Question | Answer |
magelannic clouds | small irregular galaxies that are companions to the milky way |
kiloparsec | a unit of distance equal to 1000pc, or 3,260ly |
halo | the spherical region of a spiral galaxy that contains thing scattering of stars, clusters, and amounts of gas |
nuclear bulge | the spherical cloud of stars that lies at the center of spiral galaxies |
disk component | all material confined to the plane of the galaxy |
spherical component | part of the galaxy including all matter in a spherical distributions around the center |
spiral arms | long spiral patterns of light of bright stars, clusters, gas and dust extended from center to edge of disk |
high velocity star | a star with large space velocity such stars are halo stars passing through at angles |
rotation curve | a graph of orbital velocity versus radius in the disk of the galaxy |
galactic corona | the low density extension of the halo of a galaxy |
metals | all atoms heavier than helium |
population I stars | stars rich in heavy metals than helium, relatively young, found in the disk of the galaxy |
population II stars | poor in atoms heavier than helium, old, found in the halo or globular clusters |
nucleosynthesis | the production of elements heavier than helium by fusion of atomic nuclei in stars |
spiral tracers | objects used to map the spiral arms |
density wave theory | proposed to account for spiral arms as compressions of the interstellar medium in the disk of the galaxy |
flocculent | woolly, fluffy, used to refer to certain galaxies that have woolly appearances |
self sustaining star formation | the process by which the birth of stars compresses the surrounding gas clouds and triggers the formation of more stars |
sagittarius A | the powerful radio source located at the core of the milky way |
keplarian motion | orbital motion in accord with Keplers laws of planetary motion |