| A | B |
|---|
| binary star | a double-star system |
| constellation | group of stars that form a pattern |
| nova | star that suddenly increases in brightness in just a few hours or days |
| nebula | A massive cloud of dust and gas between the stars |
| galaxy | A huge collection of stars |
| Milky Way | Our "home" galaxy, of which our Sun is only one star |
| spectroscope | An instrument that analyzes the color of light from distant |
| spectrum | A band of colors that forms when light passes through a prism |
| red shift | A shift toward the red end of the spectrum; indicates that a star is moving away from the Earth |
| Doppler effect | The apparent change in the wavelength of light that occurs when an object is moving toward or away from the Earth |
| Big-Bang theory | A theory that states that the universe began to expadn with the explosion of concentrated matter and energy |
| gravity | The force of attraction between objects |
| quasar | A distant object that gives off mainly radio waves and X-rays |
| giant star | A star with a diamter 10 to 100 times as large as our Sun |
| supergiant star | The largest category of stars; 1000 times as large as our Sun |
| white dwarf | a small, dense star |
| neutron star | The smallest category of stars |
| apparent magnitude | The brightness of a star as it appears on Earth |
| absolute magnitude | The amount of light a star actually gives off |
| Hertzprung-Russell diagram | A chart that shows the relationship between the absolute magnitude and the surface temperature of a star |
| main-sequence star | A star on the H-R diagram that has an absolute magnitude proportional to surface temperature |
| parallax | The apparent change in the position of a star in the sky due to the change in the Earth's position as the Earth moves around the Sun. |
| nuclear fusion | The process by which hydrogen atoms fuse to form helium atoms |
| corona | The outermost layer of the Sun |
| chromosphere | The layer of the Sun just outside the photosphere |
| photosphere | The layer of the Sun just outside the core |
| core | The center of the Sun |
| prominence | A violent storm on the sun that can be seen from Earth as a huge bright arch |
| solar flare | A storm on the Sun visible as a bright burst of light |
| solar wind | A continuous stream of high-energy particles released into space from the Sun's corona |
| sunspot | A dark area on the Sun's surface |
| axis | An imaginary vertical line through the center of the Earth |
| protostar | A new star |
| supernova | A tremendous explosion in which a star breaks apart, releasing enormous amounts of energy |
| pulsar | A neutron star that gives off radio waves |
| black hole | The core of a supermassive star that remains after a supernova; so strong not even light can escape |
