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| Constellation | One of 88 groups or patterns of stars used to subdivide the heavens in order to locate and name individual stars. |
| apparent magnitude | Star's relative brightness as viewed from Earth. |
| absolute magnitude | Star's brightness as it would appear at a standard distance from the star. |
| Cepheid variable | Unusual stars that regularly change brightness as they expand and contract in size. |
| light year | Distance light travels in a year; used to measure interstellar distances. |
| parallax | Apparent change in position of a distant object as one's viewing position changes. |
| supergiant | An immense star with mass up to 70 solar masses. |
| Hertxsprung Russell diagram | Graph used to classify stars based on their color/temperature class and their brightness or luminosity. |
| main sequence | A region in the Hertzsprung Russell diagram containing most stars in the universe. |
| red giant | A large, luminous reddish star that forms when a star with about the mass of the sun enters its final stages of existence as its hydrogen fuel is used up. |
| white dwarf | A hot, dense core of a dead star...no nuclear fusion or source of heat. |
| nova | Violent nuclear explosion that occurs when a white dwarf draws in hydrogen from a larger companion star in a stellar binary system. |
| supernova | The violent end of stars of greater than about 8 solar masses. |
| neutron star | City-sized, dense object that is the remnant of a supernova or collapsed white dwarf. |
| black hole | Strange astronomical object so massive and dense that its intense gravity prevents even light from escaping. |
| nebula | An immense cloud of interstellar gas and dust which may glow, reflect light or form dark regions. |
| binary star | One of a pair of gravitationally connected stars that revolve around each other. |
| star cluster | A group of stars close enough to be held together by gravity. |
| galaxy | Huge, loose mass of billions of stars, other astronomical objects and dust held together by gravity. |
| quasar | An unusual celestial object that is as bright as a galaxy but is compact and looks like a distant start in a telescope. |
| cosmology | Body of knowledge that attempts to explain how the universe began and how it changed over time. |
| red shift | Change of the observed spectrum of a star to longer wavelengths due to either distance to the star or its speed away from Earth. |
| cosmic microwave background radiation | Electromagnetic energy in the microwave band of the radio spectrum that appears to come from all directions in space. |
| protostar | A hot, dense collection of matter deep within a nebula that secular cosmologists believe will eventually form a star when nuclear fusion begins. |
| stellar evolution | In secular cosmology, the change of a star over time, starting with its birth and continuing through its aging and final death occuring over million of years. |
| dark matter | Invisible matter that secular cosmologists say must exist in the universe to create enough gravity to make their cosmological model work. |
