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51 Cards in this Set

  • Front
  • Back
spiral density wave
the theory that the massive black hole in our galaxy sends compression waves thru the galaxy and creates new spiral arms
interstellar medium
material between stars gas and dust
21 cm radiation
hydrogen spin flip –radio waves
dark matter
90 percent of matter in galaxy—
cosmic rays
particles shot out by supernova
dust grains
carbon and silicate dust between stars
emission nebula
heated glowing gasses
reflection nebula
bluish from dust reflection
molecular clouds
prime areas for formation
20% of all galaxies –lots of dust and gas—normal most abundant of spirals
elliptical galaxies
80% of all galaxies—most are dwarfs the super large ones eat others
irregular galaxies
near collisions or collisions made them—our satellite galaxies are the Magellan clouds and are irregular
standard candle
each type of galaxy has certain absolute magnitude
galaxies are not alone but in clusters
super cluster
clustering of clusters
hubbles law
the farther the faster
hubbles constant
50 to 100 km/sec/mpc
1 to 100 days –yardsticks to other galaxies
period luminosity
how we use Cepheid’s to measure distance
cosmological prinicple
averaged over large enough distances, one part of the Universe looks approximately like any other part: homogeneous and isotropic
cosmological red shift
all bodies are moving away –further the faster
cosmological horizon
how far back can we see
look back time
time since the beginning of universe
radio galaxies
colliding galaxies—main reason
quasi stellar objects –small energetic cores of early galaxies
dark matter
makes up to 90 percent of universe
dark energy
makes up 60 percent of dark matter
rotational curve
stars do not slow down as they go around the galaxy because of dark matter
orbit in clusters
galaxies orbit each other faster because of dark matter
gravitational lensing
light is bent by galaxies more than it should because of dark matter
massive compact halo objects –may be dark matter
baryonic matter
normal matter about 10 percent of galaxy
weakly interacting particles –may be dark matter
large scale structures
clusters of galaxies and clusters of cluster called super clusters
critical density
matter needed to open or close the universe
recollapsing universe
high critical density so universe stops expansion and recollapses
critical universe
—flat universe—this is what we think it is—barely expanding
coasting universe
expands forever
accelerating universe
expansion goes faster
that which dominates the baryonic materials in our universe
opposite to our matter
big bang
universe expands out rapidly
planck era
quantum ideas
grand unification of all forces
time at beginning that universe expanded quickly
cosmic microwave background
left over of early hot universe –3K now
obler's paradox
why is night sky dark—cannot have infinite size and infinite number of stars
natural selection
Darwin proposed
biology changes life
habitable zone
area around a star that life can exist
drake equation
probabilities of life that communicates in universe