| A | B |
|---|
| wavelength | the distance between the crest of one wave and the crest of the next wave |
| spectrum | occurs when you shine white light into a prism and the light spreads out to make a range of different colors with different wavelengths |
| optical telescope | a telescope that uses lenses or mirrors to collect and focus visible light |
| refracting telescope | a telescope that uses convex lenses to gather and focus light |
| reflecting telescope | a telescope that uses a curved mirror to collect and focus light |
| radio telescope | a telescope that detects radio waves from objects in space |
| constellation | imaginary patterns of stars |
| spectrograph | a device that breaks light into colors and produces an image of the resulting spectrum |
| light-year | the distance that light travels in one year |
| parallax | the apparent change in position of an object when you look at it from different places |
| main sequence | our Sun is included in this type of star |
| eclipsing binary | a system of two stars where periodically one star blocks the light from another |
| open cluster | star cluster that has a loose, disorganized appearance and contains no more than a few thousand stars |
| globular cluster | a star cluster that is round and densely packed with millions of stars |
| spiral galaxy | a galaxy that appears to have a large bulge in the middle and arms that spiral outward like a pinwheel. Our galaxy is one of these. |
| elliptical galaxy | a galaxy that looks like a round flattened ball |
| irregular galaxy | a galaxy that doesn't have a regular shape |
| quasar | active young galaxies with giant black holes at thier centers |
| scientific notation | uses powers of 10 to write very large or very small numbers in shorter form |
| big bang | a theory that states the universe formed in an instant, billions of years ago, in an enormous explosion |
| Hubble's law | a law that states; the farther away a galaxy is, the faster it is moving away from us |
| solar nebula | a large cloud of gas and dust |
| planetesimal | the outer parts of a gas and dust cloud tha later formed the planets |
| dark matter | matter that does not give off electromagnetic radiaton |
| dark energy | the force that is causing galaxies to accelerate at a faster rate than in the past |
