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Definition
| intersteller gas and dust that obscures our view when we try to peer directly through it. the gas and dust provide the raw material that all our stars in our galaxy are made up of. |
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| These are apart of a spiral galaxy but from the side view it is the disk of the galaxy. |
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| it contains more than 100 billion stars |
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Definition
| center of the disk, and it is bright and central |
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Definition
| surrounds the disk. It is nearly invisible, except for its mately 200 globular clusters of stars |
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| star properties(color,age, heavy element content) |
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Definition
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| These are apart of a spiral galaxy but from the side view it is the disk of the galaxy. |
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| it contains more than 100 billion stars |
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Definition
| center of the disk, and it is bright and central |
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Definition
| surrounds the disk. It is nearly invisible, except for its mately 200 globular clusters of stars |
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Term
| star properties(color,age, heavy element content) |
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Definition
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Term
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Definition
age:old >10 billion years
color: Redder
Heavy elements: very little |
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Definition
Age: young and old
color:bluer
Heavy elements: More with younger stars having heavy elements |
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Definition
Halo and bulge stars do not have a consistent motion
motions are more random and with more extreme orbits in shape |
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Definition
L=MVrotation d
since gravity pulls it cannot change the angular momentum
so L is conserved |
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Definition
| stars are moving in orderly orbits in same direction, with only slight bobbing up and down out of disk |
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Definition
| stars are moving in highly, elliptical orbits without order, leading to ball like structure |
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Definition
Constant orbital velocities suggest instability or spiral arms
stars throughout most of the disk orbit at the same speed
spiral arms must be more like swirling ripples in a whirlpool than like the fins of a giant pinwheel
Spiral Arms are stable structures, but the stars that compose them is continually changing |
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Definition
| Dominantly in spiral arms, no current formation in bulge and halo |
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Term
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Definition
i) cycle of birth, death of stars
ii) gas needs to cool to form stars, hot gas is emitted from supernova and in ionization nebulae
iii) heavy elements continually injected as stars go through their lives, leading to younger stars having more heavy elements |
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Term
| Models of galaxy formation |
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Definition
i) Ongoing research area with broad mechanisms in place
ii) Simple Model: protogalactic cloud collapse, stars forming in collapse to form halo, bulge, collapsing gas, dust spinning up to form disk, spiral arms
iii) Important determining factors: mergers and initial conditions (whether cloud had angular momentum, how quickly star formation occurs) and how they lead to disks, halos, etc... |
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Definition
| contain spiral arms with active star formation - subdistinctions (bars or not, a-c based on tightness of arms, size of bulge) |
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Definition
| looks like bulge only galaxy with no gas or dust or active star formation- sub distinctions (0-7 based on roundedness) |
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Definition
| intermediate between elliptical and spirals, can have dust, but no gas or star formation |
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Definition
| every other galaxy that defies these other classifications |
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Term
| How collisions effect galaxy evolution |
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Definition
i) Tidal tails from tidal forces (strong gravity stretching objects)
ii) Spirals spinning up from smaller galaxies merging
iii) Elliptical forming from spiral pairs colliding and canceling angular momentum elliptical forming from spirals) |
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Definition
i) gravity from mass and energy warping spacetime
ii) Tested by light deflection, mercury’s orbit changing |
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Definition
i) A region with enough mass within it that nothing can travel fast enough to escape it
ii) the “size” of a black hole and the event horizon as region where nothing can escape |
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Definition
| center of galaxies with enormous luminosity in varying parts of electromagnetic spectrum |
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Definition
early known example of AGN discovered by radio telescopes
they are the most luminous and can produce luminosities 1000 times that of the milky way
they were much more common early in time than today |
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Definition
| AGNs powered by accretion disk feeding supermassive black holes |
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Term
| Indirect probes of Black Hole candidates |
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Definition
i) Light Energy emission efficiency of accretion disk (10 − 40% of mc2 energy)
ii) Limit on size from time variation in emission
iii) Mass from orbital velocities of stars or gas |
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| Supermassive black holes seen in most large galaxies with relationship between super |
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Definition
| massive black hole mass and mass in bulge |
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| Distance Measurements and the Distance Ladder |
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Definition
i) Radar Ranging - determines earth-sun distance
ii) Parallax - limited by angular resolution
iii) Standard Candles - using Luminosity and Apparent Brightness |
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Definition
| known luminosities of main sequence stars |
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Definition
| luminosity vs period relationship |
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Definition
| luminosity through time variation |
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| mapped by Hubble using standard candles and measured Doppler Shifts |
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Term
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Definition
i) All distant objects are generally moving away from us
ii) The speed at which they are receding grows with distance iii) v = H0 × d where H0 = 22km/s/Mlyr is Hubble’s constant |
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Term
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Definition
i) Homogeneity - properties at every position are the same
ii) Isotropy - properties in each direction are the same
iii) Properties are true at large distances in an average sense - evidence from Cosmic |
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| Hubble’s Law is a consequence of an expanding Universe which is homogeneous and isotropic |
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Definition
| analogies of expanding balloon surface or expanding raisin cake |
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Term
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Definition
i) Big Bang - far enough in the past, the Universe was infinitely dense (does not occur at a single point, but in all of space)
ii) Time after Big Bang gives a well defined age of universe |
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Term
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Definition
i) Homogeneity - properties at every position are the same
ii) Isotropy - properties in each direction are the same
iii) Properties are true at large distances in an average sense - evidence from Cosmic |
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Term
| Hubble’s Law is a consequence of an expanding Universe which is homogeneous and isotropic |
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Definition
| analogies of expanding balloon surface or expanding raisin cake |
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Term
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Definition
i) Big Bang - far enough in the past, the Universe was infinitely dense (does not occur at a single point, but in all of space)
ii) Time after Big Bang gives a well defined age of universe |
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Definition
wavelength observed/wavelength emitted
i) Hubble’s law says that increasing z means increasing distance
ii) Farthest known objects are quasars as far as z = 8 |
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Definition
| since light travels at a finite speed, the farther away an object was when it emitted light, the younger the Universe and the object was when we observe it |
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Definition
| since the age of the Universe is finite, there is a cosmological horizon that we cannot see past yet, but in the future we can see further |
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Term
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Definition
quantity = a x variablepower
If for value of variable = v, quantity = q then if variable = f x v, quantity = fpower x q |
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