star that is undergoing nuclear fusion of hydrogen into helium. Our sun is a typical main sequence star.


a large cloud of dust and gas that can break apart into smaller pieces and form stars, large cloud of gas and dust that contracts under gravitational force and breaks apart into smaller pieces, each of which might collapse to form a star

neutron star

collapsed core of a supernova consisting of a small, extremely dense ball of neutrons


white dwarf star that explodes as it cools, temporarily becoming thousands of times brighter

open cluster

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


method of determining the distance from the earth to a star based on the shift in the apparent position of the star when viewed from different angles

planetary nebula

expanding shell of gases shed by a dying star


Early form of a star; This stage lies between the collapsing of dust and gas and the beginning of nuclear fusion


neutron star that emits two beams of radiation that sweep across space


a starlike object that may send out radio waves and other forms of energy

red shift

the change in the wavelength of light due to an object moving away from the observer.

spiral galaxy

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


a body of gases that gives off a tremendous amount of radiant energy in the form of light and heat


an extremely large, giant star


the brilliant explosion of a dying supergiant star

white dwarf

a small, hot, dim star that is the leftover center of an old star

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