Help
Options
Didn't know it?
click below
click below
Knew it?
click below
click below
Don't Know
Remaining cards (0)
Know
retry
shuffle
restart
0:00
Embed Code - If you would like this activity on your web page, copy the script below and paste it into your web page.
Normal Size Small Size show me how
Normal Size Small Size show me how
PCS Earth Science
Chapter 30 Vocabulary - Galaxies in the Universe
| Term | Definition |
|---|---|
| variable star | stars that regularly or repeatedly change in magnitude |
| RR Lyrae variable | stars with pulsation periods ranging from 1.5 hours to 1 day, generally having the same luminosity, regardless of pulsation period length |
| cepheid variable | a variable star that brightens and dims regularly, or pulses, and whose distance can be determined from its period of pulsation |
| Population 1 stars | gas and dust and bright blue stars are characteristics of |
| Population 2 stars | found in globular clusters and the halo of a galaxy. Older and less luminous than Population 1 stars. Few heavy elements, metal poor |
| spiral density wave | type of wave that creates spiral arms in a galaxy and is composed of alternating regions with variable density that rotate in a fixed pattern |
| dark matter | matter that dies not give off electromagnetic radiation |
| supercluster | gigantic threadlike or sheetlike cluster of galaxies that is hundreds of millions of light years in size |
| Hubble constant | value (H) is the rate at which the universe is expanding. Can be used to determine the distance or velocities of different galaxies or clusters of galaxies |
| radio galaxy | very bright, often giant, elliptical galaxy that emits as much or more energy in the form of radio wavelengths as it does wavelengths of visible light |
| active galactic nucleus | the unusually luminous centers of some galaxies, thought to be powered by accretion onto super massive black holes. Quasars are the brightest type of active galactic nuclei; radio galaxies also contain active galactic nuclei |
| quasar | an enormously bright, distant galaxy with a giant black hole at its center |
| cosmology | study of the universe as a totality; theory of the origin and structure of the universe |
| Big Bang Theory | is currently (2003) the dominant theory in cosmology about the early development and current shape of the universe |
| cosmic background radiation | the electromagnetic radiation left over from the big bank |
| halo | a spherical region where globular clusters are located, surrounds the Milky Way's nuclear bulge and disk |
Created by:
Ms.Sala
Popular Earth Science sets