| A | B |
|---|
| star | a large celestrial body that is composed of gas and emits light |
| doppler effect | an observed change in the frequency of a wave when the source or observer is moving |
| light year | the distance light travels in one year |
| parallax | an apparent shift in the position of an object when viewed from different locations |
| apparent magnitude | the brightness of a star as seen from Earth |
| absolute magnitude | the brightness that a star would have at a distance of 32.6 light years from Earth |
| main sequence | the location on the H-R diagram where most stars lie |
| nebula | a large cloud of gas and dust in interstellar space, a region in space where stars are born |
| giant star | a very large and bright star whose hot core has used most of its hydrogen |
| white dwarf | a small, hot, dim star that is the leftover center of an old star |
| nova | a star that suddenly becomes brighter |
| neutron star | a star that has collapsed under gravity to the point that the electrons and protons have smashed together to form neutrons |
| pulsar | a rapidly spinning neutron star that emits pulses of radio and optical energy |
| black hole | an object so massive and dense that even light cannot escape its gravity |
| constellation | a group of stars organized in a recognizable pattern |
| galaxy | a collection of stars, dust, and gas bound together by gravity |
| quasar | a very luminous object that produces energy at a high rate |
| quasi-stellar radio source | quasar |
| cosmology | the study of the origin, properties, processes, and evolution of the universe |
| big bang theory | all matter and energy in the universe was compressed into an extremely small volume that 13 to 15 billion years ago exploded and began expanding in all directions |
| cosmic background radiation | radiation uniformly detected from every direction in space, considered a remnant of the big bang |
| nuclear fusion | the combination of light atomic nuclei (atoms) to form heavier atomic nuclei (atoms) |
| spectrograph | devices that separate light into different colors or wavelengths |
| spectrum | starlight is broken into a display of colors and lines |
| types of spectra | emission, absorption, and continuous |
| blue color stars | temperature above 30,000 degress Celsius, are very hot |
| yellow color stars | temperture between 5,000 and 6,000 degrees Celsius, are medium in temperature |
| red color stars | tempertures below 3,500 degrees Celsius, are the coolest of temperatures |
| circumpolar stars | are stars that are always visible in the night sky |
| protostar | spinning particles flatten into a disk that has a central concentration of matter |
| plasma | hot, ionized gas that consists of an equal number of free moving positive ions and electrons |
| birth of a star | when a protostar begans nuclear fusion |
| supergiant stars | stars very are very large and very luminous making the easy to see in the night sky |
| planetary nebula | a cloud of gas that forms around a sunlike star that is dying |
| black dwarf | forms when a white dwarf star no longer gives off light |
| supernova | a star that explodes |
| binary stars | pair of stars that revolve around each other |
| globular star clusters | have a spherical shape and can contain up to 100,000 stars |
| open star clusters | rarely contains more than a few hundred stars and is loosely shaped |
| spiral galaxies | most common type, has a nucleus of bright stars and flattened arms that spiral around the nucleus |
| Milky Way Galaxy | is a spiral galaxy |
| ellipical galaxies | are elongated, like a stretched out football, very bright in the center |
| irregular galaxies | galaxy with no particular shape and have a lot of dust and gas |
| dark matter | makes of 23% of the universe, does not give off light, but does have detectable gravity |
| matter | everything is made of it, yet it is only 4% of the universe |
| dark energy | some unknow form of energy that opposes gravity and causes the universe to expand |
