| A | B |
|---|
| apparent | appearing to the eye or mind |
| apparent magnitude | measure of how bright an object appears from Earth |
| astronomical unit | average distance between Earth and the Sun |
| light-year | distance that light travels in 1 year |
| luminosity | true brightness of an object |
| parallax | apparent change in an object’s position caused by looking at it from two different points |
| spectroscope | instrument that spreads light into different wavelengths |
| chromosphere | orange-red layer of a star’s atmosphere, between the photosphere and the corona |
| convection zone | region above the radiative zone of a star where hot gas moves up toward the surface and cooler gas moves deeper into the interior |
| corona | wide, outermost layer of a star’s atmosphere |
| globular | round, sphere-shaped |
| Hertzsprung-Russell diagram | graph that plots luminosity v. temperature of stars |
| nuclear fusion | process that occurs when the nuclei of several atoms combine into one larger nucleus |
| photosphere | apparent surface of a star’s atmosphere |
| radiative zone | shell of cooler hydrogen above a star’s core |
| star | large ball of gas held together by gravity with a core so hot that nuclear fusion occurs |
| stellar | anything related to stars |
| black hole | object whose gravity is so great that no light can escape |
| nebula | cloud of gas and dust, where stars form |
| neutron | neutral particle in the nucleus of an atom |
| neutron star | dense core of neutrons that remains after a supernova |
| supernova | enormous explosion that destroys a star |
| white dwarf | hot, dense, slowly cooling sphere of carbon |
| Big Bang theory | states that the universe began from one point billions of years ago and has been expanding ever since |
| dark matter | matter that emits no light |
| Doppler shift | shift to a different wavelength as waves travel toward or away from the point of observation |
| galaxy | huge collection of stars |
