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93 Cards in this Set
- Front
- Back
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how many ly is the milky way galaxy?
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75,000-100,000
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how many stars in MW?
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1.1 Billion
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what is the whitish light that passes through several constellations?
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milky way
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what proved that we are in a galaxy?
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variable stars and clusters
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Name the 4 features of a galaxy
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Nuclear buldge, disk, halo, clusters
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Name the four types of variable stars
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eclipsing, mira, rr lyraes, cepheids
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how to tell eclipsing variable?
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light curve
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how to tell rr lyraes?
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1/2 to 1 day period- all have same luminsoity- all 100x mv of sun
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how to tell mira?
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long period
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how to tell cepheids?
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1-60 day period
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What did Henrietta Leavitt work with?
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Cepheids and RR Lyraes
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who created distance yardsticks using cepheids and rr lyraes?
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henrietta leavitt
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where did henrietta leavitt do her work?
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harvard college observatory
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Who discovered that we live in a galaxy?
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Harlow Shapely
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How did shapely use clusters to determine we live in a galaxy?
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used leavitts work of measuring distance using cepheids and rr lyraes, measured distance to clusters, deduced structure of galaxy
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What are two main components of our galaxy?
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Disk and sphere
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stars, open cluster, gas, dust=___
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disk
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where does start formation happen in our galaxy?
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in the disk
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how far is our sun from the center of the galaxy?
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8.5 kilaparsecs
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what types of stars are in the disk?
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o and b (blue, hot)
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what is the radius of our disk?
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12.5 kilaparsecs
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21 cm radiation
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un-ionized H photons at 21 cm radiation-able to travel through dust and measure galaxy
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age of the universe determined by the ____________
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hubble constant
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where are POP II stars located?
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in the halo
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Where are POP I stars located?
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Disk
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Why are POP II starts in the halo?
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halo is older
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why are POP I stars in the disk?
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disk is younger
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What kind of galaxy do we live in?
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sprial barred galaxy (SBb)
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What happens if a star produces elements up to Fe?
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supernova
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What is the first step in the formation of the galaxy?
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cloud of gas and dust-only H and He
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What happens in galexy formation after a cloud of gas and dust with H and He?
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Gravity contracts it
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What happens after gravity contracts a dust and gas cloud?
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1st stars- POP II's in G.C./halo the remains
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What happens when stars star forming in a galaxy?
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more contractions by gravity- disk forms- POP I stars in disk
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The density wave theory says that the spiral arms of the galaxy are______________
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compression (shock) waves
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how do compression waves make stars?
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spiral arm moves slowly, jams material together, star formation occurs
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How long is the suns orbit around the galaxy?
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240 million years
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how old is the milky way?
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5 billion years
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Who introduced the classification of galaxies?
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Edwin Hubble
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name the three types of galaxies
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elliptical, spiral, irregular
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what types of stars are in an elliptical galaxy?
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POP II stars
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is there a lot of star formation in an elliptical galaxy?
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no-little gas and dust
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do do elliptical galaxies have spiral arms?
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no
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what is the formula to measure an elliptical galaxy?
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a=horizontal
b=vertical 10(a-b)a |
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spiral galaxies have mostly______ stars in the disk
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POP I O, B
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What type of galaxy has a nuclear buldge and halo with POP II stars?
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Spiral
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What is an SO galaxy?
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Spiral with no arms- not much g&d, disk and halo
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Sa galaxy
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Spiral with tightly wound-large bulge, little gas and dust
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Sb
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Less loosly wound, smaller buldge
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Sc
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loose, small buldge, lots of gas and dust
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barred spiral
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elongated nuclear buldge
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Give an example of an irregular galaxy
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cigar galaxy, large magellanic cloud
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explain an irregular galaxy
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chaotic appearance, no arms or spirals, no smooth elliptical look, gas and dust spread out
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How far is andromeda galaxy?
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2.9 Mil. LY
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What is the most distant we can see?
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10 Bil. LY
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Look back time
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how many years ago we are seeing something as. Ex. Andromeda as we see it is actually what it looked like 2.9 Million years ago
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How can we detect distance using Cepheids?
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L or Mv and perios
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how far can we use cepheids to detect ditance?
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80 Mil. LY
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How can we use planetary nebula to measure distance?
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Look at emission lines shift
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How can we use a supernova to measure distance?
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all are aprox. same Mv- takes us out to 1000 MPC
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How can we use another galaxy to measure distance?
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ave L of galaxy is 16 billion-all have same Mv-look for average galaxy, claculate distance
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What is hubble law?
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apparent velocity of recession versus distance-ends up being straight line
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what is hubble constant?
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70km/s/mpc
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study of universe as a whole and how it all began
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cosmology
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does the universe have an edge?
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no
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how close can we get to the big bang?
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10-43
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what is olber's paradox?
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incorrectly determined the universe to be infinetly old-universe is 14 bil. yrs old. therefore, 14bil ly radius of observable portion
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what is the universe?
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everything that exists
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what is observable universe?
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what we can see (14 bil years)
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what are the three assumptions of cosmology?
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Homogeneity, Isotropy, Universality
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assumes that matter is spread out uniformly
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homogeneity
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assumes universe looks the same in every direction
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isotropy
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any observer in any galaxy sees same general makeup of the universe
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universality
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how do we know all galaxies are moving away from each other and explainding?
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red shift
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what does the sky being dark suggest?
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expansion
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what moves galaxies away from each other?
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expansion of space
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what is the redshift evidence ofexplainsion?
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galaxies with red shifts proportional to distance-red shifts are larger for distance ones
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why is there no edge to the universe?
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there is nothing for an edge to expand into-the universe IS everything that exists
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what are the three types of theories of curvature of the universe?
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closed, flat, open
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positive curvature, finite, with no edge, surface of a sphere analogy
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closed universe
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zero curvature, must be infinite because there is no edge
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flat universe
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negative curvature, saddle shaped
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infinite, no edge
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is there a center to the universe?
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no
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What did Robert Wilson and Arno Penzias discover?
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Background radiation-evidence of the big bang
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undected matter that is obviously there
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dark matter
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give an example of probable dark matter
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galaxies with more mass then is visible
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what tells us that dark matter is there?
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gravitational effects
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What is cold dark matter?
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slow moving particles
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what is hot dark matter?
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matter moving at close to speed of light
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what is the value of science?
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understanding new things
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Why do we think time has a beginning?
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time and space are inseperably linked
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What is not meant by the big bang?
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not a dense piece of matter, but pure energy
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What does COBE stand for and what does it do?
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Cosmic Background Explorer-detects background radiation, big bang
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What are some theories ofwhat will eventually happen to the universe?
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big crunch, pulsating universe
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