Astronomy12

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how many ly is the milky way galaxy?: 75,000-100,000
how many stars in MW?: 1.1 Billion
what is the whitish light that passes through several constellations?: milky way
what proved that we are in a galaxy?: variable stars and clusters
Name the 4 features of a galaxy: Nuclear buldge, disk, halo, clusters
Name the four types of variable stars: eclipsing, mira, rr lyraes, cepheids
how to tell eclipsing variable?: light curve
how to tell rr lyraes?: 1/2 to 1 day period- all have same luminsoity- all 100x mv of sun
how to tell mira?: long period
how to tell cepheids?: 1-60 day period
What did Henrietta Leavitt work with?: Cepheids and RR Lyraes
who created distance yardsticks using cepheids and rr lyraes?: henrietta leavitt
where did henrietta leavitt do her work?: harvard college observatory
Who discovered that we live in a galaxy?: Harlow Shapely
How did shapely use clusters to determine we live in a galaxy?: used leavitts work of measuring distance using cepheids and rr lyraes, measured distance to clusters, deduced structure of galaxy
What are two main components of our galaxy?: Disk and sphere
stars, open cluster, gas, dust=___: disk
where does start formation happen in our galaxy?: in the disk
how far is our sun from the center of the galaxy?: 8.5 kilaparsecs
what types of stars are in the disk?: o and b (blue, hot)
what is the radius of our disk?: 12.5 kilaparsecs
21 cm radiation: un-ionized H photons at 21 cm radiation-able to travel through dust and measure galaxy
age of the universe determined by the ____________: hubble constant
where are POP II stars located?: in the halo
Where are POP I stars located?: Disk
Why are POP II starts in the halo?: halo is older
why are POP I stars in the disk?: disk is younger
What kind of galaxy do we live in?: sprial barred galaxy (SBb)
What happens if a star produces elements up to Fe?: supernova
What is the first step in the formation of the galaxy?: cloud of gas and dust-only H and He
What happens in galexy formation after a cloud of gas and dust with H and He?: Gravity contracts it
What happens after gravity contracts a dust and gas cloud?: 1st stars- POP II's in G.C./halo the remains
What happens when stars star forming in a galaxy?: more contractions by gravity- disk forms- POP I stars in disk
The density wave theory says that the spiral arms of the galaxy are______________: compression (shock) waves
how do compression waves make stars?: spiral arm moves slowly, jams material together, star formation occurs
How long is the suns orbit around the galaxy?: 240 million years
how old is the milky way?: 5 billion years
Who introduced the classification of galaxies?: Edwin Hubble
name the three types of galaxies: elliptical, spiral, irregular
what types of stars are in an elliptical galaxy?: POP II stars
is there a lot of star formation in an elliptical galaxy?: no-little gas and dust
do do elliptical galaxies have spiral arms?: no
what is the formula to measure an elliptical galaxy?: a=horizontal
b=vertical

10(a-b)a
spiral galaxies have mostly______ stars in the disk: POP I O, B
What type of galaxy has a nuclear buldge and halo with POP II stars?: Spiral
What is an SO galaxy?: Spiral with no arms- not much g&d, disk and halo
Sa galaxy: Spiral with tightly wound-large bulge, little gas and dust
Sb: Less loosly wound, smaller buldge
Sc: loose, small buldge, lots of gas and dust
barred spiral: elongated nuclear buldge
Give an example of an irregular galaxy: cigar galaxy, large magellanic cloud
explain an irregular galaxy: chaotic appearance, no arms or spirals, no smooth elliptical look, gas and dust spread out
How far is andromeda galaxy?: 2.9 Mil. LY
What is the most distant we can see?: 10 Bil. LY
Look back time: 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
How can we detect distance using Cepheids?: L or Mv and perios
how far can we use cepheids to detect ditance?: 80 Mil. LY
How can we use planetary nebula to measure distance?: Look at emission lines shift
How can we use a supernova to measure distance?: all are aprox. same Mv- takes us out to 1000 MPC
How can we use another galaxy to measure distance?: ave L of galaxy is 16 billion-all have same Mv-look for average galaxy, claculate distance
What is hubble law?: apparent velocity of recession versus distance-ends up being straight line
what is hubble constant?: 70km/s/mpc
study of universe as a whole and how it all began: cosmology
does the universe have an edge?: no
how close can we get to the big bang?: 10-43
what is olber's paradox?: incorrectly determined the universe to be infinetly old-universe is 14 bil. yrs old. therefore, 14bil ly radius of observable portion
what is the universe?: everything that exists
what is observable universe?: what we can see (14 bil years)
what are the three assumptions of cosmology?: Homogeneity, Isotropy, Universality
assumes that matter is spread out uniformly: homogeneity
assumes universe looks the same in every direction: isotropy
any observer in any galaxy sees same general makeup of the universe: universality
how do we know all galaxies are moving away from each other and explainding?: red shift
what does the sky being dark suggest?: expansion
what moves galaxies away from each other?: expansion of space
what is the redshift evidence ofexplainsion?: galaxies with red shifts proportional to distance-red shifts are larger for distance ones
why is there no edge to the universe?: there is nothing for an edge to expand into-the universe IS everything that exists
what are the three types of theories of curvature of the universe?: closed, flat, open
positive curvature, finite, with no edge, surface of a sphere analogy: closed universe
zero curvature, must be infinite because there is no edge: flat universe
negative curvature, saddle shaped: infinite, no edge
is there a center to the universe?: no
What did Robert Wilson and Arno Penzias discover?: Background radiation-evidence of the big bang
undected matter that is obviously there: dark matter
give an example of probable dark matter: galaxies with more mass then is visible
what tells us that dark matter is there?: gravitational effects
What is cold dark matter?: slow moving particles
what is hot dark matter?: matter moving at close to speed of light
what is the value of science?: understanding new things
Why do we think time has a beginning?: time and space are inseperably linked
What is not meant by the big bang?: not a dense piece of matter, but pure energy
What does COBE stand for and what does it do?: Cosmic Background Explorer-detects background radiation, big bang
What are some theories ofwhat will eventually happen to the universe?: big crunch, pulsating universe

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